Biology Chapter 7 Flashcards
Membranes are made of
Phospholipid and protein, arranged in a fluid mosaic
There are two layers of phospholipids, with large protein molecules floating in this oily layer (most proteins go all the way across the membrane)
“Fluid” means that the membrane is liquid. “Mosaic” refers to the proteins scattered around like mosaic tiles on a floor.
Unsaturated fatty acids make the membrane
Fluid
Saturated fatty acids make the membrane
Viscous (so it does not change shape easily)
Cholesterol
Is added to some membranes as an antifreeze; organisms living in cold climates can survive temperatures below freezing because their membranes stay fluid.
What are the functions of the proteins in the membrane?
Transport, enzymes, receptors for hormones, and joining cells together
Carbohydrates (oligosaccharides) on the outside of the membrane do what?
Let the Immune system identify the cell
Carbohydrates are important in organ transplants
The donor organ has to match as closely as possible the recipient
Passive transport
The cell uses no energy. Includes diffusion and osmosis
Diffusion
The movement of molecules from high concentration to low concentration (liquid or gas)
Cells get glucose and oxygen by diffusion.
Plasma membranes
Surround cells, (plant cells also have a cell wall). Membranes are selectively permeable (only allow certain molecules through) and are roughly 10 nm thick
Osmosis
The diffusion of water through a selectively permeable membrane
Isotonic solution
Has the same water concentration as the cell, eg blood. Cells stay the same size
Hypotonic solution
Has more water than inside the cell, eg freshwater. Cells swell and may burst
Hypertonic solution
Has less water than inside the cell, eg seawater. Cells shrink (dehydrate)
