Bio revision

• Food


  Substance containing carbohydrates, lipids, proteins, minerals, vitamins, fibre, and other nutrients
• Function of food


  Goes towards building and maintaining body parts and functions
• Balanced diet


  Meal that consists of different foods in their right amounts, that provide nutrients to your body
• Factors affecting balanced diet

  • Sex
  • Age
  • Nature of activity
  • Condition of body
• Classes of foods


  • Carbohydrates (or sugars) - for energy
  • Proteins - help your body repair cells and make new ones
  • Fats (also known as lipids) - store of energy; insulation
  • Minerals (elements such as iron - to make hemoglobin in blood, and calcium - to make bone)
  • Vitamins - chemicals that ensure cells function properly, for example vitamins C and D
  • Water - about 80% of your body is water. You need to regularly drink water to ensure processes in the body are functioning properly and you remain hydrated
• Carbohydrates

  Include sugars and starch
• Carbohydrates

  • Used in respiration to produce energy
• Marathon runners

  • Often eat pasta the evening before a race
• Too much sugar

  Leads to tooth decay, obesity and sometimes diabetes
• Chewing

  Breaks up the food into smaller pieces
• Swallowing

  Food passes into the gullet
• Teeth

  Begin the task of digesting your food
• Saliva mixing with food in mouth

  Enzyme in saliva starts breaking down starch molecules
• Food moving along tube to stomach

  Mixed with more enzymes to digest proteins
• In small intestine

  1. Bile from liver breaks fat into small droplets

  2. Enzymes from pancreas digest starch, protein, and fat
• Molecules of glucose, amino acids, and fatty acids


  Pass through wall of small intestine into bloodstream
• Undigested food passing into large intestine


  Water absorbed, making it more solid
• The digested food molecules are now ready to be absorbed into the bloodstream
• Leaving the anus

  This then leaves the anus
• Chemical Digestion is a catabolic reaction that breaks down macromolecules into simpler molecules using enzymes. The simpler molecules are able to go into the cells and help the organelles perform their designed purposes
• Nutrient absorption occurs after the breakdown of carbohydrates,proteins and fats. They are absorbed from the ileum inside the small intestine which has villi that allow nutrients to enter the bloodstream 
• • The process is called lock and key hypothesis because just like a lock can only be opened by it’s key, a substance with a specific composition can only combine with the specific active site found in a particular enzyme 
  • The hypothesis is part of digestion because enzymes are significant in breaking down food and therefore are an essential part of digestion
  • Enzymes are proteins and proteins are denatured when in contact with too much heat,therefore since enzymes are proteins they stop working when heated
• • Pepsin works best in the stomach. It plays a significant role in breaking down protein
  • An example of an enzyme unaffected by changes in pH is catalase. It helps break down hydrogen peroxide in the body 
  • These enzymes are mostly called ph-neutral 
• Molecules may be 

  • Small (micromolecules)
  • Large (macromolecules)

  Macromolecules

  • Made of repeated units of small units called monomers (one) 
  • Macromolecules made of monomers can be called polymers (many)

  Molecules in food are composed of the following elements 

  • Carbon        ]
  • Hydrogen  ]   all found in food 
  • Oxygen       ]

  Others: 

  • Nitrogen 
  • Phosphorus 
  • Sulphur 
  • Protein                ]
  • Carbohydrates ]  found in foods, become part of the body 
  • fats                       ]

  Accessories 

  • Water        ]
  • Minerals  ]   not foods, do not become part of the body
  • Vitamins  ]
• Categories of lipids


  • Fats
  • Oils
• Fats


  • Found in animals
  • Solids at room temperature
• Oils


  • Found in plants
  • Liquid at room temperature
• Oils


  • Olive oil
  • Coconut oil
  • Sunflower oil
• Components found in lipids

  • Fatty acids
  • Glycerol
• When digested/broken down, lipids produce two different small molecules
• Saturated fats


  Have no double bond between two carbon atoms
• Unsaturated fats


  Have a double bond between two carbon atoms
• Functions of lipids


  • Regulating body temperature
  • Absorbing vitamins
  • Used as a source of energy during cellular respiration in the absence of carbohydrates
  • Fats around body organisms act as shock absorbance during fall or physical damage
  • Fats in skin cells provide or secrete oil to keep the skin moisturized and hydrated
• Mouth


  Breaks up food particles physically and chemically
• Salivary glands

  • Saliva moistens and lubricates food
  • Amylase digests starch to maltose
• Pharynx

  Transfers food from mouth to esophagus
• Esophagus

  Transports food
• Liver

  • Breaks down and builds up many biological molecules
  • Stores vitamins and iron
  • Destroys old blood cells
  • Destroys poisons
  • Bile aids in digestion
• Stomach

  • Stores and churns food
  • Pepsin digests proteins
  • Hydrochloric acid (HCI) activates enzymes and kills germs
  • Mucus protects stomach wall
• Gall bladder

  Stores and concentrates bile