Biology part 1a

Revision notes on the main points in Biology 1a.

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  • Created by: Harriet
  • Created on: 29-03-13 17:01

Diet

A balanced diet is key to keeping healthy

The main groups for a healthy diet are:

  • Carbohydrates - to release energy
  • Fats - to keep warm and release energy
  • protein - for growth, cell repair and cell replacment
  • fibre - to keep the digestive system working properly
  • vitamins and minerals - to keep you skin, bones, blood and everything else generally healthy
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Metabolic Rate

The amount of energy people needs varies, depending on who they are...

  •  You need energy to fuel chemical reactions inside your body. These reactions are called your metabolism and the speed at which they take place is called you metabolic rate.
  • Metabolic rate varies from person to person. This is partly because muscle needs more energy than fatty tissue, which means people with more muscle compared to fat in their body, will have a higher metabolic rate.
  • But bigger people need more energy too as they have more cells that use energy, so their metabolic rate will be higher. This means men tend to have a higher metabolic rate than women.
  • Regular exercise boosts your metabolic rate as it builds more muscle.

Your job can also affect how much energy a person needs...

  • People with more active jobs need more energy than those people whos job is quite inactive. As you move around your body needs more energy to keep all the chemical reactions happening.
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Factors Affecting Health

An unbalanced diet can affect your health...

  • If your diet is badly out of balanced you are malnourished.
  • Usually eating too much and lack of exercie is what leads to obesity, but it can also sometimes be hormonal.
  • Obesity can cause:
    • arthritis
    • type 2 diabetes
    • high blood pressure
    • heart disease
    • cance

Too much saturated fat is bad, it increases your blood cholesterol levels.

Eating too much salt is also bad - it causes high blood pressure and heart problems.

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Factors Affecting Health page 2

Eating too little can also cause problems:

People who don't eat enough also suffer from malnourishment, especially in developing countries. If a person is dangerously underweight, they are classed as anorexic. Problems caused my malnourishment depend on what part of the diet is lacking, but common affects are:

  • Slow growth (in children)
  • Fatigue
  • Irregular periods in women
  • Poor resistance to infection

Deficiency diseases are caused by a lack of vitamins and minerals in the diet. For example if a person doesn't eat enough vitamin C, then can get scurvy, which causes problems with your skin, joints and gums.
 

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Physical and Inherited Facors Affecting Health

Some physical factors - like not enough exercise - can affect your health:

  • People who exercise regularly are usually healthier than those who don't
  • Exercise increases the amount of energy used by the body and decreases the amount of stored fat. It also builds muscle so helps boost your metabolic rate.
  • This means if you exercise regularly you are less likely to suffer from obesity.
  • However just because you exercise regularly doesn't mean you ar healthy. Some people are physically fit but are also malnourished because their diet isnt balanced.

Inherited factors can also affect your health:

  • Metabolic rate can be affected by inherited factors - for example underactive thyroids are due to inherited factors, these lower your metabolic rate and can cause obesity.
  • Other people can inherit factors that affect their blood cholesterol. Cholesterol is a fatty substance that is essential for good health - it's found in every cell in your body. If your blood cholesterol levels are increased however, it can lead to health problems such as heart attacks.
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Slimming Diets

There are a lot of diets around that claim to make you lose weight (eg the Atkins Diet), however a lot of these don't actually work.

A common way to promote a new diet is to say "Celebrity A has lost x pounds using it!" But effectiveness in one person doesn't mean much. Only a large survey can tell us whether a diet is more or less effecive than just eating less and exercising more.

To lose weight all you need to do is take in less energy than you use. So diets and slimming products only work if you:

  • eat less fat or carbohydrate (so that you take in less energy), or
  • do more exercise (so you use more energy

Some claims may be true but also misleading. For example low fat bars may be low in fat, but if you do nothing else to change your diet, you might not lose weight as you still may be taking in too much energy.

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