Parts & Functions: Prokaryotic Cells

Cell Walls

• Provides rigid support and maintains the cell’s shapes

• Prevents the cell from exploding in hypnotic solutions

• Involved in classification of bacteria (Gram-positive & Gram-negative)

• Usually made of peptidoglycan

Gram-positive

bacteria have thick peptidoglycan layer

Gram-negative

bacteria has thin peptidoglycan layer and an outer membrane

Plasma Membrane

• Controls the entry and exit of substances

• Where cellular respiration occurs

Cytoplasm

• Suspends cell components like ribosomes, plasmids, and DNA

• A medium for biochemical reactions and metabolic activity

• Gel-like fluid (mostly water, salts, proteins)

Nucleoid

• Chromosomal DNA

• Stores the genetic blueprint of the organism

• Lacks nuclear envelope and irregularly shaped

Plasmids

• Contains the extra genes for antibiotic resistance, toxin production, etc.

• Can be transferred between bacteria via conjugation

• Used in genetic engineering as vectors for cloning genes

Ribosomes (70s type)

• Site of protein synthesis

• Made of RNA and protein

• Targeted by antibiotics like tetracycline and streptocycline

Capsule

• Not always present

• Provides protection

• Outermost layer of the cell

• Polysaccharide-rich

Flagella

Enabled movement within the bacteria

Monotrichous

one flagellum

Petritrichous

flagella is all over the surface

Lopotrichous

multiple flagella at one pole

Pili/Fimbrae

short, thin hair-like appendages made of protein

Fimbrae

Helps in attachment to surfaces

(Sex) Pili

Transfers DNA between bacteria during conjugation

Inclusion Bodies

• Granules found in cytoplasm

• Serves as storage sites for nutrients and energy reserves

• Helps the cell survive under nutrient-limited conditions