Transcript CYTOLOGY & HISTOLOGY

CYTOLOGY & HISTOLOGY
Lecture two
DR. ASHRAF SAID
Review
Of the first lecture
Concept 1
To study cells, biologists
use microscopes and the
tools of biochemistry
Isolating Organelles by Cell
Fractionation
 Cell fractionation
– Takes cells apart and separates the major
organelles from one another
 The centrifuge
– Is used to fractionate cells into their
component parts
Concept 2
Eukaryotic cells have internal
membranes that compartmentalize
their functions
 Two types of cells make up
every organism
– Prokaryotic
– Eukaryotic
Comparing Prokaryotic and
Eukaryotic Cells
 All cells have several basic features in common
– They are bounded by a plasma membrane They
contain a semi-fluid substance called the cytosol
– They contain chromosomes
– They all have ribosomes
 Eukaryotic cells
– Contain a true nucleus,
bounded by a membranous
nuclear envelope
– Are generally quite a bit bigger
than prokaryotic cells
– The logistics of carrying out
cellular metabolism sets limits
on the size of cells
– Have extensive and elaborately
arranged internal membranes,
which form organelles
 Prokaryotic cells
– Do not contain a nucleus
– Have their DNA located
in a region called the
nucleoid
Start
Of this lecture
Objectives of lecture two
A Panoramic View of the Pro/Eu-karyotic Cells
The Nucleus: Genetic Library of the Cell
Ribosomes: Protein Factories in the Cell
Concept 3
 The eukaryotic cell’s
genetic instructions are
housed in the nucleus and
carried out by the
ribosomes
A animal cell
ENDOPLASMIC RETICULUM (ER)
Nuclear envelope
NUCLEUS
Nucleolus
Rough ER
Smooth ER
Chromatin
Flagelium
Plasma membrane
Centrosome
CYTOSKELETON
Microfilaments
Intermediate filaments
Ribosomes
Microtubules
Microvilli
Golgi apparatus
Peroxisome
Figure 1.9
Lysosome
Mitochondrion
In animal cells but not plant cells:
Lysosomes
Centrioles
Flagella (in some plant sperm)
The Nucleus:
Genetic Library of the Cell
 The nucleus
– Contains most of the genes in the
eukaryotic cell
The nuclear envelope
 Encloses the nucleus, separating its contents
from the cytoplasm
Figure 1.10
Nucleus
1 µm
Nucleolus
Chromatin
Nucleus
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Rough ER
Surface of nuclear
envelope.
1 µm
Ribosome
0.25 µm
Close-up of
nuclear
envelope
Ribosomes:
Protein Factories in the Cell
 Ribosomes
– Are particles made of ribosomal RNA
and protein
Ribosomes
– Carry out protein synthesis
Ribosomes
Cytosol
ER
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
Figure 1.11
Large
subunit
0.5 µm
TEM showing ER and ribosomes
Small
subunit
Diagram of a ribosome
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