The document provides an overview of various cell organelles including the nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, mitochondria, peroxisomes and cytoskeleton. It describes the structure and functions of the nucleus, ribosomes and endoplasmic reticulum in detail. The endoplasmic reticulum functions to synthesize proteins and lipids and is involved in detoxification. It has two types - smooth endoplasmic reticulum and rough endoplasmic reticulum which differ in their functions.

1. Introduction To Cell Organelles
By;
Ayesha Shaukat

2. Organelles Of Cell
• Nucleus
• Ribosomes
• Endoplasmic reticulums
• Golgi apparatus
• Lysosomes
• Vacuoles
• Mitochondria
• Peroxisomes
• Cytoskeleton

3. Nucleus:

5. Nucleus:
• Most genes located in nucleus
• Average 5um in diameter
• Double membrane
• Pore complex (entry and exit)
• Chromatin
• Chromosome
• Nucleolus

6. Important Components Of Nucleus:
• Chromatin:
• DNA is organized along with the proteins into a fibrous
material is called chromatin
• In humans 46 chromosomes in its nucleus.
• Nucleolus:
• Non dividing part of nucleus, here rRNA is synthesized and
assembled here with proteins imported from cytoplasm into
the main component of ribosomes, called ribosomal unit.
• Nuclear Pores:
• Transport of different particles
• Pore complex.
• Nuclear Envelop:
• Double membranes.

7. Ribosomes Build A Cell’s Proteins:

8. Ribosomes General Features:
• Ribosomes particles made of ribosomal RNA and
proteins, are the organelle that carry out protein
synthesis; each composed of two subunits.
• Ribosomes and Nucleoli, unlike most of the organelles
are not membrane bounded structures.
• Ribosomes build proteins in two cytoplasmic locales:
• Free Ribosomes:
Suspended in cytoplasm
Bound Ribosomes:
Attached to the outside of the
endoplasmic reticulum or nuclear envelop.

9. Function of their proteins:
• Most proteins made from free Ribosomes will
function within the cytosole
• Bound Ribosomes generally make proteins that
are destined either for insertion into membrane, for
packing within certain organelles such as
Lysosomes, or for export from the cell (secretion).
• Cells that specialized in protein secretion for
instance, the cell of the pancreas and other gland
that secrete digestive enzymes.
• Both structurally same differ in functions.

10. Endomembrane system
• Many different membranes of the eukaryotic cell
are part of Endomembrane system.
• These membranes are related either through
direct physical continuity or my transfer of
membrane segment as tiny vesicles
• Despite these relationship , various membranes
are not identical in structure and function.
• Moreover thickness, molecular composition and
metabolic behavior of the membrane are not
fixed.

11. Endomembrane system regulates protein
traffic and performs metabolic functions in
the cell
Many of the different membranes of the eukaryotic
cell are part of an endomembrane system.
These carries out a variety of tasks in the cell
including synthesis of proteins and their transport
into membranes and organelles or out of the cell.
Metabolism and movement of lipids, and
detoxification of poisons.

12. The Endoplasmic Reticulum:
Biosynthetic Factory
 The endoplasmic reticulum (ER) is such an extensive network
of membranes that it accounts for more than half the total
membrane in many eukaryotic cells. (The word endoplasmic
means"within the cytoplasm,~ and reticulum is Latin for
"little net~)
 The ER consists of a network of membranous tubules and sacs
called cisternae (from the Latin cisterna, a reservoir for a
liquid).
 The ER membrane separates the internal compartment of the
ER, called the ER lumen (cavity) or cisternal space, from the
cytosole.
 Further the ER membrane is continuous with the nuclear
envelope, the space between the two membranes of the
envelope is continuous with the lumen of the ER

14.  There are two distinct, though connected,
regions of the ER. These differ in structure and
function: smooth ER and rough ER.
 Smooth ER is so named because its outer
surface lacks Ribosomes.
 Rough ER has Ribosomes on the outer surface
of the membrane and thus appears rough
through the electron microscope.
 Ribosomes are also attached to the cytoplasmic
side of the nuclear envelope's outer membrane,
which is continuous with rough ER.

16. Functions of Smooth ER
• The smooth ER functions in diverse metabolic processes,
which vary with cell type.
• These processes include synthesis of lipids, metabolism of
carbohydrates, and detoxification of drugs and poisons.
• Enzymes of the smooth ER are important in the synthesis
of lipids, including oils, phospholipids, and steroids.
• Among the steroids produced by the smooth ER in
animal cells are the sex hormones of vertebrates and the
various steroid hormones secreted by the adrenal glands.
• The cells that synthesize and secrete these hormones-in the
testes and ovaries, for example-are rich in smooth ER, a
structural feature that fits the function of these cells.

17.  Enzymes of the smooth ER help detoxify drugs and poisons,
especially in liver cells. Detoxification usually involves adding
hydroxyl groups to drug molecules, making them more soluble
and easier to flush from the body.
 The sedative phenobarbital and other barbiturates are
examples of drugs metabolized in this manner by smooth ER
in liver cells. In fact, barbiturates, alcohol, and many other
drugs induce the proliferation of smooth ER and its associated
detoxification enzymes, thus increasing the rate of
detoxification. This, in turn, increases tolerance to the drugs,
meaning that higher doses are required to achieve a particular
effect, such as sedation.
 Also, because some of the detoxification enzymes have
relatively broad action, the proliferation of smooth ER in
response to one drug can increase tolerance to other drugs as
well. Barbiturate abuse, for example, can decrease the
effectiveness of certain antibiotics and other useful drugs

18. • The smooth ER also stores calcium ions.
• In muscle cells, for example, a specialized
smooth ER membrane pumps calcium ions from
the cytosol into the ER lumen.
• When a muscle is stimulated by a nerve impulse
• Calcium ions rush back across the ER membrane
into the cytosol and calcium ion release from the
smooth ER triggers different responses.

20. • Association of tropomyosin and troponins
with actin filaments
• (A) Tropomyosin binds lengthwise along actin
filaments and, in striated muscle, is associated
with a complex of three troponins: troponin I
(TnI), troponin C (TnC), and troponin T (TnT).
In the absence of Ca2+, the tropomyosin-
troponin complex blocks the binding of myosin
to actin. Binding of Ca2+ to TnC shifts the
complex, relieving this inhibition and allowing
contraction to proceed. (B) Cross-sectional view.