2.3 - Cell Membranes

Question 1

What are three ways in which a substance can move across the cell membrane?

Answer 1

Diffusion, active transport and osmosis

Question 2

What does the fluid mosaic model describe?

Answer 2

Arrangement of molecules in the membrane

Question 3

Describe the fluid mosaic model

Answer 3

Phospholipids form a continuous bilayer which is fluid, proteins are scattered throughout

Question 4

What do receptor proteins in the cell surface membrane do?

Answer 4

Allow the cell to detect chemicals released from other cells

Question 5

What is a glycoprotein?

Answer 5

Protein and carbohydrate

Question 6

What is a glycolipid?

Answer 6

A lipid and carbohydrate

Question 7

What molecules form a barrier to dissolved substances in a cell membrane?

Answer 7

Phospholipids

Question 8

The head of a phospholipid is…
The tail is…

Answer 8

Head = hydrophilic
Tail = hydrophobic

Question 9

Describe the arrangement of phospholipids in the bilayer

Answer 9

Heads face towards the water on either side of the membrane

Question 10

Explain the importance of cholesterol in cell membrane

Answer 10

Helps animal cells that have no cell wall, creates barrier for polar substances as it is hydrophobic.

Question 11

Explain the importance of cholesterol in cell membrane

Answer 11

Helps animal cells that have no cell wall, creates barrier for polar substances as it is hydrophobic.

Question 12

How does cholesterol give the membrane stability?

Answer 12

Binds to the hydrophobic tails of the phospholipids causing them to pack more closely together.

Question 13

How does cholesterol give the membrane stability?

Answer 13

Binds to the hydrophobic tails of the phospholipids causing them to pack more closely together.

Question 14

How does temperature affect cell membranes?

Answer 14

Affects how much the phospholipids move which affects membrane structure and permeability.

Question 15

Define diffusion

Answer 15

The movement of particles from an area of high concentration to an area of low concentration across a partially permeable membrane

Question 16

What is a concentration gradient?

Answer 16

The path from an area of high concentration to of an area of low concentration

Question 17

What is a passive process?

Answer 17

No energy required

Question 18

What is simple diffusion?

Answer 18

Diffusion across a partially permeable membrane without the assistance another of molecule

Question 19

What 3 factors affect the rate of diffusion?

Answer 19

Distance, concentration gradient and surface area

Question 20

What is facilitated diffusion?

Answer 20

Diffusion of specific molecules using channel proteins or carrier proteins,

Question 21

2 types of protein in facilitated diffusion

Answer 21

Channel
Carrier

Question 22

What do carrier proteins do?

Answer 22

Move large molecules across the membrane down the concentration gradient.

Question 23

What do channel proteins do?

Answer 23

Form pores in the membrane for charged particles to diffuse through down the concentration gradient.

Question 24

Which 2 factors affect facilitated diffusion?

Answer 24

Concentration gradient
Number of proteins

Question 25

Define osmosis

Answer 25

The movement of water particles from an area water of high potential to an area of lower water potential through a partially permeable membrane.

Question 26

What is water potential?

Answer 26

The likelihood of water molecules to diffuse out of or into a solution.

Question 27

What does isotonic mean?

Answer 27

Water potential is identical across both solutions

Question 28

What factors affect the rate of osmosis?

Answer 28

Gradient Thickness Surface area

Question 29

What is active transport?

Answer 29

The movement of particles from an area of low concentration to an area of high concentration against the concentration gradient and requiring ATP.

Question 30

Explain what co transporters are and what they do

Answer 30

A type of carrier protein that binds two molecules at a time, one is used to more the other against its concentration gradient.

Question 31

Where is glucose absorbed into the bloodstream and why does it need to be co transported?

Answer 31

Absorbed through the ileum Needs to be co transported because it is going against its concentration gradient.

Question 32

Explain step 1 in the absorption of glucose

Answer 32

Sodium ions are actively transported out of the epithelial cells in the ileum into the blood by the sodium potassium pump.

Question 33

Explain step 2 in the absorption of glucose

Answer 33

Sodium ions diffuse down their concentration gradient into the epithelial cell via the sodium - glucose co-transporter proteins.

Question 34

Explain step 2 in the absorption of glucose

Answer 34

Sodium ions diffuse down their concentration gradient into the epithelial cell via the sodium - glucose co-transporter proteins.