Define Prokaryotic cell?

1. Organization of Cells:

(i) Cell is the basic structural and functional unit of living organisms. All living organisms are made up of cells.

(ii) Based on the number of cells living organisms possess, they can be classified as unicellular organisms or multicellular organisms.

(iii) The cells can be categorized into two types, i.e., prokaryotic cell and eukaryotic cell.

(iv) Prokaryotic cells have no true nucleus. This type of nucleus is called a nucleoid. Example: E.coli bacteria.

(v) Cells which has a true nucleus is called a eukaryotic cell. It is bigger than prokaryotic cells. Example: Plants and animals cell.

(vi) Cells vary in shapes and size. Epithelial cells, muscle cells, nerve cells, red blood cells, etc., are a few examples of cells having different shapes and sizes.

(vii) An outer cell membrane, a liquid cytoplasm and a nucleus are the three major parts of a typical cell. Inside a cell, there are many tiny structures called cell organelles which are responsible for providing the needs of the cell.

2. Organization of Tissues:

(i) Cells are combined to form tissues. The tissues are combined to form organs. Many organs are combined to form the organ system.

(ii) All the complex organisms consist of four basic types of tissues- Epithelial (covering), Muscular (contractile), Connective (supporting) and Nervous tissue.

3. Organ:

(i) Brain, heart, lungs, kidney, liver, etc., are different types of organs present in the human body.

(ii) The sense organ eye is concerned with vision. 

(iii) The structure of a human eye can be broadly classified into the external structure (sclera, conjunctiva, cornea, iris and pupil) and internal structure (lens, retina, optic nerve, aqueous and vitreous humour).

4. Organ System:

Our respiratory system consists of organs like trachea, bronchus and lungs which are responsible for the exchange of gases between the atmosphere and the blood.

5. Homeostasis:

(i) Homeostasis is the maintenance of a constant internal environment of the body.

(ii) Selective permeability of plasma membrane enables the cell to maintain homeostasis.

6. Diffusion:

Diffusion involves movement of molecules from the region of their higher concentration to the region of their lower concentration which can occur without a semi-permeable membrane.

7. Osmosis:

Osmosis involves movement of solvent molecules from the region of their higher concentration to the region of their lower concentration which can take place through a semi-permeable membrane.

8. Osmoregulation:

(i) Osmoregulation is the process by which an organism regulates the water balance in its body and maintains the homeostasis of the body.

(ii) The two major types of Osmoregulation are Osmoconformers and Osmoregulators.

9. Cellular Respiration:

(i) Respiration is the process in which energy is released while food is oxidised. It consists of external respiration and internal respiration or cellular respiration.

(ii) There are two types of respiration depending upon the availability of oxygen, namely aerobic respiration and anaerobic respiration.

10. Metabolism:

(i) Metabolism is the sum of chemical reactions by which living organisms sustain their life.

(ii) Metabolism can be divided into two categories, namely anabolism and catabolism.

(iii) The repeated anabolic and catabolic reactions in the metabolic process maintain the homeostatic condition of the body.