CELL BIOLOGY

Introducti
on:-
Cell
 The cell (from Latin cella, meaning "small room") is the basic structural,
functional, and biological unit of all known organisms.
 A cell is the smallest unit of life.
 Cells are often called the "building blocks of life".
 The study of cells is called cell biology, cellular biology, or cytology.
 Self replicating structure.
 First cell were observed and named by Robert Hooke in 1665 from slice of cork.
 Some organisms consists of a unicellular organism,other are multicellular.
 Diameter:- 2-120um.
 There are two type of cell :- prokaryotic cell and eukaryotic cells.
 A prokaryotic cell is a type of cell that does not have a true nucleus or membrane-
bound organelles. Organisms within the domains Bacteria and Archaea are based
on the prokaryotic cell, while all other forms of life are eukaryotic.
Constituents

 Different substances that make a cell are Collectively called

protoplasm.
 Protoplasm composed by:-
 Water – 70-80% water is present in cell
 Carbohydrates
 Lipids
 Proteins
 Electrolytes :- Sodium (Na+), potassium (K+) etc
Major Structure Present in a Cell are :-

 Cell Wall ( absent in animal cell)

 Cell Membrane
 Cytoplasm and it’s organelles
 Nucleus
Animal cell

Cell Membrane
Structure:-
 Also called as semipermeable membrane or
plasma membrane
 Extremely delicate, thin, elastic, living and
semipermeable
membrane
 Made up of two layers of lipid molecules in which
protein molecules are floating
 Can be observed under an electron microscope only
 Function:-
 Maintain shape and size of the cell
 Protects internal contents of the cell
 Regulates entry and exit of substances in and out of the
l
cel
 Maintain homeostasis
Nucleus
Structure  Dense spherical body located near the centre of the cell

:-  Present in all the cells except red blood cells and sieve tube cells
 Well developed in plant and animal cell
 Few types of cells have more than one nucleus (skeletal muscle cells)
 Nucleus has a double layered covering called nuclear mmberane
 Nuclear membrane has pores of diameter about 80-100nm
 Colourless dense sap present inside the nucleus known as nucleoplasm
 Nucleoplasm contains round shaped nucleoid and network of chromatin
fibres
 Chromosomes contain stretches of DNA called as genes
 Genes transfer the hereditary information from one generation to the next
Function:-

 Control all the cell activities like metabolism, protein synthesis, growth and
cell division
 Nucleolus synthesized RNA to constitute ribosomes
 Store hereditary information in genes
Cytoplasm
Structure:-
 It is the fluid content present inside the plasma membrane
 Jelly like material formed by 80% of water
 Present between the plasma membrane and nucleus
 Contains a clear liquid protein called cytosol and various particles
 Also contains many organelles with distinct structure and function
 Function :-
 It acts as the store of important chemicals
 It is a physical basis of all metabolic activities
 It keeps the cell fully expanded and provide turgidity
Endoplasmic Reticulum
Structure:-
 Network of tubular and vesicular structures which are interconnected with one
another
 Some parts are connected to the nuclear membrane while another are connected to the
cell membrane
 Two types :- 1. smooth endoplasmic reticulum( lack of ribosomes),2.
Rough endoplasmic reticulum (studded with ribosomes)
 Function:-
 Gives internal support to the cytoplasm
 RER synthesize secretory protein and membrane proteins
 SER synthesize lipids for cell membrane
 In liver cells SER detoxify drugs and poison
 In muscle cells SER store calcium ions
Ribosomes
Structure:-
 Ribosomes are dense spherical
granular particles which move
freely in the matrix
 They are present in cytoplasm as
well as inside the nucleus
 A ribosomes is made numerous
proteins
and RNA
 Function:-
 They play important role in protein
synthesis
 It helps in storage modification
and
packaging of products in vesicles
 It is involved in synthesis of
lysosomes
Golgi Body ( Golgi Complex )
Structure:-
 Discovered by Camillo Golgi
 Formed by stacks of 5-8 membranous sacs
 Sacs are usually flattened and are called
Cisternae
 Has two ends :- Cis face situated near the
endoplasmic reticulum and Trans face
situated near the cell membrane
 Function :-
 Modifies , sorts and packs material
synthesized in the cell
 Delivers synthesized material to various
targets inside the cell and outside the
cell
 Produce vacuoles and secretory vesicles
 Forms plasma membrane and lysosomes
 Lysosomes
Structure :-
 Small , spherical, single membrane sac
 Found throughout the cytoplasm
 Filled with hydrolytic enzymes
 Occur in most animal cells and in few types of
plant cells
 Function :-
 Help in digesting of large molecules
 Protect cell by destroying foreign invader like
bacteria and viruses
 Degradation of worn out organelles
 In dead cells perform autolysis
Vacuoles
Structure :-
 Single membrane sac filled with liquid or sap (
water , sugar and ions )
 In animal cells , vacuoles are temporary, small in
size and few in number
 In plant cells , vacuoles are large and more
in number
 May be contractile on non – contractile
 Function :-
 Store various sub including waste products
 Maintain osmotic pressure of the cell
 Store food particles in amoeba cells
 Provide turgidity and rigidity to plant cells
Mitochondria ( power house of cell )
Structure :-

 Small , rod shaped organelles bounded by two membrane – inner

and outer
 Outer membrane is smooth and encloses the contents of
mitochondria
 Inner membrane is folded in the form of shelf like inward projection
called Christae
 Inner cavity is filled with matrix which contains many enzymes
 Contain their own DNA which are responsible for many enzymatic
actions
 Function :-
 Synthesize energy rich compound ATP
 ATP molecules provides energy for the vital activities of living cells
Plastids
 Plastids consists of numerous membrane
layers embedded in a material called the
strome
 Plastids are of three types :-
Chromoplast , Leucoplast ,
Chloroplast
 Chromoplast :- They are coloured plastids
except green . They are present in flowers to attract
insects for pollination .
 Leucoplast:- They are colourless or white
plastids . They store starch , oils and protein
granules.
 Chloroplast :- They are green Coloured plastids
which are important for photosynthesis for plants .
They contain green colour pigments chlorophyll.
They are known as kitchen of cells .
 Function :-
 They manufacture food through Photosynthesis
 They provide colours to fruits and flowers to attract
Centrosome
Structure :-
 Centrosome is the membrane bound organelles present near the nucleus
 Consists of two structure called as centrioles
 Centrioles are hollow , cylindrical structure made of microtubules
 Centrioles are arranged at right angles to each other
 Function :-
 Form spindle fibres which help in the movement of chromosomes during cell
division
 Help in the formation of cillia and flagella
Cytoskeleton
Structure :-
 Formed by microtubules and microfilaments
 Microtubules are hollow tubules made up
of protein called tubulin
 Microfilaments are rod shaped thin filaments
made up of protein called actin
 Function :-
 Determine the shape of the cell
 Give structural strength to the cell
 Responsible for cellular movements
Thank you
!