Effect of Radiation on cells
Radiation is a form of electromagnetic energy. It includes ultra violet rays,X-rays,gamma rays, beta rays, neutrons, infra red rays, radio waves, etc. Radiation is obtained from sun, stars, radioactive elements and cosmic rays from the solar system.
Based on biological effects the radiations are classified into two types they are-
1. Exciting radiation and
2. Ionizing radiation.
The exciting radiation acts on the surface of the animal. They cannot penetrate into the body. They transmit their energy by excitation of the atoms of the cells and not by ionization. Ultra violet rays are exciting radiations.
Ionizing radiation cause ionization of the atoms of the cells. They can penetrate deep into the body. Ionizing radiations include X-rays, gamma rays, beta rays, neutrons, etc. The ionizing radiations also released from atom bombs. The ionizing radiation are caused by sub atomic particles e.g. Alpha particle, beta particle, neutrons, protons, etc.
Electromagnetic rays are electromagnetic waves. E.g X-rays, gamma rays, infra red rays and radio waves etc.
Biological effects of Radiation
Radiation causes the following effects on animals and cells.
- Sun burn: UV rays cause reddening of the skin. It is the sun burn. The skin become injured. The cells die and phagocytes invade, resulting in a blister. The skin peels off. The lysosomes of the cells breakdown releasing the hydrolytic enzymes. These enzymes digest the cell.
- Eye burn: Eye burn refers to the killing of the cells of the cornea(eye). It is caused by UV rays. It leads to blindness. It is also called snow blindness.
- Skin cancer: UV light produces skin cancer( carcinoma).
- Killing: UV rays kill bacteria, protozoans, eggs of marine animals, algae, fungi and cells in tissue culture.
- Photo reactivation: Visible light reverses the injuries effects of the UV rays. The bacteria, spores, viruses, animals, and plant cells, inactivated by UV rays, are photo reactivated by UV rays, are photo reactivated by treatment with visible light.
- Mitotic apparatus: Ionizing radiations rupture mitochondria.
- Mutation: Ionizing radiation cause the breaking of the hydrogen bonds between the two chains of the DNA.
- Breaking of hydrogen bonds: Ionizing radiations cause gene mutation and chromosomal mutation.
- Fracture of DNA stands: Radiation causes the breaking of DNA strands.
- Cross linking: UV radiation leads to the formation of chemical bonds between adjacent thymine residues. So adenine cannot link with the thymine. Thus the double helix becomes distorted.
- Inhibition of replication: Ionizing radiation inhibits DNA synthesis.