When these nutrients enter the body, they are large and insoluble molecules. In order for the body to be able to absorb and transport these nutrients in the bloodstream to all of the cells which need them, these molecules must be digested.
Starch is a long chain carbohydrate. It is insoluble. During digestion the enzyme carbohydrase breaks it down into single molecules of glucose which are small and soluble enough to be carried in the blood to the cells for respiration, or to be stored as glycogen in the liver.
Proteins are long chains of amino acids. During digestion the enzyme protease breaks them down into single amino acids which are small and soluble and can be used by cells to build new proteins.
Lipids are large molecules. During digestion the enzyme lipase breaks them down into fatty acids and glycerol. These can be used by the body to provide energy.
We can use different chemicals or reagents in the laboratory to detect if a food type is present or not.
Starch – the test for starch is a chemical called iodine. Iodine solution is a brown coloured liquid. If it comes into contact with starch it turns blue/black.
Glucose – The test for glucose requires a chemical called Benedict’s reagent. It is blue in colour and needs to be heated vigorously with the sample to show a colour change. If glucose is present, a range of colours may be seen which determines the relative concentration of glucose in the sample.
Protein – The test for protein requires a chemical called biuret solution. It is blue in colour but turns violet in the presence of protein.
Biuret solution contains very dilute copper sulphate and sodium hydroxide, this makes it an irritant. Complete this risk assessment for biuret solution (the first part of the risk assessment has been completed for you).
|Biuret solution is an irritant.|
|Biuret solution is an irritant.||It may spill onto the skin when pouring. It may be transferred from the fingers to the eyes.||Wear surgical gloves. Wash hands immediately after use. Wear eye protection.|