Food and digestion
Food groups
Carbohydrates
Lipids
Proteins
Minerals
Vitamins
Made of carbon, hydrogen, and oxygen
Basic carbohydrates are simple sugars
Disaccharides are 2 monosaccharides covalently bonded together
Lactose is glucose and galactose
Polysaccharides are more than 2 sugars bonded together
Glucose
Fructose
Galactose
Sucrose is glucose and fructose
Cellulose, starch, and glycogen are polysaccharides
They are used as an energy store (starch/glycogen) or for structure (cellulose)
Main source of energy (fuel for respiration)
Made of carbon, hydrogen, and oxygen
Fats
Solid at room temperature
Oils
Liquid at room temperature
Usually produced by animals
Usually produced by plants
Used for cell structure, long-term energy storage, insulation, and padding
Its building blocks are 1 glycerol joined to 3 fatty acids
Made of carbon, hydrogen, oxygen, nitrogen (sometimes sulfur)
Its building blocks are amino acids (there are 20 types)
Used for cell growth and repair
Enzymes are proteins
Kwashiorkor is a protein deficiency disease
A group of various named molecules that carry out functions in the body
Fibre
Cellulose is indigestible and therefore is fibre
A is used for chemicals in the retina and protects the eye. Deficiency causes night blindness
Elements that are needed to make molecules for the body to function
Calcium for bones
Phosphorus for various chemicals such as DNA or ATP
Sodium and chlorine for body fluids
Magnesium for cells
Iron for haemoglobin
C sticks together cells lining surfaces (such as gums). Deficiency causes scurvy
D helps bones absorb calcium and phosphate. Deficiency is rickets
Tests for food groups
Starch
Glucose
Protein
Lipid
Add the sample to a spotting tile and add a drop of iodine. If the solution turns dark blue, starch is present. If it remains yellow-brown, no starch is present
Add the sample to a test tube and add 2cm^3 of Biuret solution. Shake gently. If the solution turns lilac, protein is present. If the solution stays pale blue, no protein is present
Add the sample to a test tube and add an equal amount of ethanol. Shake. Pour the mixture into a second test tube that contains cold water. If the solution goes milky/cloudy and white, lipids are present.
Add the sample to a test tube, and add 2cm deep of water. Add a few drops of Benedict's solution (enough to make it blue). Half-fill a beaker with water and heat it on a tripod and gauze, then place the test tube in the beaker and allow the water to boil. If the solution turns brick-red, glucose is present. If it stays blue then glucose is not present
Measuring energy content of food
Find the mass of the food sample. Put 20cm3 of water in a boiling tube and clamp it diagonally. Measure the temperature. Spear the food on a mounted needle and hold it under a Bunsen burner until it catches fire. Hold it under the boiling tube until it burns out and continue relighting it until it no longer burns. Measure the temperature of the water after stirring it.
Final formula: Energy in joules per gram (J per g) = ((final temperature - original temperature) x 20 x 4.2) / mass of food (g)
Digestion
It is the chemical and mechanical breakdown of food. It converts large insoluble molecules into small soluble molecules which can be absorbed into the blood.
Sped up by enzymes
Biological catalysts
Chemical digestion
End in -ase
Peristalsis
Fibres arranged in rings are called circular muscle layer
Fibres running across the length is called longitudinal muscle layer