Kidneys-homeostasis topic

Question 1

what is the function of a nephron?

Answer 1

filter the blood to remove waste and selectively reabsorb useful substance back into the blood

Question 2

what is a nephron

Answer 2

they are long tubules surrounded by capillaries

Question 3

why doesn’t urine contain

• Glucose
• Proteins

Answer 3

• ALL Glucose is absorbed by active transport at the selective reabsorption stage in the PCT(proximal convoluted tubule)
• Proteins are too large to be filtered out of the blood

Question 4

how does filtering and absorption occur

Answer 4

1) ULTRAFILTRATION- occurs due to high hydrostatic pressure. water and small molecules are forced out of the glomerulus capillaries into the RENAL CAPSULE
2) SELECRIVE REABSORPTION occurs in the proximal convoluted tubule
3) THE LOOP OF HENLE maintains a sodium ion gradient so water can be reabsorbed by the blood
4) water moves out of the DISTAL CONVOLUTED TUBULE and COLLECTING DUCT to return back to the blood. the collecting duct then carries the remaining liquid urine.

Question 5

what is the reason for the high hydrostatic pressure in the glomerulus

Answer 5

it’s the afferent arteriole (bringing blood into the glomerulus) is wider than the efferent arteriole (carrying blood away from the glomerulus).

Question 6

how does the loop of Henle maintain a sodium ion gradient(include what happens at the base of the ascending limb of the loop of henle)

Answer 6

1) mitochondria in the walls of the cells provide energy to ACTIVELY TRANSPORT sodium ions OUT THE ASCENDING LIMB of the loop of Henle
2) causes a accumulation of sodium ions in outside of the nephron in the medulla -lowes the water potential
3) therefore the water diffuses out by osmosis into the interstitial space and then the blood capillaries- water REABSORBED INTO BLOOD
4) At the base of the ascending limb of henle- SOME SODIUM IONS DIFFUSE OUT BY DIFFUSION due to the low concentration of sodium ions as all the water has moved out

Question 7

Suggest why damage to the glomeruli can lead to urine that gives an intense purple colour after the biuret test. (2 marks)

Answer 7

1. Affects/damages basement membrane;

2. Proteins can pass into the (glomerular) filtrate/tubule;