In this presentation, the presenter has described the basics of Cell Biology. The features of a cell, types of cells, functions, components of cells etc. This will be very handy for class 7-9th standard students.
1. FUNDAMENTAL UNIT OF LIFE- CELL
PHYSIOLOGY NEWS
By
Randrita Pal (M.Sc. Human Physiology)
2. Cell
Definition-Structural and functional unit of life.
Discovery- Robert Hooke in 1665
Cell Theory- formulated in 1839 by Theodor Schwann
and Matthias Schleiden
• All living organisms are composed of cells.
• Cell is the fundamental unit of life.
• All new cells come from pre-existing cells.
PHYSIOLOGY NEWS
3. Types of organisms depending on number of cells-
Unicellular and Multicellular
Unicellular-organisms made up of one cell.
Eg. Amoeba, Paramoecium,etc
Multicellular- Organisms made up of multiple number of
cells.
Eg. Humans, animals, etc.
PHYSIOLOGY NEWS
4. Shapes and size of Cells
Cells can be of various shapes and sizes like round,
spherical, spiral, spindle etc.
Cells can be of very small cell (muscle cell) to larger size
(nerve cell).
PHYSIOLOGY NEWS
5. Types of Cells
Cells can be classified into two types- Prokaryotic and
Eukaryotic
PHYSIOLOGY NEWS
7. Structure of Cell
Cell mainly consists of these three basic components-
• Nucleus
• Cell Membrane and Cell Wall
• Cytoplasm
PHYSIOLOGY NEWS
8. Nucleus
Structure-
• Dense and spherical organelle.
• Bound by two membranes both forming nuclear envelope. This contains
pores called nuclear pores.
• Substance present inside nucleus is known as nucleoplasm.
• It contains chromosomes and they contain genes which are centers of genetic
information.
Function-
• Nucleus is the storehouse of genes. It is concerned with the transmission of
hereditary traits from the parent to offspring.
• It regulates the cell cycle.
• Nucleus controls all the metabolic activities of the cell.
PHYSIOLOGY NEWS
9. Cell Membrane
Structure
• It is the outermost layer of the cell separating the cellular contents and
outside surroundings
• It is a living part of the cell present in both plant and animal cell and
also in microorganisms.
• It is very thin, elastic and semi-permeable in nature.
• Composed of protein and lipid.
Function
• Being a semi-permeable membrane, it allows the selective passage of
molecules in and out of the cell.
PHYSIOLOGY NEWS
10. Cell Wall
Structure
• Non-living , thick freely permeable membrane
• Made up of cellulose
• Present in plant cells
Functions
• Allows the passage of all molecules in and out of the cell.
• Provides rigidity and structure to the plant cell.
• Protects the plasma membrane.
• Prevents dryness and desiccation in the cell.
PHYSIOLOGY NEWS
11. Cytoplasm
Structure
• It is a jelly-like, viscous, colourless, semi-fluid substance that occurs
between the plasma membrane and the nuclear membrane.
• The aqueous ground substance of cytoplasm is called cytosol that
contains a variety of cell organelles and other insoluble waste
products and storage products, like starch, glycogen, lipid, etc.
Function
• Contains cellular organelles.
• Acts as a source of vital molecules like amino acids, proteins, sugars,
minerals, etc.
• Acts as a base for carrying out cellular activities like metabolism.
PHYSIOLOGY NEWS
13. Nucleus
It is a very important organelle as it controls and regulates all the
activities of the cell.
It has a double membrane with pores called nuclear pores. These pores
allow passage of molecules in and out of the nucleus. The inner matrix
of the nucleus is called nucleoplasm.
There are other organelles within the nucleus ,namely—
• Nucleolus- known as the factory of ribosomes and mainly helps in
protein synthesis of the body.
• Chromosomes – They are vehicle of genes an carry genes from
parents to offspring. Genes regulate most attributes of an individual
like intelligence, height, etc.
PHYSIOLOGY NEWS
15. Mitochondria
• This is known as the ‘powerhouse of the cell’ as it produces energy
in the form of ATP(Adenosine triphosphate)
• It is aa double membrane structure which produces ATP on the
inner side of the inner membrane.
• ATP is known as the ‘energy currency of the cell’ and is used for
carrying out reactions within the body and also mechanical work.
• Offspring gets mitochondrial DNA from the mother.
PHYSIOLOGY NEWS
17. Plastids
• Present only in plant cells.
• Mainly of two types-
i. leucoplast (colourless plastid)
ii. Chromoplasts (coloured plastid)
• Plastids containing chlorophyll (green pigment) is called chloroplasts.
Pigments can be of red, blue and brown colours.
• Depending upon type of pigments, functions of plastids incude
i. Chloroplasts- known s the kitchen of plants. Plants containing
chlorophyll can make their own food by photosynthesis.
ii. Leucoplasts- they store starch, oil and proteins.
iii. Chromoplasts- impart colour to flowers which help them in
fertilization.
PHYSIOLOGY NEWS
19. Endoplasmic Reticulum (ER)
• It is a network of membranes connecting the nucleus and the cell
membrane.
• There are two types of ER namely RER and SER.
RER- Rough Endoplasmic Reticulum which appears rough due to
the presence of ribosomes on the ER.
SER- Smooth Endoplasmic Reticulum which appears smooth due to
the absence of ribosomes on its surface.
• Its main functions include
i. detoxification of poisonous material and transfer of molecules
ii. Production and transfer of proteins (mainly by RER)
PHYSIOLOGY NEWS
21. Golgi Bodies
• Camillo Golgi first identified these in the nerve cell
• They are present in each and every cell.
• They run parallel and are often categorized into Cis-Golgi
and Trans-Golgi system.
• They consist of system of membranes- bound vesicles often in
tubular parallel arrangement in stacks known as misters.
• Main function include storage, package and transfer in
vesicles.
• They also help in formation of lysosomes.
PHYSIOLOGY NEWS
23. Lysosomes
• Known as the ‘suicide bag of the cell.
• Rounded bag like structure which contains many digestive enzymes.
• Acts as cleaners and sweepers of the cell.
• They help to combat pathogenic attack or when the cell needs to die.
PHYSIOLOGY NEWS
24. Vacuole
• They act as storage sacs for solid and liquid materials.
• They are large and numerous in plant cells.
• Small or absent in animal cells.
PHYSIOLOGY NEWS
25. Cell Wall
• It is rigid , non-living fully permeable covering found in only plant cell
and in some microbes like bacteria and fungi.
• Provides rigidity and mechanical support to the cell.
• In plant cell, it is made up of cellulose.
Cell Wall
PHYSIOLOGY NEWS
26. Cell Membrane /Plasma Membrane
• It is made up of lipid bilayer consisting of lipids and proteins.
• It is semi-permeable in nature i.e. it allows the passage of selective
materials.
• Its flexibility helps to engulf food into the cell.
PHYSIOLOGY NEWS
28. Osmosis
• Passage of water/liquid from a region of its higher concentration to a region of its
lower concentration when the two solutions are separated by a semi-permeable
membrane.
• When a cell is placed in a solution where the water concentration is high and solute
content is lower then the cell, then this solution is called a hypotonic solution. In such
a case, water will move from outside the cell into the cells.
• When the cell is placed in a solution having higher solute content than the cell, it is
called a hypertonic solution. In such case, water moves out of the cell.
• The absorption of water from the soil by the roots is by osmosis.
• If water concentration of the solution is similar to that of the cell, then it is called an
isotonic solution. In such a case there will be no movement of water between cell and
its surroundings.
PHYSIOLOGY NEWS
30. Diffusion
• Movement of substance from a region of its higher concentration to a region
of lower concentration when both solutions are in direct contact.
• Plays a major role in gaseous exchange.
PHYSIOLOGY NEWS
