Structure of prokaryotic cells & of viruses

Question 1

What are the distinguishing features of prokaryotic cells?

Answer 1

• no membrane-bound organelles
• genetic material not enclosed in nucleus

Question 2

What are the structures of prokaryotic cells that are always present?

Answer 2

• cell-surface membrane
• cell wall (made of murein)
• cytoplasm
• 70S ribosomes
• circular DNA

Question 3

What are the structures of prokaryotic cells that are present sometimes?

Answer 3

• capsule
• plasmids
• flagella

Question 4

What is the difference in DNA between prokaryotic & eukaryotic cells?

Answer 4

DNA is circular & not associated with proteins in prokaryotes but is linear and associated with histone proteins in eukaryotes

Question 5

What is the difference in cell walls between prokaryotic & eukaryotic cells?

Answer 5

cell wall made of cellulose in eukaryotes (plant cells) but is made of murein in prokaryotes

Question 6

What is the difference in ribosomes between prokaryotic & eukaryotic cells?

Answer 6

eukaryotes have 80S whilst prokaryotes have 70S ribosomes

Question 7

Why are viruses described as acellular & non-living?

Answer 7

acellular - not made of cells (no cell membrane, organelles etc.)
non-living - can’t move or replicate independently

Question 8

What is the general structure of a virus particle?

Answer 8

• nucleic acids surrounded by capsid
• attachment proteins allowing virus to attach to host cells
• no cytoplasm, ribosomes, cell-surface membrane
• some are surrounded by a lipid envelope