Human Nutrition and Digestion: Question 2
Syllabus 7.2, 7.5
Farida eats a bowl of lentil and vegetable stew for dinner. Below are five events that happen to the stew inside her body, listed in a random order.
Event 1: Undigested plant fibre from the vegetables in the stew leaves Farida's body as part of her faeces.
Event 2: Farida places a spoonful of stew into her mouth and begins to chew it.
Event 3: Starch in the stew is broken down into smaller, soluble sugar molecules.
Event 4: The soluble sugar molecules produced in Event 3 pass through the lining of the gut wall into Farida's bloodstream.
Event 5: Once in the blood, some of the glucose is taken up by Farida's liver cells, which convert it into a stored carbohydrate called glycogen.
(a) For each of Events 1 to 5, name the biological process it describes. Choose each answer from: absorption, assimilation, digestion, egestion, ingestion. [5]
(b) State the region of the alimentary canal in which Event 4 mainly takes place. [1]
(c) Name one organ, other than a part of the alimentary canal itself, that releases a substance into the gut to help digest the stew, and state the substance that it releases. [2]
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Worked solution
Part (a): Naming each process
Event 1. Egestion
Undigested plant fibre cannot be broken down or absorbed, so it is removed from the body as faeces. This is egestion.
Event 2. Ingestion
Putting food into the mouth is the taking of food into the body. This is ingestion.
Event 3. Digestion
Breaking starch down into smaller, soluble sugar molecules is the chemical breakdown of a large food molecule. This is digestion.
Event 4. Absorption
The soluble sugar molecules moving from inside the small intestine into the bloodstream is absorption, the movement of nutrients from the intestines into the blood.
Event 5. Assimilation
Once glucose is already in the blood, its uptake and use by liver cells, to make glycogen, is assimilation, the uptake and use of nutrients by cells.
Part (b): Region of absorption
Event 4 takes place in the small intestine, which is the region of the alimentary canal specialised for absorbing the small, soluble products of digestion into the blood.
Part (c): An associated organ
The pancreas is an organ, separate from the alimentary canal itself, that releases digestive enzymes into the small intestine. For the starch in this stew, the pancreas releases amylase, which continues breaking down any remaining starch into simple sugars.
A different valid answer would be naming the liver and stating that it releases bile, which helps in the digestion of any fat in the stew.
Final answers
- (a) Event 1: egestion; Event 2: ingestion; Event 3: digestion; Event 4: absorption; Event 5: assimilation.
- (b) The small intestine.
- (c) The pancreas, which releases amylase (accept protease or lipase); or the liver, which releases bile.