1 pdf - د.شيماء جمال احمد

At the end of this lecture the student will be

able to:



Define The cell organelles .



Compare between prokaryotic and

eukaryotic cells.



List the types of organelles.



Describe the Mitochondrial Inheritance .



Recognize to the Mitochondrial diseases .



Recognize to the clinical features of the

diseases in this lecture.



In cell biology: an

organelle

a specialized

subunit within a cell that has a specific

function, and it is usually separately enclosed

within it`s own lipid bilayer.



The name organelle comes from the idea that

these structures are to cells what an organ is

to the body (hence the name

organelle,

the

suffix

-elle

being a diminutive).



Organelles are identified by microscopy.



There are many types of organelles,

particularly in eukaryotic cells.



While prokaryotes do not possess organelles.



The prokaryotic cell

a simple cell.

It has no nucleus.

no membrane-bound organelles.

The genetic material of a prokaryotic cell is found

in a region of the cell known as the

nucleoid.



Bacteria are a fine example of prokaryotic cells

and divide by a process known as

binary fission

;

they duplicate their genetic material, divide in

half, and produce two identical daughter cells.



The eukaryotic cell:

much more complex.

It contains a nucleus, which functions as

the control center of the cell, directing

DNA replication, transcription, and cell

growth.

Eukaryotic organisms may be unicellular

or multicellular.



One of the key features of eukaryotic cells

is the presence of membrane-bound

organelles, each with it`s own duties

Eukaryotes

Prokaryotes

fungi, plants, animals

bacteria, archaea

Typical organisms

~ 10–100 µm

~ 1–5 µm

Typical size

true nucleus with

double membrane

nucleoid region; no

true nucleus

Type of nucleus

linear molecules

(chromosomes) with

histone proteins

circular (usually)

DNA

60S and 40S

50S and 30S

Ribosomes

highly structured by

endomembranes and a

cytoskeleton

very few structures

Cytoplasmic

structure

flagella and cilia containing

microtubules; lamellipodia

&filopodia containing actin

flagella made of flagellin

Cell movement

one to several thousand

(though some lack

mitochondria)

none

Mitochondria

in algae and plants

none

Chloroplasts

single cells, colonies, higher

multicellular organisms with

specialized cells

usually single cells

Organization

Mitosis (fission or budding)

Meiosis

Binary fission (simple division)

Cell division

Eukaryotic Organelles:



Ribosomes:

ribosomes serve as the host organelle for

protein synthesis

Eukaryotes have bound ribosomes, which are

attached to endoplasmic reticula and form

proteins that tend to be exported from the cell

or sent to the membrane.

There are also free ribosomes, which exist

freely in the cytoplasm and produce proteins

that remain in the cytoplasm of the cell.

Eukaryotic ribosomes are built in a structure

called the

nucleolus

Prokaryotic ribosomes

Eukaryotic ribosomes



Smooth endoplasmic reticulum:



This is a membrane-bound organelle involved

in lipid synthesis, detoxification, and

carbohydrate metabolism.



Liver cells contain a lot of

smooth endoplasmic

reticulum (SER) because they host a lot of

carbohydrate metabolism (glycolysis).



The liver contains much SER

for another

reason—it is the site of alcohol detoxification.



It is given the name "smooth" endoplasmic

reticulum

because there are no ribosomes on

its cytoplasmic surface



This membrane-bound organelle is

termed "rough"

because of the

presence of ribosomes on the

cytoplasmic surface of the cell.



The proteins produced by this

organelle are often secreted by the

cell and carried by vesicles to the

Golgi apparatus

for further

modification.



Proteins, lipids, and other macromolecules

are sent to the Golgi to be modified by the

addition of sugars and other molecules to

form

glycoproteins



The products are then sent in vesicles to

other parts of the cell, directed by the

particular changes made by the Golgi.

In other words

: storage & packaging of

materials that will be exported from the cell.



Nucleus

: This is the control center of the cell.

In eukaryotic cells, this is the storage site of

genetic material (DNA).

It is the site of replication, transcription, and

posttranscriptional modification of RNA. It also

contains the nucleolus, the site of ribosome

synthesis.



Vacuole

: This is a storage organelle that acts

as a vault.

Vacuoles are quite large in plant cells but

small in animal cells.

Nucleus

Vacuole

Cytoskeleton



The skeleton of cells consists of three

types of fibers that provide support, shape,

and mobility to cells:



microtubules



Microfilaments



intermediate filaments

1 – Microtubules:



are constructed from

tubulin

and have a

lead role in the separation of cells during cell

division.



Microtubules are also important components

of cilia and flagella, which are structures that

aid the movement of particles .

2- Microfilaments:

are constructed from

actin

play a big part in muscular

contraction.

3- Intermediate filaments:

are constructed from a class of

proteins called

keratins

and are

thought to function as

reinforcement for the shape and

position of organelles in the

cell.



Peroxisomes:

1-are single-membrane structures found

in all eukaryotic cells. They are small,

membrane-bound structures that use

molecular oxygen to oxidize organic

molecules.

2-These are organelles containing

enzymes that produce hydrogen peroxide

as a by-product while performing various

functions, such as breakdown of fatty

acids and detoxification of alcohol in the

liver.

3- also contain an enzyme that converts

the toxic hydrogen peroxide by-product of

these reactions into cell-friendly water.



are special types of vacuoles .



contain enzymes for use in the

hydrolytic breakdown of

macromolecules .



Three ways to enter a lysosome –

phagocytosis , autophagy, and

receptor-mediated endocytosis.

Found in ALL eukaryotic cells (even in

plant cells)

Site of aerobic respiration



sugars + O

- - > ATP + CO

+ H



So it called “powerhouse of the cell”

Contain DNA which codes for

mitochondrial proteins, ribosomes,

etc.

Divide by a process similar to binary fission

when cell divides.

5. Enclosed in a double membrane system.

Inner Membrane forms the Cristae

(invaginations into interior region)

Site of energy generation (houses of

energy)

Matrix is the soluble portion of the

mitochondria

Site of carbon metabolism

Location of mDNA

Site of mitochondrial protein synthesis



Mammalian cells contain mitochondria which have

their own circular deoxyribonucleic acid (mtDNA).

Mitochondria are only passed on in the cytoplasm of

the egg so that a child inherits all mitochondria

from his mother.



There are some diseases that are some diseases that

are associated with mutations in mitochondrial DNA.

A woman with such a mutation will therefore pass it

on to all her children whilst a man with the same

mutation will not pass it on to any of his children.



There is often a wide range of severity of disease in

carriers of mitochondrial mutations. Mitochondrial

inheritance is characterized by:

1-Maternal transmission only.

2-Extreme variability in the same family.

The genetics of mtDNA differ from that of DNA in the

following unique properties:

1-The mitochondrial genome is maternally inherited:

The mother transmits her oocyte mtDNA to all of

her offspring & her daughters transmit their mtDNA

to the next generation. This is due to the fact that

during fertilization. The few mitochondria from the

sperm that enter the egg are rapidly eliminated

through unknown mechanism.

2-Mitochondria are polypoid:

Each human cell has hundreds of mitochondria

each containing 2-10 mtDNA molecules. At cell

division mitochondria and their genomes are

randomly distributed to daughter cells.

3-The mitochondrial genome has a much faster

evolution rate than the nuclear genome:



The average number of base pair difference

between two human mitochondrial genomes is

estimated to be from 9.5 to 66. This explained

by the fact that, although the mitochondrial

gamma-DNA polymerase may retain a

proofreading activity X certain types of repair

enzymes have been identified in mitochondrial

fractions.



Mitochondria lack an efficient DNA repair

system, based, for instance, on homologous

recombination or removal of pyrimidine

dimmers. In addition, the mitochondrial

genome lacks protective proteins like

histones, and is physically associated with the

inner mitochondrial membrane, where highly

mutagenic oxygen radicals are generated as

by-products of OXPHOS.

4- Normally, the mitochondrial genotype

of an individual is composed of a single

mtDNA species:

A condition known as homoplasmy.

However, the intrinsic propensity of

mtDNA to mutate randomly can

occasionally determine a transitory

condition known as heteroplasmy,

where the wild-type & the mutant

genomes co-exist intracellular.

Assorted myopathies and neuropathies observed

clinically in recent years:



neurologic disorders



ragged red fibers in muscle biopsies



weakness exacerbated by exercise



seizures



(muscle jumps)



dementia with early onsetmovement disorders



stroke-like symptoms



retinopathy



hearing loss



partial blindness



migraine headaches

Combined oxidative

phosphorylation

deficiency 5

CELL
STRUCTURE

LOCATIO
N

DESCRIPTIO
N

FUNCTIO
N

Cell Membrane

All cells



Plant - inside
cell wall



Animal -
outer layer;
cholesterol



Double layer
of
phospholipids
with proteins



Selectively
permeable



Support



Protection



Controls
movemen
t of
materials
in/out of
cell



Barrier
between
cell and
its
environm
ent



Maintains
homeosta
sis

Nucleus

All cells

except

prokaryotes



Large, oval



May contain
1 or more
nucleoli



Holds DNA



Controls
cell
activities



Contains
the
hereditary
material
of the cell

Nuclear membrane

All cells

except

prokaryotes



Surrounds
nucleus



Double
membrane



Selectively
permeable



Controls
movemen
t of
materials
in/out of
nucleus

Cytoplasm

All cells



Clear, thick,
jellylike
material
(cytosol)



Organelles
found inside cell
membrane



Contains the
cytoskeleton
fibers



Supports and
protects cell
organelles

Endoplasmic
reticulum (ER)

All cells

except

prokaryotes



Network of
tubes or
membranes



Smooth w/o
ribosomes



Rough with
embedded
ribosomes



Connects to
nuclear
envelope & cell
membrane



Carries
materials
through cell



Aids in
making
proteins

Ribosome

All cells



Small bodies
free or attached
to ER



Made of rRNA
& protein



Synthesizes
proteins

Mitochondrion

All cells

except

prokaryotes



Peanut shaped



Double
membrane



Outer
membrane
smooth



Inner membrane
folded into
cristae



Breaks down
sugar
(glucose)
molecules to
release
energy



Site of
aerobic
cellular
respiration

Lysosome

Plant -
uncommon
Animal -
common



Small and round
with a single
membrane



Breaks down
larger food
molecules
into smaller
molecules



Digests old
cell parts

nucleolus

All cells

except

prokaryotes



Found inside the
cell's nucleus



May have more
than one



Disappear
during cell
division



Make
ribosomes

Golgi Apparatus

All cells

except

prokaryotes



Stacks of
flattened sacs



Have a cis &
trans face



Modify
proteins
made by the
cells



Package &
export
proteins

Centrioles

Animal cells



Paired structures
near the nucleus



Made of a
cylinder of
microtubule
pairs



Separate
chromosome
pairs during
mitosis

Cytoskeleton

All cells



Made of
microtubules 7
microfilaments



Strengthen
cell &
maintains the
shape



Moves
organelles
within the
cell

Thank you