3.2.1.2 Structure of Prokaryotic Cells

Question 1

Define a prokaryotic cell

Answer 1

‘Before nucleus’ - does not contain a nucleus, or any membrane bound organelles

Question 2

Describe how a prokaryote is different to a eukaryote (6)

Answer 2

• DNA is circular, non-histone bound and contains no introns
• Contains no membrane bound organelles
• Has ‘no true’ nucleus, DNA is free in the cytoplasm
• Contains smaller 70S ribosomes
• Some have a capsule, one or more flagella and one or more plasmids
• Has a cell wall formed of the glycoprotein muerin

Question 3

True or false

‘Viruses are living’

Answer 3

False - they’re acellular

Question 4

Describe the structure of viruses (6)

Answer 4

• Small and require living cell to replicate
• Contains DNA/RNA
• It’s genome is surrounded by protein coat called a capsid
• It’s envelope contains attachment proteins enabling it to bind to host cells
• Has enzymes to replicate it’s genetic information inside the host cell’s DNA
• No organelles, can’t synthesise proteins or DNA

Question 5

Which polysaccharide forms fungal cell walls?

Answer 5

Chitin

Question 6

Describe the structure of a virus

Answer 6

• Acellular, non-living
• Small, requires living cell to replicate
• Contains single/double-stranded DNA/RNA
• Genome is surrounded by protein coat called capsid
• Envolope contains attachment proteisn to bind to host cell
• Has enzymes to replicate genetic information and replicate in host cells
• No organelles - can’t synthesise proteins or DNA
• Some viruses are called retroviruses e.g., HIV. These contain the enzyme reverse transcriptase allowing them to produce a copy of DNA from viral RNA