0228 principles of membrane transport

Question 1

Define a cell membrane. What are the two major components of a cell membrane

Answer 1

Cell membranes act as permeability barriers within cells and allow different sub-cellular compartments of different composition. It’s two major components are proteins and lipids

Question 2

Which end of a fatty acid is hydrophobic and which end is hydrophyllic

Answer 2

Fatty acid tail = hydrophobic. Fatty acid head = hydrophyllic. That is why in a phospholipid bi-layer the tails are in the middle

Question 3

What is the effect of heat on the fluidity of a cell membrane?

Answer 3

At room temperatures cell membranes have a gel-like consistency (lipids, ordered and packed tight). Increase in temperature leads to fluidlike consistency (lipids move around and rearrange randomly)

Question 4

Describe the 2 types of gradient that can affect the movement of a compound across a membrane

Answer 4

Concentration gradient and electrical gradient (combined is electrochemical gradient).

Question 5

What type of movement across a membrane is spontaneous (i.e. releases energy

Answer 5

Diffusion

Question 6

What types of molecules are able to diffuse across a lipid bilayer? what types of molecules cannot?

Answer 6

Small, non-polar molecules can diffuse across membranes (CO2, O2, H2O etc). Large, polar molecules and ions cannot (glucose, amino acids, etc)

Question 7

What are the 4 types of transporters

Answer 7

Pumps, uniporters, symporters and antiporters

Question 8

Define active and passive transport. Which transporters are which

Answer 8

Active = moving solutes up gradient (requires energy). Pumps, symporters and antiporters. Passive = moving solutes down gradient (release energy). Uniporters

Question 9

What is the rate of transport of the 4 types of protein transporters

Answer 9

Pump = slow. Antiporter and Symporter = medium. Uniporter/channel = fast

Question 10

Describe the movements of solutes in pumps (direction)

Answer 10

Pumps move solutes up/against a concentration gradient

Question 11

Describe the movements of solutes in antiporters ( direction)

Answer 11

Antiporters move 2 solutes in different directions. 1 solute up a gradient and the other down a gradient

Question 12

Describe the movements of solutes in symporter ( direction)

Answer 12

Symporters move 2 solutes in the same direction. 1 solute up a gradient and the other down a gradient

Question 13

Describe the movements of solutes in uniporter/channel ( direction)

Answer 13

Uniporters/channels move 1 molecule passively down a gradient