Chapter 7 - Human nutrition

Question 1

What is a balanced diet?

Answer 1

A balanced diet consists of all the food groups in the correct proportions.

Question 2

What is the function of carbohydrates?

Answer 2

Source of energy

Question 3

What are some sources of carbohydrates?

Answer 3

Breads, cereals, pasta, rice, potatoes

Question 4

What is the function of proteins?

Answer 4

Growth and repair

Question 5

What are some sources of proteins?

Answer 5

Meat, fish, eggs, pulses, nuts

Question 6

What is the function of lipids?

Answer 6

Insulation and energy storage

Question 7

What are some sources of lipids?

Answer 7

Butter, oil, nuts

Question 8

What is the function of dietary fibre?

Answer 8

Provides bulk (roughage) for the intestine to push food through it

Question 9

What are some sources of dietary fibres?

Answer 9

Vegetables, whole grains

Question 10

What is the function of vitamin C?

Answer 10

Forms an essential part of collagen protein which makes up skin, hair, gums and bones. Deficiency causes scurvy

Question 11

What are some sources of vitamin C?

Answer 11

Citrus fruit, strawberries, green vegetables

Question 12

What is the function of vitamin D?

Answer 12

Helps the body to absorb calcium and so required for strong bones and teeth

Question 13

What are some sources of vitamin D?

Answer 13

Oily fish, eggs, liver, dairy products, also made naturally by the body in sunlight

Question 14

What is the function of calcium?

Answer 14

Needed for strong teeth and bones and involved in the clotting of blood. Deficiency can lead to osteoporosis later in life

Question 15

What are some sources of calcium?

Answer 15

Milk, cheese, eggs

Question 16

What is the function of iron?

Answer 16

Needed to make haemoglobin, the pigment in red blood cells that transports oxygen

Question 17

What are some sources of iron?

Answer 17

Red meat, liver, leafy green vegetables like spinach

Question 18

What is the function of water?

Answer 18

Needed for chemical reactions to take place in cells

Question 19

What are some sources of water?

Answer 19

Water, juice, milk, fruits, vegetables

Question 20

What is scurvy?

Answer 20

Scurvy is caused by a severe deficiency in vitamin C. Its symptoms include anaemia, exhaustion, spontaneous bleeding, pain in the limbs, swelling, gum ulcerations, tooth loss. Scurvy can be treated with oral or intravenous vitamin C supplements.

Question 21

What is rickets?

Answer 21

Rickets is caused by a severe lack of vitamin D. Its symptoms include bone pain, lack of bone growth and soft or weak bones. It can be treated by consuming foods containing calcium and vitamin D or using vitamin D supplements.

Question 22

What is the path of the digestive system?

Answer 22

Question 23

What is ingestion?

Answer 23

Ingestion is the food or drink that is taken into the body through the mouth.

Question 24

What is mechanical digestion?

Answer 24

Mechanical digestion is when food is broken down into smaller pieces without chemical change to the food molecules.

Question 25

What is chemical digestion?

Answer 25

Chemical digestion is when large, insoluble molecules are broken down into small, soluble molecules.

Question 26

What is absorption?

Answer 26

Absorption is when small food molecules and ions move through the wall of the intestine into the blood.

Question 27

What is assimilation?

Answer 27

Assimilation is the uptake and use of nutrients by cells.

Question 28

What is egestion?

Answer 28

Egestion is the removal of undigested food from the body as faeces.

Question 29

What is the function of the mouth during digestion?

Answer 29

Food is ingested here, and the teeth break it down into smaller pieces during mechanical digestion.

Question 30

What is the function of the salivary glands during digestion?

Answer 30

Saliva is secreted into the mouth. The enzyme amylase in saliva begins to digest starch into maltose. Saliva lubricates the food for easy swallowing.

Question 31

What is the function of the oesophagus during digestion?

Answer 31

This tube connects the mouth to the stomach. Contractions of the walls of the oesophagus force the food downwards; this is called peristalsis.

Question 32

What is the function of the stomach during digestion?

Answer 32

Churning of the muscular stomach walls continues the process of mechanical digestion. Protease enzymes begin protein digestion. Hydrochloric acid provides a suitable pH for the enzymes and also destroys any pathogens in food.

Question 33

What is the function of the liver during digestion?

Answer 33

Bile is produced here. Biles aids the digestion of fats, as well as neutralising stomach acid as it exits the stomach.

Question 34

What is the function of the gall bladder during digestion?

Answer 34

Bile is stored here before being released into the duodenum via the bile duct.

Question 35

What is the function of the pancreas during digestion?

Answer 35

Amylase, protease and lipase enzymes are produced here before being released into the duodenum.

Question 36

What is the function of the duodenum (small intestine) during digestion?

Answer 36

Food enters the small intestine from the stomach here. The acidic stomach contents are neutralised by the bile and become slightly alkaline. Enzymes complete chemical digestion here.

Question 37

What is the function of the ileum (small intestine) during digestion?

Answer 37

Food and water are absorbed into the blood via villi in the lining of the ileum

Question 38

What is the function of the colon (large intestine) during digestion?

Answer 38

Remaining water is absorbed from food into the blood and the solid waste left behind in the colon forms faeces.

Question 39

What is the function of the rectum (large intestine) during digestion?

Answer 39

Faeces are stored here prior to egestion.

Question 40

What is the function of the anus (large intestine) during digestion?

Answer 40

Faeces leave the body via the anus; this is egestion.

Question 41

What is physical digestion?

Answer 41

Physical digestion is the breakdown of food molecules into smaller pieces without chemical change to the food molecules. Physical digestion increase the surface area of food for the action of enzymes in chemical digestion. It is mainly carried out by the chewing of teeth, the churning of the stomach and the emulsification of fates by bile in the duodenum.

Question 42

What are teeth?

Answer 42

Teeth are held firmly in the bone of the jaw. They are used for chewing to increase the surface area of the food so that it can be exposed to saliva and other digestive juices and broken down more quickly. Teeth are embedded in bone and the gums. The four types of teeth are incisors, canines, premolars and molars.

Question 43

What are incisors?

Answer 43

Incisors are chisel shapers and are used for biting and cutting.

Question 44

What are canines?

Answer 44

Canines are pointed shaped for tearing, holding and biting.

Question 45

What are premolars and molars?

Answer 45

Premolars and molars are larger, flat surfaces with ridges at the edges for chewing and grinding up food.

Question 46

Diagram of teeth structure

Answer 46

Question 47

What is enamel?

Answer 47

Enamel is the hardest substance in the body. This covers the tooth and provides a tough surface for biting and chewing.

Question 48

What is dentine?

Answer 48

Dentine is also a hard substance. It has tiny tubes running from the pulp cavity outwards which are filled with blood vessels and nerves. The tooth is a living part of the body and needs blood vessels to supply it with nutrients. The nerve senses pressure and pain.

Question 49

What is pulp cavity?

Answer 49

Pulp cavity is the hollow region inside the tooth. Pulp is the blood vessels and nerves which keep the tooth alive.

Question 50

What is cement?

Answer 50

Cement covers the dentine in the jaw and provides anchorage for tough fibres.

Question 51

What is the stomach?

Answer 51

The stomach lining contains muscles which contract to physical squeeze and mix the food with strong digestive juices that are present. This is known as the stomach churning.

Question 52

Where is bile produced?

Answer 52

Cells in the liver produce bile which is then stored in the gallbladder.

Question 53

What is bile?

Answer 53

Bile is alkaline to neutralise the hydrochloric acid which comes from the stomach to allow the enzymes in the small intestine which have a higher pH to work at their optimum. It also breaks down large drops of fat into smaller ones by emulsification. The larger surface area allows lipase to chemically breakdown the lipid into glycerol and fatty acids faster.

Question 54

What is chemical digestion?

Answer 54

Chemical digestion is the breakdown of large insoluble molecules into small soluble molecules. The role of chemical digestion is producing small soluble molecules that can be absorbed.

Question 55

What is amylase?

Answer 55

Amylases are produced in the mouth and the pancreas and secreted into the duodenum. Amylases digest starch into smaller sugars. Amylase is secreted into the alimentary canal in the mouth and the duodenum from the pancreas and digests starch into maltose which is a disaccharide. Maltose is digested by the enzyme maltase into glucose on the membranes of the epithelium lining of the small intestine.

Question 56

What is protease?

Answer 56

Proteases are a group of enzymes that break proteins down into amino acids in the stomach and small intestine. The enzymes in the small intestine having been produced in the pancreas. The two types of proteases are pepsin and trypsin.

Question 57

What is pepsin?

Answer 57

Pepsin is produced in the stomach and breaks down protein in acidic conditions.

Question 58

What is trypsin?

Answer 58

Trypsin is produced in the pancreas and secreted into the duodenum where it breaks down protein in alkaline conditions.

Question 59

What is lipase?

Answer 59

Lipase enzymes are produced in the pancreas and secreted into the duodenum. They digest lipids into fatty acids and glycerol.

Question 60

What is hydrochloric acid?

Answer 60

Hydrochloric acid kills bacteria in food and gives an acidic pH for enzymes to work in the stomach. The low pH kills bacteria in food that we have ingested as it denatures the enzymes in their cells meaning they cannot carry out any cell reactions to maintain life. Pepsin, which is produced in the stomach, is an example of an enzyme which has a very low optimum pH around pH 2, so the hydrochloric acid ensures that conditions in the stomach remain within the optimum range for pepsin to work at its fastest rate.

Question 61

What is bile?

Answer 61

Bile is an alkaline mixture that neutralizes the acidic mixture of food and gastric juices entering the duodenum from the stomach, uses emulsification to break down large drops of fats into smaller ones and it provides a suitable pH for enzyme action.

Question 62

What is absorption?

Answer 62

Absorption is the movement of digested food molecules from the digestive system into the blood (glucose and amino acids) and lymph (fatty acids and glycerol). Nutrients are absorbed in the small intestine.

Question 63

Where is water absorbed?

Answer 63

Water is absorbed in both the small intestine and the colon but most absorption of water (around 80%) happens in the small intestine.

Question 64

How is the ileum adapted for absorption?

Answer 64

The ileum is adapted for absorption as it is very long and has highly folded surface with millions of villi. These adaptations increase the surface area of the ileum, allowing absorption to take place faster and more efficiently.

Question 65

What are villi?

Answer 65

Villi are tiny, finger life projections.

Question 66

How do villi increase absorption?

Answer 66

Microvilli on the surface of the villus further increases the surface area for faster absorption of nutrients. Wall of the villus is one cell thick meaning that there is only a short distance for absorption to happen by diffusion and active transport. Well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine in the blood. Lacteal runs though the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph.