TOPIC 2 - B: cell membranes

Question 1

What are cell membranes made of?

Answer 1

Lipids (mainly phospholipids), proteins and carbohydrates

Question 2

List 3 types of proteins in the cell membrane

Answer 2

Channel proteins, carrier proteins and receptor proteins

Question 3

What do phospholipids form?

Answer 3

Barrier to dissolve substances

Question 4

Phospholipids have a

Answer 4

Hydrophilic head and hydrophobic tail

Question 5

What is the purpose of cholesterol?

Answer 5

Gives the membrane stability and fits between the phospholipids

Question 6

As proteins loose structure what happens to permeability?

Answer 6

Increases

Question 7

In normal temperatures what happens to the membrane?

Answer 7

Fluid and partially membrane

Question 8

At higher temperatures what happens to the bilayer?

Answer 8

Starts to break down as water expands putting pressure on the membrane

Question 9

What is diffusion?

Answer 9

Net random movement of particles from an area of high concentration to an area of low concentration down a concentration gradient

Question 10

Rate of diffusion affected by

Answer 10

Concentration gradient, thickness, surface area

Question 11

What is facilitated diffusion?

Answer 11

The passive movement of a particle across a cell membrane via a channel protein down a concentration gradient

Question 12

Why do charged particles diffuse slowly

Answer 12

Water soluble

Question 13

What are channel proteins?

Answer 13

A protein that forms pores in the membrane for charge proteins to diffuse through

Question 14

What are carrier proteins?

Answer 14

A protein that transports large molecules across a membrane

Question 15

Rate of facilitated diffusion depends on

Answer 15

Concentration gradient, number of channel proteins

Question 16

What is osmosis?

Answer 16

Net random movement of water through a semi permeable membrane from an area of high water potential to an area of low water potential

Question 17

If you add solutes what happens to the water potential?

Answer 17

Decreases

Question 18

What will happen if a cell is placed in a solution of higher water potential?

Answer 18

Swells

Question 19

A solution of high wp compared to inside the cell is said to be

Answer 19

Hypotonic (water moves in by osmosis)

Question 20

What will happen if a cell is placed in a solution of lower water potential?

Answer 20

Shrinks

Question 21

A solution of low wp compared to inside the cell is said to be

Answer 21

Hypertonic (water moves out by osmosis)

Question 22

Factors affecting osmosis

Answer 22

Water potential gradient, thickness, surface area

Question 23

What is active transport?

Answer 23

The net random movement of particles working against a concentration gradient from an area of lower concentration to an area of higher concentration using energy in the form of ATP

Question 24

What are co-transporters?

Answer 24

Type of carrier protein, they bind two molecules at a time. the concentration gradient of one of the molecules is used to move the other molecule against its own concentration gradient

Question 25

Describe the absorption of glucose

Answer 25

Glucose is absorbed into the bloodstream in the small intestine. The concentration is too low in the ileum for glucose to diffuse into the blood. Sodium ions are actively transported out of the epithelial cells. Sodium ions diffuse from the ileum lumen into the epithelial cell down the concentration gradient via the sodium - glucose co - transporter proteins. Glucose diffuses out of the cell into the blood through a protein channel (facilitated diffusion)