Topic 2: Prokaryotes Flashcards
What is a prokaryote?
They are single-celled organisms that are extremely small (less than 0.002nm)
They have no true nucleus,or membrane bound organelles
DNA is not enclosed in a nuclear envelope
Why are eukaryotes and prokaryotes different?
Eukaryotes are larger (up to 0.5nm), they have a distinct nucleus,nuclear envelope and chromosomes, they also contain membrane organelles
Prokaryotes are small (less than 0.002nm), they have no nucleus, dna not in a nuclear envelope, no membrane bound organelles
Name 8 features of prokaryotic cells
Single, circular DNA molecule
Cell membrane
Flagellum
Cell wall
Mesosome
Ribosomes (70s)
Capsule
Plasmid
What is the function of the single,circular DNA molecule in prokaryotes?
It contains the cells genetic information
It isnt associated with proteins (like eukaryotic DNA is)
What is the main function of the cell membrane in prokaryotes?
It controls the transport of substances in and out of the cell
What is the main function of the flagellum in prokaryotic cells?
Propels the cell from place to place
What is the main function of the cell wall in prokaryotic cells?
It protects the cell membrane
Provides rigidity, stops the cell rupturing due to osmotic pressure
What is the prokaryotic cell membrane made of?
Murein which is a glycoprotein
What is the main function of the mesosome in prokaryotic cells?
Only seen by an EM
Thought to play a role in metabolic processes e.g. respiration,ATP production, cell division
Commonly believed to be an artefact
What is the main function of Ribosomes (70s) in prokaryotic cells?
They are involved in protein synthesis
They are smaller than those found in eukaryotes
what is the function of the capsule in prokaryotic cells?
It is composed of polysaccharide
Protected the cell from the body’s immune defences (phagocytosis and antibodies) and desiccation (drying out)
What is the main function of the plasmid in prokaryotic cells?
It is circular pieces of DNA found in addition to the main DNA molecule
These replicate when the cell replicates
Contains genes for antibiotic resistance
Compare prokaryotic and eukaryotic cells
-p have no nucleus but E do
-DNA in P is circular strands not linear chromosomes like in E
- E have membrane bound organelles but P dont
-P have smaller ribosomes
-P have capsules and flagella (E dont)
-cell walls in P made of murein or peptidoglycan but E it is cellulose or chitin
Compare DNA in prokaryotic and eukaryotic cells
Eukaryotes:
- stored in nucleus
- DNA forms linear chromosomes
Prokaryotes:
- no nucleus
-DNA in circular strands not chromosomes
-additional DNA in small circles (plasmids)
How do prokaryotes replicate?
Binary fission
