Functions of Food

• Energy
  - Main source: Carbs
  - Comes from protein (deamination) and fats (ketosis) too.

• Growth of new cells (continuity) and repair existing cells, tissues, organs, etc.

• Needed for movement, active transport

• Supplies materials for metabolism.
  - Sum of all chemical reactions occuring in the body.

Elements in Food

Six Main Elements

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Nitrogen (N)

First 4 are the most common and make up 96% of an organisms weight (carbs, lipids, proteins).

• Phosphorous (P)

• Sulfur (S)

Last two are amino acids.

Five Elements Dissolved in Salts

• Sodium (Na)

• Magnesium (Mg)

• Chlorine (Cl)

• Potassium (K)

• Calcium (Ca)

We need 100mg or more of these every day.

These are also knows as mineral elements.

Three Trace Elements

• Iron (Fe)

• Copper (Cu)

• Zinc (Zn)

We need less than 100mg of each of these every day.

Biomolecules

• The molecules found or created in living things.

• Contain carbon and are also known as biochemicals.

Four main types of biomolecules are:

• Carbohydrates

• Lipids (fats, oils)

• Proteins

• Minerals

The 14 elements combine in different ratios to form different food components (biomolecular units)

e.g. plants use carbon dioxide and water to combine carbon, hydrogen and oxygen to make a biomolecule of glucode - C₆H₁₂O₆

Carbohydrates

• The main source of energy in the diet.

• Contains carbon, hydrogen, and oxygen.

• Usually in the ratio of 1C:2H:1O

Carbohydrate types

Monosaccharides

• Single sugar molecules

• Simple sugars

• Soluble in water

• Sweet to taste

• Smallest carbohydrate unit

• e.g. glucose, fructose

• Found in: fruit

Disaccharide

• Two monosaccharide sugar units joined together - known as double sugar molecules.

• Soluble in water

• Sweet to taste

• e.g. sucrose, lactose

• Found in: table sugar, milk

Polysaccharide

• Many monosaccharide sugar molecules joined together

• Not soluble in water

• Do not taste sweet

• e.g. starch, cellulose

• Found in: bread, pasta, cereals

Cellulose

• Structural carbohydrate that forms the cell walls in plants.

• Provides strength and support to plants.

• Referred to as ‘fibre’ or ‘roughage’.

• Found in vegetables and bran.

Lipids

Contain the elements carbon, hydrogen, and oxygen but in different ratio to carbohydrates.

Include fats (solid at room temp) and oils (liquid at room temp).

Basic unit of a lipid is a triglyceride which is made of three fatty acids and one glycerol.

Phospholipids are fat like substances in which a fatty acid is removed and replaced by a phosphate.

Functions of Lipids

• Long term store of energy

• Lipids under skin (subcutaneous) used for insulation.

• Provide protection to certain organs e.g. kidneys

• Phospholipids have a structural rolde in cell membranes.

Proteins

Sources of Protein:

• Fish, eggs, chicken, meat, vegetables and legumes.

What is Protein?

• Contain the elements carbon, hydrogen, oxygen and nitrogen.

• Proteins are composed of 20 amino acids.

• Peptide bonds hold amino acids together.

• Protease enzymes in the digestive system break these bonds.

• Ribosomes make these bonds during protein synthesis.

Peptide, Polypeptide, Protein

• Peptide consists of less than 20 amino acids.

• Polypeptide consists of more than 20 amino acids.

• Protein is a chain of more than 200 amino acids.