CIE IGCSE Biology Unit 7: Animal nutrition

Balanced diet

A balanced diet provide all 7 classes of nutrients in the right amount

Explain how age, gender and activity affect

the dietary needs

A child needs more energy than an adult because they have a higher basal metabolic rate (BMR) the energy is used for growth, to make new cells

Malnutrition

Daily intake of food does not meet amount required for 7 classes of nutrients

Starvation

Starvation is the result of a severe or total lack of nutrients needed for the maintenance of life.

Constipation

Lack of roughage or fibre. Roughage adds bulk to our food and keep it moving down alimentary canal, constipation is the result of lack of roughage thus making it hard to defecate

Obesity

Having too much body fat in the body

Causes:

-high intake of fatty foods

-high intake of processed foods

-too little exercise

-emotional stress leading to 'stress eating'

Scurvy

Lack of vitamin C, symptoms include bleeding and weak gums, poor wound healing

Dietary importance of carbohydrates

To provide energy

Dietary importance of fats

Helps in dissolving fat soluble vitamins (A,D,E,K)

Dietary importance of proteins

Used for growth and repair

Dietary importance of vitamin C

Needed for healing wounds

Dietary importance of vitamin D

Needed for absorption of calcium and promote bone growth

Dietary importance of calcium

Building and maintaining bones

Dietary importance of iron

Helps in transport of oxygen in red blood cell

Dietary importance of fibre (roughage)

Add bulk to food to promote bowel movement (prevent heart disease, diabetes and weight gain)

Dietary importance of water

Used for all bodily functions including digestion

Rickets

Lack of calcium causes brittle bones

Anaemia

Lack of iron or haemoglobin in blood causes tiredness

kwashiorkor

Lack of protein, symptoms are oedema (swelling of abdomen and legs), fat accumulation in liver, dry hair

marasmus

Lack of protein, symptoms are very low body mass, thin limbs, little muscle and fat

Cholesterol

Stick to arteries causing blockage

Saturated fats

Fat molecules with no double bonds, mainly comes from animal fats

Unsaturated fats

Two types of unsaturated fats

-mono-unsaturated fats: have little effect on blood cholesterol

-poly-saturated fats: help reduce cholesterol concentrations

Ingestion

The taking of substances into the body through the mouth

Digestion

Chemical or mechanical process of breaking down foodstuffs to substances that can be absorbed.

Absorption

the movement of small food molecules and ions through the wall of the intestine into the blood

Assimilation

the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells

Egestion

the passing out of food that has not been digested or absorbed, as faeces, through the anus

Chemical digestion

the breakdown of large, insoluble molecules into small, soluble molecules

Mechanical digestion

the breakdown of food into smaller pieces without chemical change to the food molecules

diarrhoea

the loss of watery faeces

Oral rehydration therapy

ORT solutions contain:

-contains water to rehydrate blood and other tissues

-sodium ions to replace ions lost from blood and tissue fluid

-glucose to provide energy for uptake of sodium ions from intestine

-ions of potassium and chloride to replace ions lost in diarrhoea

cholera

Cholera bacterium produces a toxin that causes secretion of chloride ions into the small intestine, causing osmotic movement of water into the gut, causing diarrhoea, dehydration and loss of salts from blood

protease

Enzyme that breaks down protein found in stomach, small intestine and pancreas

lipase

Enzyme that breaks down fats, found in pancreas and small intestine

amylase

Enzyme that breaks down starches into saccharides which is further broken down into the simple sugar glucose

Alimentary canal

passage from where food travels from the mouth to the anus. Includes esophagus, stomach and intestines

mouth

A medium used for mechanical digestion, breaking large food pieces into smaller pieces particles to increase surface area for chemical digestion

salivary glands

Produce saliva and enzyme amylase that breaks catalystses breakdown of starch to maltose

oesophagus

Food is rolled into a ball called a bolus and moved down to the stomach by peristalsis

stomach

Contains hydrochloric acid that kills bacteria and enzyme pepsin that digests protein into polypeptides

small intestine

contains villi for absorption of digested food

duodenum

connected to pancreas that secretes pancreatic juice that contains enzymes (amylase, trypsin, lipase) bile is also secreted from the gall bladder (bile made in liver and stored in gall bladder), bile is alkaline and neutralises the acid from the stomach as enzymes secreted from pancreas works in alkaline conditions. Bile also emulsifies fat by breaking large fat globules into smaller fat globules

ileum

Final segment of the small intestine; fine tune oraganic absorption (B12,iron,etc) picks up/absorbs any nutrients not already absorbed

pancreas

-connected to duodenum

-secretes enzymes (amylase, trypsin, lipase)

liver

-process nutrients absorbed from small intestine

-produces bile to be stored in gall bladder

-produces cholesterol

-undergoes deamination

Deamination

Amino acids can't be stored in the liver, thus liver breaks down the amino acid, one molecule is converted into carbohydrate and the other molecule is ammonia (NH4) which combines with carbon dioxide to form urea that is carried to the kidneys and filtered out, excreted in urine

gall bladder

stores bile produced by liver to be secreted to duodenum to neutralise acidic food from stomach

large intestine

Absorb water

colon

Absorb water

rectum

Stores undigested food

anus

Faeces are egested through anus, passing out indigestible food through anus is called egestion

incisors

Chisel shaped for biting and cutting

canines

Pointed for piercing and tearing

molar

Like premolars are for grinding and chewing food

premolar

Have uneven 'cusps' used in chewing, grinding

Structure of human tooth

Crown:

-enamel: hard outer layer

-dentine: bone in structure

-pulp cavity: contains nerve and blood vessels

Root:

-cement: fixes root of tooth into bony socket in the jaw

Causes of dental decay

a coating of bacteria and food on teeth, the bacteria respiring sugars in the food, producing acid which dissolves the enamel and dentine

proper care of teeth

-Brush teeth with tooth paste that contains flouride

-Eat less sugary foods to prevent bacteria to multiply and cause tooth decay

the digestion of starch in the alimentary canal

- amylase is secreted into the alimentary canal by salivary gland and breaks down starch to maltose

- maltose is broken down by maltase to glucose on the membranes of the epithelium lining the small intestine

Functions of the hydrochloric acid in gastric juice

- denaturing enzymes in harmful microorganisms in food

- giving the optimum pH for pepsin activity

Function of bile

- neutralising the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action

- emulsifying fats to increase the surface area for the chemical digestion of fat to fatty acids and glycerol by lipase

Vili

increasing the internal surface area of the small intestine to better absorb nutrients