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Alimentary system
- A detailed picture of the digestive system
- Explanation of how the body digests foods
3.1
What is the Digestive System ?
Digestion essentially occurs in a series of tubes such as the Oesophogus and Intestines as food passes through the body. A number of other organs
contribute to digestion by providing enzymes for the breakdown of food.
Mouth: The mouth is the starting point of digestion. Here the process of chewing starts to break down food and enzymes such as salivary lipase and
amylase also start to chemically break down the food.
Oesophagus: Once you swallow the food moves into the Oesophagus where continual waves of involuntary contraction push the food into the
stomach.
Stomach: The stomach has both a mechanical and a chemical function in digestion. The upper part of the smooth (involuntary) stomach muscle
relaxes to allow a large volume of food to be stored. The lower muscle then contracts in a rhythmical manner in order to churn the food inside and
mix it together with the gastric acid (mainly hydrochloric acid) and digestive enzymes Pepsin, Gelatinase and Gastric Amylase and Lipase which break
it down further. The stomach must then empty its contents into the small intestine.
Small Intestine: Whilst in the small intestine food is subjected to yet more enzymes, those from the Pancreas and from the glands within the intestine
walls which break down carbohydrates and proteins. It is also mixed with a product of the liver which is stored and released into the intestine by the
gall bladder. This is commonly known as bile. Bile works to dissolve fat so that it can be digested by the other enzymes. Rhythmic smooth muscle
contraction continues within the small intestine and pushes the digesting food through its narrow tube.
Once the food is completely broken down into its individual components it is absorbed through the intestinal walls, into the blood flow of the
capillaries which surround the intestine. To make this process faster and more efficient the intestinal walls contain numerous folds which are covered
in finger-like projections called villi. This vastly increases the surface area of the intestine wall for molecules of digested food to pass through.
Large Intestine: The large intestine continues the foods journey and is the bodies last chance to absorb any water and minerals still remaining. The
rest of the contents of the large intestine is waste such as undigestable pieces of food and fiber. This is passed through to the rectum where it is
stored until you go to the toilet
Alimentary system
A detailed picture of the digestive system
-Explanation of how the body digests foods
Cellular metabolism
Cellular metabolism is the set of chemical reactions that occur in living
organisms in order to maintain life. Cellular metabolism involves
complex sequences of controlled biochemical reactions, better known as
metabolic pathways.
• Energy systems
Explain how energy use changes
• Protein synthesis
Cellular metabolism
Protein synthesis
How is protein synthesis similar to the catalysis of a
reaction by an enzyme?
Protein synthesis is a series of chemical reactions in which
molecules are brought into contact with one another and
chemical bonds are formed and broken. The key event in
protein synthesis is the formation of bonds between
adjacent amino acids in the protein and the breaking of
bonds between the same amino acids and the tRNA
molecules that first bring the amino acids to the ribosomes.
The function of the ribosome is to bind the tRNA molecules
and then move through the ribosome. As the tRNAs are
moved, the ribosome’s configuration brings the amino acids
into contact and then severs the bonds between tRNA and
amino acid. In a general sense, RNA is acting as an enzyme
that catalyzes the reactions that form the amino acid chain.
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