examprepare

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