Chapter 7

Question 1

State what is meant by the term balanced diet for humans

Answer 1

an adequate intake of the biological molecules and energy needed to sustain the body and ensure good health and growth.

Question 2

Explain how age, gender and activity affect the dietary needs of humans including during pregnancy and whilst breast-feeding

Answer 2

Age:
Children need more energy because they have BMR. A child may weigh less but they need energy for growing. The opposite for older people.

Gender:
woman have a higher fat content than men in their bodies. fat tissue has a lower metabolic rate than muscle, so women have a lower energy requirement than men.

Activity:
People who are in more rigorous sports and physical jobs require higher energy and protein diets.

Pregnancy:
Woman need extra nutrients during pregnancy for their child and breast-feeding.

Question 3

Describe the effects of malnutrition in relation to starvation, constipation, coronary heart disease, obesity and scurvy

Answer 3

If individuals do not eat enough food from malnutrition, this can lead to starvation.
If an individual eats too much food with saturated fats and high energy contents, they can become obese.
If a person does not eat enough fibres, they can go through constipation (when the movement of food is too slow in the alimentary canal)
If an individual lacks enough vitamin C, they would get scurvy. This can cause bleeding in part of the body like the gums.
If an individual produces too much cholesterol, it can line the lining of the coronary artery; making it smaller and increasing the blood pressure.

Question 4

List the principal sources of, and describe the dietary importance of carbohydrates

Answer 4

Sources:
Pasta, bread, potatoes

Importance:
They provide us a ready source of energy that is easily respired.

Question 5

List the principal sources of, and describe the dietary importance of fats

Answer 5

Sources:
butter, cheese, nuts

Importance:
They are a long-term energy store and it is stored under the skin and around the heart and kidneys to protect our organs and work as thermal insulators.

Question 6

List the principal sources of, and describe the dietary importance of proteins

Answer 6

Sources:
meat, milk, nuts, eggs

Importance:
Cell membranes and cytoplasm need to be made out of protein and it is needed to replace old damaged cells. Overall, it is important for growth and repair in organisms

Question 7

List the principal sources of, and describe the dietary importance of vitamins

Answer 7

Sources:
VC - oranges, lemons, citrus fruits
VD - fish oil, milk, butter, also made by the skin from the sun

Importance:
VC - helps with tissue repair and resistance to disease
VD - Strengthens bones and teeth

Question 8

List the principal sources of, and describe the dietary importance of mineral salts (calcium and iron)

Answer 8

Sources:
Iron - liver, meat, cocoa, eggs
Calcium - milk, fish, green vegetables

Importance:
Iron - used in the formation of haemoglobin in the blood
Calcium - strengthens bones and teeth

Question 9

List the principal sources of, and describe the dietary importance of fibre (roughage)

Answer 9

Sources:
cabbage, sweetcorn, celery

Importance:
it helps to pass food down the gut from the mouth to the anus.

Question 10

List the principal sources of, and describe the dietary importance of water

Answer 10

Source:
freshwater lakes, seas

Importance:
Water is needed for chemical reactions to take place in solution. Blood transports substances dissolved in water, urea leaves with water as urine

Question 11

Explain the causes and effects of vitamin D and iron deficiencies

Answer 11

VD deficiency from lacking of eating citrus fruits causes soft bones and rickets and iron deficiency from lack of iron rich food causes tiredness and anaemia.

Question 12

Explain the causes and effects of protein-energy malnutrition, e.g. kwashiorkor and marasmus

Answer 12

marasmus is caused by undernutrition and kwashiorkor is caused by undernutrition of proteins, PEM (protein energy malnutrition), causing the cells of the pancreas and intestine to die. So fewer digestive enzymes are released and the surface area for absorption is reduced. Therefore the body uses protein as an energy source. For kwashiorkor, it causes oedema, sparse, dry hair, flaky skin and fat accumulation in the live. For marasmus, it causes low body mass, thin arms and legs, little muscle or fat, wizened old looking face.

Question 13

ingestion

Answer 13

the taking of substances, e.g. food and drink, into the body through the mouth

Question 14

mechanical digestion

Answer 14

the breakdown of food into smaller pieces without chemical change to the food molecules

Question 15

chemical digestion

Answer 15

the breakdown of large, insoluble molecules into small, soluble molecules

Question 16

absorption

Answer 16

the movement of small food molecules and ions through the wall of the intestine into the blood

Question 17

assimilation

Answer 17

the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells

Question 18

egestion

Answer 18

the passing out of food that has not been digested or absorbed, as faeces, through the anus

Question 19

Describe diarrhoea

Answer 19

the loss of watery faeces

Question 20

Outline the treatment of diarrhoea using oral

rehydration therapy

Answer 20

Diarrhoea causes the lose of salts and minerals and if you eat it will simply pass through. Therefore you need oral rehydration therapy in order to gain the minerals and salts you need to survive. Therefore, water containing salts and minerals is fed for the person so it can be taken in by diffusion, without passing through without absorption.

Question 21

Describe cholera

Answer 21

a disease caused by a bacterium which produces a toxin that causes secretion of chloride ions into the small intestine, causing osmotic movement of water into the gut, causing diarrhoea, dehydration and loss of salts from blood

Question 22

Identify the main regions of the alimentary canal and associated organs

Answer 22

mouth –> salivary glands –> oesophagus –> stomach –> bile duct (liver, gallbladder, pancreas) –> small intestine (duodenum and ileum) –> large intestine –> colon, rectum, anus

Question 23

Describe the functions of the regions of the alimentary canal listed above, in relation to ingestion, digestion, absorption, assimilation and egestion of food
Supplement

Answer 23

Ingestion - taking of substances into the body through the mouth.
Digestion - breaking down of large insoluble molecules into small soluble molecules so they can pass through the gut wall into the blood
Absorption - the movement of small food molecules and ions through the wall of the intestine into the blood
Assimilation - the movement of digestive food molecules into the cells of the body where they are used becoming part of the cells
Egestion - the passing out of food that has not been digested or absorbed, as faeces through the anus

Question 24

Identify the types of human teeth

Answer 24

incisors (chisel), canines (fangs), premolars (cusps) and molars (large cusps)

Question 25

Describe the structure of human teeth

Answer 25

There is the hard, outer layer of the crown called the enamel, there is the softer “bone” dentine, the pulp is a space in the tooth containing nerves and blood vessels, the nerves connect from the pulp through the gums and cement is a layer that fixes the root of the tooth into a bony socket in the jaw. There is also the gums, that keep your teeth in place and form a barrier between it and bacteria.

Question 26

Describe the functions of the types of human teeth in mechanical digestion of food

Answer 26

• incisors are for biting and cutting
• canines are for piercing and tearing
• premolars are for grinding and chewing
• molars are for chewing up food

Question 27

State the causes of dental decay

Answer 27

there is a coating of bacteria and food on your teeth. When there is a lot of sugars in the food, the bacteria respiring anaerobically sugars in the food produce an acid which dissolves the enamel and dentine. When it dissolving the tooth, that is tooth decay.

Question 28

Describe the proper care of teeth

Answer 28

You should brush 2 times a day and floss and you should eat less food containing sugar.

Question 29

State the significance of chemical digestion in the alimentary canal

Answer 29

Chemical digestion in the alimentary canal produces small, soluble molecules (using enzymes) that can be absorbed by the blood.

Question 30

State the functions of the enzymes in chemical digestion

Answer 30

• amylase breaks down starch to simpler
  sugars
• protease breaks down protein to amino acids
• lipase breaks down fats to fatty acids and glycerol

Question 31

State where, in the alimentary canal, amylase, protease and lipase are secreted

Answer 31

Amylase is secreted by the salivary glands in the mouth and pancreas, protease is secreted in the stomach and lipase is secreted in the pancreas.

Question 32

State the functions of the hydrochloric acid in gastric juice

Answer 32

it is responsible for killing bacteria in food, denaturing enzymes in harmful microorganisms in food and giving the optimum pH for pepsin/enzyme activity

Question 33

Describe the digestion of starch in the alimentary canal

Answer 33

Amylase is secreted into the alimentary canal and breaks down starch to maltose; then maltose is broken down by maltase to glucose on the membranes of the epithelium lining the small intestine. Which is then absorbed.

Question 34

Describe pepsin and trypsin

Answer 34

two protease enzymes that function in different parts of the alimentary canal. With pepsin in the stomach that breaks down protein into polypeptides and trypsin in the small intestine that breaks down proteins and polypeptides.

Question 35

Outline the role of bile

Answer 35

it neutralises the acidic mixture of food and gastric juices entering the duodenum from the stomach, it provides a suitable pH for enzyme action and emulsifies fats to increase the surface area for the chemical digestion of fat to fatty acids and glycerol by lipase

Question 36

What is the small intestine?

Answer 36

the region for the absorption of digested food

Question 37

Explain the significance of villi and microvilli in increasing the internal surface area of the small intestine

Answer 37

the villus finger shape increases the surface area of the small intestine to allow efficient nutrient absorption. They are also very thin for this efficiency. The microvilli are also microscopic projections which further increase the surface area.

Question 38

Describe the structure of a villus

Answer 38

the villus has a thin 1-cell thick wall and inside has one lacteal (lymph capillary) and a long blood capillary that surrounds it. These two can move to the left where the lymph fluid carries away fatty acids and glycerol and blood takes food molecules. They can also move from the left where the lymph comes to the villus and the blood is coming in to pick up food molecules.

Question 39

Describe the roles of capillaries and lacteals

in villi

Answer 39

The capillaries contain the blood and the lacteals contain the lymph fluid. The blood absorbs amino acids and sugar molecules in the small intestine and the lacteal absorbs the fatty acids and glycerol. This prevents too much fat exerting the blood stream too quickly.

Question 40

Where is water most absorbed in the digestive system?

Answer 40

water is absorbed in both the small intestine and the colon, but that most absorption of water happens in the small intestine

Question 41

Bile

Answer 41

emulsifies fats and neutralises the acid from the stomach