Transcript The Cell Organelles

Lecture 5: The
Cell
Microtubules and microfilaments
The Cytoskeleton ‫اهليكل اخللوى‬
A network of fibres ‫شبكة من‬
‫ االلياف‬that provide
structural support ‫تدعيم‬
to the cell. The
cytoskeleton also
functions in cell motility
‫ تحرك الخلية‬and regulation
The Cytoskeleton ‫اهليكل اخللوى‬
 The cytoskeleton is a network of fibers extending
throughout ‫ تمتد عبر‬the cytoplasm.
 The cytoskeleton
organizes ‫يرتب‬
structures
the cell.
the
and activities of
Cytoskeleton
Microtubules
‫أنيبيبات دقيقة‬
Thick
‫سميكة‬
Responsible for cell
motility, and
separation of
chromosome during
cell division.
(Tubulin protein)
Microfilaments
‫ألياف دقيقة‬
Intermediate
filaments
‫ألياف متوسطة‬
Thin
Middle
‫رفيعة‬
‫متوسطة‬
Support cell
motility and
transport materials
within the cell.
Reinforcing the cell
shape and fixing
position of
organelles.
(Actin protein)
(Fibrous protein)
Cilia and Flagella
 Microtubules are the central structural supports both cilia
‫األهداب‬
and flagella ‫األسواط‬.
 Both can move unicellular and small multicellular organisms by
propelling water outside the organism.
• Cilia usually occur in large numbers on the cell surface.
• Flagella usually occur in just one or a few per cell.
• Cilia move more like oars ‫ مجادبف‬with alternating power and recovery
strokes.
• Flagella have an undulatory movement ‫حركة تموجية‬.
• So, They differ in their beating pattern ‫أسلوب الحركة‬.
cilia
flagellum
 Cilia and flagella are formed of arms of a motor
protein (dynein ‫)بروتين الداينين‬.
 Dynein arms alternately
grab, move, and release
the outer microtubules.
 Protein cross-links limit
sliding and the force is
expressed as bending ‫إلتواء‬.
Thus, many prokaryotes are motile ‫متحركة‬
About half of all prokaryotes are capable
of directional movement ‫الحركة الموجهة‬
by the following:1- By the flagella ‫األســواط‬, scattered ‫مبعثرة‬
over the entire surface, is the most
common ‫ شائعة‬method of movement.
2- By two or more filaments ‫ألياف‬.
3- By threads ‫ خيوط‬that anchors ‫ تربط‬the cells to the substratum
‫السطح الذى تعيش عليه‬.
4- By cilia ‫ أهداب‬that differ from flagella in beating pattern
7- Cell membrane
• The plasma
membrane
functions as a
selective barrier
‫ حاجز إختيارى‬that
allows passage
of oxygen,
nutrients, and
wastes for the
whole volume of
the cell.
Cell membrane
Composed of lipids (phospholipids) and proteins
Lipid layer contains hydrophilic and hydrophobic regions
Carbohydrate chains
Hydrophilic ‫ُمحب للماء‬
Phospholipid
Hydrophobic ‫كاره للماء‬
Proteins
Comparison between Prokaryotes and Eukaryotes
Term
Prokaryotes
Eukaryotes
Size
1-10 µm in diameter
10-100 µm in diameter
Cell wall
Existed
In plant cell (not animal cell)
nucleus
No nuclear envelope but
Nucleoid
True nucleus exists with
nuclear envelope
DNA
As fibre in the nucleoid
As Chromatin (DNA and
region (plasmids in some cases) protein)
Specialized
Most of them are absent
Organells
All are existed
Cell
division
Meiotic and/or Mitotic
By Binary Fission