prokaryotic structure

Question 1

distinguishing features of prokaryotic cells

Answer 1

• cytoplasm lacks membrane-bound organelles
• so genetic material not enclosed in a nucleus

Question 2

organelles always present in a prokaryotic cell

Answer 2

• cell-surface membrane
• cell wall containing murein (glycoprotein)
• cytoplasm
• small ribosomes
• circular DNA - free in cytoplasm. not associated with proteins

Question 3

organelles sometimes present in a prokaryotic cell

Answer 3

• capsule
• plasmids (small rings of DNA)
• flagella

Question 4

compare and contrast the structure of eukaryotic and prokaryotic cells

Answer 4

• eukaryotic has membrane-bound organelles, prokaryotic doesnt
• eukaryotic has nucleus, prokaryotic doesn’t
• eukaryotic has DNA which long and linear, associated with histone proteins, prokaryotic has DNA which is short + circular, not associated with proteins
  eukaryotic has larger (80S) ribosomes, prokaryotic has smaller (70S) ribosomes
• eukaryotic has cell wall only in plants, algae and fungi containing cellulose or chitin, prokaryotic has cell wall in all cells containg murein
• prokaryotic sometimes have plasmids, flagella and capsule, eukaryotic dont ever have plasmids or capsules
• eukaryotic is larger than prokaryotic

Question 5

why are viruses acellular and non living

Answer 5

• acellular - not made of cells, no cell membrane/cytoplasm/organelles
• non-living - have no metabolism, cant independently move/respire/replicate/excrete

Question 6

describe the general structure of a virus particle

Answer 6

1. nucleic acids surrounded by a capsid (protein coat)
2. attatchment proteins allow attachment to specific host cells
3. no cytoplasm, ribosomes, cell wall, cell-surface membrane etc.
4. some also surrounded by a lipid envelope e.g. HIV