1. Need For Food Food is needed for:
Energy - provide heat and allow movement
Building Materials - For growth and tissue repair
Protection - prevent illness and disease

2. Chemicals in food Foods are separated into 3 groups:
Fats, Carbohydrates, and Proteins
All 3 types contain Carbon (C), Hydrogen (H), and Oxygen (O)
Proteins also contain Nitrogen (N)

3. Carbohydrates Energy-rich foods In plants
Excess glucose is converted into starch and cellulose - both large insoluble substances
Cellulose is indigestable - forms roughage in the diet (bulks up faeces)
In animals
Excess glucose is stored as glycogen in the liver

4. Fats Releases about twice as much energy as carbohydrates
Composed of fatty acids and glycerol
Excess fat is stored under the skin and around the kidneys
Provides insulation and padding

5. Fats Releases about twice as much energy as carbohydrates
Is composed of fatty acids and glycerol
Copy figure 12.5 in the textbook - pg. 112
Excess fat is stored under the skin and around the kidneys - provides and insulation and padding.

6. Protein
Protein is made up of many building blocks - called amino acids
Excess protein cannot be stored in the human body. Minimum daily intake is 80g - required for growth and tissue repair.
Excess protein is used for energy.
Structural proteins make up tissues - only used as an energy source in an emergency (eg starvation)

7. Anorexia
“I eat too much to die, and not enough to stay alive. I’m sitting in a riddle, waiting..”
“I want to be so skinny that I rot from view. I want to walk in the snow and not leave a footprint”
Rachel James
Taken from Manic Street Preachers, The Holy Bible - Track 7: 4st 7lb

8. Need For Digestion Every cell needs a supply of food.
Food is carried to the cells by the bloodstream.
Food must be digested first.
Digestion : breakdown of large insoluble food particles into small soluble particles for absorption into the bloodstream.

9. Teeth Teeth break food down mechanically into small pieces Omnivore
Eats both plant and animal material
Have 4 sets of teeth all of roughly equal size
Incisor - for biting
Canine - for tearing
Molar and Pre-Molar - for crushing & grinding

10. Teeth (2) Carnivore Normally only eats animal material
Long curved canine teeth - for piercing and holding
Premolars & Molars - sharp cutting edges
Carnassial teeth - at the back of the mouth, effective at shearing bone and slicing tendons

11. Teeth (3) Herbivore Only eats plant material
Incisors & Canines - on lower jaw only. Bite against a horny pad on lower jaw to crop grass.
Large space between front teeth and back teeth
Jaws move side to side so enamel ridges on teeth slide over each other - can grind down tough plant material.

12. Digestive System on food
Food passes along the alimentary canal
Associated organs connected to canal by ducts ( salivary glands, pancreas, liver)
These produce digestive juices
Food passed along the alimentary canal by peristalsis
Gut muscle contracts (squeezes) behind food, and relaxes in front of it
In the stomach, muscle contractions churn the food
Sphincter muscles open and close to let food in and out

13. Digestive Enzymes Promote the digestion of foodstuffs
Amylase: Found in saliva & pancreas
Digests starch into sugar (maltose)
Pepsin: a protease enzyme found in the stomach
Digests protein into amino acids
Works best at a low pH (acidic)
Lipase: Made in pancreas, works in small intestine
Digests fat into fatty acids
Fat digestion helped by bile (from gall bladder)
Food digestion involves several digestive enzymes