3.2.3 Transport across cell membranes (active transport)

Question 1

What is active transport

Answer 1

Active transport uses energy to move molecules and ions across membranes usually against a concentration gradient

Question 2

What type of proteins are involved in active transport

Answer 2

Carrier proteins

Question 3

How is active transport similar to facilitated diffusion

Answer 3

In both processes a molecule attaches to the carrier protein causing the protein to change shape and move the molecule across the membrane

Question 4

What are two key differences between active transport and facilitated diffusion

Answer 4

Active transport moves solutes from a low to high concentration while facilitated diffusion moves solutes from a high to low concentration and active transport requires energy while facilitated diffusion does not

Question 5

What provides the energy for active transport

Answer 5

ATP provides the energy for active transport

Question 6

How is energy released for active transport

Answer 6

ATP undergoes a hydrolysis reaction splitting into ADP and Pi which releases energy so solutes can be transported

Question 7

Which ion is used in the diagram to show active transport

Answer 7

Calcium

Question 8

What are co-transporters

Answer 8

Co-transporters are a type of carrier protein that bind two molecules at a time

Question 9

How does the concentration gradient affect the movement of molecules in co-transport

Answer 9

The concentration gradient of one molecule is used to move the other molecule against its concentration gradient

Question 10

What is an example of a co-transport system in the mammalian ileum

Answer 10

Sodium and glucose co-transport system

Question 11

How does sodium enter the ileum epithelial cells in co-transport

Answer 11

Sodium is actively transported out of the ileum epithelial cells into the blood by the sodium-potassium pump

Question 12

What happens as a result of sodium being actively transported out of the epithelial cells

Answer 12

A concentration gradient is created so sodium ions diffuse from the lumen of the ileum into the epithelial cells down their concentration gradient

Question 13

What protein facilitates the movement of sodium and glucose into the epithelial cells

Answer 13

The sodium-glucose co-transporter protein

Question 14

What is the role of the sodium-glucose co-transporter protein

Answer 14

The co-transporter protein carries glucose into the cell with sodium against its concentration gradient

Question 15

What happens to glucose once inside the epithelial cell

Answer 15

The glucose concentration inside the cell increases and glucose diffuses out of the cell into the blood down its concentration gradient via facilitated diffusion

Question 16

What are the two substances that are transported by co-transport in the mammalian ileum

Answer 16

Sodium ions and glucose

Question 17

Name one factor affecting the rate of active transport

Answer 17

The speed of individual carrier proteins

Question 18

How does the number of carrier proteins affect active transport

Answer 18

The more proteins there are the faster the rate of active transport

Question 19

Why is respiration important for active transport

Answer 19

Respiration provides the ATP needed for active transport

Question 20

What happens if respiration is inhibited in active transport

Answer 20

If respiration is inhibited active transport cannot take place

Question 21

Explain the differences between facilitated diffusion and active transport.

Answer 21

facilitated diffusion involves channel or carrier proteins while active transport only involves carrier proteins

facilitated diffusion does not use ATP while active transport uses ATP

OR

facilitated diffusion is passive while active transport is not passive

facilitated diffusion takes place down/along a concentration gradient while active transport can occur up/against a concentration gradient

Question 22

Sugar molecules enter cells via transport proteins.

Explain why transport proteins are needed to move sugar molecules into cells.

Answer 22

sugar molecules are polar OR water soluble OR not lipid soluble

(sugar) cannot pass through phospholipid bilayers OR hydrophobic core

Question 23

individuals with a diet high in glucose can develop high blood pressure.

This is due to glucose affecting the volume of blood in the body.

Use your knowledge of cell transport to explain how an increase in blood glucose levels could affect blood volume.

Answer 23

glucose lowers the water potential of the blood

water moves into the blood by osmosis (from cells or tissue fluid)

(this) increases the blood volume