Cell Membrane and Transport

Question 1

Roles of the plasma membrane

Answer 1

Controls exit/entry for substances
Isolates organelles / enzymes (can transport enzymes)
Internal transport system
Provides surface for biochemical reactions
Allows cell to change shape

Question 2

Function of phospholipids in the membrane

Answer 2

Allow lipid soluble substances to enter/leave
Prevent water soluble substances from entering/leaving
Makes membrane flexible

Question 3

Role of cholesterol in membrane

Answer 3

Provides strength
Hydrophobic- prevents water and ion loss from cell
Binds to lipid tail to restrict movement (doesn’t make them fully rigid)
Makes membrane rigid at higher temps

Question 4

Types of proteins in the membrane

Answer 4

Extrinsic- don’t span the bilayer (provide mechanical support and cell receptors)

Intrinsic- span the bilayer (carrier channel enzymes)

Question 5

Function of channel proteins

Answer 5

Form tubes that fill with water- water soluble ions can diffuse

Question 6

Function of carrier proteins

Answer 6

Binds with larger molecules (glucose,amino acids) and changes shape to transport them to the other side

Question 7

Role of glycoproteins

Answer 7

Cell surface receptors (for hormones and neurotransmitters)
Recognition sites (for lymphocytes)

Question 8

Role of glycolipids

Answer 8

Cell surface receptor for specific chemicals (identify blood group for proteins)
Attached cells to each other to form tissue

Question 9

Diffusion

Answer 9

Net movement of molecules from a region of higher concentration to lower concentration, down a concentration gradient

Question 10

Factors affecting diffusion

Answer 10

Concentration gradient
Surface area
Length/thickness of diffusion pathway

Question 11

Facilitated diffusion

Answer 11

Passive process that occurs down the concentration gradient

Question 12

What is needed for facilitated diffusion?

Answer 12

Proteins for the molecule to travel down (so diffusion only occurs at specific points on the plasma membrane

Question 13

Fick’s Law

Answer 13

Rate of diffusion is directly proportional to:

(Area of diffusion surface x Concentration Difference ) / Thickness of surface

Question 14

Similarities of simple and facilitated diffusion

Answer 14

Passive process
Occurs down the concentration gradient

Question 15

Differences between simple and facilitated diffusion

Answer 15

SD: for small non-polar molecules
FD: for all other molecules

SD: occurs across phospholipid bilayer
FD: occurs across intrinsic proteins

Question 16

Glycoproteins

Answer 16

Carbohydrates attached to extrinsic proteins

Question 17

Glycolipid

Answer 17

Carbohydrate bonded to lipid