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Biology 20

Biology 20 · Worksheets

Digestion and nutrition

Ten questions of mixed difficulty, covering Digestion. Print it, or work through it on screen — the answer key starts on its own page.

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Digestion and nutrition

Biology 20 · maddyhelps.com

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Circle the best answer for each question. Show your work in the space provided.

  1. The pH inside the stomach is about

    1. a) 2
    2. b) 9
    3. c) 5
    4. d) 7

  2. The large intestine contributes to nutrition by

    1. a) absorbing most glucose
    2. b) absorbing water and vitamins produced by its resident bacteria
    3. c) producing bile
    4. d) digesting protein

  3. Villi increase the efficiency of the small intestine by

    1. a) secreting acid
    2. b) producing digestive enzymes
    3. c) pushing food along by peristalsis
    4. d) greatly increasing its surface area for absorption

  4. The pancreas contributes to digestion by releasing

    1. a) enzymes and bicarbonate into the small intestine
    2. b) bile into the small intestine
    3. c) mucus into the oesophagus
    4. d) hydrochloric acid into the stomach

  5. Bile is produced by the

    1. a) gall bladder
    2. b) stomach
    3. c) pancreas
    4. d) liver

  6. Pepsin digests

    1. a) protein, and works best at pH 8
    2. b) protein, and works best in the acidic stomach
    3. c) starch, and works best in the mouth
    4. d) fat, and works best in the small intestine

  7. Most absorption of nutrients happens in the

    1. a) large intestine
    2. b) stomach
    3. c) small intestine
    4. d) oesophagus

  8. Starch digestion begins in the

    1. a) mouth, with salivary amylase
    2. b) large intestine, with bacteria
    3. c) stomach, with pepsin
    4. d) small intestine, with lipase

  9. Peristalsis is

    1. a) the mixing of food with enzymes in the stomach
    2. b) the absorption of nutrients into the blood
    3. c) the reflex that closes the epiglottis
    4. d) waves of smooth muscle contraction that push food along the tract

  10. Chewing food is an example of

    1. a) chemical digestion
    2. b) egestion
    3. c) mechanical digestion
    4. d) absorption

Answer key · Digestion and nutrition

Biology 20 · maddyhelps.com

  1. a) 2 — Hydrochloric acid keeps it strongly acidic, which kills most swallowed microbes and gives pepsin the conditions it needs. It also means enzymes from the mouth stop working as soon as they arrive.
  2. b) absorbing water and vitamins produced by its resident bacteria — By the time material arrives, most nutrients are gone. What remains is reclaiming water and salts, plus absorbing vitamin K and some B vitamins made by the gut bacteria.
  3. d) greatly increasing its surface area for absorption — Each villus carries microvilli, and the folding multiplies the area by a factor of hundreds. A structure that maximizes surface area for exchange shows up again in the lungs and the kidney.
  4. a) enzymes and bicarbonate into the small intestine — The bicarbonate neutralizes the acid arriving from the stomach, which raises the pH to where pancreatic enzymes work. The enzymes and the buffer have to arrive together to be useful.
  5. d) liver — The liver makes it continuously; the gall bladder only stores and concentrates it between meals. Knowing which organ makes what is worth being precise about here.
  6. b) protein, and works best in the acidic stomach — Pepsin is a protease with an unusually low optimum pH, around 2. Move it into the small intestine and it stops working, which is one reason the pancreas sends a fresh set of enzymes.
  7. c) small intestine — The small intestine is long, folded, and lined with villi and microvilli, giving it an enormous surface area. The stomach absorbs almost nothing; the large intestine mainly takes back water.
  8. a) mouth, with salivary amylase — Amylase in saliva starts breaking starch into maltose while you chew, which is why bread begins to taste sweet if you hold it in your mouth. Stomach acid then halts it until pancreatic amylase takes over.
  9. d) waves of smooth muscle contraction that push food along the tract — The muscle behind the food contracts and the muscle ahead relaxes, moving the bolus onward. It does not rely on gravity, which is why swallowing works upside down.
  10. c) mechanical digestion — Mechanical digestion breaks food into smaller pieces without changing it chemically, which gives enzymes far more surface to work on. Chemical digestion is what the enzymes then do.