Here is your sample essay on Biology


Biology is the scientific study of living beings-plants and animals. Biology is divided into two main branches-Botany and Zoology.


Botany is the study of plants such as stem, root, fruits etc.



Zoology is the study of animals such as bacteria, mammals etc


Cells are the smallest structural and functional units of living organisms (life). Cells were discovered in 1665 by Robert Hooke another scientist in 1833 Robert Brown discovered and named the nucleus in a cell.


Structure of cell

A cell has following structures:

1. Plasma membrane and cell wall-

Every kind of cell is bounded by a thin membrane called plasma membrane. The plant cell has an additional protection outside the plasma membrane called the cell wall.


2. Cytoplasm

Cytoplasm is a viscous, homogeneous and colloidal liquid that contains water, oxygen, metallic salts, amino acids, carbohydrates, lipids and proteins. It is a seat of cellular metabolism.

3. Nucleus

The nucleus is a major centrally located cellular component. It has two types of nuclear structures-the nucleolus and chromatin. Nucleolus is rich in protein and RNA (ribonucleic acid). The Chromatin is a thin, thread-like chromosome material and composed of the genetic substance DNA (deoxyribonucleic acid).


4. Chromosomes

The chromatin is condensed into two or more thick-ribbon like structure which is called chromosome. It contains many segments called genes.

5. Mitochondria

Mitochondria consists of enzymes necessary for the total oxidation of food and for release of high amount of energy in the form of ATP (adenosine triphosphate) molecules. Mitochondria is known as ‘Power house of the cell’.


6. Plastids

Plastids occur only in plant cells which are of two types-Leucoplasts and Chromo lasts.

7. Golgi apparatus

It functions in the processing and packaging of cell secretions : proteins and lipids.

8. Lipid

A type of fatty organic compound.

9. Chloroplasts-

The chloroplasts have the green pigments called chlorophyll and they are involved in the photosynthesis of food. So chloroplasts are the “Kitchens of the cells”.

10. Lysosomes-

Lysosome contains a variety of digestive enzymes. These enzymes are released when the lysosome’s membrane bursts. It acts as suicide bags in causing cell death.

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