3.2.1 Cell structure

Question 1

Compare the structure of a eukaryotic cell and a virus.

Answer 1

• Both have DNA and/or RNA.

• Both can contain enzymes (reverse transcriptase in HIV).

• Eukaryotic cells have receptors but viruses have attachment proteins.

• Eukaryotic cells have a cell surface membrane but viruses may have a lipid envelope.

• Viruses have a protein capsid but eukaryotic cells do not.

• Eukaryotic cells have ribosomes while viruses do not.

• Eukaryotic cells have a nucleus while viruses do not.

•

Question 2

Compare the DNA of a prokaryotic cell and a eukaryotic cell.

Answer 2

• Eukaryotic DNA is membrane bound in the nucleus while prokaryotic DNA is free floating.

• Prokaryotic DNA is circular while eukaryotic DNA is linear.

• Prokaryotic DNA is single stranded while eukaryotic DNA is double stranded.

• Eukaryotic DNA is longer while prokaryotic DNA is shorter.

• Eukaryotic DNA is associated with histones while prokaryotic DNA is not.

• Eukaryotic DNA has introns while prokaryotic DNA does not.

Question 3

What happens during G2 in interphase?

Answer 3

The organelles grow and divide and the energy stores (ATP is synthesised) within the cell. The cell grows.

Question 4

Why aren’t viruses alive?

Answer 4

• Not made of cells - acellular

• No metabolism

• No excretion or self replication