Proteins And Fats Of The Human Body

The Functions Of Amino Acids, Cholesterol, Lipids And Collagen

Jun 17, 2009 Roberta Goli

Proteins and fats are essential to life and play an important role in the building and the repair of cells.

Proteins are not only essential for repair and growth of cells, but they also act as chemical messengers as well as carry oxygen from lungs to cells. Fats are used as an energy source, and food provides the body with fats that the body cannot manufacture itself.

The Proteins In The Human Body

Amino Acids: amino acids are essential for the production of proteins which help the body build, grow and for cell repair. Essential amino acids refer to the amino acids animals (including humans) must obtain from food. The eight essential amino acids for an adult human are:

1. Tryptophan
2. Methionine
3. Valine
4. Threonine
5. Phenylalanine
6. Leucine
7. Isoleucine
8. Lysine

These essential amino acids can be obtained by eating beans and corn.

Serotonin: serotonin is synthesized from the amino acid tryptophan. Serotonin acts as a hormone and a neurotransmitter. It affects muscular contractions in the digestive system and also plays a role in blood clotting and mood. The body’s levels of serotonin influence dilation and constriction of blood vessels.

Collagen: collagen is made up of a chain of amino acids and is an important structural protein. It is the major component of connective tissue and provides strength and flexibility to tendons, ligaments and internal organs. Collagen is possibly the most abundant protein in the animal kingdom. Collagenous fibers are the main reason flesh doesn't get torn away from bone.

The Fats In The Human Body

Lipids: lipids are found throughout the body and include fats and cholesterol. Lipids provide a fuel source and play a role in the formation of myelin sheaths and cell membranes.

Cholesterol: the liver manufactures cholesterol and some cholesterol is acquired through the diet. Cholesterol is circulated through the body bound to lipoproteins. Cholesterol plays a part on building and repairing cells, producing sex hormones and production of bile acids which are required for digestion.

Cholesterol has a reputation as being dangerous, and while diseases such as hypertension (high blood pressure) and atherosclerosis (plaque on the inner lining of arterial wall) to some extent are hereditary, high levels of cholesterol in the blood can increase the risk of cardiovascular disease.

Cholesterol travels in the blood plasma in the form of particles. These particles are made up of thousands of cholesterol molecules as well as other lipids bound to proteins. These particles are either:

• Low-density lipoproteins (LDLs): considered the ‘bad cholesterol’ as they can be deposited in the arteries
• High-density lipoproteins (HDLs): the ‘good cholesterol’ as they may reduce cholesterol deposits.

Resource and further reading:

Campbell and Reece, 2002, ' An Introduction To Animal Structure And Function, Animal Nutrition & Circulation And Gas Exchange ', in Biology 6th edition, ed. Benjamin Cummings, San Francisco, chap 40, 41, 42.

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Serotonin

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