CYTOLOGY & HISTOLOGY
Lecture two
DR. ASHRAF SAID

Review
Of the first lecture



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

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


A animal cell
Nuclear envelope
ENDOPLASMIC RETICULUM (ER)
Rough ER Smooth ER
Nucleolus
Chromatin
Flagelium
Plasma membrane
Centrosome
NUCLEUS
CYTOSKELETON
Microfilaments
Intermediate filaments
Microtubules
Microvilli
Ribosomes
Peroxisome
Figure 1.9
Mitochondrion
Golgi apparatus
Lysosome
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
Nucleus
1 µm
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore complex
Surface of nuclear envelope.
0.25 µm
Ribosome
Rough ER
1 µm
Close-up of nuclear envelope
Nuclear lamina (TEM). Pore complexes (TEM).

Ribosomes:
Protein Factories in the Cell
 Ribosomes
– Are particles made of ribosomal RNA and protein

Ribosomes
– Carry out protein synthesis
Ribosomes
Figure 1.11
ER
Cytosol
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
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

–Accounts for more than half the total membrane in many eukaryotic cells

The ER membrane
 Is continuous with the nuclear envelope
Smooth ER
Rough ER
Figure 1.12
Nuclear envelope
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER Rough ER
Transitional ER
200 µm

The ER membrane

–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