The Fundamental Unit Of Life

 

THE FUNDAMENTAL UNIT OF LIFE

 Robert Hooke discovered Cell.

Leeuwen Hoek discovered free living cells.

Robert Brown discovered nucleus of the cell.

Purkinje discovered the fluid substance in the cell and named it as Protoplasm.

Schleiden and Schwann proposed Cell Theory.

Virchow suggested that Cell arise from pre existing cell.

 Cell – Cell is the fundamental structural and functional unit of life.

 Organism made up of single cell is called as Unicellular organism.

Eg. Amoeba, Chlamydomonas, Paramoecium, Bacteria, Euglena.

Organism made up of more number of cells is termed as Multicellular organism.

Eg. Fungi, Plants, Animals, etc.

 Cell Organelles – These are specific components within the cell with special functions.

 Features of Cell

1.      Plasma membrane

2.      Nucleus

3.      Cytoplasm

 PLASMA MEMBRANE/CELL MEMBRANE

1)     Separates the content of the cell from its external environment.

2)     Permits the entry and exit only of selected material in and out of the cell.

3)     Prevents the movement of unwanted material.

 ·        Diffusion – Spontaneous movement of substance (molecules) from the region of higher concentration to the region of lower concentration.

·        Osmosis – Movement of water molecules from the region of higher concentration to the region of lower concentration through selectively permeable membrane is called osmosis.

Eg.      1) Unicellular fresh water organisms gain water.

            2) Plant cells gain water.

            3) Roots absorb water.                                                                                                                

Selectively permeable membrane – this is the membrane which allows the movement of only selected materials through it.

HYPOTONIC SOLUTION	Medium around the cell have higher water concentration.	More water moves into the cell. Cell swells up.
ISOTONIC SOLUTION	Water concentration is same inside and outside the cell.	Same number of water molecules move in and out of the cell. Cell size remains same.
HYPERTONIC SOLUTION	Water concentration outside the cell is less than inside the cell.	More water leaves the cell. Cell shrinks.

CELL WALL – This is outer covering of plant cell.

Cell wall is made up of Cellulose.

 Plasmolysis – Plant cell loses water by osmosis and cell shrinks away from cell wall.

 NUCLEUS

Double layered covering of nucleus is called Nuclear membrane.

Nucleus contains rod shaped chromosomes

Chromosomes are composed of DNA (Deoxyribonucleic Acid)

Genes – Functional segments of DNA

Function -      1) Cellular reproduction

                        2) Determines the destiny of cell

                        3) Directs chemicals

 CYTOPLASM

This is the fluid present inside the plasma membrane. Cell organelles are present in cytoplasm.

 ENDOPLASMIC RETICULUM

Rough endoplasmic reticulum	Smooth endoplasmic reticulum
1.      Ribosomes are attached to the surface. 2.      Ribosomes serves as protein factories of the cell.	1.      Ribosomes are absent on the surface. 2.      This helps in manufacture of fat molecules.

 

Biogenesis – this is the building of cell membrane using proteins and lipids molecules.

Function –     This serves as a channel for transport of materials.

                        This provides the surface for some biochemical activities of the cell.

 GOLGI APPARATUS

This was first described by Camillo Golgi.

Function –     storage, modification and packaging of the products in vesicles

                        Complex sugar is made from simple sugar.

                        Formation of Lysosomes.

 LYSOSOMES

These are suicide bags of the cell.

Lysosomes contain powerful enzymes which are capable of digesting organic matter.

Function –     keeps the cell clean

                        Foreign material entering cell end up in Lysosomes

                        Old cell organelles end up here.

                        Lysosomes burst and the enzymes digest the entire cell.

 MITOCHONDRIA

These are Powerhouse of the cell.

Energy is released here in the form of ATP (Adenosine Triphosphate)

 PLASTIDS

This is present only in plant cells.

Chromoplasts – Coloured Plastids

Leucoplasts – Colourless Plastids

Chloroplasts – Plastids containing green pigments called chlorophyll.

 VACUOLES

These are storage sacs of the cell.

These are very small in animal cell and big in plant cell.

Vacuoles are full of cell sap.

Substances important for life are stored in cell vacuole.