IGCSE Revision- Biology
Chapter 7- Human nutrition
7.1 Diet
- Humans need six type of nutrients in their diet: Carbohydrates, proteins, fats,
vitamins, minerals and water
- A diet should also include fibre
- A diet that includes all these six things is called a balanced diet
ENERGY NEEDS
- One gram of fat contains twice as much energy as one gram of protein or
carbohydrate
- If a woman is pregnant she will eat more, to make sure the baby gets enough
calcium and iron
- People in their 50s and 60s wil eat less because their metabolism slows down
NUTRIENTS
- To make sure you eat a balanced diet, you have to eat foods that contain fat,
protein and carbohydrate
- You also need each kind of vitamin and mineral, fibre and water
CARBOHYDRATES
- Carbohydrates are needed for energy
- Staple foods include potatoes, wheat, rice and maize
- We also eat carbohydrates in sweet foods
FATS AND OILS
- Fats and oils are needed to make energy and to make cell membranes
- We store excess fat and oil under the skin, in adipose tissue
- Here is acts as an insulator, reducing heat loss from the body to the air
- It can also form a layer around body organs such as the kidneys, providing
mechanical protection for them
- We can get fat from cooking oils, meat, eggs, dairy products and oily fish
PROTEINS
- Proteins are needed to build new cells, or growth
- They are also used to make proteins, including haemoglobin, insulin and
antibodies
- We get proteins from meat, fish, eggs, dairy products, peas and beans, nuts and
seeds
VITAMINS
- Vitamins are organic substances which are only needed in tiny amounts
- If you don’t have enough vitamins you can have a deficiency disease
- Vitamin D:
- In butter egg yolk, made by skin when light falls on it
, - It is needed because it helps calcium to be absorbed and for making bones and
teeth
- Deficiency disease: Rickets. Rickets causes bones to become sot and
deformed; this disease was common in young children during the industrial
areas, who rarely go out into the sunshine
- Vitamin C:
- In citrus fruits, raw vegetables
- It is needed to make stretchy protein collagen, found in skin and other tissues;
keeps tissues in good repair
- Deficiency disease: Scurvy. Scurvy causes pain in joints and muscles, and
bleeding from gums and other places; this used to be a common disease of
sailors
MINERALS
- Minerals are inorganic substances. Only small amounts are needed for a
balanced diet
- Iron:
- In liver, red meat, egg yolk, dark green vegetables
- It is need for making haemoglobin
- Deficiency disease: Anaemia. Anaemia is when there are not enough red blood
cells so the tissues do not get enough oxygen delivered to them
- Calcium:
- In milk and other dairy products and bread
- It is needed for bones and teeth; for blood clotting
- Deficiency disease: Brittle bones and teeth; poor blood clotting
FIBRES
- Fibre helps to keep the alimentary canal working properly
- Peristalsis: Rhythmic muscular contractions that move food through the
alimentary canal
- The muscles are stimulated to do this when there is food in the alimentary canal
- Fibre helps to prevent constipation and keeps the alimentary canal working
- Sources of fibre: cereal grains, oats, wheat, barley (this is called bran), brown or
unpolished rice
WATER
- More than 60% of the human body is water
- Inside our cells, chemical reactions are happening all the time. They can only
take place if the chemicals are in a solution. It the cell dries out, the reactions
stop, and the cell dies
- The liquid part of the blood, plasma, is also mostly water. It contains many
substances dissolved in it, which is carried around the body. Water is also
Chapter 7- Human nutrition
7.1 Diet
- Humans need six type of nutrients in their diet: Carbohydrates, proteins, fats,
vitamins, minerals and water
- A diet should also include fibre
- A diet that includes all these six things is called a balanced diet
ENERGY NEEDS
- One gram of fat contains twice as much energy as one gram of protein or
carbohydrate
- If a woman is pregnant she will eat more, to make sure the baby gets enough
calcium and iron
- People in their 50s and 60s wil eat less because their metabolism slows down
NUTRIENTS
- To make sure you eat a balanced diet, you have to eat foods that contain fat,
protein and carbohydrate
- You also need each kind of vitamin and mineral, fibre and water
CARBOHYDRATES
- Carbohydrates are needed for energy
- Staple foods include potatoes, wheat, rice and maize
- We also eat carbohydrates in sweet foods
FATS AND OILS
- Fats and oils are needed to make energy and to make cell membranes
- We store excess fat and oil under the skin, in adipose tissue
- Here is acts as an insulator, reducing heat loss from the body to the air
- It can also form a layer around body organs such as the kidneys, providing
mechanical protection for them
- We can get fat from cooking oils, meat, eggs, dairy products and oily fish
PROTEINS
- Proteins are needed to build new cells, or growth
- They are also used to make proteins, including haemoglobin, insulin and
antibodies
- We get proteins from meat, fish, eggs, dairy products, peas and beans, nuts and
seeds
VITAMINS
- Vitamins are organic substances which are only needed in tiny amounts
- If you don’t have enough vitamins you can have a deficiency disease
- Vitamin D:
- In butter egg yolk, made by skin when light falls on it
, - It is needed because it helps calcium to be absorbed and for making bones and
teeth
- Deficiency disease: Rickets. Rickets causes bones to become sot and
deformed; this disease was common in young children during the industrial
areas, who rarely go out into the sunshine
- Vitamin C:
- In citrus fruits, raw vegetables
- It is needed to make stretchy protein collagen, found in skin and other tissues;
keeps tissues in good repair
- Deficiency disease: Scurvy. Scurvy causes pain in joints and muscles, and
bleeding from gums and other places; this used to be a common disease of
sailors
MINERALS
- Minerals are inorganic substances. Only small amounts are needed for a
balanced diet
- Iron:
- In liver, red meat, egg yolk, dark green vegetables
- It is need for making haemoglobin
- Deficiency disease: Anaemia. Anaemia is when there are not enough red blood
cells so the tissues do not get enough oxygen delivered to them
- Calcium:
- In milk and other dairy products and bread
- It is needed for bones and teeth; for blood clotting
- Deficiency disease: Brittle bones and teeth; poor blood clotting
FIBRES
- Fibre helps to keep the alimentary canal working properly
- Peristalsis: Rhythmic muscular contractions that move food through the
alimentary canal
- The muscles are stimulated to do this when there is food in the alimentary canal
- Fibre helps to prevent constipation and keeps the alimentary canal working
- Sources of fibre: cereal grains, oats, wheat, barley (this is called bran), brown or
unpolished rice
WATER
- More than 60% of the human body is water
- Inside our cells, chemical reactions are happening all the time. They can only
take place if the chemicals are in a solution. It the cell dries out, the reactions
stop, and the cell dies
- The liquid part of the blood, plasma, is also mostly water. It contains many
substances dissolved in it, which is carried around the body. Water is also
