Prokaryotes

What are the two major lineages of prokaryotes?

Bacteria and Archaea.

Why are prokaryotes the most abundant organisms on Earth?

They can adapt to extreme environments, including highly acidic, salty, cold, or hot conditions.

What are the three major cell shapes found in prokaryotes?

Spheres (cocci), rods (bacilli), and spirals.

What is the typical size range of prokaryotic cells?

0.5–5 µm, much smaller than eukaryotic cells (10–100 µm).

What is the function of the prokaryotic cell wall?

It maintains shape, protects the cell, and prevents it from bursting in a hypotonic environment.

What are eukaryotic cell walls made of?

Cellulose (plants) or chitin (fungi).

What is peptidoglycan, and which prokaryotes have it?

A network of sugar polymers cross-linked by polypeptides, found in bacterial cell walls.

Do archaea have peptidoglycan in their cell walls?

No, archaea have polysaccharides and proteins but lack peptidoglycan.

How do scientists classify bacteria by cell wall composition?

Using the Gram stain technique.

What is the difference between Gram-positive and Gram-negative bacteria?

Gram-positive bacteria have thick peptidoglycan layers, while Gram-negative bacteria have thinner peptidoglycan and an outer membrane containing lipopolysaccharides.

What is a capsule, and what is its function?

A sticky outer layer of polysaccharide or protein that helps prokaryotes adhere to surfaces and protect against the immune system.

What are endospores?

Metabolically inactive structures that allow bacteria to survive extreme conditions for centuries.

What are fimbriae?

Hairlike appendages that help prokaryotes stick to surfaces or other individuals in a colony.