1.3 Nutrition and Food Tests

Benedict's reagent

turns from blue to brick-red when heated in presence of sugar

Biuret reagent

Turns from blue to lilac/purple in the presence of proteins

Iodine test

Turns from yellow-brown or orange to blue-black in the presence of starch

Ethanol and water

when shaken will turn from colourless to a milky-white emulsion in the presence of lipids

Balancing energy

energy content of food eaten must be equal to energy needs as excess energy will be stored as fat

Specific heat capacity

energy to raise mass of substance by 1 degree

water = 4.2 J/g/°C

Digestion

uses energy from respiration to break down large insoluble molecules into smaller soluble molecules

Carbohydrates

Provide energy for chemical reactions and can break down into chains of sugars

Simple carbohydrate examples (energy)

• Sugars, glucose and lactose

• raise blood glucose levels fast and produce quick elevation in energy

Complex carbohydrate examples (storage)

• Cellulose, starch and glycogen

• raise blood glucose levels slowly and produce more lasting elevation in energy

Proteins

building blocks of cells and tissues that can break down into amino acids

Uses of proteins

can be structural e.g in muscle

or functional e.g enzymes/ antibodies

How are proteins used

Long chains of amino acids are separated and connected again to form different arrangements

Lipids

fats and oils that can break down into glycerol and 3 fatty acids

Uses of lipids

very good as energy storage with 1 gram containing double the energy of carbohydrates/ protein

What are biological molecules made up of

all contain carbon, hydrogen and oxygen but proteins also have nitrogen