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Chapter 6 review microbiology

1, Know the differences between prokaryotic and eukaryotic cells and chromosomes
Cell's ------
The major similarities between the two types of cells (prokaryote and eukaryote) are:

1. They both have DNA as their genetic material.
2. They are both membrane bound.
3. They both have ribosomes .
4. They have similar basic metabolism .
5. They are both amazingly diverse in forms.

The major differences :
1. eukaryotes have a nucleus and membrane-bound organelles , while prokaryotes do not.The DNA of prokaryotes floats freely around the cell. the DNA of eukaryotes is held within its nucleus.The organelles of eukaryotes allow them to exhibit much higher levels of intracellular division of labor than is possible in prokaryotic cells
2. Eukaryotic cells are, on average, ten times the size of prokaryotic cells.
3. Genomic composition and length: The DNA of eukaryotes is much more complex and therefore much more extnsive than the DNA of prokaryotesEukaryotic DNA is linear; prokaryotic DNA is circular (it has no ends)
4. Prokaryotes have a cell wall composed of peptidoglycan, a single large polymer of amino acids and sugar . Many types of eukaryotic cells also have cell walls, but none made of peptidoglycan
5. Eukaryotic DNA is complexed with proteins called "histones," and is organized into chromosomes; prokaryotic DNA is "naked," meaning that it has no histones associated with it, and it is not formed into chromosomes. Though many are sloppy about it, the term "chromosome" does not technically apply to anything in a prokaryotic cell. A eukaryotic cell contains a number of chromosomes; a prokaryotic cell contains only one circular DNA molecule and a varied assortment of much smaller circlets of DNA called "plasmids." The smaller, simpler prokaryotic cell requires far fewer genes to operate than the eukaryotic cell

2, What is a genotype? What is a phenotype?

genotype is the specific genetic makeup (the specific genome) of an individual, usually in the form of DNA. Together with the environmental variation that influences the individual, It codes for the phenotype of that individual. the sepcific set of genes an organism posseses. Two alleles type for each gene. Hyterozygous: difference alleles: Bb. Homozygous: similiar alleles: BB, bb.

phenotype of an individual organism is either its total physical appearance and constitution or a specific manifestation of a trait, such as size or eye color, that varies between individuals. it is the collection of characteristics of an organism that an investigator can observe. Gene expression and result of transcription and translation.

3. Know the structure and function of both DNA and RNA.
DNA:
1.DNA is composed of purine and pyrimidine nucleosides that contains the sugar deosyribose and a phosphate group.
2. A double helix structure consisting two chains of nucleosides coiled around each other.
3. The purine: adnine and guanine. the primidine: thymine and cytosine.
4. two strand are not positioned directing opposite one another. therefore a major groove and smaller minor groove are formed during helix backbone.
5. the two polynucleotide chains are antiparallel.

RNA:

1. The sugar in the RNA molecule is ribose. DNA's sugar is deoxyribose.
2. RNA is usually a single stranded molecule while DNA is nearly always double stranded.
3. DNA's rigid double helix structure allows for only one function (information storage) whereas RNA's greater molecular diversity results in a wider range of functions
4. RNA uses the nucleotide uracil instead of thymine
5. DNA is often 10³ to 10⁶ times larger than RNA
6. RNA is much less stable than DNA. As a single stranded molecule it has no way of reparing itself.

4. What were the historical experiments that led to the paper on the structure of DNA? Who wrote it?

1. Frederick Griffith(1928) demonstrated the phenomenon of transformation: nonvirulent bacteria could become virculent when live, non virulent bacteria were miced with dead, virulent bacteria.
2. Avery, Macleod, and McCarty (1944) demonstrated that the transforming principle was DNA.
3. Hershey and Chase (1952) showed that for the T2 bacteriophage, only the DNA was needed for infectivity. therefore they proved that DNA was the genetic material.
4. Erwin Chargaff: show that in natural DNA the number of guanine units equals the number of cytosine units and the number of adenine units equals the number of thymine units
5. Rosalind Franklin: obtained some excellent x-ray diffraction photographs of DNA' using the recent technique of the time called x-ray crystallography.

The double helix is the structure of DNA as first published by James D. Watson and Francis Crick in 1953. They constructed a molecular model of DNA in which there were two complementary, antiparallel (side-by-side in opposite directions) strands of the bases guanine, adenine, thymine, and cytosine, covalently linked through phosphodiester bonds. The four nitrogen-containing bases found in DNA are divided into two groups: purines and pyrimidines. Two-ringed bases are purines. One-ringed bases are called pyrimidines. Adenine and Guanine are purines, whilst Thymine and Cytosine are Pyrimidines.

5. How is DNA replicated? What enzymes are needed? Where does DNA polymerase function? What does DNA ligase do? What is Theta replication? What are replication forks?

1. DNA is replicated by uncoiling of the helix, strand separation by breaking of the hydrogen bonds between the complementary strands, and synthesis of two new strands by complementary base pairing.Replication begins at a specific site in the DNA called the origin of replication.

2. DNA replication is bidirectional from the origin of replication. unwinding enzymes called DNA helicasescause the two parent DNA strands to unwind and separate from one another at the origin of replication to form two "Y"-shaped replication forks(The actual site of DNA replication where free deoxyribonucleotides hydrogen bond with the nucleotides on each unwound parent DNA strand.)

3. These replication forks are the actual site of DNA copying.Helix destabilizing proteins bind to the single-stranded regions so the two strands do not rejoinEnzymes called topoisimerases produce breaks in the DNA and then rejoin them in order to relieve the stress in the helical molecule during replication.

4. As the strands continue to unwind and separate in both directions around the entire DNA molecule, new complementary strands are produced by the hydrogen bonding of free DNA nucleotides with those on each parent strand.As the new nucleotides line up opposite each parent strand by hydrogen bonding, enzymes called DNA polymerases join the nucleotides by way of phosphodiester bonds. In the end, each parent strand serves as a template to synthesize a complementary copy of itself, resulting in the formation of two identical DNA molecules.

5. one parent strand - the one running 3' to 5' and called the leading strand (def) - can be copied directly down its entire length (see Fig. 17). However, the other parent strand - the one running 5' to 3' and called the lagging strand (def) - must be copied discontinuously in short fragments (Okazaki fragments) of around 100-1000 nucleotides each as the DNA unwinds.During this process, Finally, the DNA fragments themselves are hooked together by the enzyme DNA ligase.

6. the DNA molecules may attach to the cytoplasmic membrane and, as the cell elongates, the two DNA molecules are physically separated

Theta replication: DNA replication of prokaryotes.

6. Compare the structure of plasmids in bacterial cells to the structure of the bacterial chromosome. What is the role of plasmids in bacterial cells?

Prokaryotic cells (bacteria) contain their chromosome as circular DNA. Usually the entire genome is a single circle, but often there are extra circles called plasmids. The DNA is packaged by DNA-binding proteins. Plasmids are typically circular dsDNA molecules which range in size from 2 Kb to 100 Kb. These plasmids will be supercoiled in the cell

plasmid is an extra-chromosomal element, often a circular DNA. Plasmids are small molecules of double stranded, helical, nonchromosomal DNA.lasmids usually contain between 5 and 100 genes. Plasmids are not essential for normal bacterial growth and bacteria may lose or gain them without harm. They can, however, provide an advantage under certain environmental conditions. For example, under normal environmental growth conditions, bacteria are not usually exposed to antibiotics and having a plasmid coding for an enzyme capable of denaturing a particular antibiotic is of no value. three important elements:

• An origin of replication:Since a plasmid is (by definition) an extrachromosomal element, it cannot make use of any origin of DNA replication in a chromosome. That is, DNA synthesis within (i.e. copying of) a plasmid depends on its having an origin of DNA synthesis of its own. Obviously, if a plasmid couldn't be copied, it would be rapidly diluted out in a population of dividing cells because it couldn't be passed on to daughter cells
• A selectable marker gene (e.g. resistance to ampicillin):carrying a plasmid puts a cell at a selective disadvantage compared to its plasmid-free neighbors, so the cells with plasmids grow more slowly. Cells that happen to "kick out" their plasmid during division may be "rewarded" by having a higher rate of growth, and so these plasmid-free (sometimes referred to as "cured") cells may take over a population. If a plasmid contains a gene that the cell needs to survive (for example, a gene encoding an enzyme that destroys an antibiotic), then cells that happen to kick out a plasmid are "punished" (by subsequent death) rather than "rewarded" (as in the previous scenario). That selective pressure helps to maintain a plasmid in a population.
• A cloning site (a place to insert foreign DNAs)
• Plasmids are sometimes called "vectors", because they can take DNA from one organism to the next. Not all vectors are plasmids, however. We commonly use engineered viruses, for example bacteriophage lambda, which can carry large pieces of foreign DNA
• Plasmids code for synthesis of a few proteins not coded for by the nucleoid.

7. support the statement "DNA replication if semiconservtive"
8.State the central dogma of protein synthesis.
DNA-------(transcription)-------RNA--------(translation)--------Protein.
Transcription is the making of an RNA molecule off a DNA template. Translation is the construction of an amino acid sequence (polypeptide) from an RNA molecule.

9. three major types of RNA( produced by transcription)
mRNA: messenger RND carries the message to encode protein in a condon.
rRNA: a component of the ribosomes
tRNA: anti-codon: transfer RNA

10. What controls the expression of genes? What is an operon? Remember that the enzyme in bacteria that degrades lactose is ß-galactosidase, not lactase (lactase works in larger organisms)
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookGENCTRL.html
http://www.sumanasinc.com/webcontent/anisamples/majorsbiology/lacoperon.html

11. What were the experiments of Jacob and Monod? How does the lac operon work? What are the promotor, or operator sites on DNA, which molecule is the repressor, or inducer? Explain
promoter is a DNA sequence that enables a gene to be transcribed. The promoter is recognized by RNA polymerase, which then initiates transcription.

• RNA polymerase I: transcribes genes encoding ribosomal RNA
• RNA polymerase II: transcribes genes encoding messenger RNA and certain small nuclear RNAs
• RNA polymerase III: transcribes genes encoding tRNAs and other small RNAs

An operator is a segment of DNA that regulates the activity of the structural genes of an operon it is linked to, by interacting with a specific repressor or activator. It is a regulatory sequence for shutting a gene down or turning it "on".In negative inducible operons, a regulatory repressor protein is bound to the operator and it prevents the transcription of the genes on the operon. If an inducer molecule is present, it binds to repressor and changes its conformation so that it is unable to bind to the operator. This allows for the transcription of the genes on the operator. In negative repressible operons, transcription of the genes on the operon normally takes place. Repressor proteins are produced by a regulator gene but they are unable to bind to the operator in their normal conformation. However repressor molecules can bind to the repressor protein and change its conformation so that it can bind to the operator. The activated repressor proteins bind to the operator and prevent transcription.
A repressor is a DNA-binding protein that regulates the expression of one or more genes by decreasing the rate of transcription. This blocking of expression is called repression.Repressor proteins are coded for by regulator genes. Repressor proteins then attach to a DNA segment known as the operator. By binding to the operator, the repressor protein prevents the RNA polymerase from creating messenger RNA.

12. What is mutation? How does it occur?name three mutagens and its effects on bacterial DNA.
Mutation: An error during DNA replication that results in a change in the sequence of deoxyribonucleotide bases in the DNA.
Spontaneous mutation (def) occurs naturally (a normal mistake rate) about one in every million to one in every billion divisions and is probably due to low level natural mutagens normally present in the environment. Induced mutation (def) is caused by mutagens, substances that cause a much higher rate of mutation.
Spontaneous mutation :

1. Mechanisms of mutation

a. Substitution of a nucleotide (point mutations (def)): substitution of one deoxyribonucleotide for another during DNA replication (see Fig. 1). This is the most common mechanism of mutation. Substitution of one nucleotide for another is a result of tautomeric shift, a rare process by which the hydrogen atoms of a deoxyribonucleotide base move in a way that changes the properties of its hydrogen bonding. For example, a shift in the hydrogen atom of adenine enables it to form hydrogen bonds with cytosine rather than thymine. Likewise, a shift in the hydrogen atom in thymine allows it to bind with guanine rather than adenine.

b. Deletion or addition of a nucleotide (frameshift mutations (def)): deletion or addition of a deoxyribonucleotide during DNA replication (see Fig. 2 and Fig. 3).

2. Results of mutation

One of four things can happen as a result of these mechanisms of mutation and the resulting change in the deoxyribonucleotide base sequence mentioned above:

a. A missense mutation (def) occurs. This is usually seen with a single substitution mutation and results in one wrong codon (def) and one wrong amino acid (see Fig. 4).

b. A nonsense mutation occurs (def). If the change in the deoxyribonucleotide base sequence results in transcription (def) of a stop or nonsense codon (def), the protein would be terminated at that point in the message (see Fig. 5).

c. A sense mutation (def) occurs. This is sometimes seen with a single substitution mutation when the change in the DNA base sequence results in a new codon still coding for the same amino acid (see Fig. 6). (With the exception of methionine, all amino acids are coded for by more than one codon.)

d. A frameshift mutation occurs (def). This is seen when a number of DNA nucleotides not divisible by three is added or deleted. Remember, the genetic code is a triplet code where three consecutive nucleotides code for a specific amino acid. This causes a reading frame shift and all of the codons and all of the amino acids after that mutation are usually wrong (see Fig. 7); frequently one of the wrong codons turns out to be a stop or nonsense codon and the protein is terminated at that point.

b. Induced mutation (def) is caused by mutagens, substances that cause a much higher rate of mutation.

Chemical mutagens generally work in one of three ways.

• Some chemical mutagens, such as nitrous acid and nitrosoguanidine work by causing chemical modifications of purine and pyrimidine bases that alter their hydrogen-bonding properties. For example, nitrous acid converts cytosine to uracil which then forms hydrogen bonds with adenine rather than guanine.
• Other chemical mutagens function as base analogs. They are compounds that chemically resemble a nucleotide base closely enough that during DNA replication, they can be incorporated into the DNA in place of the natural base. Examples include 2-amino purine, a compound that resembles adenine, and 5-bromouracil, a compound that resembles thymine. The base analogs, however, do not have the hydrogen-bonding properties of the natural base.
• Still other chemical mutagens function as intercalating agents. Intercalating agents are planar three-ringed molecules that are about the same size as a nucleotide base pair. During DNA replication, these compounds can insert ir intercalate between adjacent base pairs thus pushing the nucleotides far enough apart that an extra nucleotide is often added to the growing chain during DNA replication. An example is ethidium bromide.

Chemical mutagens can also activate what is called SOS repair that can lead to further mistakes in DNA base pairing (see below).

Certain types of radiation can also function as mutagens.

• Ultraviolet Radiation. The ultraviolet portion of the light spectrum includes all radiations with wavelengths from 100 nm to 400 nm. It has low wave length and low energy. The microbicidal activity of ultraviolet (UV) light depends on the length of exposure: the longer the exposure the greater the cidal activity. It also depends on the wavelength of UV used. The most cidal wavelengths of UV light lie in the 260 nm - 270 nm range where it is absorbed by nucleic acid.

  In terms of its mode of action, UV light is absorbed by microbial DNA and causes adjacent thymine bases on the same DNA strand to covalently bond together, forming what are called thymine-thymine dimers (see Fig. 8). As the DNA replicates, nucleotides do not complementary base pair with the thymine dimers and this terminates the replication of that DNA strand. However, most of the damage from UV radiation actually comes from the cell trying to repair the damage to the DNA by a process called SOS repair. In very heavily damaged DNA containing large numbers of thymine dimers, a process called SOS repair is activated as kind of a last ditch effort to repair the DNA. In this process, a gene product of the SOS system binds to DNA polymerase allowing it to synthesize new DNA across the damaged DNA. However, this altered DNA polymerase loses its proofreading ability resulting in the synthesis of DNA that itself now contains many misincorporated bases. (Most of the chemical mutagens mentioned above also activate SOS repair.)

• Ionizing Radiation. Ionizing radiation, such as X-rays and gamma rays, has much more energy and penetrating power than ultraviolet radiation. It ionizes water and other molecules to form radicals (molecular fragments with unpaired electrons) that can break DNA strands and alter purine and pyrimidine bases.

13. Describe the ways that bacteria can repair DNA damage or replication errors
damage reversal--simplest; enzymatic action restores normal structure without breaking backbone 1. This is one of the simplest and perhaps oldest repair systems: it consists of a single enzyme which can split pyrimidine dimers (break the covalent bond) in presence of light. 2. X-rays and some chemicals like peroxides can cause breaks in backbone of DNA. Simple breaks in one strand are rapidly repaired by DNA ligaseMicrobial mutants lacking ligase tend to have high levels of recombination since DNA ends are recombinogenic (very reactive).

damage removal--involves cutting out and replacing a damaged or inappropriate base or section of nucleotides. 1. base excision repair: The damaged or inappropriate base is removed from its sugar linkage and replaced. These are glycosylase enzymes which cut the base-sugar bond. example: uracil glycosylase--enzyme which removes uracil from DNA. The enzyme recognizes uracil and cuts the glyscosyl linkage to deoxyribose.The sugar is then cleaved and a new base put in by DNA polymerase using the other strand as a template. Mutants lacking uracil glycosylase have elevated spontaneous mutation levels (C to U is not fixed, which leads to transitions) and are hyper-sensitive to killing and mutation by nitrous acid (which causes C to U deamination). 2. mismatch repair: This process occurs after DNA replication as a last "spellcheck" on its accuracy. In E. coli, it adds another 100-1000-fold accuracy to replication. It is carried out by a group of proteins which can scan DNA and look for incorrectly paired bases (or unpaired bases) which will have aberrant dimensions in the double helix. The incorrect nucleotide is removed as part of a short stretch and then the DNA polymerase gets a second try to get the right sequence. 3. nucleoride excision repair: This system works on DNA damage which is "bulky" and creates a block to DNA replication and transcription (so--UV-induced dimers and some kinds of chemical adducts). It probably recognizes not a specific structure but a distortion in the double helix. The mechanism consists of cleavage of the DNA strand containing the damage by endonucleases on either side of damage followed by exonuclease removal of a short segment containing the damaged region. DNA polymerase can fill in the gap that results.

damage tolerance--not truly repair but a way of coping with damage so that life can go on. 1.recombinal repair This is a repair mechanism which promotes recombination to fix the daughter-strand gap--not the dimer--and is a way to cope with the problems of a non-coding lesion persisting in DNA.his type of recombinational repair is generally accurate (although it can cause homozygosis of deleterious recessive alleles) and requires a homolog or sister chromatid. 2. A second type of recombinational repair which is used primarily to repair broken DNA ends such as are caused by ionizing radiation and chemical mutagens with similar action is the non-homologous end-joining reaction. 3. mutagenic repair.An alternative scenario for a DNA polymerase blocked at a dimer is to change its specificity so that it can insert any nucleotide opposite the dimer and continue replication ("mutate or die" scenario).

14. What is a transposon? Who did the research and why is it important?

Transposons are sequences of DNA that can move around to different positions within the genome of a single cell, a process called transposition. In the process, they can cause mutations and change the amount of DNA in the genome. Transposons are also called "jumping genes" or "mobile genetic elements". Discovered by Barbara McClintock early in her career, the topic went on to be a Nobel winning work in 1983.

1. class I: Retrotransposons work by copying themselves and pasting copies back into the genome in multiple places. Initially retrotransposons copy themselves to RNA (transcription) but, in addition to being translated, the RNA is copied into DNA by a reverse transcriptase (often coded by the transposon itself) and inserted back into the genome.

2. Class II transposons move by cut and paste, rather than copy and paste, using the transposase enzyme. Different types of transposase work in different ways. Some can bind to any part of the DNA molecule, and the target site can therefore be anywhere, while others bind to specific sequences. The transposase then cuts the target site to produce sticky ends, cuts out the transposon and ligates it into the target site, and then fills in the sticky ends with the corresponding base pairs.

15.What is replica plating –how does it work – and why is it important in identifying bacterial mutants?

replica plating is a technique in which one or more secondary Petri plates containing different solid (agar-based) selective growth media (lacking nutrients or containing chemical growth inhibitors such as antibiotics) are inoculated with the same colonies of microorganisms from a primary plate (or master dish), reproducing the original spatial pattern of colonies. The technique involves pressing a velvet-covered disk to a primary plate, and then imprinting secondary plates with cells in colonies removed by the velvet from the original plate. Generally, large numbers of colonies (roughly 30-300) are replica plated due to the difficulty in streaking each out individually onto a separate plate.

The purpose of replica plating is to be able to compare the master plate and any secondary plates to screen for a selectable phenotype. For example, a colony which appeared on the master plate but failed to appear at the same location on a secondary plate shows that the colony was sensitive to a substance on that particular secondary plate. Common screenable phenotypes include auxotrophy and antibiotic resistance.

Replica plating is especially useful for negative selection. For example, if one wanted to select colonies that were sensitive to ampicillin, the primary plate could be replica plated on a secondary Amp⁺ agar plate . The sensitive colonies on the secondary plate would die but the colonies could still be deduced from the primary plate since the two have the same spatial patterns from ampicillin resistant colonies. The sensitive colonies could then be picked off from the primary plate.By increasing the variety of secondary plates with different selective growth media, it is possible to rapidly screen a large number of individual isolated colonies for as many phenotypes as there are secondary plates.

16. What is the Ames test and why is it useful and important? What microbe is involved?

to test for mutagenic properties of a chemical compound. A compound is said to be mutagenic if it causes a change in the DNA (deoxyriboneucleic acid) of a living cell or organism. The test is named after its inventor, Bruce Ames.

using strains of bacteria, generally Escherichia coli or Salmonella typhimurium that already have a single mutation, for example, a strain that cannot produce histidine, an amino acid that is essential for the bacterium to grow if not provided externally with essential nutrients. Cultures of the bacteria are grown in an agar containing dish so that a "lawn" of bacteria is present.

The experimental cultures are exposed to the agent to be tested while the positive control cultures are exposed to a known mutagen to confirm that there has been no contamination of the strain. Strains of bacteria are available which have been genetically modified such that only a certain type of mutation (i.e. a base pair mutation or a frameshift mutation) will cause the strand to revert to a normal state, not requiring nutrients to grow. If the mutation screened for has in fact occurred, dense spots in the colonies will form. A certain number of spots may form due to random mutation not caused by the agent; therefore, data analysis using control dishes is necessary. Occasionally a tested agent will be toxic enough to simply kill the bacterial culture in which case a "thin lawn" is observed.

posted by C-T @ 5:12 PM 0 comments

Chapter 7 Genetic Enginnerring

1, How does gene exchanged in bacteria?
1,Lateral gene transfer (LGT) is any process in which an organism transfers genetic material (i.e. DNA) to another cell that is not its offspring.
2,vertical transfer occurs when an organism receives genetic material from its ancestor, e.g. its parent or a species from which it evolved.

2, Gene transfer in Prokaryotes?
Horizontal gene transfer is common among bacteria, even very distantly-related ones. This process is thought to be a significant cause of increased drug resistance; when one bacterial cell acquires resistance, it can quickly transfer the resistance genes to many species.
three common mechanisms for horizontal gene transfer:

• Transformation, the genetic alteration of a cell resulting from the introduction, uptake and expression of foreign genetic material (DNA or RNA). This process is relatively common in bacteria, but less common in eukaryotes. Transformation is often used to insert novel genes into bacteria for experiments, or for industrial or medical applications. See also molecular biology and biotechnology.
• Transduction, the process in which bacterial DNA is moved from one bacterium to another by a bacterial virus (a bacteriophage, commonly called a phage).
• Bacterial conjugation, a process in which a living bacterial cell transfers genetic material through cell-to-cell contact.

3, Gene transfer in eukaryotic?
horizontal gene transfer has also occurred within eukaryotes, from their chloroplast and mitochondrial genome to their nuclear genome. chloroplasts and mitochondria probably originated as bacterial endosymbionts of a progenitor to the eukaryotic cell. Horizontal transfer of genes from bacteria to some fungi, especially the yeast Saccharomyces cerevisiae has been well documented.

4,Describe Griffith's experiments that led to the discovery of the transforming factor.
Griffith's experiment was conducted in 1928 by Frederick Griffith which was one of the first experiments suggesting that bacteria are capable of transferring genetic information, otherwise known as the “transforming principle”, which was later discovered to be DNA. Griffith used two strains of Pneumococcus (which infects mice), a S (smooth) and a R (rough) strain. The S strain covers itself with a polysaccharide capsule that protects it from the host's immune system, resulting in the death of the host, while the R strain doesn't have that protective capsule and is defeated by the host's immune system.

In his experiment, bacteria from the S strain were killed by heat, and their remains were added to R strain bacteria. It turned out that the formerly harmless R strain now was able to kill its host. It had been transformed into the lethal S strain, obviously by a transforming principle that was somehow part of the dead S strain bacteria.

Today, we know that the DNA of the S strain bacteria had survived the heating process, and was taken up by the R strain bacteria. The S strain DNA contains the genes that form the protective polysaccharide capsule. Equipped with this gene, the former R strain bacteria were now protected from the host's immune system and could kill it.

5, what is genetic recombination?

is the transfer of DNA from one organism to another. The transferred donor DNA may then be integrated into the recipient's nucleoid by various mechanisms.

6, what is transformation? what is transduction? what is conjungation? what do plasmid do?

Transformation is the uptake of a DNA fragment from the surrounding environment and the expression of that genetic information in the recipient cell, which the recipient has acquired a characteristic that is previously lacked.

During transformation, DNAfragments (usually about 20 genes long) from a dead degraded bacterium bind to DNA binding proteins on the surface of a competent recipient bacterium. Nuclease enzymes then cut the bound DNA into fragments. One strand is destroyed and the other penetrates the recipient bacterium. This DNA fragment from the donor is then exchanged for a piece of the recipient's DNA by means of Rec A proteins.

1, A donnor bacterium disintegrates and liberates its DNA fragments into the surrounding environment.
2, A competent, live bacterium takes up a fragment of the DNA containing a few genes. The fragment travels through the cell wall and membrane of the recipient bacterium.
3, the fragment enters the recipient's cytoplasm.
4, in the cytoplasm, enzymes degrade one strand of the DNA helix. Stimultaneously, an enzyme degrades a strand from the a strand from the recipient's chromosome.
5, the strand of donor DNA replaces the strand of the recipient DNA, and the trnsformation is complete. Reproduction of the bacterium by binary fission will lead to a population of the transformed bacteria.

the mechanism for DNA transfer involes 1----binding of the DNA fragment, 2----passage of a single-strand molecule into the recipient, and 3-----incorporation into the bacterial chromosome.

8, what are hfr cells? what is the f plasmid? what is the R plasmic? what is the RTF plasmic?
hfr cell----is a bacterium with a conjugative plasmid (often F) integrated into its genomic DNA. Genetic recombination in which fragments of chromosomal DNA from a male donor bacterium are transferred to a female recipient bacterium following insertion of an F+ plasmid into the nucleoid of the donor bacterium. Involves a sex (conjugation)pilus.
http://student.ccbcmd.edu/courses/bio141/lecguide/unit4/genetics/recombination/conjugation/hfr.html

f plasmid-----A plasmid coding only for a sex pilus. a double-strand of loop of DNA existing apart from the baterial chromosome.

R plasmic-----A plasmid having genes coding for multiple antibiotic resistance and often a sex pilus.

RTF plasmic

7, what is conjungation?
Conjugation is the transferof DNA from a living donor bacterium to a recipient bacterium. In Gram-negative bacteria, a sex pilus (def) produced by the donor bacterium binds to the recipient. The sex pilus then retracts, bringing the two bacteria in contact. In Gram-positive bacteria sticky surface molecules are produced which bring the two bacteria into contact. DNA is then transferred from the donor to the recipient.

(a)conjugation between an F+ cell and an F- cell, when the F plasmic is transferred from a F+ donnor cell, the F- cell becomes an F+ cell as a resulte of the presence of an F plasmid.
1, conjugation sex pilus connects the F+ to the F- cell. 2, rolling circle replication and transfer of F- factor from the original of the transfer. (oriT) 3, Both cells now are F+.

(b)conjugation between an hfr cell and an F- cell, allows for the transfer of some chromosomal DNA from donor to recipient cell.
1, the hfr donor cell has the F plasmic integrated into the donor's chromosomes. 2, a sex pilus forms between the donor and the recipient cells, and replication of one strand of the donor's DNA begins a t the oriT site and passes into the recipient cell. 3, usually only a portion of the donor DNA enters the recipient cell before the conjugation strand replaces a complementary portion of the recipient's DNA. The recombnination is now complete, and the new genes can be expressed by the recipient.

8, What is transduction?
Transduction is the transfer of fragments of DNA from one bacterium to another bacterium by a bacteriophage (def).( a virus that infects and replicates within a bacterium. There are two types of transduction: generalized transduction and specialized transduction.

Generalized transduction:: durng reasnduction, a virus carries random DNA fragments from a donor bacterium to a recipient bacterium. The DNA fragment may recombine with the recipient cell.
1, the process of transduction begins when a virulent bacteriophage attaches to the surface of a host bacterial cell.
2, the DNA from the virulent phage enters the cytoplasm of the bacterium.
3, the viral DNA multiplies by encoding additional strands of phage DNA, as well as other phage protein components. The host DNA is fragmented in small piecies.
4, during replication, a bacterial DNA fragment accidentally gets packaged into a phage head during phage replication, producing a defective phage particle. most phage particles contain the normal phage DNA.
5, at the end of the replication process, all the new phage particles are repleased from the bacterium.
6, the virulent phage particles will go to to replicate in their host bacterial cells and have no bearing on transduction. transduction occurs when a defective phage interacts with a bacterial cell.
7, the phage DNA enters the host cell. but note that the DNA is bacterial DNA not the normal phage DNA.
8, the bacterial DNA fragment does not encode new phage particles but it can intergrate into the bacterial DNA and transduce the cell. Thus, the new host cell has acquired DNA from another bacterium.

Specialized transduction: a virus carries specified genes from a donor bacterium to a recipient bacterium. the process involves lysogeny and results in a recombinant cell.

1, specialized transduction begins as a temperate bacteriophage attaches to the surface of a host bacterial cell.
2, the DNA of the temperate phage enters the bacterial cytoplasm.
3, the viral DNA integrate into the bacterial DNA. now it is called a prophage. Here the prophage has inserted between bacterial genes A and D. Bacteria can undergo binary fission with each new cell carry the prophage.
4, at some point later, the prophage is cut of the bacterial DNA and phage DNA replication occurs as a lytic cycle.
5, if the prophage excision is precise, new temperate virus will form.
6, if the excision is not precise, the prophage will alone some of bacterial DNA. so the new phage each carry gene D from the donor bacterium.
7, later, the defective virus finds a new bacterial host cell.
8, the DNA enters the host cell cytoplasm.
9, the viral DNA integrates with the bacterial DNA in the process of lysogeny. but in doing so, through recombination gene D from the previous bacterium also integrates into the recipients cell;s chromosome. the recipiente cell thus acquires a gene from the dono bacterium and is transduced.

9, explain the unique place of the virus in the process of bacterial transduction; what is the result in the terms of disease? examples?
Transduction requires a virus to carry the DNA fragment from donor to recipient cell. The virus that participates in reansduction is called a bacteriophage, or simply phage.it was assumed to ba s type of poisonbecause they dissolve bacteria. today we recoginize them as viruses composed of a core of DNA or RNA surrounded by a coat of protein. phages that participate in transduction are transducing phage. In the replication cycle of a bacteriophage, the phage interacts with bacteria in two ways. 1, the phage invades the bacterium, then replicates itself and destroys the bacterium as new phage are replease---lytic cycle. phages that cause lysis is virulent phages. 2, phage interact with bacteria also involves invasion of the bacterium but without cell lysis. in this case, the phage DNA encodes a repressor protein that inhibits its own replication. The phage DNA often forms a closed circle that alogns next to the bacterial chromosome before integrateing into the bacterial chromosome. this process is called lysogeny. and the phages that participage in lysogeny is temperate phages.

10, what is genetic engineering?
the use of bacterial and microbial genetics, including the isolation, manipulation, and control of gene expression had far-reaching ramifications, leading to an entirely new field.

posted by C-T @ 3:36 PM 0 comments

Chapter 5, membrane dynamics

Cell membrane dynamics

Cell membrane: 1, human body is made of trillions of cells that must communicate and cooperate with each other while maintaining their separate identities. 2, cell membrane plays a key role in this because it is the barrier that separate the intracellular compartment from signals outsite the cell.

Singal transduction: at cellular level refers to the movement of signals from outside the cell to inside.

http://web.indstate.edu/thcme/mwking/signal-transduction.html

Membrane: two different meaning: 1, the simplest membrane, the plasma membrane, or cell membrane, is the membrane that sourrounds the cell. 2, membrane is also used to describe epithelial tissues that line a cavity or separate two compartments( they are actually tissues: thin, trnaslucent layers of cells. thin, translucent layer of cells)

Examples of the second type of membrane: mucous membranes in the mouth and vagina, the peritoneal membrane that lines the inside of the abdomen, the pleural membrane that covers the surface of the lungs, the pericardial membran that surrounds the heart.

Cell membranes: a double layer of phopholipid with protein molecules inserted in them.

Material moving into that out of cells must cross the cell membrane. Anything that enters and leaves the body through an epithelial tissues passes through two cell membranes. If a membrane allows a substance to pass through it, it is said to be permeable to the substance.( peameare, to pass through). If a membrane does not allow a substance to pass, it is said to be impermeable.

Phospholipid membrane:s 1, surround the contents of the cytoplasm( cell membrane) and 2, divide the interior of the cell into compartments such as the nucleus, mitochondria, endhoplasmic reticulum, and Golgi apparatus. ( make membraneous organelles)

What are the functions of cell membrane?
1, physical isolation: the cell membrane is a physical barrier that separates the inside of the cell( cytosol or intracellular fluid) from the surrounding extracellular fluid.
2, regulation of exchange with the environment: the cell membrane controls the entry of ions and nutrients, the elimination of wastes, and the release of secretory products.
3, communication between the cell and its environment: the cell membrane is in direct contact with both the cytosol ( the intracellular fluid) and the extracellular fluid(ECF). It contains receptors that allow the cell to recognize and respond to molecules or changes in its external environment. any alternation in the cell membrance may affect cell's activities.
4, structural transport: cell membrane proteins hold proteins of the cytoskelton in place to maintain cell shape. they also create specialized junctions between adjacent cells or between cells and the extracellular matrix. these junctions stabilize the structure of tissues.

posted by C-T @ 5:51 PM 0 comments

Chapter 3 cells and tissues

Chapter 3

Cell: a vast collection of molecules makes up the cell, the basci functional unit of most living thing.

What is the basic function of cell?
Cells take in oxygen and nutrients, they extract energy from the nutrients for growth, repaire, and reproduction, and they get rid of waste such as carbon dioxide.

What is cell biology?
the study of how cells work.

What is the central theme of physiology?
Coorperation between cells is a central theme of physiology.

What is zygote?A zygote (Greek: ζυγωτόν) is a cell that is the result of fertilization. That is, two haploid cells—usually (but not always) an ovum from a female and a sperm cell from a male—merge into a single diploid cell called the zygote (or zygocyte).
Animal zygotes undergo mitotic cell divisions to become an embryo. Other organisms may undergo meiotic cell division at this time (for more information refer to biological life cycles).Twins and multiple births can be monozygotic (identical) or dizygotic (fraternal).

What is differentiation?
a process that developing cells take on more than 200 different shapes and functions. delective gene expression.

How does differentiation occur?
Each cell inherites the same genetic information in its DNA, but no cell uses all of it. only selected genees are activated. the final shape and size of a cell and its contents reflect its function.

Composition of cell
Cell----cytoplasm, nucleus,cell membrane
Cytoplasm---cytosol, organelles
Organells-----nonmembrancous organells, membranous organells.
Nonmembranous organells: cytoskeleton, centrioles, centerosomes, cilia, flagella, ribosomes, vaults.
Membranous organells: mitochoria, endoplasmic reticuluc, Golgi apparatus,lysosomes, perocisomes.

cell membrane
the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. It separates a cell's interior from its surroundings and controls what moves in and out. Cell surface membranes often contain receptor proteins and cell adhesion proteins. There are also other proteins with a variety of functions. These membrane proteins are important for the regulation of cell behavior and the organization of cells in tissues.
Hydrophlici phophate head, hydrophobic lipi tail.
Some of these proteins simply adhere to the membrane (extrinsic or peripheral proteins), whereas others might be said to reside within it or to span it (intrinsic proteins – more at integral membrane protein). Glycoproteins have carbohydrates attached to their extracellular domains. Cells may vary the variety and the relative amounts of different lipids to maintain the fluidity of their membranes despite changes in temperature. Cholesterol molecules (in case of eukaryotes) or hopanoids (in case of prokaryotes) in the bilayer assist in regulating fluidity

Function of glycoproteins and glycolipids on membrane extracellusr surface.

What is the function of cemm membrane?
1, gateway, 2, barrier 2, regulate exchange between the cell the ECF.

Cytoplasm in cludes cytosl and organells
Cytosol: is semigelatinous substance. contains: 1, dissolved nutrients 2, ions 3, waster products 4, particles of insoluable materials(inclusions) is the internal fluid of the cell, and a portion of cell metabolism occurs here. Proteins within the cytosol play an important role in signal transduction pathways and glycolysis. They also act as intracellular receptors and form part of the ribosomes, enabling protein synthesis.The cytosol is not a "soup" with free-floating particles, but is highly organized on the molecular level. As the concentration of soluble molecules increases within the cytosol, an osmotic gradient builds up toward the outside of the cell. Water flows into the cell, making the cell larger. To prevent the cell from bursting apart, molecular pumps in the plasma membrane, the cytoskeleton, the tonoplast or the cell wall (if present), are used to counteract the osmotic pressure.

Nonmembranous organelles: in direct contact with the cytosl. movement of material between these organeleesa nd the cytosl does not require transport across a membrane. these organelles can be divided into two groups: 1, those made from RNA and protein, 2, those made from insouble protein fiber (cytoskeleton, centrosomes, and centrioles, cilia, and flagelaa)

Ribosomes: is an organelle composed of rRNA and ribosomal proteins (known as a Ribonucleoprotein). It translates mRNA into a polypeptide chain (e.g., a protein). It can be thought of as a factory that builds a protein from a set of genetic instructions. Ribosomes can float freely in the cytoplasm (the internal fluid of the cell) or bind to the endoplasmic reticulum, or to the nuclear envelope. Since ribosomes are ribozymes, it is thought that they might be remnants of the RNA world.
Ribosomes consist of two subunits (Figure 1) that fit together (Figure 2) and work as one to translate the mRNA into a polypeptide chain during protein synthesis (Figure 3). Each subunit consists of one or two very large RNA molecules (known as ribosomal RNA or rRNA) and multiple smaller protein molecules. Crystallographic work has shown that there are no ribosomal proteins close to the reaction site for polypeptide synthesis. This suggests that the protein components of ribosomes act as a scaffold that may enhance the ability of rRNA to synthesise protein rather than directly participating in catalysis.
1, (polyribosome)Free ribosomes usually produce proteins used in the cytosol or organelle in which they occurthey are free in solution and not bound to anything within the cell.
2, (fixed ribosomes) certain proteins are synthesized by a ribosome they can become "membrane-bound". The newly produced polypeptide chains are inserted directly into the ER by the ribosome and are then transported to their destinations. Bound ribosomes usually produce proteins that are used within the cell membrane or are expelled from the cell via exocytosis.

Three sizes of protein fibers in the cytoplasm:
The protein fibers in the cytoplasm are classified by their diameter. the thinnest, microfilament--actin(protein); larger intermediate filament----myosin(muscle protein), Keratin (hair and sking_ and neurofilament (nerve cell); Thick filaments-----intermediate myosin filaments combine; microtubules ---tubulin.
microtubules combine to form more compex structures of centrioles, cilia, and flagelaa.

The important functions of cytoskeleton
1, mechanical strength to the cell, determing the shape of the cell. the cytoskeleton helps to support microvilli to increase the surface for absorption.
2, the fibers stabilized the positions of organelles.
3, transport materials into the cell and within the cytoplasm.
4,fibers of the cytoskeleton connect with protein fibers in the extracellular space, linking cells to each other and to support material outside the cell, allow transfer of information from one cell to another.
5, enables certain cells to move, (white cell and squeeze out of blood vessels and travel to sites of infection.

Centrosomes and centriole ( associated with microtubules)
centrosomes: regions of darkly staining material close to nucleus. act as cell's microtubule-organizine center, where tubulin molecules are assembled into microtubules.
centrosome contain two centrioles: each centriole is a cylindrial bundle of 27 microtubules, arranged in nine triplet. Cells that can't not undergo cell division, lack centrioles.

Cillia and flagella (movable hairlike structures)
cilia: short, hair like structures projecting from the cell surface.the surface of a cilium is a continuation of the cell membrane, and its core contains nine pairs of microtubules surrounding a central pair. the microtubules terminate inside the cell at the basal body. its movement creats currents and sweep fluids or secretions across the surface.
flagella: same microtubules arrangement but larger. only one or two flagela. are found on free-floating single cell. the function is to push the cell through fluid with wave like movements of the flagellum.

Many membranous organelle's membrane have lumen(cavity of a hollow tube)

What is the function of those membranes?
1, the membrane barrier allows the organells to contain substances that might be harmful to the cell if they were free.
2, It also allows the cell to separate different funtions.

Mitochondria(ATP production): are small sperical to elliptical organelles with an unusual double wall. The outer membrane of the wall gives the mitochondrion its shape. the inner membrane if folded into leaflet called cristae. They are studded with proteins, including ATP synthase and a variety of cytochromes. The cristae provide more surface area for chemical reactions to occur within the mitochondria. This allows cellular respiration (aerobic respiration since the mitochondria requires oxygen) to occur. matrix contains enzyme, ribosomes, granuels, and DNA. intermembrane space space between the outer and inner memberanes is a region plays an important role in the production of ATP. The number of mitochondria is depend on the energy a cell needs.

Why mitochondira is unusual?
1, in matrix, they have their own DNA, this mitochondrial DNA, along with the ribosomes, means it can produce their own proteins. why? because, mitchodira are the descendants of bacteria that invaded cells millions of years ago. the bacteria developed a mutual relationship with host and becomme an integral part of the host cell.
2, their ability to replicate themselves even when the cell not undergoing cell division. this process is aided by the presence of mitochondrial DNA that allows the organeels to direct their own duplication. small daugher mitochondria pinching off an enlarged parent. then produces more engery with the duplicated mitochonrial.

The endoplasmic reticulum( the site of protein and lipid synthesis)
ER, is a netword of interconnected membrane tubes. that are a continuation of the outer nuclear membrane. 1, Rought ER(with ribosomes) and2, Smooth ER.
Three major functions: 1, synthesis, 2, storage 3, transport of biomolecules.

SER: the main site for the synthesis of fatty acid, steroids, and lipids. Phospholipids for the cell memrabne are procued here, cholesterol is modified into steroid hormones, such as the sex homones. the SER of liver and kiney cells detoxifies or inactivate drugs.

RER: main site for the synthese of protein. protein assembled on ribosomes attached to the surfaced of RER, then inserted into the lumen, where they undergo chemical modification. most of these proteins are packaged into vesicles that pinch off from the RER, then scross the cytosol to the Golgi apparatus.

Golgi apparatus( package protein into membrane-bound vesicles)
1, consists of 5 or 6 hollow curved sacs stacked on top of each other and conncected so that they share a single lumen.
2, the convex side of the stack faces the RER and receives the transport vesicles from it.
3, these transport vesicles fuse with the membranes of the golgi sac and discharge their contents into its lumen.
4, as the proteins move through teh sac, they may be modified by enzymes. long proteins into smaller protein, or carbohydrates attached to proteins to make glycoproteins.
5,the processed proteins are enclosed in a membrane-bound vesicles thatp inch off from the concave face of the golgi and move out into the cytosole.

Vesicles: 1, secretory vesicles: contain proteins that will be exported to other parts of the body. Secetion is the process by which a cell release a substance into the extracelluar space.
2, storage vesicles: never leave the cytoplasm, lysosomes are the major storage vesicles of the cell.

Lysosomes: intracelluar digestive system.
small, spherical storage vesicles that membrane-bound granules. they contain powerful enzymes and act as the digestive system of the cell.
1, they take up bacteria or old organelles, such as mitochondria, and use enzyme to break down them into component molecules. those molecules that can be reused are reabsorbed into the cytosole, while the rest are dumped out of the cell.
2, the digestive enzymes are not always kept ioslated within the membranes of the organelles. lysosomes release their enzymes to dissovle extracelluar support material, the inappropriate release of lysosomal enzymes has been implicated in certain diease state.
3, cells allow that enzymes of their lysosomes to come in contact with the cytoplasm, leading to self digestion of all or part of the cell.

Why enzyme do not destory the cell that contains them?
Because these enzymes are activated only by very acid conditions, 100times more acid than the normal cytoplasm. when lysosome first pinch off from the Golgi appratus, their pH is the same as that of the cytosol, 7.0-7.3. the enzyme then is inactive. it only activate at 4.8-5.0

What is lysosomal storage disease?
lysosomes are effective because they lack specific enzymes. Tay-Sachs disease. Infant with that disease have defective lysosomes that fail to break down glycolipids in nerve cell. al=ccumulation of the glycolipid in the cells cause the nervous system dysfunction, including blindness and loss of coordination.

Peroxisomes( contain enzymes that neutralize toxin)
They are storage vesicles that smaller than lysosomes. the main function:1, degrade long-chain fatty acids and 2, potentially toxin foreign molecules. Perixisomes get their name from the breakdown of fatty acids generate hydrogen peroxide. (H2)2), a toxic moledcule. Peroxisome convert this peroxide to oxygen and water by using the enzyme catalase. its disorders disrupt the normal processing of lipids and disrupt the normal function of the nervous system by altering the structure of nerve cell membranes.

Nucleus ( control center)
contains: DNA, genetica material controls all cell processes.
Nuclear envelope: two membrane structure that separates the nucleus from the cytoplasmic compartment. the outer membrane is connected with the ER, and both memebranes of the envelope are pierced by pores. communication between the nucleus and cytosol occurs through the nuclear pore complexes large protein complexes with a central channel. ions and small molecules move freely through this channel when it is open, but proteins and RNA must be transported by a process that uses energy. this requirment allows the cell to restric large molecules such as DNA to the nucleus and enzymes to nucleus and cytoplasm.

Chromatin: celling that are not dividing, most DNA appears as randowmly scatteded granular material.
A nucleus also contain from 1 to 4 larger dark-staining bodies of DNA, RNA, and protein called nucleoli. which contain the genes and proteins that control the synthesis of RNA for ribosomes.

TISSUE
Tissue:cells assemble into larger untis called tissues.

Cell junction: collections of cells held together by specialized connection called cell junctions.

Histology: study of tissues structure and function is known as histology.
1, shape and size of the cells
2, how the cells are arranged in the tisseus( scattered, layers)
3, how the cells are connected to each other
4, the amount of extracellular material that is present in the tissues.

What are four primary tissues types in human body?
1, epithelial 2, connective 3, muscle 4, neural or nerve

Matrix: is extracelluar material that is synthesized and secreted by the cells of a tissues. When matrix proteins attach to proteins in the cell membrane, they provides a means of communication between the cell and its external environment. the amount of matrix in a tissues caries. nerve and muscle have little matrix, but the connective tisseus, cartilage, bone and blood have matrix that occupies as much volume as their cells. the consistency of matrix varies from watery (blood and lymph) to rigid (bone) . in many tissues, matrix is composed of comeplex glycoprotein molecules mixed with insoluable protein fibers. the protein fibers provide strength and anchor cells to the matrix.

CAMs: membrane proteins known as cell adhesion molecules.

Cell junction hold cells together to form tissues: 1, adhesive junction 2, tight junctions 3, gap junctions.

Adhesive junction: are recognizable by the dense glycoprotein bodies: plaques. lie just inside the cell membranes in the region where the two cells connect. the protein linkage of adesive cell junction is very strong, it allows sheets of tissue in skin and lining body cavities to resist damage from stretching and twisting. however, it can be broken. a blister results: fluid accumulates in the resulting space and the payer separate. 1, desmosomes 2, adherens junctions. desmosomes: created by membrane spanning protein called cadherins that connenct each other across the intercellular space. and link to intermediate filaments of the cytoskeleton. it may be small points of contact( spot desmosomes) or bands that encircle the entire cell (belt desmosomes). Hemidesmosomes: use integrins to anchor cell to matrix glycoproteins . Adherens junction, similar to semosomes but not as strong. also use caherins.

Tight junction: serve to prevent the movement of material past the cells they link. cells fuse together with occludins. thereby making a barrier. occur next to adherens junction. the combination is called a junction complex.(tight and adherens).

Comparision between tight and adherens: tight junction: very little can pass from one side of the wall to other. adherens, allow material to pass.

Gap junction: create cytoplasmic bridges between adjacent cells so that chemical and electrical signal pass rapidly from one cell to the next. uses protein connexins, resemble holow revet with narrow channels throught their centers. Small molecules and ions move through the channels from cell to cell. very important in cell to cell communication in many tissues, including liver, pancrease...

Function of epithelial tissues.
1, act as a barrier to keep water in the body and invaders such as bacteria out.
2, control the movement of material between the external environment and the extracellular fluid of the body. nutrients, gasses, and wastes much often across several different epithelia in their passage beteen cells and outside world.
3, is specialized to manufacture and secret chemicals into the blood or to the external environment. sweet and saliva are substances secreted by epithelia into the environment. hormones, signal molecules used to maintain hoeostasis, are secreted into the blood.

Structure of epithelia:
1, a thin layer of extracellular matrix that lies between the cells and their underlying tissues: basal lamina, basement membrane. : a network of fine protein filaments embedded in glycoprotein. the filaments hold the epithelial cells to the underlying cell layer.
2, cell junction in epithelia: leaky : adhesive junctions leave gaps or pore and allow molecules to pass across the epethelium cells. (capillary blood vessels) tight: selective to what can pass and what can not pass. (liver)

Types of epithelia:
1: sheets of tissues that lie on the surface of the body or that line the inside of tubes and hollow organs : a, simple (one cell think) b, squamous: (three cells) c, columnar.
2, secretory epithelia that synthesize and release substances into the extracelluar space.

Five functional types of epithelia:
1, exchange epithelia: permit rapid exchange of material, gases.
2, transport epethelia: selective in the intestinal tract, and the kidney
3, ciliated epithelia: in the airway of the respiratory system and in the female reproductive tract. (nontransporting ,moving fluid and particles)
4, protective epithelia: surface of the body and inside the openings of the body cavities. prevent exchange, stratified, toughened by keratin.many layers.short life span.
5, secretory epithelia: synthesize and release substances into the extracelluar space or into blood.

What are the characteristics of transporting epethelia?
1, one layer cell, but much thicker. mostly cuboidal or columnar in shape.
2, the apical membrane is the surface of the cell that faces the lumen. has microvilli.increase the surface area for transport. basolateral membrane face the ECF also increase the cell's surface area.
3, cells are tight to very tight junctions. means that material must move into an epithlial cell on one side of the tissue and out of the cell on the other in order to cross the epithelium.
4, most cell that transport material have numersou mitochondria to provide energy for transport.

Gland: secretory cells group together to form a multicellular gland. :1, exocrine glands 2, endocrine glands.

Exocrine glands: release their secretion into the external enironment. most exocrine glands release their products through open tubes as ducts. Typical exocrine glands include sweat glands, salivary glands, mammary glands and many glands of the digestive system.

What are the two types of secretion exocrine glands secrete?
1, serous secretion: watery solutions, many of them contain enzymes.tears, sweats and digestive enzymes.
2, mucous secretions: sticky solution containing glycoproteins and proteoglycan. Goblet cells are single exocrine cells that produce mucus.

Endocrine glands:ductless glands that secrete chemical messengers called hormones that circulate within the body via the bloodstream to affect distant organs. Hormones act as "messengers", and are carried by the bloodstream to different cells in the body, which interpret these messages and act on them.
The endocrine system links the brain to the organs that control body metabolism, growth and development, and reproduction.The endocrine system regulates its hormones through negative feedback. Increases in hormone activity decrease the production of that hormone. The immune system and other factors contribute as control factors also, altogether maintaining constant levels of hormones. (pituiary gland, throid gland, pancreas.)

Connective tissues provide rupport and barriers.
the distinguishing characteristic if the presence of extensive extracelluar matrix containing widely scattered cells. the cells secrete and modify the matrix of the tissue.

Stucture of connective tissue
1, the matrix of connective tissue if a ground substance of glycoproteins and water in which insoluble fiberous protein fibers are aaranged. ( one can me watery matrix of blood, the other is the hardened matrix of bone, inbetween are solutions of glycoproteins that vary in consistency from syrupy to gelatinous)
2, the cells lie embedded within the extracellular matrix. fixed : if cells remain in one place, they are responsible for local maintenance, tissue repair, and energy storgage. mobile : if cells can move from place to place, mainly for defense.
3, cells can modify the matrix by adding, deleting , or rearranging molecules. -blast: on a connective tissue cell indicates a cell that is either growing or secreting extracelluar matrix. cells that breaking down matrix are --clast. cells that are neither growing, secreting nor breaking ---cyte(cell).
4, connective cells produce fibers of the matrix. 1: collagen: most abundant protein in human, 1/3 of human dry weight. most diverse. 2, elastin: coiled, wavy protein that returns to original length after being stretched. 3, fibrillin: elastin combines to form filaments and sheets of elastic fibers. 4, fibronectins: important in would healing and blood clotting.

Types of connective tissues
1, loose 2, dense.

Loose connective tissues: elestic tissues that underlie skin and provide support for small glands.

Dense connective tissues: primary function is strength or flexibility.: tendons, ligaments, and sheath that surround muscle and nerves. collagen fibers are the dominant type.

Tendons:muscule to bones.

Ligaments: bone to bone. because contains elastic fibers in addition to collagen fiber.

Adipose tissue: make up of adipocytes or fat cells. white fat: a single enormous lipid droplet, adult, brown fat: multiple lipid droplet, infant.

Blood : watery matrix. lack insoluble protein but contains soluble proteins.

Cartilage and bone: supporting connective tissues,: dense ground substances contains closely packed fibers. Cartilage: solid, flexible lack of blood supply, nutrients and oxygen must reach the cells of cartilage by diffusion. very slow. Bone: matrix is calcified because it contains mineral deposits which gave strength and rigidy.

Why muscle and neural tissues called the excitable tissues?
because their ability to generate electrical signals called action potentials.

Muscle: contract and produce force and movement. 1, cardiac muscle 2, smooth muscle 3, skeleton muscle

Neural tissues: 1 neurons: carry information in the form of chemical and electrical signals from one part of thte body to another. concentrated in the brain and spinal cord, also include a network that extends to every part of the body. 2, Glial cells, support cells for neurons.

Growth: is a process that most people associate with the period from birth to adulthood..

Cell death occur two ways: one messay and one tidy.
Necrosis: cells die from physical trauma, toxin, lack of oxygen when their blood supply is cut off.
Apoptosis: programmed cell deaeth. cell suicide, a complex process regulated by multiple chemical signals.

If cells in adult body are constanting dying, where do their replacement come fomr?
in most case, they come from mature cells of the same tyep that are still able to make mitosis.
the exceptions are blood cells and nerve and mucels cells. blood cells are formed from unddifferntiated precursor cells called stem cells, that are found in the bone marrow.

posted by C-T @ 12:02 PM 0 comments