lecture 3-5

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The Cell Organelles
‫عضيــات الخلي ـ ـ ــة‬
‫المادة الوراثية‬
‫الشبكة اإلندوبالزمية‬
‫نوية‬
‫النواة‬
‫الجدار النووى‬
‫سوط حركي‬
‫جسم مركزي‬
‫ريبوسوم‬
‫جهاز جولـﭽـى‬
‫حلمات دقيقة‬
‫غشاء بالزمى‬
‫ميتوكوندريا‬
‫جسم ُمحلل‬
‫الهيكل الخلوي‬
‫المادة الوراثية‬
‫الشبكة اإلندوبالزمية‬
‫نوية‬
‫النواة‬
‫الجدار النووى‬
‫سوط حركي‬
‫جسم مركزي‬
‫ريبوسوم‬
‫جهاز جولـﭽـى‬
‫حلمات دقيقة‬
‫غشاء بالزمى‬
‫ميتوكوندريا‬
‫جسم ُمحلل‬
‫الهيكل الخلوي‬
1. The nucleus
- The nucleus contains most of the genes in an eukaryotic cell.
- The nucleus averages about 5 µm in diameter.
• a. Nuclear envelope
Structure:
• The nucleus is separated from the cytoplasm by a double
membrane ‫غشاء مزدوج‬.
• Where the double membranes are fused, a pore ‫ ثقوب‬is formed
Functions:
1. Pores allows macromolecules to pass through.
2. The nuclear membrane ‫ الغالف النووى‬is maintaining the
shape of the nucleus
b. Chromatin
Structure:
• Within the nucleus, the DNA
and associated proteins are
organized into fibrous
material, chromatin.
• At the time of division, the
chromatin fibers coil up ‫تلتف‬
to be seen as separate
structures, chromosomes.
Each eukaryotic species
has a characteristic
number of chromosomes
‫رقم ُم َميـٍز من الكروموسومات‬.
- A typical human cell
has 46 chromosomes (23
pairs), but sex cells
(ovum and sperm) have
only 23 chromosomes.
b. Chromatin
Functions:
1. Chromatin have genes that determine
‫ تحدد‬the general characters ‫الصفات العامة‬
of organism.
2. The nucleus directs protein synthesis
by synthesizing messenger RNA(mRNA).
– The mRNA travels to the cytoplasm and
combines with ribosome where the
primary structure of a specific protein is
formed.
c. Nucleolus ***
Nucleolus is a dark region involved in
the production of ribosomes.
2. Ribosomes ***
• Ribosomes contain ribosomal RNA (rRNA) and protein.
• A ribosome is composed of two subunits ‫ وحدتين‬that
combine ‫ تتحد‬to direct protein synthesis ‫تخليق البروتين‬.
‫حرة‬
‫مرتبطة‬
•
In the nucleolus, ribosomal RNA (rRNA) is
synthesized into ribosomal subunits (rRNA +
proteins).
•
The subunits pass from the nuclear pores to the
cytoplasm where they combine to form
ribosomes.
- Cell types that synthesize large quantities of
proteins have large numbers of ribosomes (e.g.
pancreas)
Ribosomes are 2 types:1. Free ribosomes are suspended ‫ معلق‬in the cytosol and
synthesize proteins that function within the cytosol.
2. Bound ribosomes are attached to ‫ ملتصق بـ‬the outside
of the endoplasmic reticulum.
– This type of ribosomes synthesize proteins that are
either included into membranes or for secretion
outside the cell.
3- The Endomembrane System
a) The endoplasmic reticulum manufactures membranes and
performs many other biosynthetic functions
b) The Golgi apparatus finishes, sorts, and ships cell products
c) The Lysosomes are digestive compartments
d)
The Vacuoles have diverse functions in cell maintenance
a)- Endoplasmic
•
reticulum
The ER includes
membranous tubules
•
ER manufacturers
membranes and performs
many other biosynthetic
functions
a)- Endoplasmic
•
reticulum
There are two types of ER
that differ in structure and
function.
1. Smooth ER looks smooth
because it lacks ribosomes.
2. Rough ER looks rough ‫خشنة‬
because ribosomes (bound
ribosomes) are attached to
its membranes.
a)- Endoplasmic
reticulum
• The smooth ER:
- It is rich in enzymes and
plays a role in metabolic
processes.
- Its enzymes synthesize lipids
(oils, phospholipids, and
steroids, including the sex
hormones ‫)الهرمونات الجنسية‬.
- Extensive in the liver ( it
helps to detoxify drugs and
poisons )
a)- Endoplasmic
reticulum
• The rough ER: it contains ribosomes
- is the main site of protein
synthesis.
- It is especially abundant ‫ متوفرة‬in
those cells that secrete
proteins.
- These secretory proteins are
packaged in transport
vesicles that carry them to
other parts of the
endomembrane system
‫‪4‬‬
‫‪Secretory‬‬
‫‪Protein inside‬‬
‫‪transport vesicle‬‬
‫بروتين افرازي في داخل‬
‫حويصلة ناقلة‬
‫‪Transport vesicle‬‬
‫‪buds off‬‬
‫تبرعم الحويصلة الناقلة‬
‫‪Ribosome‬رايبوزوم‬
‫‪3‬‬
‫‪chain Sugar‬‬
‫سلسلة سكر‬
‫‪1‬‬
‫‪Glycoprotein‬‬
‫بروتين سكري‬
‫‪Rough ER‬‬
‫الشبكة االندوبالزمية المحببة‬
‫‪2‬‬
‫‪Polypeptide‬‬
‫عديد البيبتيد‬
‫‪Synthesis and packaging of a secretory protein by the rough ER‬‬
‫بناء وتغليف البروتين اإلفرازي في الشبكة االندوبالزمية المحببة‬
b)- Golgi apparatus:
• The Golgi apparatus function is manufacturing ‫تصنيع‬,
sorting, packaging ‫تغليف‬, and shipping materials to
outside the cell.
• Many transport vesicles ‫ حويصالت ناقلة‬from the ER travel to
the Golgi apparatus for modification ‫ تعديل‬of their
contents.
• Golgi apparatus also manufactures polysaccharides.
• The Golgi apparatus is extensive specially in secretory
cells.
‫وعاء ناقل‬
c)-
Lysosomes ‫األجسام ال ُمحللة‬
• The lysosome is a membrane-bounded sac of enzymes
that digests macromolecules.
• The lysosomal enzymes and membrane are
synthesized by rough ER and then transferred to the
Golgi apparatus and then to lysosomes.
• Lysosomal enzymes can hydrolyse proteins, fats,
polysaccharides, and nucleic acids.
• These enzymes work best at pH = 5 (acidic).
• While rupturing ‫ إنفجار‬lysosomes can destroy the cell
by autodigestion (autophagy) ‫الهضم الذاتى‬.
• Lysosomes can fuse with food vacuoles ‫الفجوة‬
‫ الغذائية‬to digest food, (when a food item is brought
into the cell by phagocytosis).
• Lysosomes can also fuse with another organelle
or part of the cytosol. This process of
autophagy called recycling which renews the
cell
Digestive
Enzymes
‫انزيمات هاضمة‬
‫جسم هاضم‬Lysosome
membrane Plasma
‫الغشاء البالزمي‬
Lysosome fusing with a food vacuole and digesting food
‫الجسم الهاضم أثناء اندماجه مع فجوة غذائية و قيامه بهضم الغذاء‬
Digestive
Enzymes
‫انزيمات هاضمة‬
‫جسم هاضم‬Lysosome
membrane Plasma
‫الغشاء البالزمي‬
Food vacuole
‫فجوة غذائية‬
Lysosome fusing with a food vacuole and digesting food
‫الجسم الهاضم أثناء اندماجه مع فجوة غذائية وقيامه بهضم الغذاء‬
Digestive
Enzymes
‫انزيمات هاضمة‬
‫جسم هاضم‬Lysosome
membrane Plasma
‫الغشاء البالزمي‬
Food vacuole
‫فجوة غذائية‬
Lysosome fusing with a food vacuole and digesting food
‫الجسم الهاضم أثناء اندماجه مع فجوة غذائية وقيامه بهضم الغذاء‬
Digestive
Enzymes
‫انزيمات هاضمة‬
‫جسم هاضم‬Lysosome
membrane Plasma
‫الغشاء البالزمي‬
Digestion
‫الهضم‬
Food vacuole
‫فجوة غذائية‬
Lysosome fusing with a food vacuole and digesting food
‫الجسم الهاضم أثناء اندماجه مع فجوة غذائية وقيامه بهضم الغذاء‬
‫جسم هاضم‬Lysosome
Vesicle containing
damaged mitochondrion
‫حويصلة تحتوي على ميتوكوندريا تالفة‬
Lysosome fusing with vesicle containing damaged
organelle and digesting and recycling its contents
‫الجسم الهاضم أثناء اندماجه مع فجوة تحتوي‬
‫عضيات تالفة ليقوم بهضمها وإعادة تدويره محتوياتها‬
‫جسم هاضم‬Lysosome
Vesicle containing
damaged mitochondrion
‫حويصلة تحتوي على ميتوكوندريا تالفة‬
Lysosome fusing with vesicle containing damaged
organelle and digesting and recycling its contents
‫الجسم الهاضم أثناء اندماجه مع فجوة تحتوي‬
‫عضيات تالفة ليقوم بهضمها وإعادة تدوير محتوياتها‬
‫جسم هاضم‬Lysosome
Vesicle containing
damaged mitochondrion
‫حويصلة تحتوي على ميتوكوندريا تالفة‬
Digestion
‫الهضم‬
Lysosome fusing with vesicle containing damaged
organelle and digesting and recycling its contents
‫الجسم الهاضم أثناء اندماجه مع فجوة تحتوي‬
‫عضيات تالفة ليقوم بهضمها وإعادة تدوير محتوياتها‬
d)- Vacuoles ‫الفجوات‬
•
Vesicles and vacuoles are membrane-bound sacs
‫ أكياس ذات أغشية‬with varied functions.
•
Vacuoles have diverse functions in cell maintenance
•
Types of vacuoles :
1. Food vacuoles ‫فجوة غذائية‬, from phagocytosis, fuse with
lysosomes.
2. Contractile vacuoles ‫فجوة منقبضة‬, found in freshwater
protists, pump excess water out of the cell.
3. Central vacuoles ‫ فجوة مركزية‬are found in many mature
plant cells.
Animal cell
Peroxisomes ( microbodies)
• Peroxisomes
are organelles found in
virtually all eukaryotic cells.
• Peroxisomes were identified
as organelles by the Belgian
cytologist Christian de Duve in
1967 after they had been first
described by a Swedish
doctoral student, J. Rhodin in
1954.
Peroxisomes :
Functions:
1-A major function of the peroxisome
is the breakdown of very long
chain fatty acids through betaoxidation to smaller molecules that
are transported to mitochondria for
fuel.
Peroxisomes :
2- They contain oxidative enzymes that transfer hydrogen
from various substrates to oxygen
(An intermediate product of this process is hydrogen
peroxide (H2O2), toxic ‫ سام‬but the peroxisome has another
enzyme that converts H2O2 to water).
3- They detoxify alcohol and other harmful compounds.
Thus, it exists extensively in the liver cells
Mitochondrion:
• is a membranebound organelle found in
most eukaryotic cells
• the main energy
transformer of cells
• Mitochondria have a smooth outer membrane and a highly
folded inner membrane forming cristae ‫نتوءات‬.
• The inner membrane encloses the mitochondrial matrix, a fluidfilled space with DNA, ribosomes, and enzymes.
Mitochondrion
• Mitochondria are the sites of cellular respiration,
generating ATP (Adenosine TriPhosphate) from the catabolism
‫ هدم‬of sugars, fats, and other fuel sources in the presence of
oxygen.
• In addition to supplying cellular energy, mitochondria are
involved
in
other
tasks
such
as
signaling,
cellular
differentiation, cell death, as well as the control of the cell
cycle and cell growth.
THE CYTOSKELETON
‫الهيكل الخلوي‬
Copyright © 2009 Pearson Education, Inc.
The Cytoskeleton ‫الهيكل الخلوى‬
• The cytoskeleton is a network of
fibers extending throughout the
cytoplasm
Functions:
• The cytoskeleton organizes the
structures and activities of the cell.
• functions in cell motility.
Nucleus
‫نواة‬
Nucleus
‫نواة‬
Actin subunit
‫وحدة آكتين فرعية‬
Fibrous subunits
‫وحدات ليفية فرعية‬
7 nm
Microfilament
‫خيط دقيق‬
Tubulin subunit
‫وحدة توبيولين فرعية‬
10 nm
Intermediate filament
‫خيط متوسط‬
Fibers of the cytoskeleton
‫ألياف الهيكل الخلوي‬
25 nm
Microtubule
‫انيبية دقيقة‬
Cytoskeleton
Microtubules
Microfilaments
Intermediate
filaments
Thick ( hollow tubes)
Thin
Middle
(resist compression)
(resist tension)
(resist tension)
-Responsible for cell motility
)cilia & flagellum)
- separation of chromosome
during cell division.
- Cell motility (muscle
cell)
- Transport materials
-Tracks for organelles movement across the cell.
-Reinforcing the cell
shape
- fixing position of
organelles.
Cilia and Flagella
• Microtubules are the central
structural supports both cilia
‫ األهداب‬and flagella ‫األسواط‬.
• Both can move unicellular and
small multicellular organisms
by propelling water outside the
organism.
‫أهداب‬Cilia
Cilia on cells lining the respiratory tract to sweep
mucus of our lungs
‫األهداب الموجودة على الخاليا المبطنة للقناة التنفسية‬
‫سوط‬Flagellum
Undulating flagellum on a sperm cell
‫سوط متموج على خلية الحيوان المنوي‬
Both cilia and flagella have the same ultrastructure.
-Both have a core of microtubules sheathed by the plasma
membrane.
-Nine doublets (9 + 2 pattern) of microtubules arranged around
a pair at the center.
-Flexible “wheels” of proteins connect outer doublets to each other
and to the core.
- The outer doublets
are also connected
by motor proteins.
- The structure of cilium
and flagellum is
identical to that of
centriole.
Cilia and flagella are formed of arms of a motor protein •
).‫(بروتين الداينين‬dynein
Addition of phosphate group from ATP to dynein and its –
removal causes conformation changes in the protein.
Dynein arms alternately –
grab, move, and release
the outer microtubules.
Protein cross-links limit –
sliding and the force is
expressed as bending.
Cilia
Flagella
usually occur in large 
numbers on the cell
surface.
usually occur in just one or 
a few per cell.
move more like oars with 
have an undulatory 
movement.
alternating
power
and
recovery strokes.
So, They differ in their beating pattern
cilia
flagellum
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