Health
Structure of the digestive system
The digestive system breaks down food into tiny particles which are absorbed into the blood.
These particles provide energy for the body to grow, repair itself and remain healthy.
Digestion starts in the mouth, teeth break the food down and mix it with enzymes in the saliva : the oesophagus is a thin tube and connects the mouth to the stomach : the liver releases a chemical called bile into intestines, bile breaks down lipids in the food : the stomach is a muscular bag that mixes food & drink with acid : The pancreas releases enzymes into intestines and break down carbohydrates, protein and lipids in food.
In the small intestine carbs, proteins and lipids digest, the nutrients produced are absorbed into blood : In the large intestine, food which cannot be broken down-mainly fibre - passes into the large intestine, water's absorbed into blood : Any undigested food passes into the rectum where it is stored as faeces : the anus is the opening at the very end of the digestive system through which faeces leaves the body
Digestive enzymes
Mechanical digestion involves physically breaking down food substances into smaller particles to more efficiently undergo chemical digestion but chemical digestion, through a process called hydrolysis, uses water and digestive enzymes to break down the complex molecules
The human body digests carbohydrates, proteins and fats.
These carbohydrates, proteins and fats are digested into nutrients and absorbed into the body.
Enzymes are biological catalysts which speed up reactions including digestion.
Enzymes are protein molecules which act as catalysts to speed up reactions. They are not used-up in these reactions.
Enzymes can be grouped into two types : Those that break larger molecules apart (like digestive enzymes) and those that join larger molecules together (like plants making glucose in photosynthesis)
The molecules that enzymes act upon are called substrates. An enzyme is specific for its substrate like a key is for its lock. This is called the 'lock and key model'
Carbohydrase are in the mouth, pancreas and small intestine : protease are in the stomach, pancreas and small intestine : lipase are in the pancreas and small intestine
Food energy
Food is a store of energy, transferred from the food to the consumer.
'Food energy' is measured in joules (J) or kilojoules (kJ.)
Food types (groups) have different amounts of energy.
Different people need different amounts of energy.
Healthy diet
Food is a store of chemical energy, which is transferred to the consumer when eaten.
Stored energy from the food is transferred to the animal that eats it (the consumer).
Each individual requires a specific amount of food, depending on their energy requirements.
This energy from plants and animals keeps the consumer alive and allows it to carry out its activities.
A balanced diet contains the correct amount of all food groups.
The food groups are: carbohydrates, lipids, proteins, vitamins, minerals, dietary fibre and water.
Each food group has its own role to play within a healthy diet.
To keep healthy, it is vital to eat a balanced diet. This means eating the right amount from different food groups. Too much may cause obesity and too little may cause malnutrition.