active transport- across cell membranes

Question 1

how are carrier proteins involved in active transport

Answer 1

similar to facillitated diffusion- a molecule attaches to the carrier protein, the protein changes shape and this moves the molecule across the membrane releasing it the other side

Question 2

what are the differences between active transport and facillitated diffusion

Answer 2

• active transport often moves solutes from a low to high concentration whereas in facillitated diffusion they always move from a high to low concentration
• active transport requires energy whereas facillitated diffusion does not

Question 3

where and how does active transport get energy

Answer 3

• atp is a common source of energy in the cell and is produced by respiration
• atp undergoes a hydrolysis reaction, splitting into adp and pi (inorganic phosphate) which releases energy so that the substance can be transported

Question 4

what does the hydrolysis reaction of atp to adp and pi do

Answer 4

releases energy so that the substance can be transported

Question 5

role of cotransporters in active transport

Answer 5

• they bind two molecules at a time
• the concentration gradient of one of the molecules is used to move the other molecules against its own concentration gradient

Question 6

factors effecting the rate of active transport

Answer 6

• the speed of individual carrier proteins- the faster they work the faster the rate of active transport
• the number of carrier proteins present
• the rate of respiration in the cell and the availability of atp
  (if respiration is inhibited then active transport cannot take place)

Question 7

where is glucose absorbed into the bloodstream

Answer 7

small intestine- from the lumen of the ileum

Question 8

describe how glucose is absorbed into the bloodstream from the ileum of the small intestine by co transport

Answer 8

1- sodium ions are actively transported out of the ileum epithelial cells 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 inside the cell
2- this causes sodium ions to diffuse from the lumen of the ileum into the epithelial cell, down their concentration gradient. they do this via sodium glucose co transporter proteins
3- the cotransporter carries glucose into the cell with the sodium. As a result, the concentration of glucose inside the cell increases
4- Glucose diffuses out of the cell into the blood, down its concentration gradient through a protein channel by facillitated diffusion