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Cell Biology: A Brief Overview

This document provides a basic introduction to cell biology, focusing on the distinctions between prokaryotic and eukaryotic cells. It begins by defining the cell as the fundamental unit of life and highlighting its essential components: cell membrane, cytoplasm, and genetic material.

The text then differentiates viruses from cells, stating that viruses are acellular, lacking the structures and functions of a cell. They depend on host cells for replication and lack their own metabolism.

The majority of the text focuses on prokaryotes, the earliest life forms on Earth. They are single-celled organisms lacking a distinct nucleus and membrane-bound organelles. Prokaryotes are further classified into archaea and bacteria, differing at the molecular level.

Prokaryotic cells come in various shapes and arrangements, and their structure is detailed through transmission electron microscopy. The text emphasizes the constant elements, including the cell wall (composed of peptidoglycan), plasma membrane, cytoplasm, nucleoid, ribosomes, and polyribosomes. Optional elements include a capsule, plasmids, flagella, pili, fimbriae, chromatophores, gas vesicles, and endospores.

Prokaryotes primarily reproduce through binary fission, where a single cell divides into two identical daughter cells. This rapid division leads to significant population growth.

The final portion of the text shifts to eukaryotes, defined by their possession of a true nucleus and membrane-bound organelles. Eukaryotic cells are found in both single-celled (protists) and multicellular organisms (animals, plants, and fungi). They are typically larger and more complex than prokaryotes.

The document concludes by examining animal and plant cells, highlighting their key differences, such as the presence of a cell wall and chloroplasts in plant cells. The text also discusses the unique case of red blood cells (erythrocytes), which are eukaryotic but lose their nucleus upon maturation, allowing for greater oxygen transport.

CELL BIOLOGY
Dr. Madani S.
2023/2024
.1

The Cell
The cell is the fundamental, structural, functional, and reproductive unit of life that can function autonomously (respiration, metabolism, cell division, and movement).
All cells share some basic features:  Cell membrane
 Cytoplasm
 Genetic material
The cell is an enclosed compartement
CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024

Are Viruses
considered as
cells?
CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024

Viruses
Viruses are not considered cells. They are akaryotes (acellular), which means they lack the basic structures and functions of a cell.
Viruses do not have a nucleus, cytoplasm, or membrane-bound organelles. They are also unable to reproduce on their own or have their own metabolism. Instead, they rely on host cells to replicate their genetic material and produce new virions.
CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024

 Prokayotic Cells (Prokaryotes)

CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024

Prokayotes
1- Definition:
Prokaryote ( Greek “before nucleus”) known to be the earliest on earth.
They include two domains :
Archaea: Primitive Prokaryotes, found in extreme environment Bacteria also called (eubacteria): Modern
Prokaryotes, found everywhere and can
be helpful or harmful
 Archaea and Bacteria are different at the
molecular level
CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024

Prokayotes
1- Definition:
Prokaryote ( Greek “before nucleus”) Single-celled(Unicellular) microorganisms Lacks a distinct nucleus ( genetic material is
free within the cell)
 Lacks organelles due to the absence of
internal membranes
Ribosomes are present
Very small size : 10 μM in length and Increased complexity than Prokaryotes CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024

Eukayotes
 They have a nuclear membrane and nucleolus
Mitochondria, Golgi apparatus, endoplasmic reticulum, chloroplast, and lysosomes are
present.
 The genetic material is present on more than one chromosome.
 They have the histone proteins
 The cell wall is made up of cellulose.
 The plasma membrane acts as the mitochondrial membrane carrying respiratory enzymes. Cell respiration is done via the mitochondria.
 Cell division involves mitosis and meiosis (gametes) .  The gene exchange involves sexual reproduction
CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024

Eukayotes
Animal Cell
 Have circular or irregular shape
 Contain the same organelles as the plant cell except for : Cell Wall and
Chloroplast
Can contain many smaler vacuoles
than a plant cell
 Can have cilia and flagella
 Size: 10-30 μM
CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024

Eukayotes
Micrograph of epithelial cells Observed with the light microscope
CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024
Transmission Electron Micrograph Of an epithilal cell

Eukayotes
Plant Cell
 Have a regular shape
 typically larger than animal cells Contain the same organelles as
the animal cell + Cell Wall and
Chloroplast
 Contain a large vacuole
 Lack of flagella and cilia
 Size: 10-100 μM
CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024

Eukayotes
Plant Cell
Micrograph of plant cells Observed with the light microscope
CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024
Transmission Electron Micrograph Of a plant cell

Eukayotes
CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024
Plant cell
Animal Cell

Are red blood cells considered as Eukaryotes?

CELL BIOLOGY/ 1st Academic year / Dr. MADANI S. /2023-2024

Eukayotes
Erythrocytes
Erythrocytes also called Red blood cells are unique eukaryotes in that they lose their nucleus when they mature. This allows them to carry more oxygen, as there is more room for hemoglobin, the protein that binds to oxygen. Red blood cells also have a flattened, biconcave shape, which increases their surface area and allows them to exchange oxygen and carbon dioxide more efficiently.