🩶 3.2.1.2 Structure Of Prokaryotic Cells And Of Viruses

Question 1

Compare eukaryotic cells and prokaryotic cells.

Answer 1

• Eukaryotic cells are bigger than prokaryotic cells
• Eukaryotic cells have 80s ribosomes where as prokaryotic cells have 70s
• Eukaryotic cells have membrane bound organelles whereas prokaryotic cells don’t
• Eukaryotic cells never have capsule/flagella/plasmids but prokaryotic cells sometimes have capsule/flagella/plasmids

Question 2

Describe the endosymbiont theory ?

Answer 2

Mitochondria and chloroplast were once prokaryotic/bacterial cells and formed a mutualistic relationship with eukaryotes. This caused them to have a double membrane and also explains the presence of 70s ribosomes and circular DNA in these organelles

Question 3

What are the features of prokaryotic cells ?

Answer 3

• one or more plasmids (not in all prokaryotes)
• cell membrane
• cell wall (made of murein)
• capsule (not in all prokaryotes)
• circular DNA
• 70s ribosomes
• flagellum (not in all prokaryotes)

Question 4

What is the one virus we need to know about?

Answer 4

HIV (human immunodeficient virus)

Question 5

What is HIV?

Answer 5

A spread of bodily fluids (e.g sex, sharing needles)

Question 6

Describe a virus ?

Answer 6

Acellular- they contain no cells and are just a collection of proteins
Non living - this means the don’t carry out any metabolic reactions e.g respiration/photosynthesis

Question 7

What are the components of HIV ?

Answer 7

• nucleic acid (RNA)
• attachment proteins
• reverse transcriptase
• phospholipid envelope (derived from a membrane)
• capsid (protects the nucleic acid)

Question 8

Describe what happens during a HIV infection.

Answer 8

1- The attachment proteins of the HIV bind to the receptor proteins of the helper T cell because they are complementary. This allows the HIV’s nucleic acid to be injected into the host cell.
2- The RNA is converted into DNA via the enzyme reverse transcriptase.This is then integrated into the hosts DNA.
3- The viral DNA is transcribed into viral proteins
4- The viral DNA causes the host to assemble the viral protein, into viruses
5- The viruses burst out of the T helper cell - destroying it and using part of the cell membrane as a phospholipid envelope
6- The viruses infect other T helper cells and make their numbers gradually decrease - making them more susceptible to other diseases.