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Genetics
1. PRESENTATION
ON
STRUCTURES & FUNCTIONS OF
CELL ORGANELLES IN PLANT CELL
Submitted to : Submitted by:
Dr. N. K. Sharma Sanjay Kumar Sanadya
Professor M.Sc. PBG previous
2. CELL ORGANELLES
Various membranous bound structures that are found within a cell are known as cell
organelle.
Cell organelles is studied with the help of electron microscope.
Various cell organelles present in a plant cell as follow :-
S.no Cell organelles S. No Cell organelles
1 Cell wall 8 Plastid
2 Plasma membrane 9 Vacuole
3 Nucleus 10 Ribosome
4 Endoplasmic Reticulum 11 Peroxisome
5 Golgi bodies 12 Cytoskeleton
6 Lysosome 13 Sphaerosome
7 Mitochondria
3. 1.CELL WALL
Discovered by Robert hooke.
• Outermost part of the cell is always non-living is called cell wall.
• Parts of cell wall are :-
1. Primary cell wall :-
It is thin and elastic and lies between middle lamella.
• It is mainly consists of cellulose, hemicellulose.
2. Secondary cell wall :-
It is innermost layer of cell wall and lies between primary cell wall and plasma
membrane.
3. Middle lamella :-
Common layer between adjacent cells.
It is consists of calcium and magnesium pectate.
It is developed during cell division i.e., cytokinesis
4. Cell wall
Function:-
1. To protect
inner parts of
cell.
2. To give definite
shape to the
cell.
3. To provide
mechanical
support to the
tissues.
5. 2. PLASMA MEMBRANE
Cytoplasm surrounded on the outer surface by a living, thin, selectively permeable and
flexible boundary known as plasma membrane.
The cell membrane possess carbohydrates, lipids and proteins.
1. Carbohydrates present in the form of oligosaccharide of the glycolipids &
glycoproteins.
2. Lipids mainly phospholipids such as lecithin, cephalin, cholesterol etc.
3. Two type of proteins are present in plasma membrane :-
(A)Integral protein
(B) peripheral protein
It’s thickness about 75-100 A˚ and three layered protein-lipid-protein membranes.
Bilayer of phospholipids are 35 A˚ thick layer, the protein layer are 20-25 A˚ thick layer.
Lipids layer is hydrophobic and protein layer is hydrophilic type.
Function :-
1. Ingestion of material through endocytosis.
2. Egestion of waste materials from cell through exocytosis.
3. It checks the entry of toxic elements.
6.
7. 3.NUCLEUS
First discovered by Robert brown in 1833.
It is also called controlling Centre of the cell.
The nucleus may be different shape and size.
1. Nuclear membrane
It is double layer boundary of the nucleus which is about 200 A˚ thick.
2 . Nucleolus
A spherical body found in the nucleus.
Granular region is 150-200 A˚ in diameter contains proteins and RNA.
3. Chromatin
It is partly culmed and tangled mass of nucleoprotein fibers in which consists DNA,
proteins, RNA and other compounds complexes.
Function :-
1. Inheritance of characters.
2. Protects chromosomes from cytoplasmic effects.
3. Permits transports of material between cytoplasm and nucleus.
4. Formation of ribosomes and synthesis of RNA.
8.
9. 4. Endoplasmic Reticulum
The presence of a network of reticulum of tiny tabular structures scattered in the
cytoplasm.
ER is attached to nuclear membrane on one side & plasma membrane on the other.
ER have three components, viz., tubules, vesicles, cisternae.
It is two type -
1. Rough ER
Presence of ribosomes on the membranes.
2 . Smooth ER
Absence of ribosome on the membranes.
Function :-
1. Protein, lipid, glycogen synthesis.
2. Acts as inter cellular transport system for various substances.
3. Provides passage for mRNA from nucleus to the cytoplasm.
4. Detoxification
5. Precursor of secretory material to golgi bodies.
10.
11. 5.Golgi bodies
Also called golgi complex, dictyosome, Dalton complex, idiosome.
Densely stained reticular structures near nucleus.
Golgi body is made up of four parts -
1. Cisternae -
flat disc like shaped, sacs like structure many cisternae are arranged in a stack.
2. Tubules –
branched & irregular tube like structure associated with cisternae.
3. Vacuoles –
Large spherical structure associated to tubules.
4. Vesicles –
Spherical structure arise from budding from tubules.
function:-
1. Cell secretion.
2. Synthesis of cell wall.
3. Formation of lysosome.
12.
13. 6. Lysosome
It is Membrane bound vesicular structures formed by the process of packaging in the golgy
body.
Presence of almost all type hydrolytic enzymes which is active at acidic pH (pH =5) viz.,
lipases, proteases, carbohydrases etc.
In higher plants lysosome are less frequent.
Function :-
1. Intracellular digestion
2. Extracellular digestion
3. Autolysis
(0.1 -0.8 μm)
membrane
(single unit)
lysosome
Acid hydrolases
pH=5
Nucleases
Proteases
Lipases
Phospholipases
Glycosidases
14. 7. Mitochondria
Given by C. Benda
Also called power house of cell.
Mitochondrion membranes :-Double layer membrane
Each membrane is 60-75 A˚ thick &separated by a space called perimitochondrial space.
Cristae :-
Inner membrane has a series of inside folds.
It has F1 particles or oxysomes which is site of Electron Transport System.
Matrix :-
Space between cristae into the inner chamber.
It’s have DS circular DNA molecules, 70S ribosomes, amino acids, enzymes and others
elements.
Function :-
1. Site of aerobic respiration.
2. Semi autonomous organelles.
3. Oxidation of carbohydrates, lipids & proteins.
4. Cytoplasmic inheritance
15.
16. 8. Plastid
Discovered by Haeckel.
It is found in all plants cells which is basis of presence of pigments can be classified into:-
1. Chromoplast :-
carotenoid pigments like carotene, xanthophyll & other are present.
This gives yellow, orange or red colour to the part of the plants.
2. Leucoplast :-
colourless plastids of various shapes and sizes with stored nutrients:
Amyloplasts store carbohydrates.
elaioplasts stores oils and fats.
aleuroplasts stores proteins.
3. Chloroplast:-
also called kitchen of cell.
it is contains chlorophyll and carotenoid pigments which are responsible for trapping of
light energy.
This gives green colour of part of the plant.
17. Chloroplast
It is found in the mesophyll cells of leaves may be various shape and sizes.
Parts of chloroplast:-
Membranes :
Double membrane bound layer separated by a space peri-chloroplastidial space.
Stroma :-
The Space limited by the inner membrane is called stroma.
Component of stroma :-
1. Thylakoids :
A number of flatted membranous sacs are present called thylakoid which is arranged in
stacks called grana. Each chloroplast contains 20-100 granum.
2 others: DS circular DNA, 70S Ribosomes, enzymes, other material are present in
stroma.
Function:-
1. Site of photosynthesis.
2. Cytoplasmic inheritance.
3. Chloroplasts impart the pleasing greenary to the earth.
4. chloroplast stores vitamin K, E RUBISCO protein and ions.
18.
19. 9. Vacuole
Single Unit Membrane bound space found in the cytoplasm.
It contains water, sap, excretory product & other materials.
It membrane called tonoplast.
in plant cell the vacuoles can occupy up to 90% of the volume of the cell.
Function :-
1. Transport of ions and other material against concentration gradients.
2. To maintain high internal water pressure.
3. Physical support of plant tissues.
tonoplast
cell sap
Vacuole
Water
Sap
Mineral matter
Excretory product
20. 10. Ribosome
Densely stained granular structures in which is consists of RNA, proteins which are not
surrounded by any membrane.
It is smallest cell organelles also called protein factory of cell.
In lower prokaryotes , mitochondria and chloroplast present in 70S type & in eukaryotes
present in 80 S type ribosome.
In ribosome two sub unit are present:
Large sub unit –binding site of t-RNA.
Small sub unit – binding site of m-RNA.
A-site :- accepter site for t-RNA.
P-site :- site for growing polypeptide chain.
Function :-
1. Protein synthesis.
Polysome :- at the time of protein synthesis, several ribosomes become attached to mRNA
with the help of smaller sub unit.
21.
22. 11. Peroxisome
These are membrane bound vesicles that contains powerful oxidizing agents like hydrogen
peroxide.
Function:-
1. photorespiration (glycolate pathway):-In the plant cell, presence of light oxygen is used
and
carbon di oxide is formed like normal respiration.
1. It is involved in β-oxidation of fatty acid.
membrane
peroxisome
Oxidizing
agents
23. 12. Cytoskeleton
A network of protein fibers extending across and around the cell called
cytoskeleton.
In cytoskeleton consists of three classes of fibers:
1. Microtubules: these tubules are 150-200 A˚ in diameter ;which is made up
of tubulin molecules arranged in series.
It is associated with cell wall in plants
Function:
1. Transport cell wall material from golgy body to outside the cell.
2. During cell division, formation of spindle fibers.
2. Actin filaments
It is composed of contractile protein, Actin.
Function:-
1. to exert force to change cell shape internally .
24. 3. Intermediate
filaments
It is network of specific
protein fibers like
keratin, desmin,
vimentin and
neurofilament.
Function :-
1. They provide rigidity
to cell shape.
25. 13.Sphaerosome
Sphaerosome are vesicles of 0.5-1 μm diameter surrounded by a membrane, and contain up
to 98% lipid.
it is present in plant cell only, & contain some acid phosphatases enzyme.
Function
1. Major site of lipid synthesis and storage in plants.
mambrane
Sphaerosome
• Acid phosphatase
• Lipid synthesized
enzyme
26. Key References:-
Singh, B.D. 2013. Genetics. Kalyani Publishers, New Delhi
Singh, P. 2009. Elements Of Genetics. Kalyani Publishers, New
Delhi
