CELL – STRUCTURE

AND

FUNCTIONS

DR. ABHA VERMA

Ph. D (Biotechnology)

First to View CellsFirst to View Cells

• In 1665, Robert Hooke used a microscope to examine a thin slice of cork (dead plant cells)

• What he saw looked like small boxes

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First to View CellsFirst to View Cells

• Hooke is responsible for naming cells

• Hooke called them “CELLS” because they looked like the small rooms that monks lived in called Cells

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Anton van Leeuwenhoek

• In 1673, Leeuwenhoek(a Dutch microscope maker), was first to view organism (living things)

• Leeuwenhoek used a simple, handheld microscope to view pond water & scrapings from his teeth

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Beginning of the Cell TheoryBeginning of the Cell Theory

• In 1838, a German botanist named Matthias Schleidenconcluded that all plants were made of cells

• Schleiden is a cofounder of the cell theory

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Beginning of the Cell TheoryBeginning of the Cell Theory

• In 1839, a German zoologist named Theodore Schwannconcluded that all animals were made of cells

• Schwann also cofounded the cell theory

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Beginning of the Cell TheoryBeginning of the Cell Theory

• In 1855, a German medical doctor named Rudolph Virchow observed, under the microscope, cells dividing

• He reasoned that all cells come from other pre-existing cells by cell division

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CELL THEORY

• All living things are made of cells

• Cells are the basic unit of structure and function in an organism (basic unit of life)

• Cells come from the reproduction of existing cells(cell division)

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The Cell

Cells are the basic structural units of living organisms.

Some organisms are made up of a single cell and some are made up of many cells.

The number of cells in a tall tree or an animal like an elephant or human being are billions and trillions of cells.

Organisms made up of many cells are called multicellular organisms. Eg: a tree, an elephant.

Organisms made up of only one cell are called unicellular organisms. Eg: amoeba, paramaecium.

Shape of cellsCells are of different shapes.

Some cells keep changing their shape. Eg : amoeba, white blood cells in human beings.

Some cells are spherical, round, elongated, spindle shaped, or branched.

Size of cells

Cells in living organisms are of different sizes. They may be as small as millionth

of a meter (micrometre or micron) or large as a few centimetres.

The smallest cell is the cell of mycoplasma (0.1 to 0.5 micrometre).

The largest cell is the egg of an ostrich (17cm x 13cm).

PARTS OF A TYPICAL EUBACTERIA /PROCARYOTIC CELL

Outermost layer, non living ,rigid Found in bacterial cells, fungal cells and plant cells.Made up of

complex polysaccharide named peptidoglycan (sugar + aa) or murein in bacteriaChitin (nitrogenous polysaccharide) in fungusCellulose (most abundant carbohydrate) in plant cell

FUNCTION :Rigidity, mechanical support and protection

CELL WALL कोशिका शित्ति

Bacterial cell wall structure

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Also contains calcium and magnesium pectateswhich are partially solubilised to make ripen fruit soft

CELLULOSE

LIGNIN

PECTIN

PLANT CELL WALL

Primary cell wall

Secondary cell wall

Middle lamella

Cell or Plasma MembraneCell or Plasma Membrane

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

• Present in all cells, just below the cell wall in plant cells,

• outermost membrane in animal cells

• Composed of double layer of phospholipids and proteins

• Phospholipids Heads contain glycerol & phosphate and are hydrophilic (attract water)

• Phospholipids Tails are made of fatty acids and are hydrophobic (repel water)

• Make up a bilayer where tails point inward toward each other

• Can move laterally to allow small molecules (O2, CO2, & H2O to enter)

The Cell Membrane is FluidThe Cell Membrane is Fluid

Molecules in cell membranes are constantly moving and changing

CELL MEMBRANE कोशिका झिल्ऱीFUNCTION : Provides definite shape and act as mechanical barrier between the external and the internal environment of cell.The flexibility of the membrane help the cell to engulf food and other substances from its external environment by endocytosis while expell toxic materials by exocytosis.Phagocytosis and Pinocytosis

(िक्षकाणुक्रिया / कोशिका-ऩायन)

अक्रियआवागमन ववसरण

Permeability (ऩारगम्यिा) - regulates the movement of molecules in and out of the cell.

Passive transport. (अक्रियआवागमन)Diffusion (ववसरण) - movement of solute ववऱेयOsmosis (ऩरासरण) - movement of water ववऱयन

Facilitated diffusion (सुववधा ववसरण) - movement of solute through a protein channel

Active transport (सक्रियआवागमन)

सान्द्रिा

अधधऩारगम्य झिल्ऱी

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