Active Transport & Glucose transport

Question 1

What is active transport?

Answer 1

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

Question 2

What is the purpose of ATP in active transport?

Answer 2

• Directly move molecules
• Individually move molecules using a concentration gradient which has already been set up by active transport ( Co-transport ).

Question 3

What does Active Transport require?

Answer 3

Energy ( ATP ).

Question 4

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

Answer 4

• Active transport moves solutes usually from a low to high concentration, facilitated diffusion they move from high concentration to low concentrations.
• Active transport requires energy, facilitated diffusion does not.
• Carrier proteins molecules which act as pumps are involved.
• Process is highly selective, only specific substances are transported.

Question 5

How is ATP produced?

Answer 5

Respiration

Question 6

How does ATP provide energy?

Answer 6

• ATP undergoes a hydrolysis reaction, splitting into ADP and Pi ( inorganic phosphate ).
• This splitting releases energy so that the solutes can be transported.

Question 7

What is the process of a single molecule being transported?

Answer 7

• Carrier proteins span the plasma membrane, and bind to the molecule/ion that is to be transported, on one side of it.
• Molecule or ion binds to the receptor sites on the carrier protein.
• On the inside of the cell/organelle, the ATP binds to the protein resulting in the ATP splitting into ADP and a phosphate molecule, and thus the protein molecule changes shape and opens to the opposite side of the membrane.
• The molecule or ion is then released to the other side of the membrane.
• The phosphate molecule is released from the protein which results in the protein reverting to its original shape, ready for the process to be repeated.
• The phosphate molecule recombines with the ADP to form ATP during respiration.

Question 8

What is the sodium-potassium pump process?

Answer 8

• Potassium ions are actively taken in from the surroundings whilst sodium ions are actively removed

Question 9

How do co-transporters work?

Answer 9

• 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 10

What is an example of how co transporters work?

Answer 10

• Sodium ions move into a cell against down their concentration gradient.
• Glucose will also be moved into the cell against its concentration gradient.

Question 11

What is the purpose of micro-villi?

Answer 11

• They provide a larger surface area for the insertion of carrier proteins through which diffusion and active transport can take place.

Question 12

Where are micro-villi found?

Answer 12

Epithelial cells lining the ileum.

Question 13

How can transport across membranes be increased?

Answer 13

• Increasing the number of micro-villi.

* Increase the number of protein channels and carrier proteins in any given area of membrane, a larger density.

Question 14

Why is there are a greater concentration of glucose within the ileum?

Answer 14

Carbohydrates are being continuously digested.

Question 15

Why is glucose being continuously removed from the ileum?

Answer 15

• The blood is down a concentration gradient to the blood, thus the glucose can move via facilitated diffusion from inside the ileum into the blood.
• Blood is being constantly circulated by the heart, so glucose is absorbed is continuously being removed by cells as they use it up during respiration.
• This also helps maintain the concentration gradient between the inside of the ileum and blood

Question 16

How does glucose enter the ileum epithelium?

Answer 16

• Sodium ions are actively transported out of the ileum epithelial cells, into the blood, by the sodium potassium pump. This will create a concentration gradient - there is now a higher concentration of sodium ions in the lumen of the ileum than inside the cell.
• This causes sodium ions to diffuse from the lumen of the ileum into the epithelial cell, down the concentration gradient ( done via the sodium-glucose co transporter proteins ).
• Co transporter carries glucose into the cell with the sodium. The concentration of glucose inside the cell increases.
• Glucose diffuses out of the cell, into the blood, down the concentration gradient through a protein channel by facilitated diffusion.

Question 17

What factors affect rate of active transport?

Answer 17

• Speed of individual carrier proteins, faster they work, faster the rate of active transport.
• Number of carrier proteins present, the more proteins, the faster the rate of active transport.
• Rate of respiration, and availability of ATP, if respiration is inhibited, active transport can’t take place.