Chapter 5 Nutrition - Lecture Notes
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Jurongville Secondary School Secondary 3 Express Biology Notes Syllabus 5100 Name: _________________________ (
)
Class: Sec 3___ Chapter 4: 4.1
Date: ____________
Nutrition
Food: Its uses and components • •
•
• Class
Food: A store of raw materials and potential energy. Organisms need food: o As a source of energy for the chemical reactions that take place in the body to keep it alive and active o For growth provide substances needed for making new cells and tissues o For making important chemicals in the body e.g haemoglobin, enzymes, hormones o For maintaining health Food is made of: o Nutrients = Carbohydrates + Fats & Oils + Proteins + Vitamins (all Organic) + Minerals (Inorganic) o Water o Fibre Organic matter / substance Contains Carbon Components
Sources
1
Importance
Carbohydrates (contain C, H, O)
Monosaccharides (simple sugars)
(H: O ratio = 2:1)
Disaccharides (Complex sugars) o
Formed when 2 simple sugars combine with elimination of a water molecule
Polysaccharides (Macromolecules) Made up of thousands of simple sugar units (glucose) Components Fats: solid at r.t.p Oils: liquid at r.t.p o
Class Fats (contain C, H, O), but less O compared to Carbohydrates
Fats = Fatty acids + Glycerol
Examples: o Glucose o Fructose o Galactose o Reducing sugars (sweet fruits & honeys)
o
Examples: o Maltose (Reducing) = Glucose + Glucose
o
o
Made up of amino acids (a.a) (22 types)
o
Lactose (Reducing) = Glucose + Galactose
•
Sucrose (nonreducing) = Glucose + Fructose Examples: o Starch (green plts) o Glycogen (animals) o Cellulose (plants) In each, the glucose is linked differently Sources o Meat, Milk, lard, butter, egg yolk (from animals) o Oils in nuts and seeds (from plants) o
(H:O > 2:1) Proteins (contain C, H, O, N)
o
Main source of energy To form supporting structures (eg. Cellulose cell wall in plts) Converted to other organic compounds eg. Fats & amino acids For formation of nucleic acids (DNA)
o
Each protein is unique o may contain some or all of the amino acid molecules the way each a.a is arranged determines what type of protein it is
Lean meat, fish, eggs, milk, cheese (from animals) Beans & Cereals (from plants)
Essential a.a: cannot be made by the body, must be obtained from food
2
Importance o As a source of energy o To form part of the cell membrane o As solvents for fatsoluble vitamins and some hormones o As an insulator to prevent excessive heat loss from skin o For growth & repair of worn-out parts o Source of energy o For producing enzymes, hormones, antibody, haemoglobin, etc
Vitamins & Minerals
Refer to handout
Refer to handout
Needed in small amounts for the healthy functioning of our body To prevent deficiency diseases Many vitamins also function as coenzymes needed for chemical reaction occurring in cells
o
o o
4.2 Tests to show presence of carbohydrates, fats and proteins Test For
Chemical reagent used Iodine solution
Starch Reducing sugars (maltose & Glucose) Fats
Benedict’s Solution Ethanol
Test For
Chemical reagent used Biuret solution
Proteins
How test is carried out Put a few drops on the substance to be tested Add equal volume to a solution of the substance to be tested and heat in water bath at 90°C A dried sample of the substance to be tested is mixed in ethanol. Mixture is then poured into a test-tube of water How test is carried out Add 1cm3 of sodium hydroxide to 2cm3 of the substance to be tested. Shake thoroughly. Then add 1% Copper sulphate solution drop by drop, shaking after each drop
Result Blue-black colour is starch is present (brown if absent) Red, orange, yellow or green precipitate if present (Blue if absent) Water turns cloudy if fat is present. (White emulsion) (Remains clear is absent) Result Violet colour observed if proteins is present. (Remains blue if absent)
4.3 Balanced Diet • It is a diet which contains o
Enough carbohydrates and fats to meet our energy needs
o
Enough proteins of the right kind (contains all the essential a. a) for growth and repair
3
o •
Enough vitamins, minerals, water and fibre for maintaining good health
Energy Value of Food 1g of Carbohydrate 1g of Protein 1g of Fats
•
16 kJ of energy 17 kJ of energy 38 kJ of energy
The dietary requirement of an individual is dependent on o
Activity: The more active a person is, the greater the amount of energy needed
o
Age: Teenagers/young adults need more energy per kg body mass than young children and old people
o
Sex: For the same body size and age, men use up more energy than women
4
)
Class: Sec 3___ Chapter 4: 4.1
Date: ____________
Nutrition
Food: Its uses and components • •
•
• Class
Food: A store of raw materials and potential energy. Organisms need food: o As a source of energy for the chemical reactions that take place in the body to keep it alive and active o For growth provide substances needed for making new cells and tissues o For making important chemicals in the body e.g haemoglobin, enzymes, hormones o For maintaining health Food is made of: o Nutrients = Carbohydrates + Fats & Oils + Proteins + Vitamins (all Organic) + Minerals (Inorganic) o Water o Fibre Organic matter / substance Contains Carbon Components
Sources
1
Importance
Carbohydrates (contain C, H, O)
Monosaccharides (simple sugars)
(H: O ratio = 2:1)
Disaccharides (Complex sugars) o
Formed when 2 simple sugars combine with elimination of a water molecule
Polysaccharides (Macromolecules) Made up of thousands of simple sugar units (glucose) Components Fats: solid at r.t.p Oils: liquid at r.t.p o
Class Fats (contain C, H, O), but less O compared to Carbohydrates
Fats = Fatty acids + Glycerol
Examples: o Glucose o Fructose o Galactose o Reducing sugars (sweet fruits & honeys)
o
Examples: o Maltose (Reducing) = Glucose + Glucose
o
o
Made up of amino acids (a.a) (22 types)
o
Lactose (Reducing) = Glucose + Galactose
•
Sucrose (nonreducing) = Glucose + Fructose Examples: o Starch (green plts) o Glycogen (animals) o Cellulose (plants) In each, the glucose is linked differently Sources o Meat, Milk, lard, butter, egg yolk (from animals) o Oils in nuts and seeds (from plants) o
(H:O > 2:1) Proteins (contain C, H, O, N)
o
Main source of energy To form supporting structures (eg. Cellulose cell wall in plts) Converted to other organic compounds eg. Fats & amino acids For formation of nucleic acids (DNA)
o
Each protein is unique o may contain some or all of the amino acid molecules the way each a.a is arranged determines what type of protein it is
Lean meat, fish, eggs, milk, cheese (from animals) Beans & Cereals (from plants)
Essential a.a: cannot be made by the body, must be obtained from food
2
Importance o As a source of energy o To form part of the cell membrane o As solvents for fatsoluble vitamins and some hormones o As an insulator to prevent excessive heat loss from skin o For growth & repair of worn-out parts o Source of energy o For producing enzymes, hormones, antibody, haemoglobin, etc
Vitamins & Minerals
Refer to handout
Refer to handout
Needed in small amounts for the healthy functioning of our body To prevent deficiency diseases Many vitamins also function as coenzymes needed for chemical reaction occurring in cells
o
o o
4.2 Tests to show presence of carbohydrates, fats and proteins Test For
Chemical reagent used Iodine solution
Starch Reducing sugars (maltose & Glucose) Fats
Benedict’s Solution Ethanol
Test For
Chemical reagent used Biuret solution
Proteins
How test is carried out Put a few drops on the substance to be tested Add equal volume to a solution of the substance to be tested and heat in water bath at 90°C A dried sample of the substance to be tested is mixed in ethanol. Mixture is then poured into a test-tube of water How test is carried out Add 1cm3 of sodium hydroxide to 2cm3 of the substance to be tested. Shake thoroughly. Then add 1% Copper sulphate solution drop by drop, shaking after each drop
Result Blue-black colour is starch is present (brown if absent) Red, orange, yellow or green precipitate if present (Blue if absent) Water turns cloudy if fat is present. (White emulsion) (Remains clear is absent) Result Violet colour observed if proteins is present. (Remains blue if absent)
4.3 Balanced Diet • It is a diet which contains o
Enough carbohydrates and fats to meet our energy needs
o
Enough proteins of the right kind (contains all the essential a. a) for growth and repair
3
o •
Enough vitamins, minerals, water and fibre for maintaining good health
Energy Value of Food 1g of Carbohydrate 1g of Protein 1g of Fats
•
16 kJ of energy 17 kJ of energy 38 kJ of energy
The dietary requirement of an individual is dependent on o
Activity: The more active a person is, the greater the amount of energy needed
o
Age: Teenagers/young adults need more energy per kg body mass than young children and old people
o
Sex: For the same body size and age, men use up more energy than women
4
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