cell and its organelles
DESCRIPTION
For the students of Veterinary ScienceTRANSCRIPT
Principles of Genetics &
Population Genetics
AGB 121
2012-13
Dept. Of Animal Genetics and Breeding
Veterinary College
Hebbal, Bangalore -24
Cell and its Organelles
Cell is the basic unit of organization of living matter.
It is the unit of biological activity delimited by a semi permeable membrane and capable of self reproduction in medium free of other living systems.
Cellular organisms have either prokaryotic or eukaryotic cells.
2/1/2013 2Dr. R. Jayashree, Asst. prof(AGB)
2/1/2013 3Dr. R. Jayashree, Asst. prof(AGB)
Prokaryotic cells
Composed of primitively organized
cytoplasm and nucleus.
Nuclear substance is not separated
by nuclear membrane from
cytoplasm.
Cytoplasm does not have
endoplasmic reticulum, Golgi
complex.
e.g: Blue green algae & Bacteria
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Eukaryotic cell
Have true nucleus with nuclear
membrane.
Nucleus has chromosomes,
nucleolus and nucleoplasm.
The cytoplasm is enclosed in
plasma membrane and has
cell organelles
Other organelles
Mitochondria, Endoplasmic reticulum, Vacuoles,
Lysosomes, Chloroplasts,Centrioles & Ribosomes.
2/1/2013 5Dr. R. Jayashree, Asst. prof(AGB)
2/1/2013 6Dr. R. Jayashree, Asst. prof(AGB)
Features Animal Cell Plant cell
Size
Cell wall
Plastids
Vacuoles
Golgi
apparatus
Centrosomes
and
centrioles
Small
Absent
Absent except
in Euglena
Large numbers
are present
Single highly
complex
Present.
Large
Rigid cell wall cellulose
Present
Large single in the
centre.
Simpler unit called
dictyosomes.
Absent
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PLASMA MEMBRANE
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Consists of Lipids 20-40 %, Proteins-55-75% and Carbohydrates-1-5%
Plasma Membrane
• Protection of cells from injury.
• Passage of substances in and out of cell by
selective permeability.
• Absorption, Secretory, Excretory and waste
product removal.
• Determine antigen specificity
• Helps in movement of unicellular organisms
like Amoeba.
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Functions:
Cytoplasm
Is a Jelly like semi fluid mass of protoplasm
excluding nucleus but includes all other
components-cytoplasmic matrix, cell
organelles & cell inclusions.
Contains water in liquid state and other
particles like minerals, sugars, amino acids,
tRNA, nucleotides, vitamins, proteins and
enzymes in colloidal state.2/1/2013 10Dr. R. Jayashree, Asst. prof(AGB)
Functions of cytoplasm
• Provides raw materials to cell organelles
• Exchange of materials between cell organelles
• Biosynthesis of fat, nucleotides, proteins,
co-enzymes etc
• Catabolic activities.
• Uniform distribution of various materials
• Cytoplasmic streaming or cyclosis
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Mitochondria
Power house of the cell (production of ATP)
Cylindrical, length -5-10 micron,
Diameter- 0.5-1.0 micron
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Mitochondria
• Two membranes-Outer membrane is smooth
and permeable & Inner membrane is folded
to from involutions called cristae
• Two Chambers- Outer chamber contains
enzymes and inner chamber contains
proteins, ribosomes, RNA, mitochondrial
DNA, enzymes of Kreb’s cycle, amino acid
synthesis and fatty acid metabolism
2/1/2013 13Dr. R. Jayashree, Asst. prof(AGB)
Functions of Mitochondria
• Oxidation of food materials
• Matrix has enzymes for synthesis of
fatty acids.
• Synthesis of amino acids
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Endoplasmic Reticulum
Provides surface for
attachment of Ribosome's
Helps in packaging of
polypeptides to produce
proteins & enzymes.
Does not have Ribosome's.
Helps in synthesis of fat
inside cells and adipose
tissue.
Rough Smooth
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Endoplasmic Reticulum
Inter connection of membrane linked channels that run
through the cytoplasm.
Channels contain fluid called endoplasmic matrix.
Exists in three forms
Cisternae- Sac like formed bundles and lie parallel to
one another actively involved in synthetic activity.
Vesicles- Oval rounded sacs also called as
microsomes.
Tubules- Tube like structures connecting cisternae and
Vesicles2/1/2013 16Dr. R. Jayashree, Asst. prof(AGB)
Function of EPR
Synthesis of glycogen and glygenolysis in liver, sterols and hormones in testes and ovary, formation of Visual pigment from Vitamin A in retinal cells.
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GOLGI APPARUTUS
Golgi complex
Camillo Golgi in 1898
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GOLGI APPARATUS
Complex protoplasmic structure made up of
smooth membrane saccules or cisternae, a
network of tubules with vesicles and
vacuoles.
Shape is not fixed depending on the
physiological state the shape varies.
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Structure of Golgi
Complex
Cisternae: 4-8 membrane bound saccules or
cisternae. They have two side -convex side
called forming face & concave side called
maturing face.
Tubules: In the form of network towards the
periphery and maturing face of golgi apparatus.
They inter connect different cisternae.
2/1/2013 20Dr. R. Jayashree, Asst. prof(AGB)
Vesicles: Small sacs of Smooth
(containing secretary substance called
secretion vesicles) & coated vesicles
have rough surface and elaborate
membrane proteins)
Vacuoles-modified form of cisternae.
Some function as lysosomes.2/1/2013 21
Function of Golgi complexSecretion vesicles contain zymogen granules,
are sent out of the cells through exocytosis or reverse pinocytosis.
Transformation of membrane: Convert one type of membrane to another and recycling of plasma membrane.
Form glycoprotein from protein of EPR
Synthesis of complex carbohydrates such as pectin, mucoploysaccharaids, hemicellulose,cellulose etc.
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Function of Golgi complex
Hormones: Production of hormones by endocrine glands, formation of matrix of connective tissue, synthesis of retinal pigments in chick embryo.
Formation of acrosome.
Vitelogenesis- formation of oocytes and development of yolk.
Formation of lysosomes
Store house of digestive enzymes.
Membrane vesicles join the region of cytokinesis and produce new plasmalemma
2/1/2013 23Dr. R. Jayashree, Asst. prof(AGB)
LYSOSOMES- Suicidal bags
•Small vesicles bounded by a single membrane.
•Contain hydrolytic enzymes in the form of
minute crystalline or semi crystalline granules.
•Important enzymes- Phosphatases, sulphatases,
proteases, nucleases, liposases and glycosidases.
2/1/2013 24Dr. R. Jayashree, Asst. prof(AGB)
Types of Lysosomes
Primary –Newly pinched of vesicles from golgi apparatus.
Secondary- Fusion of primary lysosomes with phagosomes and also known as digestive vacuoles.
Residual bodies or tertiary lysosome- throw out the residues and undigested food materials into the external environment by exocytosisAutophagic vaculoes- formed by fusion of primary lysosomes and worn out organelles
2/1/2013 25Dr. R. Jayashree, Asst. prof(AGB)
Functions of Lysosmes
• Intracellular digestion of food
• Lysosomes of leucocytes eliminate foreign proteins, toxic substances, bacteria and other microorganisms.
• Provide nutrition during starvation by hydrolyzing organic food.
• Removal of old ,aged and useless organelles.
• Provide enzymes for sperm penetration
2/1/2013 26Dr. R. Jayashree, Asst. prof(AGB)
Functions of Lysosmes- contd
Essential for cell division by overcoming
agents that cause repression of mitotic
cycles.
Lysosome related nucleases might result in
mutation, breakage of chromosomes and
blood cancer.
Lysosomes remove carcinogens by
engulfing and separating them.
2/1/2013 27Dr. R. Jayashree, Asst. prof(AGB)
ENDOSOMES & ENDOCYTOSIS
Membrane-bound vesicles,
formed via a complex family
of processes collectively
known as endocytosis.
The basic mechanism involves
the invagination (folding
inward) of a cell's plasma
membrane to surround
macromolecules or other
matter diffusing through the
extracellular fluid.
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Sphaerosomes
Small cell organelles bounded by single
membrane take part in storage and
synthesis of fat.
They arise from endoplasmic reticulum
and have some lysosome activity.
2/1/2013 29Dr. R. Jayashree, Asst. prof(AGB)
Peroxisomes or Microbodies
Small cell organelles with single membrane
which absorbs molecules of oxygen and take
part in oxidation other than those involved in
respiration.
2/1/2013 30Dr. R. Jayashree, Asst. prof(AGB)
Types of Microbodies
Peroxisomes- contain enzymes for
peroxidase synthesis.
Glycoxysomes-contains enzymes for
beta oxidation of glyoxylate.
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RIBOSOMES
• Tiny organelles composed of approximately
60 percent RNA and 40 percent protein.
• In eukaryotes, ribosomes are made of four
strands of RNA.
• In prokaryotes, they consist of three strands
of RNA.
• Protein and RNA complex responsible for
protein synthesis. 2/1/2013 32Dr. R. Jayashree, Asst. prof(AGB)
Ribosomes
Organelle ribosome- found in
mitochondria
Cytoplasmic ribosome - remain
attached to Endoplasmic reticulum.
Size of ribosome is measured in
Svedberg Unit.
2/1/2013 33Dr. R. Jayashree, Asst. prof(AGB)
Ribosomes
May occur in linear or helical groups called
as polyribosome and connected with thick
strand of mRNA.
Polyribosomes are found during active
protein synthesis.
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Functions of Ribosome
Protein synthesis
Storage of rRNA
Temporary storage of
protein and finally
transfer it to the
cytoplasmic reticulum.
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Microfilaments
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Microfilaments
Ultra microscopic rods
or protein filaments made
of actin like lobule
protein molecule.
Microfilaments associate
to form hexagonal bundle
are contractile.
2/1/2013 37Dr. R. Jayashree, Asst. prof(AGB)
Microfilaments-Functions• Cytoplasmic streaming
• Microvilli are maintained through support provided by microfilaments.
• Spindle apparatus formation.
• Movement of fibroblast to undulation of microfilaments.
• Associated with cleavage furrow at the time of cytokinesis.
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MICRO TUBULES
• Straight, hollow cylindrical
organelles.
• Functions, ranging from
transport to structural support
(Cytoskeleton)
• Help in movement of cilia and
flagella
• Movement of nuclei during cell
division2/1/2013 39Dr. R. Jayashree, Asst. prof(AGB)
CILIA AND FLAGELLAAre essential for the locomotion of
individual organisms in
unicellular organisms.
In multicellular organisms, cilia
function to move fluid or
materials past an immobile cell as
well as moving a cell or group of
cells..
Passage of eggs in oviduct
Conjugation and fusion of gametes
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CENTRIOLES
• Self-replicating organelles
made up of nine bundles of
microtubules and are found
only in animal cells.
•They appear to help in organizing cell
division, but aren't essential to the process.
•Complex formed of centrioles and
cytoplasm is called centrosome or central
apparatus. 2/1/2013 41Dr. R. Jayashree, Asst. prof(AGB)
Centrioles
Prior to nuclear division the two centrioles
present in a centrosome move to opposite
poles.
Centrioles possess a whorl of nine
peripheral fibrils and each fibril is made
up of three sub fibrils called triplet fibril.
2/1/2013 42Dr. R. Jayashree, Asst. prof(AGB)
Functions-Centriole
• The distal centrioles give
rise to axial filament or tail
in spermatozoa
• Basal bodies formed from
centrioles give rise to cilia
and flagella.
Formation of nucleating centres.
Forming poles of the spindle
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CHLOROPLAST[PLASTIDS]
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CHLOROPLAST
Surrounded by a double membrane, containing stacked membranes.
Responsible for photosynthesis, the trapping of light energy for the synthesis of sugars.
Contains DNA, and like mitochondria is believed to have originated as a captured bacterium.
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VACUOLES
Membrane surrounded "bags" that contain water
and storage materials in plants.
2/1/2013 46Dr. R. Jayashree, Asst. prof(AGB)
NUCLEUS
2/1/2013 47Dr. R. Jayashree, Asst. prof(AGB)
Nucleus
(Robert brown in 1831)
It is a specialized double membrane
bound protoplasmic body, which
contains all the genetic information for
controlling cellular metabolism and
transmission of posterity.
Cells have single nucleus.
2/1/2013 48Dr. R. Jayashree, Asst. prof(AGB)
Nuclear envelope or Karyotheca
• Made of two lipoproteins and trilaminar membrane. Contains large number pores or perforations.
• Inner membrane is smooth
•Outer membrane may be smooth or may be rough on the cytoplasmic surface.
•Two membranes are separated by a electron transparent perinuclear space.
2/1/2013 49Dr. R. Jayashree, Asst. prof(AGB)
Nucleoplasm or Nuclear sap or
Karyolymph
• Transparent semifluid colloidal substance which
fills nucleus.
• Contains nucleosides and number of enzymes
(DNA polymerase, RNA polymerase and
nucleoside phosphorylase)
• For synthesis and function of DNA, RNA,
nucleoproteins etc.
• Some proteins are essential for spindle formation.
2/1/2013 50Dr. R. Jayashree, Asst. prof(AGB)
ChromatinHereditary DNA-protein fibrillar complex
Chromatin is in the form of overlapping and coiled fibres
which appear to produce a network of chromatin
reticulum.
Chromatin fibres are disrtibuted through out the
nucleoplasm.
2/1/2013 51Dr. R. Jayashree, Asst. prof(AGB)
Euchromatin and Heterochromatin
Euchromatin contains
functional genes.
Heterochromatin is a
condensed region believed
to be genetically inert.
During prophase the
chromatin fibres
condenses to form
chromosomes
2/1/2013 52Dr. R. Jayashree, Asst. prof(AGB)
Nucleolus (Fontana in 1781)
Is a naked round structure which is attached
to the chromatin at specific region called
Nucleolar organizer region.
NOR regions of chromosome associated
with nucleolus and containing genes for
rRNA.
Commonly 1-4 nucleoli are found in a
nucleus.2/1/2013 53Dr. R. Jayashree, Asst. prof(AGB)
Nucleolus
Has four components
Amorphus matrix –
homogenous ground substance-
protein
Granular part- Granules of
Protein, RNAFibrillar portion- made of protein-RNA to be
precursor of granules.
Chromatin portion- that part of chromatin
associated with nucleolus2/1/2013
54
Nucleolus- Function
Principle site of
development of
ribosomal RNA
Centre of formation of
ribosomes
Forms nucleo proteins
Essential for formation of spindle fibres
during nuclear division.2/1/2013
55
• Possess genetic information
• Controls all cellular activities.
• Variations are caused due to changes in genetic material
• Helps in cell growth and membrane development.
• For cell differentiation by allowing certain sets of genes.
• Cell replication
Functions of Nucleus
2/1/2013 56Dr. R. Jayashree, Asst. prof(AGB)
Thank you
2/1/2013 57Dr. R. Jayashree, Asst. prof(AGB)