Lesson 3

Question 1

What does the proximal convoluted tube (PCT) do?

Answer 1

Do selective reabsorption to reabsorb nearly all organic nutrients

Question 2

What is selective reabsorption?

Answer 2

Process where useful products such as glucose are absorbed back into blood as filtrate flows through the nephron

Question 3

What happens by the time filtrate reaches end of PCT?

Answer 3

Filtrate becomes isotonic (same water potential) to blood

Question 4

Name products reabsorbed and mechanism in which they do so

Answer 4

• All glucose and aa - Secondary AT using co-transport with Na+
• Most mineral ions - AT or co-transport
• Most water - Osmosis down water potential gradient
• Some filtered proteins and urea - Diffusion

Question 5

Describe some adaptations of PCT for selective absorption

Answer 5

• Large SA due length and large number per kidney
• Cuboidal epithelial cells with micro villi for more SA and basal channels
• Many mitochondria to make ATP for AT
• Tight junctions to prevent seepage of reabsorbed materials back into filtrate, and close association with peritubular capillaries

Question 6

What is water potential?

Answer 6

Tendency for water to leave a solution via osmosis

Question 7

Describe behaviour of water in hyper and hypotonic solutions with cells

Answer 7

• Hypo - WP of external solution is less negative (higher) than solution inside a cell so water flows into cell
• Hyper - WP of external solution is more negative (lower) than solution inside a cell so water flows out of cell