2.2 Transport across cell membranes

Question 1

What are the main components of a membrane?

Answer 1

Lipids, proteins and carbohydrates

Question 2

What is the cell membrane mainly made up of?

Answer 2

Phospholipids

Question 3

What are the components of a phospholipid?

Answer 3

• a polar hydrophilic phosphate head
• two non-polar hydrophobic fatty acid tails
• glycerol

Question 4

Why is the structure of the cell membrane know as the ‘fluid mosaic model’?

Answer 4

Molecules are able to move and there are proteins embedded within the phospholipids

Question 5

What is a phospholipid?

Answer 5

A lipid with a phosphate group attached

Question 6

What role do phospholipids play in the cell membrane?

Answer 6

They form a barrier against water soluble substances and allow lipid soluble substances to pass through

Question 7

What are intrinsic proteins?

Answer 7

Proteins that span the entire width of the cell membrane

Question 8

What role do intrinsic proteins play in the cell membrane?

Answer 8

Allow water soluble molecules to pass through

Question 9

What are extrinsic proteins?

Answer 9

Proteins on a single layer of the cell membrane

Question 10

What role do extrinsic proteins play in the cell membrane?

Answer 10

They act as receptors

Question 11

What are glycoproteins?

Answer 11

Glycogen bonded to a protein

Question 12

What role do glycoproteins play in the cell membrane?

Answer 12

They act as antigens

Question 13

What is cholesterol?

Answer 13

A lipid within the membrane

Question 14

What role does cholesterol play in the cell membrane?

Answer 14

It regulates the fluidity of the cell membrane to maintain rigidity and structure

Question 15

What is water potential?

Answer 15

The likelihood of water molecules diffusing into or out of a cell or solution

Question 16

How is water potential affected by an increase in solutes?

Answer 16

Adding solutes decreases the water potential

Question 17

What is the water potential of pure water?

Answer 17

0 kPa

Question 18

Is facilitated diffusion an active or passive process?

Answer 18

Passive

Question 19

What types of molecules diffuse through channel and carrier proteins?

Answer 19

Large, polar or charged molecules

Question 20

What are channel proteins?

Answer 20

Pores in the membrane for charged particle to pass through. Each channel is specific to a particular particle.

Question 21

What are carrier protein?

Answer 21

Proteins that allow large molecules to diffuse through the membrane. Each carrier protein is specific to a different molecule.

Question 22

What is facilitated diffusion?

Answer 22

Diffusion of large or polar molecules through the membrane via channel or carrier proteins in the phospholipid bilayer.

Question 23

What is a co-transporter?

Answer 23

A type of carrier protein that binds to two molecules at the same time

Question 24

What is a symport protein?

Answer 24

Protein that transports both substances in the same direction

Question 25

What is an antiport protein?

Answer 25

Protein that transports the two substances in opposite directions

Question 26

Name three factors that affect the rate of active transport

Answer 26

- rate of respiration / ATP production - number of carrier proteins on membrane - speed of carrier proteins

Question 27

How does a sodium-potassium pump build a concentration gradient?

Answer 27

Each time the carrier protein pumps, an extra positive ion is released, making the outside more positive than the inside