Cellular processes: Cell membrane structure and function

Question 1

fluid mosaic model

Answer 1

seas of lipids that proteins float in
8nm flexible layer
half and half lipid and protein
- phospholipids
- glycolipids
- cholesterol - can change the structure and function of bilayer
leaflets can be asymmetric

Question 2

fluidity

Answer 2

lipid tail length: longer = less fluid
double bond numbers - more fluid
amount of cholesterol - more = less fluid

Question 3

membrane proteins

Answer 3

Integral - extend or across membrane
peripheral - attached to inner OR outer surface of membrane (easy to remove)

Question 4

integral proteins

Answer 4

amphipathic
non-polar hydrophobic regions coiled into helices that span membrane hydrophobic core
hydrophilic ends interact with aqueous solution

Question 5

membrane protein functions

Answer 5

receptors
cell identity markers
linkers
enzymes
ion channels
transporter proteins

Question 6

molecular structure and selective permeability

Answer 6

• non-polar non charged can cross
• lipid soluble (steroids,fatty acids, some vitamins can cross
• small uncharged polar (water, urea, CO2) can cross
• large uncharged polar molecules can’t cross (glucose and amino acids)
• ions can’t cross

Question 7

energy storage

Answer 7

cells work like capacitors by separating charge and thus storing energy. at a moment can open ion channels to generate electricity by allowing ions to move. different ion gradients
Na+ high outside - always flows
K+ low outside - no net movement because of slightly negative in cell
Cl- high outside - electrical gradient says out but concentration says stay in

Question 8

laws of diffusion

Answer 8

• greater the difference faster the rate of diffusion
• faster in higher temps
• larger molecules = slower
• surface area increases rate
• distance slows rate
• thus The rate of diffusion sets a limit on the size of cells of about 20 µm

Question 9

gradients across membrane

Answer 9

• concentration: non charged molecules will diffuse down gradient
• electrochemical: ions influenced by membrane potential as well as concentration (positive flows to negative, negative to positive, inside of the cell is negative -80mv)

Question 10

osmosis

Answer 10

Net movement of water through a selectively permeable membrane from an area of high water concentration to an area of lower water concentration
membranes can have water channels