Digestion

In this chapter, we learnt about how the food we eat gets into our body to produce energy for our daily activities.

We need food to:

-Provide us with energy for our daily activities

-Maintain a healthy body

-Grow new cells

-Repair worn out cells

There are 3 main types of nutrients, Carbohydrates, Proteins and Fats.

Carbohydrates

-Our immediate source of energy

-Found in food like rice, bread and noodles

-Exist in different forms such as starch, sucrose, maltose and glucose

Proteins

-Large molecules made up of amino acids

-Makes enzymes

-Found in food like fish, meat and eggs

Fats

-Large insoluble molecules made up of glycerol and fatty acids

-Found in food like butter and cheese

-Stored under our skin and acts as an insulator

The nutrients in the food we eat has to pass through the gut walls and into the blood vessels, in order to be carried through the bloodstream to all parts of the body. However, the gut walls has small openings which only allow molecules small enough to pass through, hence, most nutrients has to be broken down into smaller molecules, as they are too big, in order to be able to pass through the gut walls, and this process is called Digestion.

Enzymes

Enzymes are complex proteins that speed up the rate of chemical reactions by breaking down large molecules into smaller molecules. Enzymes remains unchanged at the end of chemical reactions.

Type of Enzymes:

Enzymes                                       Acts on                                Digested products

Amylase                                       Starch                                    Maltose

Maltase                                        Maltose                                 Glucose

Protease                                       Proteins                                 Amino acids

Lipase                                          Fats                                       Fatty acids and glycerol

The Human Digestive System

Mouth -> 

Food is chewed in the mouth with the teeth (helps to cut and grind the food into smaller pieces). The saliva in the mouth also wets the food to allow it to be swallowed easier. There are also Amylase in the saliva which digests starch into maltose.

Oesophagus ->

 No digestion occurs here. The food is pushed down to the stomach by the peristalsis movement of the Oesophagus.

The stomach ->

The gastric juice in the stomach contains protease which digests proteins and hydrochloric acid which helps protease to work faster. The acid also kills any bacteria present in the food.

The small intestine ->

The liver and the pancreas is connected to the small intestine. There are 3 type of fluids found in the small intestine. 1) Intestinal juice contains enzymes such as maltase, proteases and lipase which digests maltose, protein and fats respectively. 2) Pancreatic juice which contains amylase, protease and lipase, which digests starch, protein and fats accordingly. 3)Bile which is produced by the liver. Bile emulsify the fats to break them up into smaller oil droplets, which increases the surface area of the oil so that it can be digested more quickly by the lipase enzymes.

The process of digestion ends in the small intestine, and the undigested matter, together with water and mineral salts, is passed into the large intestine. The large intestine then absorbs the water and mineral salts. The rest of the waste product are then stored in the Rectum and eventually passed out through the anus in a process called Egestion.