The three food groups in a cheese sandwich are: •Carbohydrates- this is found in the bread and gives us energy. Carbohydrates should be around 50% of your diet. •Protein-this is found in the cheese and helps us grow. •Fats- also known as lipase are found in the cheese, they are needed for energy but too much fatty food can be unhealthy.
First the cheese sandwich will go into your mouth.the teeth and jaws work to break up the food into smaller pieces, making it easier to digest. Saliva in the mouth contains a enzyme called Amylase, this enzyme breaks down starch into glucose. This is because starch molecules are large and insoluble, so by breaking the down it becomes smaller and easier to digest.
The food then travels down the oesophagus, it is a long tube in your neck. It can take as little as 2 seconds for food to travel down there to the stomach. The muscles of the oesophagus contract (peristalsis) to move food down to the stomach. The epiglottis at the back of your throat closes to prevent food from travelling down the windpipe/trachea.
In just 5 seconds the broken down cheese sandwich will enter the stomach. In the stomach there is HCl/stomach acid. This kills the harmful micro-organisms that may be in the food. The stomach contains protease, amylase and lipase enzymes; these break down the food into molecules which can then be absorbed in the small intestine. In the stomach there is a substance called bile. This helps the digestion of fats. Bile is stored in the gall bladder. It is released into the duodenum.
Next the food goes into the small intestine. In here the food is digested more into simple molecules and is also put into the blood. The insoluble molecules are then pushed into the large intestine. Any undigested food is squeezed into the large intestine. Mainly the fibres are found in here. The waste material in the large intestine are called faeces. Too much water in the faeces causes diarrhoea, but too little water in the faeces causes constipation.
This diagram shows us how protease, amylase and lipase enzymes work in the digestive system. It is an example of a lock and key mechanism.