Structure of prokaryotic cells and viruses

Question 1

Prokaryotic cells

Answer 1

• smaller than eukaryotes
• no nucleus or nuclear envelope
• e.g bacteria

Question 2

Cell wall

Answer 2

• made up of murein
• physical barrier that excludes certain substances and protects against damage and osmotic lysis
• 10-80nm

Question 3

Cell-surface membrane

Answer 3

acts as a semi-permeable layer that controls the entry and exit of chemicals
* contains 70s ribosomes, smaller than ones in eukaryotes, that synthesise proteins

Question 4

Circular strand of DNA

Answer 4

possess the genetic information for the replication of bacterial cells

Question 5

plasmids

Answer 5

smaller circular pieces of DNA that reproduce themselves and give bacterium resistance to harmful chemicals
* possesses genes that may aid the survival of bacteria in adverse conditions, e.g. produces enzymes that break down antibiotics
* are used extensively as vectors in genetic engineering

Question 6

Capsule

Answer 6

protects bacterium from other cells, viruses and host attacks and helps groups of bacteria to stick together for further protection
* mucilaginous slime around the cell wall

Question 7

Flagellum

Answer 7

• used for locomotion (movement)
• there could be more than one

Question 8

Viruses

Answer 8

acellular, non-living particles
* smaller than bacteria
* contain nucleic acids such as DNA and RNA
* can only multiply inside living host cells
* invade and reproduce inside host cells and other organisms

Question 9

Capsid

Answer 9

encloses the nucleic acid of viruses within a protein coat

Question 10

Attachment proteins

Answer 10

allow the virus to identify and attach to a host cell