Transcript CYTOLOGY & HISTOLOGY Lecture three DR. ASHRAF SAID

CYTOLOGY & HISTOLOGY
Lecture three
DR. ASHRAF SAID
Review
Of the second lecture
Concept 3
 The eukaryotic cell’s
genetic instructions are
housed in the nucleus and
carried out by the
ribosomes
Start
Of this lecture
Objectives of lecture three
The Endoplasmic Reticulum: Biosynthetic Factory
Lysosomes: Digestive Compartments
Concept 4
The endomembrane system
regulates protein traffic and
performs metabolic functions in
the cell
 The endomembrane system
– Includes many different
structures
The Endoplasmic Reticulum:
Biosynthetic Factory
The endoplasmic reticulum
(ER)
–Accounts for more than half
the total membrane in many
eukaryotic cells
The ER membrane
 Is continuous with the nuclear envelope
Figure 1.12
Smooth ER
Rough ER
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
Nuclear
envelope
Transitional ER
Rough ER
200 µm
The ER membrane
There are two distinct
regions of ER
–Smooth ER, which lacks
ribosomes
–Rough ER, which contains
ribosomes
Functions of ER
Smooth
 The smooth ER
– Synthesizes lipids
– Metabolizes
carbohydrates
– Stores calcium
– Detoxifies poison
Rough
 The rough ER
– Has bound ribosomes
– Produces proteins and
membranes, which are
distributed by transport
vesicles
The Golgi Apparatus: Shipping and
Receiving Center
 The Golgi apparatus
– Receives many of the transport vesicles produced in
the rough ER
– Consists of flattened membranous sacs called
cisternae
Functions of the Golgi
apparatus include
 Modification of the products of the rough
ER
 Manufacture of certain macromolecules
Functions of the Golgi
apparatus
Golgi
apparatus
Figure 1.13
cis face
(“receiving” side of
Golgi apparatus)
1 Vesicles move
2 Vesicles coalesce to
6 Vesicles also
form new cis Golgi cisternae
from ER to Golgi
transport certain
Cisternae
proteins back to ER
3 Cisternal
maturation:
Golgi cisternae
move in a cisto-trans
direction
5 Vesicles transport specific
proteins backward to newer
Golgi cisternae
0.1 0 µm
4 Vesicles form and
leave Golgi, carrying
specific proteins to
other locations or to
the plasma membrane for secretion
trans face
(“shipping” side of
Golgi apparatus)
TEM of Golgi apparatus
Lysosomes:
Digestive Compartments
A lysosome
– Is a membranous sac of hydrolytic
enzymes
– Can digest all kinds of macromolecules
Lysosomes carry out intracellular digestion by
phagocytosis
1 µm
Nucleus
Lysosome
Lysosome contains
active hydrolytic
enzymes
Food vacuole
fuses with
lysosome
Hydrolytic
enzymes digest
food particles
Digestive
enzymes
Lysosome
Plasma membrane
Digestion
Food vacuole
(a) Phagocytosis: lysosome digesting food
Figure 1.14 A
Figure 1.14 B
Autophagy
Lysosome containing
two damaged organelles
1µm
Mitochondrion
fragment
Peroxisome
fragment
Lysosome fuses with
vesicle containing
damaged organelle
Hydrolytic enzymes
digest organelle
components
Lysosome
Digestion
Vesicle containing
damaged mitochondrion
(b) Autophagy: lysosome breaking down damaged organelle