Human Nutrition

Biological Molecules

Biological molecules are the building blocks to make cells and other key structures to make living organisms.

You get them through eating.

They give you the ability to:

  • Make more cells

  • Grow

  • Provide energy

  • Keep you healthy

The most important of these three molecules you need are:

  • Carbohydrates

    • Composed of carbon, oxygen and hydrogen

    • Used by the body for respiration to release energy

    • We get it in the form of starch

      • Carbohydrates are stored as starch in plants

      • Carbohydrates are stored as glycogen in animals

    • Starch is insoluble and can’t be absorbed by the body.

    • Enzymes are required to break them down.

  • Lipids

    • Composed of carbon, oxygen and hydrogen

    • Fats and oils

      • Used to make cell membranes, provide insulation, protect organs and as a secondary energy store

    • They are made of one glycerol and three fatty acids

    • Too much fat can lead to heart disease, especially saturated fats and cholesterol

  • Proteins

    • Composed of carbon, oxygen, hydrogen and nitrogen.

    • All cells contain protein

    • It is used for growth and repair of tissues

    • Proteins are made of amino acids.

Food tests

Starch

Place 5ml of sample in a test tube

Put 3 drops of iodine in the test tube

If there is a colour change of brown/orange to blue/black, iodine is preset

Repeat 3 times for more reliable results

Glucose

Place 5ml of sample in a boiling tube

Put 3 drops of Benedict’s solution in the boiling tube

Place boiling tube in a water bath for 5 minutes

Remove from the water bath then shake

If there is a colour change of blue to brick red, glucose is preset

Repeat 3 times for more reliable results

Protein

Take 5ml of sample and place in a boiling tube.

Add 3 drops of biuret, then shake.

If there is a colour change of blue to lilac, protein is present

Lipids

Take 5ml of sample and place it in a boiling tube

Place 5ml of ethanol and 5ml of water in the boiling tube then shake

If there is a colour change of transparent to cloudy lipids are present

Balanced Diet

Balanced Diet - All the essential nutrients in correct amounts

A lack of iron causes anaemia. Symptoms are tiredness and shortness of breath due to a lack of haemoglobin

Enzymes

Enzymes have an optimum temperature and pH. If they are overheated (past 55C) they become denatured. Their active site is irreversibly changed.

Salivary Amylase is produced in the salivary glands

Protease is produced in the pancreas

  • Pepsin is produced in the stomach

Lipase is produced in the pancreas

Digestion

Four processes:

  • Ingestion

  • Digestion

  • Absorption

  • Egestion

Villi

Soluble food molecules ( 1g3fa ) diffuse into the bloodstream in the villi.

Adaptations:

  • Large surface area to volume ratio for increased absorption

  • Villi are one cell thick so they have a short diffusion distance

  • Villi have a good blood supply which creates a large concentration gradient