3.6.4.3 Control of blood water potential

Question 1

2 kidney function

Answer 1

Excretion
Osmoregulation

Question 2

Kidney Structure

Answer 2

Cortex & Medulla

Renal Artery / Veins
pyramids
Pelvis
Ureter (urine) –> Bladder

Nephron

Question 3

3 process in nephron + brief description

Answer 3

Ultrafiltration – Blood is filtered out of the glomerulus at the Bowman’s capsule to form filtrate
Selective reabsorption – Usable materials are reabsorbed in convoluted tubules (both proximal and distal)
Osmoregulation – The loop of Henle establishes a salt gradient, which draws water out of the collecting duct

Question 4

nephron structure

Answer 4

Bowman’s Capsule
Glomerulus
Proximal Convoluted Tubule
Loop of Henle
Distal Convoluted Tubule
Collecting Duct

Vasa Recta (throughout)

Question 5

Ultrafiltration process in Nephron

Answer 5

• Hydrostatic pressure is high in the glomerulus.
• Fluid (water, salts, urea, glucose, amino acids) is forced out into the capsule.
• Fluid moves through fenestrations between the endothelial cells of the capillary and the spaces between the podocytes.
• Cells and proteins are too large to pass through and remain in the blood.

1. Blood is filtered by the basement membrane, which lies between the glomerulus and Bowman’s capsule
2. Glomerular blood vessels are fenestrated (have pores) which means blood can freely exit the glomerulus
3. The podocytes of the Bowman’s capsule have gaps between their pedicels, allowing for fluid to move freely into the nephron

The basement membrane is size-selective and restricts the passage of blood cells and large proteins.

Question 6

Reabsorption process in Nephron (amino Acid) - cotransport

Answer 6

• Sodium ions are actively pumped out of the PCT by the Na+K+ATPase pump using ATP.
• Sodium ions inside the cell are at a lower concentration than in the lumen.
• Sodium moves into the cell from the lumen down its concentration gradient through a carrier (cotransport) protein.
• AA moves in with it against its concentration gradient, creating a high concentration inside the cell.
• AA moves into the blood by facilitated diffusion from a high concentration inside to a low concentration in the blood where it is quickly removed by the flow, maintaining a concentration gradient.

Question 7

3 adaptation of the cell for reabsorption

Answer 7

1. Microvilli / Folded cell-surface membrane provide a large surface area
2. Many channel/carrier proteins for facilitated diffusion;
3. Many carrier proteins for active transport;
4. Many channel/carrier proteins for co-transport;
   Accept ‘cotransport protein’ for type of transport protein.
5. Many mitochondria produce ATP OR Many mitochondria for active transport;
6. Many ribosomes to produce carrier/channel proteins;
   Accept abundant rough endoplasmic reticulum for many ribosomes, but abbreviation is not enough.

Question 8

Describe another method by which the animal live in extreme dry places could obtain water. [2]

Answer 8

It could produce metabolic water
Using oxygen & aerobic respiration

from water (product) + fatty acid

Question 9

How diabetes lead to glucose appear in urine

Answer 9

High blood Glucose (>10 mol dm -3)
Filtrate — Cotransporter Saturated = Renal threshold
Not all glucose is reabsorbed
some appear in urine