CELLS: Active Transport

Question 1

Active transport

Answer 1

The movement of molecules or ions into or out of a cell form a region of lower concentration to a region of higher concentration using ATP and carrier proteins.

Question 2

The movement of molecules or ions into or out of a cell form a region of lower concentration to a region of higher concentration using ATP and carrier proteins.

Answer 2

Active transport

Question 3

In active transport, what is ATP used for?

Answer 3

• to directly move molecules
• to individually move molecules using a concentration gradient which has already been set up by active transport - co-transport.

Question 4

What type of proteins are involved in active transport?

Answer 4

Carrier proteins.

Question 5

What are the two main differences between active transport and facilitated diffusion?

Answer 5

• Active transport usually moves soluted from a low to a high concentration - in facilitated diffusion, they always move from a high to a low concentration.
• Active transport requires energy - facilitated diffusion does not.

Question 6

Describe the direct active transport of a single molecule or ion:

Answer 6

• Carrier proteins span length of membrane and bind to molecule/ion on one side of membrane.
• Molecule/ion binds to receptor sites on carrier proteins.
• On inside of organelle, ATP binds with protein, causing it to split into ADP and a phosphate molecule.
• Protein molecule changes shape and opens to the opposite side of the membrane.
• Molecule/ion is released to other side of the membrane.
• Phosphate molecule released from protein which causes the protein to revert to original shape, ready for the process to repeat.
• ADP then recombines with phosphate to form ATP, during respiration.

Question 7

Give an example of an occasion when one ion/molecule is move into a cell at the same time one is being removed:

Answer 7

Sodium-potassium pump.

Question 8

Co-transporters.

Answer 8

A type of carrier protein that bind to two molecules at a time.

Question 9

Briefly describe the role of co-transporters:

Answer 9

1. They bind two molecules at a time.
2. Concentration gradient of one of the molecules is used to move the other molecule against its own concentration gradient.

Question 10

What factors affect the rate of active transport?

Answer 10

• Speed of individual carrier proteins.
• Number or carrier proteins present.
• Rate of respiration of the cell and the availability of ATP.

Question 11

How does the speed of individual carrier proteins affect the rate of active transport?

Answer 11

The faster they work, the faster the rate of active transport.

Question 12

How does the number of carrier proteins present affect the rate of active transport?

Answer 12

The more proteins there are, the faster the rate.

Question 13

Hows does the rate of respiration and availability of ATP affect the rate of active transport?

Answer 13

If respiration is inhibited, active transport cannot take place.

Question 14

How s glucose absorbed in the mammalium ileum?

Answer 14

Co-transport.

Question 15

What is the mammalian ileum?

Answer 15

Small intestine in mammals.

Question 16

In the ileum, why is there an issue with glucose diffusing into the blood?

What must happen to overcome this?

Answer 16

The concentration is too low for it to diffuse into the blood.

So, glucose is absorbed from the lumen of the ileum by co-transport.

Question 17

What happens in the sodium-potassium pump?

Answer 17

• Sodium ions are actively removed from the cell/organelle.
• Potassium ions are actively taken in from surroundings.

Essential for important processes, such as the creation of nerve impulses.

Question 18

7 ponts

Describe the co-transport of glucose in the mammalian ileum:

Answer 18

• Sodiumions actively transported out of the ileum epithelial cells, into blood, by sodium-potassium pump.
• Concentration of sodium ions in lumen higher than inside cell.
• Causes sodium ions to diffuse from the lumen into the epithelial cell, down concentration gradient.
• Do this via sodium-glucose co-transporter proteins.
• Co-transporter carries glucose into the cell with the sodium.
• Results in concentration of glucose inside the cell increasing.
• So, glucose diffuses out of cell, into the blood, down the concentration gradient through a protein channel by facilitated diffusion.

Question 19

A type of carrier protein that bind to two molecules at a time.

Answer 19

Co-transporters.

Question 20

Why is co-transport an indirect form of active transport?

Answer 20

• Sodium ion concentration gradient, rather than ATP directly, that powers the movement of glucose and amino acids into the cells.