Chemical Composition of Living Organisms

Elements in the Living Body

• Only about 25 elements out of 92 naturally existing elements are present in the living body.
• These elements are present in different locations in the body in different forms.

Most Common Elements in the Living Body

• The most common 4 elements in the living body are Carbon, Hydrogen, Oxygen, and Nitrogen.
• Other essential elements include Sulphur, Phosphorous, Sodium, Potassium, Calcium, Magnesium, Iron, and Chlorine.

Elements Percentage in the Human Body

• Diagram 1.1 shows the percentages of main elements in the human body.

Classification of Chemical Compounds

• Chemical compounds can be divided into two categories: organic compounds and inorganic compounds.
• Organic compounds contain carbon, while inorganic compounds do not contain carbon.

Biological Molecules

• Biological molecules are organic compounds that build up living matter.
• There are four types of biological molecules:
  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic acids

Inorganic Molecules

• Inorganic molecules include water, minerals, and gases.
• These molecules are essential for the maintenance of life.