Biological Molecules


  • Found in Pasta, Rice and Sugar
  • Provide Energy
  • Made up of simple sugars
  • Contains the elements Carbon, Hydrogen and Oxygen
  • Starch and Glycogen are large complex carbohydrates
  • Smaller units are glucose and maltose
  • Test for glucose-Use benedicts reagent
  • Benedicts reagent starts blue and will go green, yellow, orange and brick red.
  • The more glucose present the more towards the brick red the colour.
  • Test for starch-Iodine solution
  • Positive test= Orange to Blue/Black
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  • Made up of long chains of amino acids
  • Contain the elements Carbon, Nitrogen, Hydrogen and Oxygen
  • Found in meat and fish products
  • Needed for Growth and repair to provide energy in emergencies
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  • Found in dairy products and oily fish
  • Provides energy 
  • Acts as an energy store
  • Provides insulation
  • Made of Fatty acids and Glycerol 
  • Contain Carbon, Hydrogen and Oxygen
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  • Vitamins A, C and D
  • Vitamin A found in liver-improves vision and keep your skin and hair healthy
  • Vitamin C found in citrus fruits-prevents scurvy
  • Vitamin D found in eggs-needed for calcium absorption
  • Calcium and Iron
  • Calcium found in dairy products-needed to make bones and teeth
  • Iron found in red meat-needed to make haemoglobin for healthy blood
  • Water-all bodily functions need water to be able to function
  • Water is easily lost via sweating, breathing and urinating
  • Dietary fibre found in wholemeal bread- aids the movement of food through the digestive tract
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Energy from Food

  • To see how much energy food contains we can do a calorimetry experiment
  • Burn food under boiling tube full of water
  • Take tempereature of water at the start and the end
  • Calculation= Energy in Food (J) =Mass of Water (g) x Temperature change (C) x 4.2
  • Energy per gram of food = Energy in food/Mass of food
  • To Improve the acuracy of this experiment you can wrap the boiling tube in foil to minimise heat loss
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Enzymes and Digestion

  • Starch, Proteins and fats are large insoluble molecules.
  • They need to be broken down into smaller soluble molecules to pass through the wall of the intestines in the digestive system
  • Amylase converts Starch into Maltose
  • Maltase converts Moltose into Glucose
  • Proteases converts proteins into Amino acids
  • Lipases converts Lipids into Glycerol and Fatty Acids
  • Bile is produced in the liver and stored in the gall bladder
  • Bile neautralises stomach acid and emulsifies fats
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The Digestive system-The Alimentary Canal

  • Includes the mouth, the oesophagus, the stomach, the small intestine, the large intestine, and the anus
  • Other organs involved are: The liver, the gall bladder and the panreas
  • Mouth-Teeth grind food
  • Saliva produced, saliva contains amylase
  • Oesophagus-connects mouth to stomach
  • Uses peristalsis to push food along (muscular contractions to squeeze the food)
  • Stomach-contains hydrochloric acid which kills bacteria and gives the right pH for enzymes to work
  • Contains the enzyme pepsin (which is a protease)
  • Small intestine- Produces Protease, Amylase and Lipase to help digestion
  • This is where absorption of nutrients takes place
  • Large intestine-This is where water is absorbed from food
  • Anus- Any food not digested is expelled here as faeces
  • Pancreas- Produces Protease, Amylase and Lipase to be released into the small intestine
  • Liver- Where Bile is produced
  • Gall Bladder- Where Bile is stored before being released into the small intestine
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The 5 main stages of Digestion

  • Ingestion- Taking food into the body
  • Digestion- Break down of food in the body, this can be mechanical and chemical
  • Absoption- Digested food absorbed into the body
  • Assimilation- The digested food is used by the cells in the body
  • Egestion- Anything not used is got rid of by the body

Villi in the small intestine help with absorption of nutrients

  • They have a large surface area
  • They are covered in microvilli to help increase surface area
  • They have blood vessels to help absorption of nutrients into the blood stream
  • The walls of the villi are thin to help diffusion of small molecules
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