AQA Biology Unit one Keeping healthy

Diet and exercise Regular exercise and a balanced diet are needed to keep

the body healthy. Too little food leads to a person being underweight and prone to certain types of illness, while too much food and not enough exercise leads to a person being overweight and other types of ill health.

Nutrients A mixture of different types of food in the correct amounts is

needed to maintain health. The main food groups are carbohydrates, fats and

proteins. This table summarises some typical sources of these

nutrients and why our bodies need them.

Carbohydratespotatoes, pasta, bread, bananas, sugar and rice

a source of energy for life processes

Fatscheese, butter, margarine and oils

a source of energy for life processes: fats are also needed to make cell membranes and to insulate our bodies

Proteinsmeat, fish, eggs and cheese

growth and repair - building cells

Mineral ions and vitamins are also important in a healthy diet. They are needed in small amounts for healthy functioning of the body.

small amounts for healthy functioning of the body. Imbalanced diets An imbalanced diet causes a person to become malnourished. For

example: too little food may lead to a person being underweight too much food may lead to a person being overweight. A poor diet may also lead to deficiency diseases. For example, too

little vitamin D in the diet can lead to rickets, which affects the proper growth of the skeleton. Type 2 diabetes is also a problem related to poor diet. Note that you do not need to know how the nutrients work or the effects of any particular deficiency in the diet for your exam.

Exercise If someone’s diet consists of food with a lower energy content than the

amount of energy their body uses, the person will lose body mass. Metabolic rate Respiration is a chemical reaction that allows cells to release energy

from food. The metabolic rate is the speed at which such chemical reactions take place in the body and varies because of several factors, including age, gender and inherited factors.

Metabolic rate is also affected by the: proportion of muscle to fat in the body amount of exercise and other physical activity. The metabolic rate increases as we exercise and stays high for a while

afterwards. People who exercise regularly are usually healthier than people who don't.

Other factors affect health too, including inherited factors. For example, the cholesterol level in the blood can affect health. Cholesterol is made in the liver and is needed for healthy cell membranes. However, too much cholesterol in the blood increases the risk of heart disease and diseased arteries.

Quick Test Q1

What is 'the metabolic rate'?

A ) The speed at which our food is digested B) The speed at which chemical reactions take place in our

bodies C) The speed at which we eat

Q2 After exercise: ? A) the metabolic rate stays permanently high B) the metabolic rate stays permanently low C) the metabolic rate stays high for a while

What is it best to have for a healthy heart?

A high proportion of HDL compared to LDL

A low proportion of HDL compared to LDL

A lot of cholesterol in the diet

Answers Q1 What is 'the metabolic rate'? The speed at which chemical reactions take place in our

bodies

Q2

After exercise: the metabolic rate stays high for a while

Q3

What is a feature of low-density lipoproteins (LDLs)?

A feature of LDLs is they carry cholesterol from the liver to the cells of the body.

Q4 What is it best to have for a healthy heart? It is best to have a high proportion of HDL compared to LDL

for a healthy heart.