Digestion Food and diet:
Summary Table of nutrients
Running Heart
Disease testing for starch
Food enters the body at the mouth (ingestion)
The food that we eat contain chemicals needed by our body. These chemicals are called nutrients
Before these
nutrients can be absorbed into the blood stream they need to be broken
down into simple chemicals.
This process is called DIGESTION and is
brought about by enzymes.
Digestion actually starts in the mouth as saliva contains an enzyme which turns STARCH into SUGAR.
After the food is digested the nutrients are absorbed into the blood
Most digestion and absorption takes place in the small intestine.
Unwanted food is then egested (removed) from the body through the anus.
The liver stores food and lets it slowly back into the blood as it is needed.
(the liver is also responsible for trying to remove toxins from the blood).
Soluble waste chemicals which pass into the blood are converted into urea and excreted (removed) by the kidneys (along with any excess water) and stored in the bladder as urine.
Summary showing the order of events:| Process: | Ingestion | Digestion | Absorption | Excretion |
| What happens | Taking in food | Breaking down food using enzymes | Nutrients entering the blood | Removal of waste products |
| Location | Mouth | Stomach and Intestines | Small intestine | Kidneys |
Diet
A diet is the type food we eat.
A balanced diet is selecting sensible foods so we have the right proportion of all the nutrients we need.
The table below shows the nutrients that need to be present in a balanced diet| Nutrient | Why the nutrient is needed | Example foods |
| Carbohydrate | The main source of ENERGY for movement, warmth, cell repair, growth | Sugar and starch eg potato, bread, |
| Fat | Energy. Easier for our body to store than carbohydrate. Helps insulate the body from cold. | Dairy food (milk, cheese), oils |
| Protein | Body building. eg muscle growth, Repairing and building cells. | Meat, soya, cheese |
| Vitamins | Needed in small amounts to keep our body healthy
eg Carrot (vit A) Marmite, bread (vit .B), Fresh fruit (vit C) Liver (vit D), Green veg. (vit.E). Vitamin. C helps stop a disease called scurvy |
Fresh fruit and vegetables. |
| Minerals | Needed to keep us healthy
eg calcium (strong bones): a lack of calcium can cause rickets. iron (making blood): a lack of iron can cause anaemia |
Milk and cheese (calcium); vegetables (eg spinach is rich in iron) |
| Dietary fibre* | Helps digestion. Helps reduce the risk of heart disease by lowering cholesterol. | Brown bread, vegetables, cereal |
| Water* | Water is the main part of all living cells. Our body is 75% water. | drinks , fruit |
* strictly speaking water and fibre are NOT nutrients.
Fibre contains no food value but helps us to digest food by providing bulk.
We lose water all the time (eg by sweating and breathing out water vapour) and it needs to be replaced. A lack of water will make us ill far quicker than lack of food.
Milk is an important food as it contains most nutrients. It is rich in calcium so is an important food for growing children, however it does not provide a balanced diet. Other foods are needed to provide those nutrients not in milk.
Our muscles move more and so need more food and oxygen from the blood.
This causes the following changes in our body:
1. Our heart pumps quicker to get the blood to the muscles quicker.
2. We breath faster to replace transfer more oxygen to the blood (and remove the waste carbon dioxide).
3. We sweat more. As the sweat evaporates it helps cool the body and remove excess heat.
Heart disease
Heart disease can be caused by too much fat which clogs the arteries reducing the flow of blood to the
heart. Exercise helps reduce the risk by speeding the flow up blood up which helps clear the arteries.
How to help reduce the risk of heart disease:
Testing
for
Starch
Add iodine solution
which turns a blue-black colour
We use this test when doing an experiment to show that a leave is carrying out
photosynthesis