Active Transport

Question 1

What is active transport?

Answer 1

Active movement of ions or polar molecules from a lower concentration to a higher concentration using a carrier protein. This movement against the conc gradient requires energy from ATP. Since the ATP is produced in respiration m, oxygen is also required.

Question 2

What do carrier proteins do in active transport?

Answer 2

Carrier proteins act as pumps. Their shape is specific and complements the shape of the molecule they carry. Carrier proteins carry larger or charged molecules through the membranes as they cannot diffuse through the lipid bilayer

Question 3

What molecules can be actively transported by carrier proteins?

Answer 3

• non lipid soluble
• large and water soluble (polar molecules)
• ions

Question 4

How is one way flow ensured in active transport?

Answer 4

ATP changes the shape of the carrier protein in active transport and hence on one side of the membrane the shape of the protein will complement the specific molecule to be transported. Once energy has been used by the carrier protein it changes shape and releases the specific molecule. This ensures one way flow

Question 5

What stops the movement of molecules by active transport?

Answer 5

Anything which inhibits ATP production
Eg cyanide - a respiratory inhibitor which stops ATP production

Question 6

What are co transporters and what are they used for?

Answer 6

Co transporters are a type of carrier protein. They bind two molecules at a time. The concentration gradient of one molecule is used to move the other molecule against its own concentration gradient

Question 7

What do epithelial cells lining the ileum contain?

Answer 7

• Microvilli (finge rlike projections to increase the surface area
• have an increased number of protein channels and carrier molecules in their membranes

Question 8

What is the method of co- transport?

Answer 8

Step 1 - sodium ions are actively transported out of the epithelial cells in the ileum into the blood, by the sodium- potassium pump. This creates a conc gradient - there is now a higher conc of sodium ions in the lumen of the ileum than inside the cell

Step 2 - this causes sodium ions to diffuse from the lumen of the ileum into the epithelial cell, down their conc gradient. They do this via the sodium glucose co transporter proteins.
The co transported carries glucose into the cell with the sodium as a result the concentration of glucose inside the cell increases

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