Cell theory

• • Theory is a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained.
• • Microscope is an instrument that makes an enlarged image of a small object, thus revealing details too small to be seen by the unaided eye.
• Anton van Leeuwenhoek, observed living cells in pond water, which he called "animalcules" (1673)
• Robert Hooke was the first person to see cells, he was looking at cork and noted that he saw "a great many boxes. First to coined the term “cell”. (1665)
• Theodore Schwann is zoologist who observed tissues of animals had cells (1839)
• Mattias Schleiden is a botanist, who observed tissues of plants contained cells (1845)
• Rudolph Virchow also reported that every living thing is made of up vital units, known as cells. He predicted that “cells come from other cells”. (1850)
• Every living organism is made of one or more cells.
• The cell is the basic unit of structure and function. (life)
• All cells arise from pre-existing cells.
• Cell membrane

  • Structure: A double membrane composed of lipids and proteins. Present both in plant and animal cells.

  • Function: Provides shape, protects the inner organelles of the cell and acts as a selectively permeable membrane.
• Centrosome

  • Structure: Composed of centrioles and found only in the animal cells.

  • Function: It plays a major role in organizing the microtubule and cell division.
• Chloroplast

  • Structure: Present only in plant cells and contains a green-coloured pigment known as chlorophyll.

  • Function: Sites of photosynthesis.
• Cytoplasm

  • Structure: a jelly-like substance, which consists of water, dissolved nutrients and waste products of the cell.

  • Function: responsible for the cell’s metabolic activities.
• Endoplasmic reticulum

  • Structure: a network of membranous tubules, present within the cytoplasm of a cell.

  • Function: forms the skeletal framework of the cell, involved in the detoxification, production of lipids and proteins.
• Golgi apparatus

  • Structure: membrane-bound, sac-like organelles, present within the cytoplasm of the eukaryotic cells.

  • Function: it is mainly involved in secretion and intracellular transport.
• Lysosome

  • Structure: a tiny, circular-shaped, single membrane-bound organelles, filled with digestive enzymes.

  • Function: helps in the digestion and removes wastes and digests dead and damaged cells. Therefore, it is also called as the “suicidal bags”.
• Mitochondria

  • Structure: an oval-shaped, membrane-bound organelle, also called as the “powerhouse of the cell”.

  • Function: the main site of cellular respiration and also involved in storing energy in the form of ATP molecules.
• Nucleus

  • Structure: the largest, double membrane-bound organelles, which contains all the cell’s genetic information.

  • Function: controls the activity of the cell, helps in cell division and controls the hereditary characters.
• Peroxisome

  • Structure: a membrane-bound cellular organelle present in the cytoplasm, which contains the reducing enzyme.

  • Function: involved in the metabolism of lipids and catabolism of long-chain fatty acids.
• Ribosome

  • Structure: Non-membrane organelles, found floating freely in the cell’s cytoplasm or embedded within the endoplasmic reticulum.

  • Function: Involved in the synthesis of proteins.
• Vacuole

  • Structure: A membrane-bound, fluid-filled organelle found within the cytoplasm.

  • Function: Provide shape and rigidity to the plant cell and help in digestion, excretion, and storage of substances.
• Cells

  - Cell membrane

  - Centrosome

  - Chloroplast

  - Cytoplasm

  - Endoplasmic Reticulum

  - Glogi Apparaturs (Golgi body)

  - Lysosome

  - Mitochondria

  - Nucleus

  - Peroxisome

  - Ribosome

  - Vacuole
• All cells have, cell membrane, cytoplasm, DNA or cell's genetic material.