Prokaryotes and viruses Flashcards
What type of organisms are prokaryotes in
- Usually single-celled organisms
- Whose DNA is suspended freely in the cytoplasm
What does Prokaryote mean
Before the nucleus
Describe the structure of a generalised bacterial cell
- Capsule
- Murein cell wall
- Cell membrane
- Plasmids
- Ribosomes
Describe the function of a capsule
Protects bacteria from other cells, and helps bacteria adhere (stick together)
Describe the function of a murein cell wall
A physical barrier that protects against mechanical damage and osmotic lysis
Describe the function of a cell membrane
- Controls the entry and exit of chemicals
- Contains a phospholipid bilayer
Describe the function of a plasmid
Genes that aid bacterial survival in adverse conditions (e.g. resistance to antibiotics)
What size are ribosomes in prokaryotes
Smaller 70s
Contrast prokaryotes and eukaryotes
- 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
Compare and contrast the DNA in eukaryotes and prokaryotes
- 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
What evidence supports the theory that chloroplasts and mitochondria are evolved from prokaryotic cells
- Both have 70s ribosomes
- Both divide through binary fission
- Both contain circular single stranded DNA
Describe the process of binary fission
- 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
Describe the structure of human immunodeficiency virus (HIV)
- Lipid envelope
- Attachment protein
- Caspid
- Matrix
- Reverse transcriptase
- RNA
Describe the structure of human immunodeficiency virus (HIV)
- Lipid envelope
- Attachment protein
- Caspid
- Matrix
- Reverse transcriptase
- RNA
Describe the function of a lipid envelope
- Controls the entry and exit of substance
- Contains phospholipids
Describe the function of an attachment protein
- Enables the virus to attach to host cells, with a complimentary receptor
- HIV attaches to T-helper cells, a type of white blood cell
Describe the function of Capsid
- A protein coat that encloses nucleic acid
Describe the function of a matrix
- Structural proteins linking the viral envelope with the virus core
- Similar to cytoplasm
Describe the function of reverse transcriptase
An enzyme that converts RNA to DNA, so it can be inserted into the host cell
(important in HIV replication)
What genetic material is in HIV
RNA
