Topic 2B - Year 1 - Cell Membranes - Active transport

Question 1

What is active transport?

Answer 1

Active transport is the use of energy ti move particles across the cell membrane against the concentration gradient , from a low concentration to a high concentration.

Question 2

What parts of the membrane are used in active transport?

Answer 2

Carrier proteins

Co-transporters

Question 3

What is a similarity between active transport and facilitated diffusion?

Answer 3

They both use carrier proteins.

Question 4

How does ATP give energy to the process active transport?

Answer 4

ATP breaks down into ADP an Pi , breaking the bond between the phosphate groups releases energy.

Question 5

In active transport what happens to the carrier protein in order to begin moving particles against the concentration gradient?

Answer 5

A phosphate group breaks from ATP , this activates the carrier protein giving it energy and thus changing its shape allowing it to transport the molecule across the membrane.

Question 6

What are co-transporters?

Answer 6

Co-transporters are a type of carrier protein

Question 7

Explain how a co-transporter works?

Answer 7

A co transporter binds two molecules at a time , it uses the concentration gradient of one molecule to move the other molecule against its concentration gradient.

Question 8

How does co transport work in the small intestine ?

Answer 8

Glucose is absorbed into the blood from the ileum which is a part of the small intestine. The concentration of glucose is higher in the blood than it is in the ileum thus the glucose must be moved out of the small intestine by active transport so that it can enter the blood stream , this occurs using co transport.

step 1
Firstly sodium ions are actively transported out of the epithelial cells in the ileum (part of the small intestine) into the blood by a sodium potassium pump.

This creates a concentration gradient as there is now a higher concentration of sodium ions in the lumen of the ileum than in the ileum itself.

Step 2
The concentration gradient makes the sodium ions diffuse from the lumen into the epithelial cell down their concentration gradient. This is possible as the diffusion is facilitated by sodium-glucose co-transporter proteins.

The co transporter proteins carries the glucose from the lumen of the ileum into the epithelial cells with he sodium as the sodium moves down its concentration gradient.

As a result the concentration of glucose inside the epithelial cell increases.

Step 3
glucose diffuses out of the cell , into the blood down its concentration gradient through a protein channel by facilitated diffusion.

Question 9

Which factors affect the rate of active transport?

Answer 9

The speed of the carrier proteins - carrier proteins that work more quickly allow for a quicker rate of active transport

The number of carrier proteins present , more cariier proteins means an increased rate of active transport.

The rate of respiration in a cell , if a cell does not respire very much it will not synthesis very much ATP , this mean active transport will be restricted as ATP is essential to the process.