cell membrane structure and transport across membranes

Question 1

What is diffusion?

Answer 1

net movement of particles from a high concentration to a low concentration

Question 2

What is facilitated diffusion?

Answer 2

large, charged particles diffuse through carrier proteins from a high concentration to a low concentration

Question 3

what factors effect rate of diffusion?

Answer 3

-concentration gradient: the bigger the difference the faster the diffusion
-diffusion distance: the thinner the surface the faster the diffusion
-surface area: larger the surface area the faster the rate if diffusion
(for facilitated diffusion more channel proteins increases the rate of diffusion)

Question 4

What is osmosis?

Answer 4

the net movement of water molecules across a semi-permeable membrane from a high water potential to a low water potential

Question 5

What is the water potential of pure water?

Answer 5

zero

Question 6

What is active transport?

Answer 6

movement of molecules from a low concentration to a high concentration using energy

Question 7

How is energy released in active transport?

Answer 7

ATP undergoes hydrolysis and slips into ADP + Pi

Question 8

What is the structure of a phospholipid?

Answer 8

-phosphate group head
- glycerol
- fatty acid tail

Question 9

What are the features of the head and tail of a phospholipid?

Answer 9

-hydrophobic tail, will not interact with water
-hydrophilic head, will interact with water

Question 10

What are intrinsic and extrinsic proteins?

Answer 10

extrinsic - occur in the surface of bilayer
intrinsic - span the bilayer from one side to the other, e.g. channel proteins

Question 11

what is the function of cholesterol in the bilayer?

Answer 11

-provides strength
-reduces lateral movement
-makes the membrane less fluid at high temperatures

Question 12

what is the function of glycolipids in the bilayer?

Answer 12

-made up of a carbohydrate bonded with a lipid
-act as cell surface receptors

Question 13

what is the function of glycoproteins in the bilayer?

Answer 13

-carbohydrate attached to a protein
-act as cell surface receptors

Question 14

What does the ‘fluid mosaic’ model of the plasma membrane mean?

Answer 14

fluid = phospholipids can move relative to each other, flexible structure that can change shape
mosaic = proteins embedded in the bilayer vary in shape and size