Prokaryotes and viruses

Question 1

What type of organisms are prokaryotes in

Answer 1

• Usually single-celled organisms
• Whose DNA is suspended freely in the cytoplasm

Question 2

What does Prokaryote mean

Answer 2

Before the nucleus

Question 3

Describe the structure of a generalised bacterial cell

Answer 3

• Capsule
• Murein cell wall
• Cell membrane
• Plasmids
• Ribosomes

Question 4

Describe the function of a capsule

Answer 4

Protects bacteria from other cells, and helps bacteria adhere (stick together)

Question 5

Describe the function of a murein cell wall

Answer 5

A physical barrier that protects against mechanical damage and osmotic lysis

Question 6

Describe the function of a cell membrane

Answer 6

• Controls the entry and exit of chemicals
• Contains a phospholipid bilayer

Question 7

Describe the function of a plasmid

Answer 7

Genes that aid bacterial survival in adverse conditions (e.g. resistance to antibiotics)

Question 8

What size are ribosomes in prokaryotes

Answer 8

Smaller 70s

Question 9

Contrast prokaryotes and eukaryotes

Answer 9

• Prokaryotes are smaller than eukaryotes
• Prokaryotes have no membrane organelles, eukaryotes do
• Prokaryotes have smaller 70S ribosomes, whereas eukaryotes have large (80S ribosomes)
• In prokaryotes DNA is not associated with proteins, in eukaryotes DNA is associated with histone proteins
• In eukaryotes, DNA is found in the nucleus whereas in prokaryotes DNA is found in the cytoplasm
• Prokaryotes have a murein cell wall, whereas eukaryotic cells have cellulose cell walls (plants only, fungal cells have chitin cell walls, animals do not have cell walls)
• Prokaryotes may have plasmids (circular DNA), whereas eukaryotes have linear DNA
• Prokaryotes may have an outer mucilaginous layer called a capsule, eukaryotes do not

Question 10

Compare and contrast the DNA in eukaryotes and prokaryotes

Answer 10

• Both have identical nucleotide structure
• Both nucleotides are joined by phosphodiester bonds
• Prokaryotic DNA is circular, whereas eukaryotic DNA is linear
• Prokaryotic DNA is shorter
• Eukaryotic DNA is wrapped around proteins called histones, whereas prokaryotic DNA is not associated with proteins

Question 11

What evidence supports the theory that chloroplasts and mitochondria are evolved from prokaryotic cells

Answer 11

• Both have 70s ribosomes
• Both divide through binary fission
• Both contain circular single stranded DNA

Question 12

Describe the process of binary fission

Answer 12

• The circular DNA replicates, both copies attach to the cell membrane
• The plasmids replicate
• The cell membrane begins to grow between the 2 DNA molecules, and pinches inwards
• A new cell wall forms between the 2 molecules, dividing the original cell into 2 daughter cells

Question 13

Describe the structure of human immunodeficiency virus (HIV)

Answer 13

• Lipid envelope
• Attachment protein
• Caspid
• Matrix
• Reverse transcriptase
• RNA

Question 14

Describe the structure of human immunodeficiency virus (HIV)

Answer 14

• Lipid envelope
• Attachment protein
• Caspid
• Matrix
• Reverse transcriptase
• RNA

Question 15

Describe the function of a lipid envelope

Answer 15

• Controls the entry and exit of substance
• Contains phospholipids

Question 16

Describe the function of an attachment protein

Answer 16

• Enables the virus to attach to host cells, with a complimentary receptor
• HIV attaches to T-helper cells, a type of white blood cell

Question 17

Describe the function of Capsid

Answer 17

• A protein coat that encloses nucleic acid

Question 18

Describe the function of a matrix

Answer 18

• Structural proteins linking the viral envelope with the virus core
• Similar to cytoplasm

Question 19

Describe the function of reverse transcriptase

Answer 19

An enzyme that converts RNA to DNA, so it can be inserted into the host cell
(important in HIV replication)

Question 20

What genetic material is in HIV

Answer 20

RNA