Assistant Professor in Botany

1. Seema vijay (Sr.No.-22)
Assistant professor(Botany)
Dr.B.R.Ambedker Govt.P.G.College Nimbahera (Raj)
HRDC Guru Jambleshwar University of Science & Technology
Hisar(Hariyana)
Faculty Induction Program – 3
Topic- The cell organelles

2. Table of Contents
1. Cell Organelles definition
2. Cell membrane
3. Cell Wall
4. Cytoplasm
5. Chloroplast
6. Endoplasmic Reticulum (ER)
7. Nucleus
The Cell Organelles

3. Cell membrane
Cell Organelles definition
The Cell organelle is a specialized entity present inside a particular type of cell
that performs a specific function.
Cell consist of nucleus, plasma membrane and cytoplasm. Other than this different structures
like Endoplasmic Reticulum(ER), Golgi body, Lysosomes, Mitochondria, Plastids and
Vacuoles are also present. All of these are cell organelles.
Structure of cell membrane - 1. It consists of a phospholipid bilayer along
with two types of proteins like embedded proteins and peripheral proteins
that function is the movement of particles in and out of the cell.
2. The most abundant lipid is phospholipid which contains a polar head and
non polar tails.
3.The embedded proteins act as channels for the transfer of particles across
the cell.
4.The peripheral proteins function as to provide mechanical support to the
structure of the cell.

4. Functions of cell membrane
•The cell membrane provides mechanical support that facilities the shape of
the cell.
•It regulates what can be allowed to enter and exit the cell through channels,
acting as a semi-permeable membrane.
•It generates and distributes signals in and outside of the cell for the proper
functioning of the cell and all the organelles.
•It allows the interaction between cells required during tissue formation and
cell fusion.

5. Cell Wall- An additional non-living layer present outside of the cell membrane.
In a plant cell, the cell wall is made up of cellulose, hemicellulose, and proteins
while in a fungal cell, it is composed of chitin.
A cell wall is multilayered with a middle lamina, a primary cell wall, and a
secondary cell wall.
Middle lamina contains polysaccharides that provide adhesion and allows binding
of the cells to one another.
After middle lamina is the primary cell wall which is composed of cellulose. The
last layer, which is not always present, is the secondary cell wall made of
cellulose and hemicellulose.
Functions of Cell Wall-
•1.Gives Mechanical Strength:
•2. Maintains Cell Shape:
•3. Controls Cell Expansion ..
•4. Controls Intercellular Transport:
• 5. Protects Against Infective Organisms:
• 6. provide a semi-permeable surface for molecules to pass in and out of the cell.

6. Cytoplasm -Cytoplasm refers to everything present inside the cell except the nucleus
.
Structure
The cytoplasm consists of a cytosol; a gel-like substance that contains other matter; cell
organelles; smaller cell-like bodies bound by separate membranes; and cytoplasmic
inclusions; insoluble molecules that store energy and are not surrounded by any layer.
The cytoplasm is colorless and has about 80% water along with various nutrients
required for the cell.
• Functions of cytoplasm
• Most of the vital cellular and enzymatic reactions like cellular respiration and
translation of mRNA into proteins occur in the cytoplasm.
It acts as a buffer and protects genetic materials as well as other organelles from
damage due to change in the pH of the cytosol.
cytoplasm helps in the movement of materials inside the cell by a process
termed cytoplasmic streaming..

7. Chloroplast – It is a type of plastid that is involved in photosynthesis in plants.
•Chloroplast contains an essential pigment called chlorophyll necessary to trap
sunlight for the production of glucose.
Structure
•It is a double-membraned structure with its own DNA which is inherited from the
previous chloroplast.
•These are usually lens-shaped with shape and number varying according to cells.
They have an outer membrane, an inner membrane, and a thylakoid membrane that
enclosed the gel-like matric called the stroma.
•The outer and inner membrane is porous and allows transport of materials while the
stroma contains DNA, chloroplast ribosomes, proteins, and starch granules.
Functions
•The chloroplast is the primary center for light-dependent and light-independent
reactions during photosynthesis.
•Different proteins present in chlorophyll are involved in the regulation of
photorespiration.

9. Endoplasmic Reticulum (ER) – It is present as an interconnection of tubules that
are connected to the nuclear membrane in eukaryotic cells.
There are two types of ER based on the presence or absence of ribosomes on them:
1.Rough ER (RER) with ribosomes attached on the cytosolic face of Endoplasmic
Reticulum and thus is involved in protein synthesis
2.Smooth ER (SER)which lacks ribosomes and has a function during lipid synthesis.
Structure of ER
Endoplasmic Reticulum exists in three forms like- cisternae, vesicles, and tubules.
(a) Cisternae are sac-like flattened, unbranched structures .
(B) Vesicles are spherical structures that carry proteins throughout the cell.
(C) Tubules are tubular branched structures forming a connection between cisternae
and vesicles.
Functions of ER
•1. ER contains many of the enzymes required for several metabolic processes,
and the surface of the ER is essential for other operations like diffusion, osmosis,
and active transport.
•2. One of the crucial functions of ER is the synthesis of lipids like cholesterol and
steroids.
•3. Rough ER allows for the modification of polypeptides emerging out of the
ribosomes to prepare secondary and tertiary structures of the protein.
•4. ER also synthesizes various membrane proteins and has a crucial role in

11. • Nucleus- The nucleus is a membrane-bound organelle that contains genetic material
(DNA) of eukaryotic organisms.It is separated from the cytoplasm by a nuclear
membrane.
As the nucleus regulates the integrity of genes and gene expression.
Structure of nucleus-
1.Nuclear Membrane-
•The nuclear membrane is a double-layered structure that encloses the contents of
the nucleus. The outer layer of the membrane is connected to the endoplasmic
reticulum.
Like the cell membrane, the nuclear envelope consists of phospholipids that form
a lipid bilayer.
2.Nucleoplasm-
•Nucleoplasm is the gelatinous substance within the nuclear envelope.
•Also called karyoplasm, this semi-aqueous material is similar to the cytoplasm .
•The nucleolus and chromosomes are surrounded by nucleoplasm.
•Nucleoplasm also supports the nucleus by helping to maintain its shape.

13. 3.Nucleolus-
•Contained within the nucleus is a dense, membrane-less structure
composed of RNA and proteins called the nucleolus.
• The nucleolus helps to synthesize ribosomes by transcribing and
assembling ribosomal RNA subunits. These subunits join together to form
a ribosome during protein synthesis.
4. Chromatin net –
The chromatin is the network of the cell nucleus, which contains all the DNA of the
nucleus of the cell. The DNA in the nucleus is packaged by the histone proteins .
The protein and DNA complex is called chromatin.

14. Function of nucleus –1. It controls the hereditary characteristics of an
organism.
•2.The organelle is also responsible for protein synthesis, cell division, growth,
and differentiation.
•3.Storage of hereditary material, the genes in the form of long and thin DNA
(deoxyribonucleic acid) strands, referred to as chromatin.
•4.Storage of proteins and RNA (ribonucleic acid) in the nucleolus.
•5.The nucleus is a site for transcription in which messenger RNA (mRNA) are
produced for protein synthesis.
•6.During the cell division, chromatins are arranged into chromosomes in the
nucleus.
•7.Production of ribosomes (protein factories) in the nucleolus.