WJEC GCSE Biology 2.6 Role of the Kidney in Homeostasis Exam Questions

About WJEC GCSE Biology 2.6 Role of the Kidney in Homeostasis

This Unit 2 topic explains how the kidneys remove waste and control the water content of the blood. You need to label the excretory system and a kidney section, and describe the structure of a nephron and its blood supply. You must explain filtration under pressure and selective reabsorption of glucose, salts and water, and how ADH changes the concentration of urine. The topic covers what urine tests can reveal, such as glucose indicating diabetes. It ends with dialysis and kidney transplants, including tissue matching and immunosuppressant drugs. Testing artificial urine for protein and glucose is the specified practical, linking back to food tests in 1.3.

What you need to know

• Kidney functions The kidneys regulate the water content of the blood and remove waste such as urea. Label the kidneys, renal artery, renal vein, ureters, bladder and urethra, and the direction of blood flow.
• Nephron Each kidney contains many nephrons. Blood enters a knot of capillaries (glomerulus) inside the Bowman's capsule, then filtrate passes along the tubule and collecting duct. Know the nephron's blood supply.
• Filtration and reabsorption High pressure forces small molecules (water, glucose, salts, urea) out of the blood into the capsule; cells and proteins are too large and stay in the blood. All glucose, and some salts and water, are selectively reabsorbed back into the blood.
• Urine Urine contains water, urea and salts and passes down the ureter to the bladder. Blood or protein in urine can show kidney disease; glucose can indicate diabetes. Testing artificial urine for protein and glucose is the specified practical.
• ADH If the blood is too concentrated, more ADH is released, so more water is reabsorbed and a small volume of concentrated urine is made. If there is too much water, less ADH is released and more dilute urine is produced.
• Kidney failure Dialysis machines pass blood alongside dialysis fluid across a partially permeable membrane; urea and excess salts diffuse out, while glucose is kept in by having the same concentration in the fluid. A transplant needs a matched tissue type and immunosuppressant drugs to reduce rejection.

Common mistakes in 2.6 Role of the Kidney in Homeostasis

• Writing that the kidney filters out urea only. Filtration removes all small molecules; useful ones such as glucose are then reabsorbed.
• Saying ADH makes more urine. ADH increases water reabsorption, so less, more concentrated urine is produced.
• Stating that proteins are filtered then reabsorbed. Proteins and blood cells are too large to be filtered, so finding them in urine suggests kidney damage.
• Describing a transplant without mentioning rejection. The donor kidney must be a close tissue match and the patient takes immunosuppressant drugs for life.

Try three 2.6 Role of the Kidney in Homeostasis exam-style questions