section 3 (5)distinguish between active and passive transport and relate these to processes occurring in the mammalian kidney

Question 1

What is passive transport?

Answer 1

• the movement of substances without the expenditure of energy
• diffusion and osmosis are examples
• substances move down the concentration gradient

Question 2

what is active transport?

Answer 2

• the movement of substances using the expenditure of energy
• can move substances against the concentration gradient
• may involve using a carrier protein against a cell membrane

Question 3

What is the role of passive transport in a mammalian kidney?

Answer 3

• diffusion is involved in the filtration and secretion of some nitrogenous wastes
• osmosis moves water: for example in tubules, descending loop of Henle and collecting duct

Question 4

What is the role of active transport in a mammalian kidney?

Answer 4

• moves glucose and amino acids as well as salts and inorganics. e.g sodium ions across the nephron.
• carries out reabsorption and secretion
• “sodium pump” mechanisms in kidney tubules

Question 5

Explain sodium pump mechanisms

Answer 5

• Salts and other ions are moved back into the kidney from the urine. this causes water to be drawn out from the urine as well through osmosis, hence controlling water and salt levels (selective reabsorption)