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Халдарбекова Лаура Нуржановна

Cellular Organization

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26.03.2017

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• A cell is the structural and functional unit of all life forms. • All living organisms, whether plants or animals, are made up of microscopic units called cells. • The cell occupies the same central position in biology as the atom in the physical sciences. • Organisms may be broadly classified into two kinds: – Unicellular – Multi-cellularIt was the British botanist Robert Hooke who, in 1665, while examining a slice of bottle cork under a microscope, found its structure resembling the box-like living quarters of the monks in a monastery, and coined the word “cells”

Cellular Organization2.pptx

Some Facts about Cells • • The word cell is derived from the Latin word “cellula” which means “a little room” • • • It was the British botanist Robert Hooke who, in 1665, while examining a slice of bottle cork under a microscope, structure resembling living quarters of the monks in a monastery, and coined the word “cells” found the its box-like

Some Facts about Cells • • The Dutch scientist A.V. in 1674, Leeuwenhoek, the minute discovered forms of life such as bacteria and single celled animals in a drop of water • • In 1831, Robert Brown discovered the nucleus in the cell • • In the year 1838, Matthias Schleiden, a German botanist, first proposed the idea that all plants consist of cells

Some Facts about Cells • • In 1839, Theodor Schwann, another German botanist, asserted that all plants and animals are made up of cells • • J.E. Purkinje, in 1839, used the term protoplasm to describe the juicy, slimy gelatinous contents of the cell • • In 1885, Rudolf Virchow expressed that all cells arise from pre-existing cells

Some Facts about Cells • • In 1940, two German Scientists, Ruska and Knoll, invented the electron microscope • • Man is estimated to have about 100 trillion (1014 ) cells in number • • The cells that make up our body are so small that you could fit over 200 of them on the full stop at the end of this sentence.

Cells: An Introduction • • A cell is the structural and functional unit of all life forms. • • All living organisms, whether plants or animals, are made up of microscopic units called cells. • • The cell occupies the same central position in biology as the atom in the physical sciences. • • Organisms may be broadly classified into two kinds: • – Unicellular • – Multi-cellular

Cells: An Introduction • • All living beings, plants and animals, start their life with a single cell. • • Some organisms exist as a single cell and carry out the various metabolic life processes such as assimilation, respiration, reproduction, excretion, etc., that are essential for their survival. • • These are known as unicellular organisms. • • Example: Yeast, bacteria, chlamydomonas, amoeba

Some Unicellular Organisms Amoeba Paramecium Chlamydomona

Cells: An Introduction • • Some cells divide and give rise to organisms with more than one cell, these organisms are termed as multi- cellular. • • Example: animals, humans, most plants

Some Multi-cellular Organisms Cells from the cheek

Structure of a Cell • • Cells vary in shape and size. They may be oval, spherical, rectangular, polygonal, spindle shaped, star shaped, rod-shaped or totally irregular like the nerve cell. • • The diversity in cells is in accordance with the role or function it has to perform as part of the tissue or organ system. • • In general, there is no typical shape for cells.

Various Cells from the Human Body

Structure of a Cell • • Each cell has got certain specific components within it known as cell organelles, each of which performs a special function • • A cell is able to live and perform all its functions because of these organelles • • These organelles together constitute the basic unit called the cell • All cells have the same organelles, no matter what their function is or what organism they are found in

Structure of a Cell • • There are three features in almost every cell: • – Plasma Membrane • – Nucleus • – Cytoplasm • • All activities inside the cell and interactions of the cell with its environment are possible due to these features

Plasma Membrane or Cell Membrane • • Cell membrane is present in both plant and animal cells. • • It is living, elastic and made of proteins and lipids (fats). • • Its function is to provide a mechanical barrier for the protection of the inner cell contents and to regulate the movement of molecules in and out of the cell. • • It is called a selectively permeable membrane

Cell Wall • • The cell wall is present only in plant cells and lies outside the plasma membrane • • It is made up of a complex polysaccharide (carbohydrate) called cellulose. • • Its function is to give strength and rigidity to the cell. It is non-living. • • Cell walls permit the cells of plants, fungi and bacteria to withstand hypotonic external media without bursting

Nucleus • • This is a prominent, spherical or oval structure found at the centre of the cell. • • It is the controlling centre of all cell activities and has been described as the brain of the cell. • • It regulates all metabolic and hereditary activities of the cell • • It also plays a central role in cellular reproduction - the process by which a single cell divides and forms two new cells

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