CELL ORGANELLES

DISCUSSANT
MERYLLE JOYCE D. DATU
THE
THE

THE CELL
TOPICS:
 Cell Organelles
 Introduction
 Three Major Parts of the Cell
 The other Cell Organelles

THE CELL
 Cell is the fundamental and
functional unit of all living organisms.
 Cells can come in different shape
and size. No one cell type is exactly
like the other, but they have same
basic parts and certain functions
common to all cells.
 Cytology: the study of the structure and
function of the cell. It was developed
during the past 60 years with the aid of
microscope and sophisticated
biochemical research.

TYPES OF CELL
PROKARYOTIC EUKARYOTIC
 Prokaryotes are the most numerous
and widespread organisms on earth.
They are the first form of life on Earth
 Prokaryotic cells are smaller than
Eukaryotic cells (ranges 1-5 µm). It
has very simple structure unlike
eukaryotic cells yet they are able to
carry on necessary processes of life.
 Each prokaryotic cell is composed of
Plasma Membrane, Cytoplasm,
Nucleus (Nucleoid) and Cell Wall.
 Eukaryotes is the more complex type
of cell and has organelles.
 Eukaryotic cells ranges 10-30 µm and
it has a more complex cell structure
with its various subcellular organelles.
 Each eukaryotic cell is composed of
Plasma Membrane, Cytoplasm,
Nucleus, Endoplasmic Reticulum,
Golgi Apparatus, Ribosome,
Mitochondria and etc.
 Bacteria and Archaea
 Plants, Animals and Fungi

THE CELL
What’s found inside a cell?
All living organisms are made up of cells,
which are the tiniest units. This cells are made up
of much even smaller organ-like structure called
Organelles.
Cell Organelles
A small organ-like structure present inside
the cell. Just like organs in the body,
each organelle contributes in its own way to helping
the cell function well as a whole.
It is described as metabolic machinery of the
cell and each type of organelle is engineered to carry
own specific function.

THE CELL
CATEGORIES OF CELL ORGANELLES
Without membrane:
Some cell organelles like ribosomes are not
bounded by any membrane. They are present in
prokaryotic as well as eukaryotic organisms.
Single membrane-bound:
Some organelles are bounded by a single
membrane. For example, vacuole, lysosome, Golgi
Apparatus, Endoplasmic Reticulum etc.
Double membrane-bound:
Cell organelles like nucleus, mitochondria
and chloroplast are double membrane-bound
organelles.

THE CELL
ENDOSYMBIOTIC THEORY
Membrane Bound
Membrane in the cell organelles maintain the essential differences
between cytosol and intracellular environment.
It provides functionally specialized aqueous spaces with each
organelle.
A predatory way of life helps to explain another feature of
eukaryotic cells. Eukaryotic cells is said to be formed because eukaryotic
cells engulfed another organism and became one.

THREE
MAJOR PARTS
OF THE CELL
THREE
MAJOR PARTS
OF THE CELL

THREE MAJOR PARTS
1. Plasma Membrane
2. Nucleus
3. Cytoplasm

THREE MAJOR PARTS
Nucleus
The nucleus is a highly specialized organelle
that serves as the information processing and
administrative center of the cell.
This organelle has two major functions: it
stores the cell's hereditary material, or DNA, and it
coordinates the cell's activities, which include growth,
intermediary metabolism, protein synthesis, and
reproduction (cell division).
Nucleus is a membrane-bound organelle that
contains genetic material (DNA) of eukaryotic
organisms. It is the largest organelle inside the cell
taking up about 10% of the entire cell volume. This
makes it one of the easiest organelles to identify under
the microscope. The shape of the nucleus usually
conforms the shape of the cell.

NUCLEUS
Unlike a bacterium, which generally consists of
a single intracellular compartment surrounded by a
plasma membrane, a eukaryotic cell is elaborately
subdivided into functionally distinct, membrane-
enclosed compartments. Each compartment, or
organelle, contains its own characteristic set of enzymes
and other specialized molecules, and complex
distribution systems transport specific products from
one compartment to another
Structure of the Nucleus
 Chromosome
 Nucleolus
 Nuclear Envelop
 Nucleoplasm

NUCLEUS
In the nucleus, chromosomes are
thread-like structures made up of strands
of DNA and the histone proteins.
Chromosomes in the nucleus are tightly
packed which makes it possible for very large
amounts of the genetic material (DNA) to be
contained in such a small space
Chromosome
For DNA to function, it can't be
crammed into the nucleus like a ball of
string. Instead, it is combined with proteins
and organized into a precise, compact
structure, a dense string-like fiber called
chromatin.

NUCLEUS
Nucleoplasm is the jelly-like fluid
enclosed in the Nucleus in which the
nucleoli and chromatids are suspended.
Nucleoplasm
Also known as karyoplasm/nucleus
sap, the nucleoplasm is a type of protoplasm
composed of enzymes, dissolved salts, and
several organic molecules. In addition, the
nucleoplasm helps cushion and thus protect
the nucleolus and chromosomes while also
helping maintain the general shape of the
nucleus.

NUCLEUS
In the same way that the nucleus is the most
prominent organelle of the cell, the nucleoli is the most
prominent structure of the nucleus. Unlike the
nucleus, however, this dense structure lacks its own
membrane.
Nucleoli
The nucleolus is a membrane-less organelle
within the nucleus that serves as the site where
ribosomes are assembled and it is the cell's protein-
producing structures. Through the microscope, the
nucleolus looks like a large dark spot within the
nucleus. A nucleus may contain up to four nucleoli,
but within each species the number of nucleoli is
fixed.

NUCLEUS
The nuclear envelope is a double-layered
membrane that encloses the contents of the nucleus.
The nuclear membrane is one of the aspects that
distinguish eukaryotic cells from prokaryotic cells.
Whereas eukaryotic cells have a nucleus bound
membrane while prokaryotes don’t have.
Nuclear Envelope
The nuclear envelope encloses the DNA and
defines the nuclear compartment. This envelope
consists of two concentric membranes, which are
penetrated by nuclear pore complexes.

NUCLEUS
Inner nuclear membrane
contains specific proteins that act as anchoring
sites for chromatin and for the nuclear lamina, a
protein meshwork that provides structural support for
the nuclear envelope.
Outer nuclear membrane
Surrounds the inner membrane and is
connected to the membrane of the ER which creates
continuity between the nucleus and the external
environment . Like ER, it is also studded by
ribosomes.
Perinuclear Cisterna
Between the inner and outer membrane is the
fluid-like “moat” or space. It is continuous with the
Endoplasmic Reticulum.

NUCLEUS
Nuclear Pores
Present on the nuclear membrane are
nuclear pores (made up of proteins) through
which substances enter or leave the cell (RNA,
proteins, etc). This is also where the two
membrane fused.
These pores regulate the passage of
molecules between the nucleus and cytoplasm,
permitting some to pass through the membrane,
but not others. Building blocks for building DNA
and RNA are allowed into the nucleus as well as
molecules that provide the energy for constructing
genetic material.

CYTOPLASM
Cytoplasm is the cellular material outside the nucleus and inside
the plasma membrane. It is the site of most of the cellular activities, so it
is often refer to as “Factory Area”.
Early scientist believed that cytoplasm was a structure less gel, the
electron microscope revealed that it has three major components.
CYTOPLASM
CYTOSOL INCLUSION ORGANELLES

CYTOPLASM
Cytosol
Cytosol is the semi-transparent fluid that
suspends the other elements or components of the
cell. Dissolved in the cytosol, which is largely
water, are the nutrients and the variety of other
solutes.
Characteristics:
Composed of 80-90 & water and 10 % of
organic and inorganic compounds. Colloidal,
viscous and jelly like.
Function:
Contains enzymes and biochemical that are
responsible for the metabolic processes inside the
cell.

CYTOPLASM
Inclusions
It includes the fat droplets common in fat
cells, glycogen granules, pigments such as
melanin, mucus and other secretory products and
various chemicals.
Inclusions are not functioning unit, but
chemical; substances that may or may be present,
depending on the specific cell type.

CYTOPLASM
Organelles
Also called Cytoplasmic Organelles. Literally
“little organs”, are the specialized cellular
compartments with each performing its own job to
maintain the life of the cell.
Each Cellular Organelle perform its
designated function while coordinating with other
cell organelles.

Cytoplasmic Organelles/
Cell Organelles

CELL ORGANELLES
Endoplasmic Reticulum
About half the total area of membrane in a
eukaryotic cell encloses the labyrinthine spaces
of the endoplasmic reticulum (ER).
Endoplasmic means inside (endo) the
cytoplasm (plasm). Reticulum comes from the
Latin word for net. Basically, an endoplasmic
reticulum is a plasma membrane found inside
the cell that folds in on itself to create an
internal space known as the lumen.

CELL ORGANELLES
Endoplasmic Reticulum
A system of fluid-filled cisterns that coiled
and twist through the cytoplasm. Its serves as
the “network of channels” within the cell that
carries the substances from one part of the cell
to another.
ROUGH
ENDOPLASMIC
RETICULUM
ENDOPLASMIC
RETICULUM
SMOOTH
ENDOPLASMIC
RETICULUM

CELL ORGANELLES
ROUGH Endoplasmic Reticulum (RER)
The rough endoplasmic reticulum is so-called
because its surface is studded with ribosomes.
Essentially, almost all of the building materials are
formed in or on it, it is sometimes referred to as
“Factory”.
Rough Endoplasmic Reticulum provides a surface
for the synthesis of protein which are destined either
for secretion to the cell exterior or for other organelles.
Without an rough endoplasmic reticulum, it
would be a lot harder to distinguish between proteins
that should leave the cell, and proteins that should
remain.

CELL ORGANELLES
SMOOTH Endoplasmic Reticulum (SER)
The continuation of the Rough ER but its surface
is not studded with ribosomes.
The smooth endoplasmic reticulum provides
surface for lipid synthesis and steroid. These are fat-
based molecules that are important in energy storage,
membrane structure, and communication
The smooth endoplasmic reticulum is also
responsible for detoxifying the cell and Fat
Metabolism. Every cell has a smooth endoplasmic
reticulum, but the amount will vary with cell function.
For example, the liver, which is responsible for most of
the body’s detoxification, has a larger amount of smooth
endoplasmic reticulum.

CELL ORGANELLES
Ribosomes
A tiny round, dark bodies made of
proteins and variety of RNA called ribosomal
RNA (rRNA).
Ribosomes are the actual sites of protein
synthesis in the cell. Some ribosomes float free
in the cytoplasm while others are attached in
the membranes (ER).
Ribosome is composed of 2 sun units:
the large ribosomal unit and small ribosomal
unit.

CELL ORGANELLES
Golgi Apparatus
Golgi Body or Golgi Apparatus appears as
a stack of flattened membranous sacs that is
associated with swarms of tiny vesicles.
Discovered by Camillo Golgi in 1898.
The primary function of the Golgi
apparatus is to process (modify) and package
the macromolecules such as proteins and
lipids that are synthesized by the cell (brought
by the ER through transport vesicles. .

CELL ORGANELLES
Golgi Apparatus
As the proteins “tagged” for exports
accumulate on the Golgi Apparatus, the sacs
swell. The swollen end that is filled with
proteins, pinch off and form secretory vesicles
which travels to membrane and fuse to it or be
released outside of the cell.
In addition for its package-for-release
functions, the Golgi body pitches off the sacs
containing proteins and phospholipid destined
to become part of the plasma membrane and
packages hydrolytic into membranous sacs
called Lysosome.

CELL ORGANELLES
Mitochondria
A double membrane bound organelle
that is usually depicted as threadlike (mitos is
thread) or a sausage-shaped organelle.
Just like a factory can’t run without
electricity, a cell can’t run without energy. ATP
(adenosine triphosphate) is the energy currency
of the cell, and is produced in a process known
as cellular respiration. Though the process
begins in the cytoplasm, the bulk of the energy
produced comes from later steps that take place
in the mitochondria.

CELL ORGANELLES
Mitochondria
Since mitochondria supply most of the
ATP in the cell, they are referred to as the
“power house” of the cell.
Mitochondria are also somewhat unique
in that they are self-replicating and have their
own DNA, almost as if they were a completely
separate cell. (Endosymbiotic Theory)

CELL ORGANELLES
Vacuole
Vacuoles serve as the cell's storage centers of food
and other necessary materials. The vacuole further
functions in the removal of unwanted structural materials,
the containing of several waste products and small
molecules
This large compartment is enclosed by a membrane
called the tonoplast, which is selectively permeable to
certain solutes within the cytosol. Vacuoles sequester waste
products and in plant cells store water. They are often
described as liquid filled space and are surrounded by a
membrane. Some cells, most notably Amoeba, have
contractile vacuoles, which can pump water out of the cell if
there is too much water.

CELL ORGANELLES
Lysosomes
Tiny circular single membrane-bound
structure. Lysosomes are small (about 1 µm)
vesicle that originates at the Golgi Body.
Found in all eukaryotic cells.
It contains Lysozyme and other digestive
enzyme that breaks down foreign materials
that enters the cell.
Lysosome is also in charge in breaking
down worn out parts of the cell and may
destroy the entire cell through the process
called “autolysis” if the cell is damaged or
deteriorating.

CELL ORGANELLES
Peroxisome
Peroxisome is a membranous sacs
containing powerful oxidase enzyme that uses
molecular oxygen to detoxify a number of
harmful or poisonous substances.
Like the lysosome, the peroxisome is a
spherical organelle responsible for destroying its
contents. Unlike the lysosome, which mostly
degrades proteins, the peroxisome is the site of
fatty acid breakdown.
Unlike lysosome that comes from Golgi
Body, Peroxisome replicate itself by simply
pinching in half.

CELL ORGANELLES
Plastids
Plastids are an auto-self replicating and
membrane-bound organelle containing various
photosynthetic pigments; they are the sites
photosynthesis.
TYPES:
1.Leucoplast –Colourless plastid (serves the the
storage)
2.Chromoplast –Coloured Plastid – blue, red,
yellow (impart colour to flowers which help in
pollination)
3.Chloroplast – Green plastid (involved in
photosynthesis)

CELL ORGANELLES
Cytoskeleton
Running throughout the cytoplasm is the system of fibers. An
elaborate network of protein structures extends throughout the cytoplasm.
This protein fibers acts as “bones and muscle” of the cell.
TYPES:
1. Microtubules
2. Microfilaments
3. Intermediate Filaments
Cytoskeleton is also
responsible for both cell organelles’
movement and stability.
Cytoskeletal fiber and all of it serve to strengthen, support and
stiffen the cell as well as giving cell its shape.

CELL ORGANELLES
Cytoskeleton
Microtubules
A tube-like structure that determine
the overall shape of the cell and the
distribution of the organelles.
They also help provide pathways for
secretory vesicles to move through the cell,
and are even involved in cell division as they
are a part of the mitotic spindle, which pulls
homologous chromosomes apart.

CELL ORGANELLES
Cytoskeleton
Microfilament
Microfilament are most involved in cell
motility and in charge in cell shape.
Microfilaments are the thinnest part of
the cytoskeleton, and are made of actin [a
highly-conserved protein that is actually the
most abundant protein in most eukaryotic
cells]. Actin is both flexible and strong,
making it a useful protein in cell movement.

CELL ORGANELLES
Cytoskeleton
Intermediate Filament
Intermediate Filament is a strong and
stable rope-like that help to form
desmosome and provide internal guide wire
to resist the pulling forces on the cell.
It is smaller than the microtubules,
but larger than the microfilaments, the
intermediate filaments are made of a variety
of proteins such as keratin and/or neuro
filament. They are very stable, and help
provide structure to the nuclear envelope
and anchor organelles.

CELL ORGANELLES
Cell Wall
The cell wall, located outside the cell membrane, is
a tough layer that provides the rest of the cell with
structure support and protection. Cell walls are present in
plants, fungi, algae, some archaea, and bacteria cells, but
not in animal cells.
The cell wall confers the shape and rigidity to
bacterial cell and helps it withstand the intracellular
turgor pressure that can build up as a result of osmotic
pressure.
The composition of the Cell wall varies depending
on the organism. Cell wall of Plants are made up of
Cellulose while the cell wall of bacteria are made up of
peptidoglycan.

THE ORGANIZATION
AND COORDINATION
BETWEEN & AMONG
CELL ORGANELLES
“THE PROTEIN TRANSPORT”

To understand the eukaryotic cell, it is essential to
know how the cell creates and maintains these
compartments, what occurs in each of them, and how
molecules move between them.
An animal cell contains about 10 billion (1010) protein
molecules of perhaps 10,000 kinds, and the synthesis of
almost all of them begins in the cytosol. Each newly
synthesized protein is then delivered specifically to the cell
compartment that requires it.
By tracing the protein traffic from one compartment to
another, one can begin to make sense of the otherwise
bewildering maze of intracellular membranes

PROTEIN TRANSPORT
The synthesis of all proteins begins on ribosomes in the cytosol. Their
subsequent fate depends on their amino acid sequence, which can contain
sorting signals that direct their delivery to locations outside the cytosol.
Most proteins do not have a sorting signal and consequently remain in
the cytosol as permanent residents. Many others, however, have specific
sorting signals that direct their transport from the cytosol into the nucleus,
the ER, mitochondria, plastids, or peroxisomes; sorting signals can also
direct the transport of proteins from the ER to other destinations in the cell.
To understand the general principles by which sorting signals operate,
it is important to distinguish three fundamentally different ways by which
proteins move from one compartment to another.

PROTEIN TRANSPORT
Proteins can move in Different ways:
1. Gated transport
proteins move between the cytosol and the nucleus (which are
topologically equivalent) through nuclear pore complexes in the nuclear
envelope. The nuclear pore complexes function as selective gates that actively
transport specific macromolecules and macromolecular assemblies, although
they also allow free diffusion of smaller molecules.
2. Transmembrane transport
transmembrane protein translocators directly transport specific
proteins across a membrane from the cytosol into a space that is topologically
distinct. The transported protein molecule usually must unfold to snake
through the translocator. The initial transport of selected proteins from the
cytosol into the ER lumen or mitochondria, for example, occurs in this way.

PROTEIN TRANSPORT
Proteins can move in Different ways:
3. Vesicular transport
membrane-enclosed transport intermediates— which may be small,
spherical transport vesicles or larger, irregularly shaped organelle
fragments—ferry proteins from one compartment to another. The transport
vesicles and fragments become loaded with a cargo of molecules derived from
the lumen of one compartment as they bud and pinch off from its membrane;
they discharge their cargo into a second compartment by fusing with the
membrane enclosing that compartment

DISTINCT FAMILIES/GROUPS WITHIN THE CELL
1. Nucleus and Cytosol
communicate with each other through
nuclear pore complexes and are thus topologically
continuous
2. All organelles (secretory and endocytic pathways)
it includes the ER, Golgi apparatus,
endosomes, and lysosomes, the numerous classes of
transport intermediates such as transport vesicles
that move between them, and possibly peroxisomes
4. The Plastids
3. The Mitochondria

THE TRANSPORT OF MOLECULES BETWEEN THE NUCLEUS AND THE CYTOSOL
THE TRANSPORT OF MOLECULES BETWEEN THE
NUCLEUS AND THE CYTOSOL
A bidirectional traffic occurs continuously between the
cytosol and the nucleus.
 proteins that function in the nucleus—including histones, DNA
and RNA polymerases, gene regulatory proteins, and RNA-
processing proteins—are selectively imported into the nuclear
compartment from the cytosol, where they are made. At the same
time, tRNAs and mRNAs are synthesized in the nuclear
compartment and then selectively exported to the cytosol.
This transport process is complex. Ribosomal proteins, for
instance, are made in the cytosol and imported into the nucleus,
where they assemble with newly made ribosomal RNA into particles.
The particles are then exported to the cytosol, where they assemble
into ribosomes. Each of these steps requires selective transport
across the nuclear envelope.

THE TRANSPORT OF MOLECULES BETWEEN THE
NUCLEUS AND THE CYTOSOL
Nuclear Pore Complexes
Large, elaborate structures known as nuclear pore
complexes (NPCs) perforate the nuclear envelope of all
eukaryotes. It has four structural building blocks: column
subunits, annular subunits, lumenal subunits, and ring
subunits.
Each NPC contains one or more aqueous passages,
through which small water-soluble molecules can diffuse
passively. Large proteins, however, traverse the NPC much
more slowly while; proteins larger than 60,000 daltons can
barely enter by passive diffusion. This size cut-off to free
diffusion is thought to result from the NPC structure.

References:
References:
Alberts, B. et, al. (2008). Molecular Biology of The Cell. Fifth Edition.
chapter 12, pp. 695-723.
Burton, G and Engelkirk, P. (2011). Microbiology for the Health
Sciences: Chapter 2. The Cell Structure and Taxonomy. Seventh Edition.
Pp. 41-53.
Marieb, E. (2012). Essentials of Human Anatomy and Physiology:
Developmental aspects of Cells and Tissues. pp. 56-90.
Davidson, M. (2019). Molecular Expressions: Cell Biology and
Microscopy. Available at:
file:///C:/Users/asus/Downloads/Cell%20Organeles/Molecular%20Expre
ssions%20Cell%20Biology_%20The%20Cell%20Nucleus.html
The Fundamental Unit of Life Cell Organelle. Available at:
file:///C:/Users/asus/Downloads/Cell%20Organeles/Cell%20Organelle_
%20Organelles,%20Structure,%20Functions,%20Videos%20and%20Exam
ples.html

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