Human Diet & Digestion (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Biology): Flashcards
Exam code: 0654 & 0973
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Balanced diet
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Cards in this collection (40)
Balanced diet
A diet containing all the food groups in the correct proportions to keep the body healthy.
List the components of a balanced diet and what each is needed for.
Carbohydrates — for energy.
Proteins — for growth and repair.
Lipids (fats and oils) — for energy and insulation.
Vitamins and minerals — to keep the body healthy.
Fibre — to help food move through the gut.
Water — for chemical reactions and transport.
is needed in the diet for the growth and repair of tissues.
Protein
Dietary (roughage) helps food move through the gut and prevents constipation.
fibre
What causes scurvy and what are its symptoms?
Caused by a lack of vitamin C.
Symptoms include bleeding gums and poor wound healing.
What causes rickets and what is its effect?
Caused by a lack of vitamin D (or calcium).
Leads to soft, weak bones that bend (e.g. bowed legs).
A lack of vitamin C in the diet causes the deficiency disease .
scurvy
List the organs food passes through in the alimentary canal, in order.
Mouth
Oesophagus
Stomach
Small intestine (duodenum and ileum)
Large intestine (colon and rectum)
Anus
What is the function of the stomach?
It churns food and produces hydrochloric acid and protease enzymes to begin the digestion of protein.
What are the two main functions of the small intestine?
Digestion of food is completed here.
The digested nutrients are absorbed into the blood.
What is the function of the large intestine?
It absorbs water from the undigested food, forming faeces.
The produces bile, which is then stored in the gall bladder.
liver
The produces digestive enzymes that are released into the small intestine.
pancreas
Physical (mechanical) digestion
The breakdown of food into smaller pieces without changing the chemical molecules.
Why is physical digestion important?
It increases the surface area of the food, so enzymes can act on it faster during chemical digestion.
Give two examples of physical digestion in the body.
Chewing of food by the teeth in the mouth.
Churning of food by the muscular wall of the stomach.
Physical digestion increases the of food for enzymes to work on.
surface area
How does the stomach carry out physical digestion?
Its muscular wall churns the food, mixing it with digestive juices and breaking it into smaller pieces.
Physical digestion breaks food into smaller pieces without any change to the molecules.
chemical
Chemical digestion
The breakdown of large, insoluble food molecules into small, soluble molecules.
Why is chemical digestion needed?
Large food molecules are insoluble and cannot be absorbed.
Chemical digestion breaks them into small soluble molecules that can be absorbed into the blood.
What are the products of digesting carbohydrates, proteins and lipids?
Carbohydrates → simple sugars (e.g. glucose).
Proteins → amino acids.
Lipids → fatty acids and glycerol.
Chemical digestion breaks large insoluble molecules into small molecules.
soluble
Proteins are broken down into during chemical digestion.
amino acids
What does amylase do, and where is it made (Extended)?
Made in the salivary glands and the pancreas.
Breaks down starch into simple reducing sugars.
What does protease do, and give an example?
Breaks down proteins into amino acids.
Example: pepsin, made in the stomach.
What does lipase do, and what are its products?
Breaks down lipids (fats).
Products: fatty acids and glycerol.
Amylase breaks down starch into .
simple reducing sugars
Protease enzymes break down proteins into .
amino acids
Lipase breaks down fats into fatty acids and .
glycerol
What are the roles of hydrochloric acid in the stomach (Extended)?
Kills harmful bacteria and pathogens in food.
Provides the acidic pH (about pH 2) that is the optimum for the protease enzyme pepsin.
Hydrochloric acid gives the stomach a low (acidic) of about 2.
pH
Stomach acid harmful bacteria taken in with food.
kills
Why does the stomach need to be acidic for protein digestion?
The stomach protease (pepsin) works fastest in acidic conditions, so hydrochloric acid provides its optimum pH.
Bile
A greenish-yellow alkaline fluid made in the liver and stored in the gall bladder; it neutralises stomach acid and emulsifies fats.
What are the two functions of bile (Extended)?
Neutralises the acidic mixture from the stomach, providing the alkaline pH needed by enzymes in the small intestine.
Emulsifies fats (lipids) into small droplets.
Emulsification
The breaking up of large fat droplets into many small droplets.
Why is emulsification of fats important?
It increases the surface area of the fats, so lipase can break them down faster.
Bile is made in the liver and stored in the .
gall bladder
Bile is , so it neutralises stomach acid in the small intestine.
alkaline
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