Introduction: Cells• Cell – basic unit of life

• Based on the organization of their cellular structures, all living cells can be divided into two groups: eukaryotic and prokaryotic

• eukaryotic cell types - Animals, plants, fungi, protozoans, and algae

• prokaryotic cell types - bacteria

Prokaryotic Cells• much smaller (microns) and more simple than

eukaryotes

• prokaryotes are molecules surrounded by a membrane and cell wall.

• they lack a true nucleus and don’t have membrane bound organelles like mitochondria, etc.

• large surface-to-volume ratio : nutrients can easily and rapidly reach any part of the cells interior

Dr Ekta Chourasia

Structure of A Prokaryotic Cell

Structure of A Prokaryotic Cell• Outer layer – two components:

1. Rigid cell wall2. Cytoplasmic (Cell/ Plasma) membrane –

present beneath cell wall

• Cytoplasm – cytoplasmic inclusions, ribosomes, mesosomes and nucleus

• Additional structures – plasmid, slime layer, capsule, flagella, fimbriae (pili)

Function of Cell Components

• Cell wall 1. Shape, rigidity2. 10-25 nm thick3. Composed of peptidoglycan/ mucopeptide (N

acetyl glucosamine & N acetyl muramic acid)

• Cytoplasmic membrane – semipermeable membrane: controls the inflow and outflow of metabolites

Function of Cell Components• Ribosomes – protein synthesis

• Mesosomes – 1. Multilaminated structures formed as

invaginations of plasma membrane2. Principal sites of respiratory enzymes3. Coordinate nuclear & cytoplasmic division

during binary fission

• Intracytoplasmic inclusions – reserve of energy & phosphate for cell metabolism

Additional Organelles1. Plasmid –

• Extranuclear genetic elements consisting of DNA

• Transmitted to daughter cells during binary fission

• May be transferred from one bacterium to another

• Not essential for life of the cell• Confer certain properties e.g. drug

resistance

Additional Organelles

2. Slime layer & capsule – • Viscous layer secreted around the cell wall.• Protects bacteria from lytic enzymes• Inhibits phagocytosis

3. Flagella – organs of locomotion

4. Fimbriae/ Pili – 10-20µ long, organs of adhesion

The Cell, Structure & Function

والوظيفة, التركيب الخليةThe structure of a Prokaryotic cell ?

Cell WallProtects the cell and maintains its shapeThick cell wall with little lipid: Gram positive Thin cell wall with 2 layers: Gram negative

Capsule Some bacteria have a slimy layer of Polysaccharides for protection.

70s Ribosomes

protein synthesis

Flagellum motility

Nuclear Material

Genetic material : DNA

Plasmid rings of genetic material for antibiotic Resistance

Mesosome For Respiration