Chemical Composition of the Cell

Chemical Composition of the Cell

Chemical compounds in the cell can be divided into two major groups:

Organic compounds

Inorganic compounds  

Organic compounds are chemical compounds that contain the element carbon. Organic compounds in the cell include carbohydrates, protein, lipids and nucleic acids. Some of these compounds are synthesised by the cell itself.

Water is an inorganic compound which is composed of hydrogen and oxygen. It is an important compound in the cell.

Percentage of Body Weight	Element	Usage
65%	Oxygen	This element is obviously the most important element in the human body. Oxygen atoms are present in water, which is the compound most common in the body, and other compounds that make up tissues. It is also found in the blood and lungs due to respiration.
18.6%	Carbon	Carbon is found in every organic molecule in the body, as well as the waste product of respiration (carbon dioxide). It is typically ingested in food that is eaten.
9.7%	Hydrogen	Hydrogen is found in all water molecules in the body as well as many other compounds making up the various tissues.
3.2%	Nitrogen	Nitrogen is very common in proteins and organic compounds. It is also present in the lungs due to its abundance in the atmosphere.
1.8%	Calcium	Calcium is a primary component of the skeletal system, including the teeth. It is also found in the nervous system, muscles, and the blood.
1.0%	Phosphorus	This element is common in the bones and teeth, as well as nucleic acids.
0.4%	Potassium	Potassium is found in the muscles, nerves, and certain tissues.
0.2%	Sodium	Sodium is excreted in sweat, but is also found in muscles and nerves.
0.2%	Chlorine	Chlorine is present in the skin and facilitates water absorption by the cells.
0.06%	Magnesium	Magnesium serves as a cofactor for various enzymes in the body.
0.04%	Sulfur	Sulfur is present in many amino acids and proteins.
0.007%	Iron	Iron is found mostly in the blood since it facilitates the transportation of oxygen.
0.0002%	Iodine	Iodine is found in certain hormones in the thyroid gland.

The Importance of Organic Compounds in the Cell

1. Carbohydrates

• Supply energy for cell processes
• A means of storing energy
• Give structural support to cell walls

2. Lipids

• Store large amounts of energy over long periods of time
• Act as an energy source
• Play a major role in the structure of the cell membranes
• Act as a source of metabolic water
• Reduce the loss of water by evaporation

3. Proteins

• Act as building blocks of many structural components of the cell ; required for growth
• Form enzymes which catalyse chemical reactions
• Form hormones which control growth and metabolism

4. Nucleic acids

• Contain the genetic information of cells
• Play a vital role in protein synthesis

The importance of water in the cell

• Water is important for life because its chemical and physical properties allow it to sustain life.
• Water is a polar molecule which consists of 2 hydrogen atoms and 1 oxygen atom. A polar molecule is a molecule with an unequal distribution of charges. Each molecule has a positively charged and a negatively charged end. Polar molecules attract one another as well as ions. Because of this property, water is considered the solvent of life.
• It is the transport medium in the blood
• It acts as a medium for biochemical reactions.
• Water helps in the maintenance of a stable internal environment within a living organism. The concentration of water and inorganic salts that dissolve in water is important in maintaining the osmotic balance between the blood and interstitial fluid.
• It helps in lubrication.
• Water molecules have very high cohesion. Water molecules tend to stick to each other and move in long unbroken columns through the vascular tissues in plants.