Balanced Diet

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Balanced Diet

Energy Balance:

  • Energy is obtained from food
    • Main energy from carbohydrates (glucose) and fats
    • Proteins are used for growth and repair first
    • Excess proteins is converted to energy
  • Out of balance
    • More energy/food than required obesity
    • Less energy/food than required starvation
  • Types of carbohydrates:
    • Intrinsic sugars: found within cells (fruits)
    • Extrinsic sugars: sugars that have been added to food (processed food)
    • Milk sugars: found in milk products


Polysaccharides (cellulose) that cannot be broken down by enzymes in the gut

  • Reduce absorption of carbohydrates
  • Reduce hunger

Prevent constipation (need plenty of water)

  • Speed up passage of food through intestine
  • Less time for toxins to accumulate
  • This reduces risk for colon cancer


Non-starch polysaccharides (e.g. glycogen)

  • Control appetite
  • Prevent appendicitis, colon cancer, haemorrhoids, constipation

Store and transport energy

Glucose is the main energy source in the brain


Source of chemical P.E. (energy reserve)

Phospholipids are essential for plasma membranes

Essential fatty acids are precursors of other important substances

Needed to absorb fat-soluble vitamins

Maintain body temperature


Required for growth and repair in cells and tissues (children require more!)

Carrier (change shape for different molecules) for water-soluble molecules such as glucose

Ion channels (sodium and chloride ions)

Pumps use energy to move water-soluble molecules and ions

Enzymes, which speed up chemical reactions at the edge of the membrane

Receptors enable hormones and nerve transmitters to bind to specific cells

Recognition sites, which identify a cell as being of a particular type

Adhesion molecules for holding cells to extracellular matrix


Often interact with enzymes to speed up metabolic reactions



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