Presentation on theme: "Need For Food Food is needed for:"— Presentation transcript:
1Need For Food Food is needed for: Energy - provide heat and allow movementBuilding Materials - For growth and tissue repairProtection - prevent illness and disease
2Chemicals in food Foods are separated into 3 groups: Fats, Carbohydrates, and ProteinsAll 3 types contain Carbon (C), Hydrogen (H), and Oxygen (O)Proteins also contain Nitrogen (N)
3Carbohydrates Energy-rich foods In plants Excess glucose is converted into starch and cellulose - both large insoluble substancesCellulose is indigestable - forms roughage in the diet (bulks up faeces)In animalsExcess glucose is stored as glycogen in the liver
4Fats Releases about twice as much energy as carbohydrates Composed of fatty acids and glycerolExcess fat is stored under the skin and around the kidneysProvides insulation and padding
5Fats Releases about twice as much energy as carbohydrates Is composed of fatty acids and glycerolCopy figure 12.5 in the textbook - pg. 112Excess fat is stored under the skin and around the kidneys - provides and insulation and padding.
6ProteinProtein is made up of many building blocks - called amino acidsExcess 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)
7Anorexia“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 JamesTaken from Manic Street Preachers, The Holy Bible - Track 7: 4st 7lb
8Need 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.
9Teeth Teeth break food down mechanically into small pieces Omnivore Eats both plant and animal materialHave 4 sets of teeth all of roughly equal sizeIncisor - for bitingCanine - for tearingMolar and Pre-Molar - for crushing & grinding
10Teeth (2) Carnivore Normally only eats animal material Long curved canine teeth - for piercing and holdingPremolars & Molars - sharp cutting edgesCarnassial teeth - at the back of the mouth, effective at shearing bone and slicing tendons
11Teeth (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 teethJaws move side to side so enamel ridges on teeth slide over each other - can grind down tough plant material.
12Digestive System on food Food passes along the alimentary canalAssociated organs connected to canal by ducts ( salivary glands, pancreas, liver)These produce digestive juicesFood passed along the alimentary canal by peristalsisGut muscle contracts (squeezes) behind food, and relaxes in front of itIn the stomach, muscle contractions churn the foodSphincter muscles open and close to let food in and out
13Digestive Enzymes Promote the digestion of foodstuffs Amylase: Found in saliva & pancreasDigests starch into sugar (maltose)Pepsin: a protease enzyme found in the stomachDigests protein into amino acidsWorks best at a low pH (acidic)Lipase: Made in pancreas, works in small intestineDigests fat into fatty acidsFat digestion helped by bile (from gall bladder)Food digestion involves several digestive enzymes