Flashcards in Biology Chapter 7 Deck (23):
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
Saturated fatty acids make the membrane
Viscous (so it does not change shape easily)
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
The cell uses no energy. Includes diffusion and osmosis
The movement of molecules from high concentration to low concentration (liquid or gas)
Cells get glucose and oxygen by diffusion.
Surround cells, (plant cells also have a cell wall). Membranes are selectively permeable (only allow certain molecules through) and are roughly 10 nm thick
The diffusion of water through a selectively permeable membrane
Has the same water concentration as the cell, eg blood. Cells stay the same size
Has more water than inside the cell, eg freshwater. Cells swell and may burst
Has less water than inside the cell, eg seawater. Cells shrink (dehydrate)
Active transport requires
What are the three types of active transport?
Pumps, exocytosis, endocytosis
Membrane proteins that transport chemicals.
Sodium is pumped out of the cell, potassium is pumped in.
Examples of pumps are
Large molecules are pulled into the cell.
Phagocytosis - to do with endocytosis
Solids brought in.
Eg white blood cells eat bacteria.
Pinocytosis - to do with endocytosis
Liquids brought in.
Eg cells around blood vessels