Selective Reabsorption

Question 1

Where does it occur?

Answer 1

In the proximal convoluted tubule

Question 2

What is selective reabsorption?

Answer 2

The process of reabsorbing substances like glucose amino acids from the PCT into the blood
Ensures useful molecules are retained and waste products e.g. urea are excreted

Question 3

1st step?

Answer 3

Sodium ions are actively transported out of the PCT epithelial cells into surrounding capillaries, using ATP and sodium-potassium pumps
Creates a low Na+ concentration inside the epithelial cells

Question 4

2nd step?

Answer 4

Sodium ions move into the PCT cells from the lumen down the conc gradient via co-transport proteins
As sodium diffuses, it brings glucose/amino acids with it

Question 5

3rd step?

Answer 5

Glucose/amino acid is now in the PCT cell so can leave by facilitated diffusion into the blood capillaries
(High concentration in the PCT cell and a low concentration in the blood)

Question 6

4th step?

Answer 6

As solutes are reabsorbed, water follow by osmosis, down the water potential gradient
85% of water is reabsorbed at this stage

Question 7

Microvili?

Answer 7

Increases surface area for reabsorption

Question 8

Many mitochondria?

Answer 8

Provides ATP for active transport of Na+

Question 9

Basal infoldings?

Answer 9

They are folds in the membrane at the base of the PCT cells containing Na/K+ pumps
Increases surface area for Na+/K+ pumps

Question 10

Many carrier proteins?

Answer 10

For co-transport of glucose and amino acids

Question 11

Channel proteins?

Answer 11

Facilitated diffusion of glucose and amino acids