Excretion

Question 1

Where in the nephron is glucose selectively reabsorbed into the blood capillaries (1)

Answer 1

Proximal Convoluted Tuble (PCT)

Question 2

Which regions of the nephron are present in the cortex (4)

Answer 2

PCT

DCT

Bowman’s capsule

Collecting duct

Question 3

Where in the nephron are podocytes located (1)

Answer 3

Bowman’s capsule

Question 4

Explain how the longer loop of Henle is able to assist desert animals in preventing excessive water loss (3)

Answer 4

Mineral ions are actively pumped out from the ascending limb into the medulla

Which results in the water potential of the medulla becoming more negative

And leads to the absorption of more water from the collecting duct

Question 5

Why is there no glucose/amino acids present in urine (1)

Answer 5

All glucose and amino acids are reabsorbed at the PCT due to the reabsorption of useful molecules

Question 6

Why doesn’t the glomerulus filtrate contain any large proteins (2)

Answer 6

Large molecules cannot leave the blood plasma due to basement membrane which prevents large molecules from entering the bowman’s capsule

Question 7

Why does urea concentration increase between the filtrate and urine (1)

Answer 7

The removal of water from the tubule due to reabsorption results in urea being more concentrated

Question 8

State precisely where the cells that detect a decrease in the water potential of the blood plasma are found (1)

Answer 8

Walls of hypothalamus

Question 9

What cells detect the decrease in the water potential of the blood plasma (1)

Answer 9

Osmoreceptors

Question 10

Name the part of the adrenal gland that releases aldosterone (1)

Answer 10

The cortex

Question 11

Suggest and explain what effect the action of aldosterone will have on the secretion of ADH (2)

Answer 11

The water potential of the blood will become more negative and ADH secretion will increase

Question 12

State the name of the mechanism that results in the decreasing of aldosterone secretion (1)

Answer 12

NEGATIVE FEEDBACK

Question 13

Which part of the nephron are the walls impermeable to water (1)

Answer 13

Ascending limb of loop of Henle

Question 14

Which part of the nephron is glucose reabsorbed into the blood (1)

Answer 14

Proximal convoluted tubule

Question 15

Which parts of the nephron do ADH act on the walls (2)

Answer 15

Collecting duct

Distal convoluted tubule

Question 16

Which part of the nephron contains podocytes (1)

Answer 16

Bowman’s capsule

Question 17

Which part of the nephron is most of the water reabsorbed into the blood (1)

Answer 17

Proximal convoluted tubule

Question 18

Explain the role of the loop of Henle in the production of urine (5)

Answer 18

Mineral ions are actively pumped out from the upper part of the ascending limb and diffusing out into the descending limb

This results in the water potential of the medulla becoming more negative due to the ions being in it’s environment.

The walls of the descending limb are permeable to water and so as a result, water is removed from the descending limb via osmosis

Question 19

Name the organ that produces urea (1)

Answer 19

The liver

Question 20

Suggest why a high intake of protein in the diet will be likely to result in high concentration of urea in the urine (5)

Answer 20

High intake of protein leads to a large amount of amino acids whereby excess amino acids cannot be stored

This results in amino acids being deaminated whereby the amine group is converted to ammonia.

This results in a large amount of ammonia entering the ornithine cycle so that it can be converted to urea

This conversion results in an increased blood concentration of urea and in turn leads to more urea in the urine.

Finally, the high concentration of urea in the blood results in increased water absorption from urine

Question 21

Suggest what condition is indicated by the presence of glucose in a person’s urine (1)

Answer 21

Diabetes

Question 22

State the substance that is being tested for in urine when a pregnancy test is carried out (1)

Answer 22

hCG

Question 23

Explain how the glomerulus is able to perform its function (3)

Answer 23

The afferent arteriole has a greater diameter than that of the efferent arteriole

Which results in the build up of hydrostatic blood pressure.

The walls of the glomerulus have small pores which allows ultrafiltration to occur

Question 24

Describe the features of the glomerulus and Bowman’s capsule that allow them to perform their function effectively (4)

Answer 24

• The afferent arteriole is wider than the efferent arteriole
• There is a higher hydrostatic pressure in the glomerulus than in the Bowman’s capsule
• The wall of the capillary has gaps that allow the passage of substances
• The basement membrane stops the removal of large molecules

Question 25

Suggest two ways in which the structure of aquaporins prevent the passage of ions (2)

Answer 25

It’s channel is too narrow for ions to pass through

And the positive charge in the channel repels the positively charged ions

Question 26

Explain the likely effect on blood cells if the water potential of the plasma was allowed to increase significantly (2)

Answer 26

Water potential of the plasma would be higher than that of the blood cells

Resulting in water entering blood cells whereby the bloods cells could potentially burst from swelling

Question 27

Name the type of monomer that makes up a molecule of ADH and the bind that joins the monomers together (2)

Answer 27

Amino acids joined by peptide bonds

Question 28

Suggest where ADH is removed from the blood and describe what then happens to the ADH molecule (3)

Answer 28

It is ultrafiltered from the blood and due to it being a small molecule, ADH will be present in urine and will get excreted in due time