Biological membranes

Question 1

Function of Glycoproteins

Answer 1

branching carbohydrate portion of a protein which acts as a recognition site for chemicals
role in cell adhesion and act as receptors for chemical signals

Question 2

Function of Glycolipids

Answer 2

acts as a recognition site
antigens

Question 3

Function of Cholesterol

Answer 3

stability/flexibility of protein
positioned between phospholipids

Question 4

What is an extrinsic protein

Answer 4

a protein partly embedded into the bilayer e.g glycoproteins or glycolipids

Question 5

What is an intrinsic protein

Answer 5

a protein embedded all the way through the bilayer e.g. channel or carrier proteins

Question 6

Channel proteins

Answer 6

provide a hydrophilic pathway for passive movement of polar molecules or ions down a conc gradient

Question 7

Carrier Protein

Answer 7

important role in both passive transport and active transport
the carrier protein changes to allow molecules to pass through

Question 8

How does the temp affect the membrane

Answer 8

Increased temp gives the phospholipids more energy and will move more, making it more fluid, increasing permeability
very high temps causes the membrane to break down completely and intrinsic proteins will denature

Question 9

Diffusion:
Definition
Factors that affect it

Answer 9

diffusion is the net movement of particles from an area of higher conc to an area of lower conc
temp - the higher the temp, the high the rate of diffusion, too high = denature
conc difference - the greater difference between the 2 regions, the faster diffusion is
in membranes:
surface area
thickness of membrane

Question 10

Facilitated diffusions

Answer 10

diffusion using channel proteins or carrier proteins
NO ENERGY
DOWN A CONC GRADIENT

Question 11

Active transport

Answer 11

net movement of molecules from an area of low conc to an area of high conc using energy

Question 12

How do carrier proteins allow molecule through via active transport?

Answer 12

1 - molecule being transported binds to the receptor in the carrier protein on the outside of the cell
2 - on the inside of the cell ATP binds to the carrier protein where its hydrolysed into ADP and Pi
3 - Binding the Pi to the carrier protein causes it to change shape opening up into the cell
4 - molecule is released into the cell
5 - Pi is released from the carrier protein and recombines with ADP to ATP
6 - the carrier protein returns to its original shape

Question 13

Osmosis

Answer 13

net movement of water molecules across a partially permeable membrane (passive)

Question 14

what is water potential?

Answer 14

if a cell has lower WP then water will move into the cell
pure water is 0kPa

Question 15

osmosis in animal cells

Answer 15

hypotonic - lower WP (in cell), water enters, cell bursts (cytolysis) (turgid in plants)
hypertonic - higher WP (in cell), water leaves, cell shrivels (crenation) (plasmolysis in plants)