CYTOLOGY & HISTOLOGYLecture 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 CellsThe Nucleus: Genetic Library of the CellRibosomes: 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

Rough ER Smooth ER

Centrosome

CYTOSKELETON

Microfilaments

Microtubules

Microvilli

Peroxisome

Lysosome

Golgi apparatus

Ribosomes

In animal cells but not plant cells:LysosomesCentriolesFlagella (in some plant sperm)

Nucleolus

Chromatin

NUCLEUS

Flagelium

Intermediate filaments

ENDOPLASMIC RETICULUM (ER)

Mitochondrion

Nuclear envelope

Plasma membrane

Figure 1.9

The Nucleus:Genetic Library of the Cell

The nucleus– Contains most of the genes in the

eukaryotic cell

Nucleus

NucleusNucleolus

Chromatin

Nuclear envelope:Inner membraneOuter membrane

Nuclear pore

Rough ER

Porecomplex

Surface of nuclear envelope.

Pore complexes (TEM). Nuclear lamina (TEM).

Close-up of nuclearenvelope

Ribosome

1 µm

1 µm

0.25 µm

The nuclear envelope Encloses the nucleus, separating its contents

from the cytoplasmFigure 1.10

Ribosomes:Protein Factories in the Cell

Ribosomes– Are particles made of ribosomal RNA

and protein

Ribosomes Cytosol

Free ribosomes

Bound ribosomes

Largesubunit

Smallsubunit

TEM showing ER and ribosomes Diagram of a ribosome

0.5 µm

Ribosomes– Carry out protein synthesis

ER Endoplasmic reticulum (ER)

Figure 1.11

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

Smooth ER

Rough ER

ER lumenCisternae

RibosomesTransport vesicle

Smooth ER

Transitional ER

Rough ER 200 µm

Nuclearenvelope

Figure 1.12

The ER membrane

There are two distinct regions of ER–Smooth ER, which lacks

ribosomes

–Rough ER, which contains ribosomes

Functions of ER

The smooth ER– Synthesizes lipids

– Metabolizes carbohydrates

– Stores calcium

– Detoxifies poison

The rough ER– Has bound ribosomes

– Produces proteins and membranes, which are distributed by transport vesicles

Smooth Rough