Ch.2.a healthy diet

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Information about Ch.2.a healthy diet

Published on November 27, 2016

Author: reem_bakr


1. A healthy diet Chapter 2 Biology

2. Nutrients • A chemical that is needed by the body to keep it in good health is called a nutrient. • The human body needs a large number of different nutrients to keep it healthy. • Can you list the five groups of nutrients? • They are: Carbohydrates Fats Proteins Vitamins and Minerals

3. • In addition to these nutrients the body also needs water (70% of the body) • Water is important as it: (a) provides support for the cells (b) carries dissolved materials around the body and (c) helps in controlling body temperature. • Fibre is also needed by the body.

4. A healthy diet • The body needs the range of nutrients mentioned previously to keep healthy. • Everyone should eat a balanced diet to eats those nutrients. • Regular eating of high energy snacks (sweets, chocolate, ice-cream and chips) between meals unbalances the diet and can lead to the body becoming overweight. • High energy snacks should be kept to a minimum. • Overweight people have to make more effort than normal to move so they tend to exercise less, which leads to heart problems over time. • A food guide pyramid reminds you that you should eat large amounts of foods at the bottom and small amounts from foods at the top.

5. 1) Carbohydrates • Structure: 1) Made from the elements of carbon, hydrogen and oxygen. 2) These atoms are linked together to form molecules of sugar • There are different kinds of sugar molecules but the most commonly occurring is glucose. • Glucose molecules link together to form starch. • Glucose and starch are the most commonly known molecules. • Other examples of known carbohydrates is cellulose.

6. 2) Fats • Structure: Made large nos. of carbon and hydrogen atoms linked into long chains together with a few oxygen atoms. • There are 2 kinds of fat: (a) Solid fat: Produced by animals ex. Lard (b) Liquid fat: Oil produced by plants. Ex. Sunflower oil.

7. 3) Proteins • Structure: Made of carbon, hydrogen, oxygen and nitrogen atoms. Some of the proteins also have sulphur atoms. The atoms of these elements join together to form amino acids. Amino acids join together to form proteins.

8. 4) Vitamins • Structure: Vitamins are needed in small amounts. • When vitamins were first discovered they were named after letters of the alphabet. • Later on, when the chemical structure of the molecules were found out, they were given chemical names.

9. 5) Minerals • The body needs 20 minerals. • Some minerals such as calcium are needed in large amounts. • Other minerals like zinc are needed in tiny amounts (trace elements)

10. How the body uses nutrients

11. 1) Carbohydrates • Carbohydrates contain a large amount of energy that can be released quickly. • They are used as a fuel to keep the body alive.

12. 2) Fibre • Cellulose is a carbohydrate which makes up the walls of plant cells. • The cellulose in food is known as the dietary fibre. • It is found in foods such as: - Whole meal bread - Fruits and - Vegetables

13. • We cannot digest fibre but it helps move food along the intestines. • As the fibre moves through the large intestine bacteria feeds on it (this adds bulk to the food). • This helps the muscles of the large intestine push the food along. • Fibres also take up water like a sponge and this makes the undigested foods which form the faeces soft and easy to release from the body. • If a person’s diet lacks fibre, he may suffer from bowel problems such as constipation.

14. 3) Fats • Fat are needed for the formation of cell membranes. • They contain even larger amounts of energy than carbohydrates, but, energy is released slower. • In mammals fat forms a layer under the skin to insulate the mammal and keep them warm in cool conditions

15. 4) Proteins • Proteins are needed for building the structures inside cells and in the formation of tissues and organs. • They are needed for the repair of the body, to repair damages parts (cut skin) and to replace tissues that are constantly being worn away (ex. Lining of the mouth) • Enzymes are also made up of proteins.

16. 5) Minerals • Each mineral has more than one use. • Example: 1) Calcium: a) make strong bones and teeth. b) Needed to make muscles work. c) Helps blood to clot. (Lack of calcium can lead to weak bones and high blood pressure) 2) Iron: Used to make haemoglobin.

17. 6) Water • About 70% of a humans body is water. • The body can survive only for a few days without a drink of water. • Every chemical reaction in the body takes place in water. • The blood is made mainly of water (transports blood components around the body). • Water cools down the body by evaporation of sweat from the skin.

18. 7) Vitamins • Each vitamin has one or more use in the body.

19. Vitamin Effect on the body Good sources A 1) Allow the eyes to see in dim light 2) Involved in making the mucus lining to the respiratory , digestive and excretory systems (protects against infection from micro-organisms) Milk, liver, cod- liver oil B₁ (Thiamin) 1) Prevents digestive disorders 2) Prevents beriberi disease Bread, milk, brown rice, soybean, potato C Prevents scurvy disease (gums bleed and circulatory system is damaged) Blackcurrant, orange, lemon, papaya, guava D Prevents rickets disease (bones become soft and leg bones of children may bend).

20. The amount of nutrients in food

21. Keeping a balance • Amount of nutrients in food has been found out by experiments and calculation. • The amounts are usually for 100 g of food. • To remain healthy a person must eat a balanced diet (all nutrients)

22. Malnutrition • If a diet provides too few nutrients or too many nutrients malnutrition occurs. • Lack of vit. C causes scurvy. • Lack of iron causes anemia. • Too much protein is broken down and converted into glycogen (carb.) which is stored in the liver and part is turned into urea (excreted in urine) • Too much carbohydrates and fats causes obesity (extremely overweight). • Anorexia nervosa (Fear of gaining weight and eat a little) can cause death.

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