The kidneys of a healthy individual filter 178 dm³ day^-1 of fluid from the glomeruli into the renal capsules. However, only 1.5 dm³ day^-1 of urine is produced.

What percentage of the filtrate is reabsorbed back into the blood?

Patients with kidney failure can be treated in different ways.

Which statement describes a feature of peritoneal dialysis?

1 - urea and mineral ions pass into the tissue fluid

2 - blood is passed over an artificial membrane to remove toxins

3 - the patient receives immunosuppressant medication

The image below shows the structure of the nucleotide base guanine.

Bird droppings are known as guano because they contain a high proportion of guanine. Unlike mammals, birds excrete nitrogenous waste as guanine instead of urea. Guanine is synthesised from ammonia in the liver.

The statements below relate to guanine, which of the statements correctly explains why birds excrete guanine?

1 - ammonia is more toxic than guanine

2 - urea is more soluble in water than guanine

3 - guanine has a high proportion of nitrogen

Damage to the hypothalamus results in lower water potential of the blood.

What explains these observations?

The hormone aldosterone is produced by the adrenal cortex. Excess production of aldosterone can result in high blood pressure.

The statements describe processes that occur as a result of aldosterone secretion:

1 - Na⁺/K⁺ pumps in the collecting duct of the kidney move 3 Na⁺ ions into the blood and 2 K⁺ ions out of the blood

2 - Cl^- ions enter the blood to maintain electrochemical balance

3 - H⁺ ions enter cells lining the kidney tubules

Which statement(s) explain(s) why excess aldosterone production can result in high blood pressure?

Antidiuretic hormone (ADH) is required for osmoregulation.

What is a region of the nephron that is responsive to ADH?

The diagram below shows the structure of an amino acid. Four regions are labelled A to D.

Which region is removed from the amino acid to produce urea?

What process occurs at the proximal convoluted tubule (PCT)?

Which substance is not normally found in urine due to being reabsorbed in the nephrons?

What effect does dehydration have on urine concentration?

What is the outcome when the blood ADH level is high?

What triggers the release of ADH from the posterior pituitary gland?

What does the loop of Henle establish in the medulla to aid water reabsorption?

Excess amino acids are metabolised in the liver. What is this process called?

What is a primary waste product of metabolism that the liver is responsible for processing?