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Nutrition and

Biomolecules

Food Chemistry

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Functions of food

1. Energy source – 90% used to make

ATP

2. Materials Source - for growth, repair,

defence

3. Continuity – replacement of cells and

reproduction

4. Metabolism - maintaining cells at

high level of chemical efficiency

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• Metabolism - all reactions in living body

• Anabolism building up of substances – input

of energy required

• E.g. photosynthesis, DNA replication, RNA

formation, muscle building

• Catabolism – breaking down of complex

molecules – e.g. digestion

• Enzymes protein biological catalysts,

catalyse reactions [speed up – not used up in]

• Respiration – release of energy from food

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Protein

• Chemical elements C, H, O, N also P and

S

• Biomolecular sub-units – Amino Acids [20]

• Linked by peptide bonds

• One or more chains

• Differ in sequence and number of a.a.’s

• Made in ribosomes

• Sources meat, fish, eggs, milk, cheese,

pulses

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Roles

• Structural

• Keratin in hair, skin – protects

• Myosin in muscle

• Metabolic

• Enzymes – protein biological catalysts

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Other roles

• Antibodies

• Haemoglobin

• Chlorophyll

• Insulin

• Collagen

Shapes

• Globular or Fibrous

• Amino acids join together at angles

• so as the protein forms it becomes folded

• It can form a long fibre

• Or it can become a ball

• The function of a protein (enzyme) depends on

its shape

• If we heat much above 60oC or shake it

become denatured i.e. It loses its function8

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CarbohydrateChemical elements C, H, O [ H:O ratio 2:1 ]

Monosaccharides [1 sugar unit]

Glucose [C6H12O6], fructose, galactose

Disaccharides [2 sugar units]

Maltose, sucrose [C12H22O11], lactose

Polysaccharides [many sugar units]

Starch [plants], glycogen [animals]

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Types of carbohydrates

Sugar

• Found in honey, jam, sweets , fizzy drinks,

alcohol.

• [Most processed foods have sugar added]

• Provides energy [quickly]

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Carbohydrates continued

Starch

• Found in potatoes, flour, bread, pasta,

rice, cakes etc.

• Provides energy [ more slowly over a

longer period]

• Test for with iodine which goes from

brown to blue/black if starch is present.

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Carbohydrates continued

Fibre [cellulose]

• Found in whole-grain cereals [e.g.

Weetabix, Shredded Wheat etc.]

and vegetables.

• Function to retain water and prevent

constipation and also cancer of the

bowel.

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Carbohydrate Roles

Structural

• Cellulose – plant cell walls – glued together

to make rigid structure

• Chitin – cell walls of fungi, insect cuticles

Metabolic

• Energy source – respiration of glucose

• Energy store

– Starch in plants

– Glycogen in animals

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Lipids [fats]

• Chemical Elements C, H, O

• Glycerol + 3 fatty acids

• Fat solid at RTP

• Oil liquid at RTP

• Lipids rich in saturated fatty acids [found

mainly in animal fats] are associated with

heart disease

• Sources – meat, milk, butter, cheese,

olives, maize, sunflower seeds

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Glycerol Fatty Acid

Fatty Acid

Fatty Acid

Glycerol

Fatty Acid

Fatty Acid

PO4

Lipid

Phospholipid

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RolesStructural

• Phospholipid forms plasmalemma

• Insulates organs e.g.kidney

• Cuticle of leaves

Metabolic

• Storage of excess carbohydrate

• Energy by respiration

• Hormones – some are lipids

• Stores fat soluble vitamins e.g. D

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Other

• Heat Energy store – twice energy of

carbohydrates per gram

• insulation – sub-cutaneous layer

• Protection – pads on feet and hands

• Waterproofing – sebum on hair and skin

• Storage – adipose tissue

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Vitamins

• Non-protein substance required in tiny

amounts for healthy metabolism

• Vitamin C [Ascorbic Acid]

• Water soluble

• Found in fresh fruit [citrus] and

vegetables

• Deficiency disease [caused by lack of] –

scurvy – bleeding gums and poor wound

healing

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• Vitamin D [caliciferol]

• Fat soluble

• Source – dairy products,liver, fish oils etc.

• Made by skin in sunlight

• Deficiency disease

• – rickets in children – bowed legs

• - Osteomalacia in adults

• Needed to absorb Ca from gut and also tooth and bone formation

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Minerals

• Soluble inorganic salts that contain

essential elements

• 6 macro major – need in large amounts

– C, H, O, N, P and S

• 5 micro small amounts needed

– Na, K, Ca, Mg and Cl

• Trace Elements only tiny amounts needed

(mg) – Fe, Cu and Zn

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Examples of required minerals

Plants

• Ca – make middle lamella

• Mg – make chlorophyll

Animals

• Ca – bones and teeth

• Fe – Haemoglobin to transport O2

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Roles

• Present in compounds that make hard

parts of bodies

• Present in compounds that form soft

tissues

• Maintain correct fluid concentration of

cell and body fluids

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Water

• Transport medium for blood cells etc.

• Excellent solvent – good medium for

chemical processes

• Strong cohesion [ sticking to itself] and

adhesion [sticking to other substances]

– transpiration stream

• Temperature stable – needs a lot of

heat to change temperature

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• Participant in metabolic reactions

– Anabolism – removes water

– Catabolism – adds water

– Photosynthesis – uses

– Respiration – produces

• Participant in movement into and out of cells – medium for movement

• Control of cell shape – osmosis causes turgor pressure – guard cell opening

• Component of cytoplasm

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Hormones as regulators of

metabolic activity

• Are signal that activate specific

metabolic programs in their target

cells by

a) Influencing transport of materials

across membranes

b) Activating or inhibiting enzymes

c) Activating or inhibiting genes and

thus influence protein synthesis

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Metabolism influenced by

hormonesInsulin

• Uses

1.Uptake of amino acids and glucose by living cells

2.Protein synthesis

3.Lipid formation

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Balanced Diet

• One that contains the correct amounts of

carbohydrates, proteins, fats, vitamins,

minerals and water.

• Depends on age, the sex of the individual

and the activities being undertaken by the

individual.

• Teenagers should intake 12000 kJ for

boys and 9600 kJ for girls per day

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Dieting• Most people who go on a diet do so

because they are overweight.

• It usually means that the intake and variety of food is reduced drastically.

• This is bad because it does not give a balanced diet and the weight lost is usually put back on very quickly.

• To lose weight you must reduce the amount of fatty foods and eat more fruit and vegetables.

• Undernourished

• Not enough food

• At its worst starvation

• Over 1/3 of the worlds population is

undernourished

• Malnourished

• The wrong proportions of the various food types

• Too much fat leads to obesity, coronary heart

disease

• Too much sugar can lead to diabetes

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How to loose weight

• Reduce fat intake

• Reduce alcohol intake

• Increase vegetable, fruit and cereal

intake

• Increase exercise

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Food Tests

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FatsBrown Paper Test

• Rub some fat [butter] on brown paper

• Rub water on another piece

• Dry paper

• If a translucent spot stays its a fat.

• [translucent means lets light through

but you can’t see through it]

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StarchIodine Test

• Add some iodine solution

[brown] to the suspected starch

e.g. bread and potato.

• If it goes from brown to

blue/black then starch is present

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Proteins• Place sample in test tube [albumen]

• Add sodium hydroxide solution and mix

• [caution sodium hydroxide solution is

caustic - burns skin]

• add a few drops of copper sulphate

solution.

• If it turn from blue to purple/violet then

protein is present

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Reducing Sugars• Place some glucose in a test tube

• Dissolve in water

• Add Benedict’s Solution [or Fehling’s solution A +B and mix] which is blue

• Place in a hot water bath at <100oC for 3 minutes

• If it turns red/orange then glucose [ a Reducing Sugar] present

1. Give 4 functions of food

2. Test for starch

3. Elements present in proteins

4. Test for protein

5. Two elements with ratio 2:1 in carbohydrates

6. Test for reducing sugars

7. Name a water [fat] soluble vitamin, its source

and a disease caused by a lack of it.

8. What are these types of diseases called?40

9. Test for fats

10.Give the uses of roughage.

11.What is a balanced diet?

12.What does malnourished mean?

13.What is a fat composed of?

14.Fat / oil

15.Saturated – source and difference

16.Macro, micro and trace elements.

17.What is a trace element?

18. two examples of minerals needed by (a)

plants and (b) animals and what each does41

Answers

1. Give 4 functions of food [4] energy / material

source / continuity / metabolism

2. Test for starch [4] add iodine / starch present

brown / to blue-black / absent stays brown

3. Elements present in proteins [6] C, H, O, N, S,

P

4. Test for protein [3] add biuret reagent / blue to

lilac if present

5. Elements in carbohydrates with ratio [4] C,H,O

/ 2H : 1O 42

6. Test for reducing sugars [4] Benedict’s / heat

gently / blue / to red pptte

7. Name a water [fat] soluble vitamin, its source

and a disease caused by a lack of it. [3] C,

citrus fruits, scurvy

8. What are these types of diseases called? [1]

deficiency

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9. Test for fats [3] brown paper / permanent /

translucent spot

10.Give the uses of roughage [3] prevent

constipation / eases digestive transit / absorbs

water / prevents cancer

11.What is a balanced diet? [2] All nutrients / in

correct amounts

12.What does malnourished mean? [3] Too much

or too little / of one or more / food types

13.What is a fat composed of? [3] Glycerol / 3 /

fatty acids

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14.Difference between fat and oil [3] fat solid /

oil liquid / room conditions

15.Saturated – source and difference [2] animals

/ forms cholesterol

16.List [7] (a) Macro, C H O N S P (b) micro Na K

Ca Mg and Cl (c) trace elements Fe, Cu, Zn.

17.What is a trace element? [2] Only needed / in

tiny amounts

18. Two examples of minerals needed by [8] (a)

plants Mg, Chlorophyll Ca Pectate and (b)

animals Fe Haemoglobin Ca Bones and teeth45