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Lesson: Chapter 6 — Human body processes

Putting the chapter together 2 of 3

The exercise

Questions that pull the chapter together, each with a worked answer.

Question 1 — digestion

Food passing along the alimentary canal

  1. Name the enzyme in saliva and the food it acts on.
  2. Why is bile not an enzyme, and what does it do?
  3. Give two ways the small intestine is suited to absorption.

The answer

  1. Salivary amylase; it acts on starch.
  2. It breaks no chemical bonds; it emulsifies fats into small droplets so lipase can act on them.
  3. Any two of: it is long; its lining carries villi; the villi have thin walls and a rich blood supply.

Question 2 — breathing and respiration

From the air to the cells

  1. Describe what the intercostal muscles and diaphragm do when you breathe in.
  2. Write the word equation for aerobic respiration.
  3. Why do muscles ache after a sprint?

The answer

  1. Both contract: the ribs lift and the diaphragm flattens, so the chest grows and air flows in.
  2. glucose + oxygen gives carbon dioxide + water + energy.
  3. Anaerobic respiration builds up lactic acid in them.

Question 3 — excretion

Making urine

  1. Name the three steps by which a nephron makes urine.
  2. Glucose is found in a person's urine. What might this show?
  3. Why is removing faeces not excretion?

The answer

  1. Ultrafiltration, selective reabsorption, secretion.
  2. Diabetes: blood glucose is too high for the kidneys to reabsorb it all.
  3. Faeces are mostly undigested food, never made by the cells' metabolism.

Question 4 — blood and circulation

The heart and vessels

  1. Trace blood from the right atrium back to the right atrium.
  2. Why is the wall of the left ventricle the thickest?
  3. Give two habits that lower the risk of atherosclerosis.

The answer

  1. Right atrium, right ventricle, pulmonary artery, lungs, pulmonary veins, left atrium, left ventricle, aorta, body, vena cava, right atrium.
  2. It pumps blood all round the body, which needs the highest pressure.
  3. Any two of: regular exercise, less saturated fat, not smoking, a healthy weight.

Question 5 — co-ordination

Nerves and hormones

  1. Put the parts of a reflex arc in order.
  2. Name the hormone that lowers blood glucose, and where it is made.
  3. How does the body cool itself on a hot day?

The answer

  1. Receptor, sensory neuron, relay neuron, motor neuron, effector.
  2. Insulin, from the beta cells of the islets of Langerhans in the pancreas.
  3. By sweating, and by widening the blood vessels of the skin.