Biology hand book is very useful for the students for quick revision for exams.

Biology hand book is useful all the competitive exam aspirants related to biology

We took utmost care to prepare definitions in this Biology hand book.


                                                      1.CELL – STRUCTURE & FUNCTION


Cell is the smallest biological unit capable of carrying out all of the fundamental activities of life. It is basic unit of structure and function.



plant cell



animal cell


Unicellular organism: Amoeba, Paramecium, chlamydomonas are the single celled and are called unicellular organisms the single cell is capable of performing all life processes like obtaining food, respiration, respiration growth and reproduction.

multicelluar organisms Living organisms which have more than one cell is called multicelluar organism’s Basic life out by variety of cells.

Pseudopodia are false feet or the structures formed by unicellular organism to capture food or for locomotion.

Cells were first observed by Robert Hooke in 1665

Antoine van Leeuwenhoek was the first to see living bodies under microscope which had constructed him.

Robert Brown was the first person to observe “Nucleus” in epidermis of orchid leaves.

Plant cells differ from those of animals in having an additional layer around the cell membrane termed cell wall.

Cell wall: Cell wall is outer most non-living cellulose layer that surrounds entire cell, including cell membrane. Cell wall gives strength and rigidity to plants.

Cell exhibits variety of shapes and sizes and numbers.

Cell Membrane: Cell membrane is thin flexible layer that surrounds cell and which controls all that enters and leave the cell.

The smallest cell 0.1 to 0.5 micrometers (Microns) is found in bacteria. A human liver and kidney cell is 20 to 30 micrometer in size.

Human Nerve cell:

Human nerve cell is nearly about 90 to 100cm. The largest cell, measuring nearly 17cm × 18cm, is egg of an ostrich.

Contractile vacuole: Contractile vacuole is sac like cell organelle which pumps fluid in cyclic manner.

Albert calude is father of cell biology.

Cell organisms like mitochondria, plastids, Ribosome’s, Endoplasmic reticulum, Golgi apparatus, lysosomes and vacuoles are important because they carry very crucial function in cells.

Plasma Membrane


Selectively permeable membrane: Plasma membrane allows certain substances to pass through it hence membrane it is called selectively permeable membrane. It is composed of lipids and proteins

Chromoplasts: Chromoplasts are coloured plastids present only in plant cells.

Leucoplasts: Leucoplasts are colourless plastids present only in plant cells.

Cytoplasm: Cytoplasm is part of protoplasm excluding nucleus.

Lysosomes cause destruction of cell hence they are called suicidal bags.

Hormone: An organic substance produced in small amounts at one site in an organism and transported to another site where it act.

Enzyme: An organic catalyst which catalyses a reaction with in a cell.

Mitochondria: Cell power house and is seat for cellular respiration.

Cristae: Folds of inner membrane of mitochondria.

Cisternae: Enclosed spaces in cytoplasm of cell, which get separated from around substance by cytoplasmic membrane.

Nucleus The nucleus regulates and controls all functions and determines characteristics of organisms and involved in cell division.

Endoplasmic reticulum transports substances and are two types.

  • Rough Endoplasmic reticulum: It is site of protein manufacture.
  • Smooth Endoplasmic reticulum: Helps in the manufacture of fat molecules and lipids.
  1. Chloroplasts trap energy of sunlight and transform to chemical energy in photosynthesis.
  2. Vacuoles: Large empty spaces which are visible.
  3. Matthias, Jacob schleiden and Theodar schwam together formed cell theory.
  4. Camillo Golgi observed Golgi body, made of several membranes. Its function is package of various substances. The number of Golgi bodies is large in those cells that secrete hormones and enzymes.


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