CHEMICAL ELEMENTS THAT MAKE UP
Carbohydrates
Carbon, hydrogen (2), oxygen = CH2O
Fats
Carbon, hydrogen, oxygen
Proteins
Carbon, hydrogen, oxygen, nitrogen, sulphur
MONOSACCARIDE
DISACCARIDE
POLYSACCARIDE
glucose
maltose
starch
AMINO ACIDS
DIPEPTIDE
POLYPEPTIDE
1 amino acid
2 amino acids
e.g. protein
CARBOHYDRATES
PROTEINS
peptide bonds join amino acids together
3 fatty acid molecules and 1 glycerol molecule form a lipid. Lipids come in three forms: liquid
(oils), semi-solid (wax) and solid (fats)
Principal source:
Carbohydrates bread, rice, potatoes,
pasta, cereal
Fats
meat, dairy products, nuts
Proteins
meat, fish, cheese,
vegetables
fresh fruits and vegetables
Vitamins C
Vitamin D
Certain types of fish
sunlight
Calcium
cows’ milk, vegetables
Iron
breakfast cereals, liver,
meat, nuts, green
vegetables
wholemeal bread and
pasta, fruits and
vegetables, nuts, seeds
Fibre
Water
Importance:
Carbohydrates are the body’s main source of fuel.
They give us our energy. They’re needed for our
body to function properly
Energy, absorbing certain vitamins, maintaining cell
membranes
Tissue growth and repair, maintaining immune
system, making essential hormones and enzymes
It can protect cells from damage, it can prevent
cataracts. A lack of vitamin C can cause scurvy.
Promotes calcium absorption in the gut and bone
growth. A lack of vitamin D can cause bones to
become thin and brittle, and can cause rickets.
For bone growth, for muscles to contract and relax
properly. Lack of calcium can cause rickets.
Helps make red blood cells (key component of
haemoglobin). Lack can cause anaemia, fatigue and
hair loss.
Aids digestion but doesn’t get digested
It is necessary for the digestion and absorption of
food; helps maintain proper muscle tone; supplies
oxygen and nutrients to the cells; rids the body of
wastes
TEST FOR:
Starch
IODINE
A solution or solid can be tested for starch by adding iodine to it. If the
solution or solid (such as a potato) turns black-blue, starch is present. If
no starch is present, the iodine remains the colour it is.
Reducing BENEDICT’S A food product can be tested for reducing sugars such as glucose or
sugars
REAGENT lactose. Dissolve a food sample in boiling water. Add a small amount of
Benedict’s reagent. Over the next four to ten minutes, as the solution
cools, it should begin to change colour. If glucose is present, the colour
will change to green, yellow, orange or red/brown (from very little to a
lot of glucose present in the solution)
Protein
AQUEOUS
To test whether a mixture contains protein, or peptide bonds, add a
COPPER(II) small amount of the mixture to a test tube along with an equal amount
SULPHATE of a strong base (e.g. sodium hydroxide, potassium hydroxide, etc.).
Mix these together, and add a few drops of aqueous copper(II)
sulphate. Swirl the mixture around; if protein is present, the mixture
will turn purple. If no protein is present, the mixture will turn blue.
Fats
ETHANOL
To test for fat in a solution, add 2cm3 of ethanol to a few drops of the
solution in a test-tube, and shake the mixture well. Add 2cm3 of water.
If the solution contains fat, a cloudy white suspension will form at the
top of the solution.
Microorganisms are used in the manufacture of yoghurt for the formation of typical yoghurt
flavour and texture.