human nutrition

Question 1

balanced diet

Answer 1

A balanced diet is a diet in which all the components needed to maintain health are present in appropriate proportions.

Question 2

The necessary food groups are:

Answer 2

Carbohydrates Proteins Lipids Vitamins Minerals Dietary Fibre Water

Question 3

Answer 3

Question 4

Answer 4

Question 6

Answer 6

Question 7

There are different types of malnutrition depending on the cause of the imbalance

Answer 7

They include:

Starvation

Coronary heart disease

Constipation

Obesity

Question 8

Protein Energy Malnutrition

Answer 8

In many countries in the world, droughts, natural disasters, wars and a poor economy can lead to mass malnutrition in large areas of the country

The two types of malnutrition most common in these situations are termed ‘protein energy malnutrition’ (PEM)and they are:Kwashiorkor – caused by a lack of protein in the diet, most common in children under 2.

Often caused by poverty as high protein foods tend to be more expensive and scarcer.

Children suffering from kwashiorkor are always underweight for their age but they often have a swollen abdomen as their diet may contain a lot of carbohydrate

Marasmus – the most severe form of PEM, where there is a lack of both protein and energy in the diet.

People suffering from this have a much lower body weight than normal and look emaciated

Question 9

Dietary Needs of Different Individuals

Answer 9

Question 10

Food taken into the body goes through 5 different stages during its passage through the alimentary canal (the gut)

Answer 10

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

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

Chemical digestion – the breakdown of large, insoluble molecules into small, soluble molecules

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

Assimilation – the movement of digested 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 11

Ingestion

Answer 11

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

Question 12

Mechanical digestion

Answer 12

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

Question 13

Chemical digestion

Answer 13

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

Question 14

Absorption

Answer 14

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

Question 15

Assimilation

Answer 15

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

Question 16

Egestion

Answer 16

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

Question 17

Answer 17

Question 18

Answer 18

Question 19

Answer 19

Question 20

Answer 20

Question 21

Answer 21

Question 22

Answer 22

Question 23

Answer 23

Question 24

Diarrhoea Causes and Treatment

Answer 24

Diarrhoea is the loss of watery faeces from the anus

If it is severe and continues for a long time, it can lead to death

Severe diarrhoea can cause the loss of significant amounts of water and ions from the body, causing the tissues and organs to stop working properly

It can be effectively treated by oral rehydration therapy

This is a drink with a small amount of salt and sugar dissolved in it

There are many causes of diarrhoea, one of which is infection with Vibrio cholerae bacteria, which causes the disease cholera

Question 25

How does Vibrio Cholerae Cause Diarrhoea?

Answer 25

ingested via infected water or food, if it enters the small intestine it can cause illness in the following way:

Bacteria attach to the wall of the small intestine

They produce a toxin

The toxin stimulates the cells lining the intestine to release chloride ions from inside the cells into the lumen of the intestine

The chloride ions accumulate in the lumen of the small intestine and lower the water potential there

Once the water potential is lower than that of the cells lining the intestine, water starts to move out of the cells into the intestine (by osmosis)

Large quantities of water are lost from the body in watery faeces

The blood contains too little chloride ions and water

Question 26

mechanical digestion is mainly carried out by

Answer 26

the chewing action of the teeth, the churning action of the stomach and the emulsification of fats by bile in the duodenum

Question 27

They are used for

Answer 27

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

Question 28

Incisors

Answer 28

chisel shaped for biting and cutting

Question 29

Canines

Answer 29

pointed for tearing, holding and biting

Question 30

Premolars and molars

Answer 30

larger, flat surfaces with ridges at the edges for chewing and grinding up food

Question 31

Answer 31

Question 32

Dental Decay

Answer 32

Tooth decay and gum disease are both caused by bacteria

Many bacteria live in the mouth and most are harmless, however some form a sticky film with saliva, called plaque, which coats teeth and the areas where they attach to gums

To begin with, plaque is soft and easy to remove, however if it hardens and forms tartar, it cannot be removed by brushing

Tartar around the edges of teeth and gums can allow bacteria to work their way into roots, causing gum disease and loss of teeth

If sugar is left in the mouth after eating, bacteria in plaque will feed on it

They use it in respiration and turn it into acids

The acids gradually dissolve the enamel coating of the teeth, working its way into the dentine

Dentine is softer than enamel and so dissolves more easily and quickly

This is tooth decay and if not dealt with, can cause painful infections and loss of teeth

Question 33

Dental Health

Answer 33

Reducing the amount of sugar eaten can prevent tooth decay

Brushing teeth regularly removes the buildup of plaque that can cause gum disease and removes the sugars in the mouth so bacteria cannot turn them into acids and cause tooth decay

Teeth should be brushed with a fluoride toothpaste as this helps to strengthen enamel and reduce damage from acids

Regular visits to a dentist ensures that any signs of gum disease or tooth decay can be dealt with promptly

Question 34

The purpose of digestion is to

Answer 34

break down large, insoluble molecules (carbohydrates, proteins and lipids) into small, soluble molecules that can be absorbed into the bloodstream

Question 35

Digestion mainly takes place chemically, where

Answer 35

bonds holding the large molecules together are broken to make smaller and smaller molecules

Question 36

Chemical digestion is controlled by …which are produced in different areas of the… system

Answer 36

• enzymes
• digestive

Question 37

There are three main types of digestive enzymes

Answer 37

carbohydrases, proteases and lipases

Question 38

Carbohydrases

Answer 38

Amylase is secreted into the alimentary canal in the mouth and the duodenum (from the pancreas) and digests starch to maltose (a disaccharide)

Maltose is digested by the enzyme maltase into glucose on the membranes of the epithelium lining the small intestine

Question 39

Proteases

Answer 39

Protein digestion takes place in the stomach and duodenum with two main enzymes produced:

Pepsin is produced in the stomach

Trypsin is produced in the pancreas and secreted into the duodenum

Question 40

Lipases

Answer 40

Lipase enzymes are produced in the pancreas and secreted into the duodenum

They digest lipids into fatty acids and glycerol

The digestion of fats (lipids) to fatty acids and glycerol

Question 41

The Role of Hydrochloric Acid

Answer 41

The stomach produces several fluids which together are known as gastric juice

One of the fluids produced is hydrochloric acid

This kills bacteria in food and gives an acid pH for enzymes to work in the stomach

Question 42

How is a Low pH Helpful in the Stomach?

Answer 42

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, produced in the stomach, is an example of an enzyme which has a very low optimum pH – around pH 2

The hydrochloric acid produced in the stomach ensures that conditions in the stomach remain within the optimum range for pepsin to work at its fastest rate

Question 43

The Role of Bile

Answer 43

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

Bile production and secretion

Bile has two main roles:

It is alkaline to neutralise the hydrochloric acid which comes from the stomach. The enzymes in the small intestine have a higher (more alkaline) optimum pH than those in the stomach

It breaks down large drops of fat into smaller ones. This is known as emulsification. The larger surface area allows lipase to chemically break down the lipid into glycerol and fatty acids faster.

Question 44

emulsification is an example of …digestion,

Answer 44

mechanical

Question 45

How is the Ileum Adapted for Absorption?

Answer 45

The ileum is adapted for absorption as it is very long and has a highly folded surface with millions of villi (tiny, finger like projections)

These adaptations massively increase the surface area of the ileum, allowing absorption to take place faster and more efficiently

Question 46

Structure and Adaptations of a Villi

Answer 46

Microvilli on the surface of the villus further increase surface area for faster absorption of nutrients

Wall of 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 through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph

Question 47

Structure and Adaptations of a Villus

Answer 47