Prokaryotes And Viruses Flashcards
What does Woese’s tree of life show ?
Classification of living organisms based on appearance and behaviour
What 4 structures do all cells have in common ?
- cell membrane
- cytoplasm
- ribosomes
- cell wall
What is the function of the cell membrane ?
A barrier that separates the inside of the cell from the outside environment
What is the function of the cytoplasm ?
Aqueous mixture of macromolecules, ions and ribosomes
What is the function of ribosomes?
Protein synthesizing structures
What is the function of the cell wall ?
Provides structural strength and prevents osmotic lysis
What are the 3 domains of life?
- bacteria
- archaea
- eukaryotes
What is archaea ?
Anaerobes living in low oxygen
What are the structures found in prokaryotes ?
- no membrane enclosed organelles
- cell membrane
- ribosomes
- plasmids
- nucleoid
- cell wall
- some have flagella
What is an organelle ?
A part of a cell that does a specific job
What is a plasmid ?
A small, circular, double stranded DNA molecule
What is morphology ?
It enables micro - organisms to cope with their environment and is a tool for gaining a competitive advantage
List some other prokaryotic cell structures ?
- pilus/superciliary structures
- flagella
- fimbriae
- capsule
What is the cell envelope ?
It is made up of 2 to 3 layers :
- interior cell membrane
- cell wall
- capsule (in some bacteria)
What is pilus ?
Hairlike projections on the outside of the cell which attach bacteria to substrates and act as sex organs
They originate in the cell membrane and protrude out the cell wall
What is flagella ?
Long hairlike structures that provide means of locomotion (swimming)
They originate in the cell membrane and protrude through the cell wall
What is fimbriae ?
Protein tubes from the cell membrane which stick bacteria to surfaces
What is a capsule ?
A polysaccharide which keeps bacteria from drying out and protects it from phagocytosis by other microorganisms
Describe the structure and function of the cell membrane
It is made up of a phospholipid bilayer and proteins
It is selectively permeable so nutrients can move in and waste can move out
Describe the structure and function of the cell wall
It is made up of peptidoglycan
It gives the cell its shape and protects it from the environment
It helps to anchor appendages
It prevents osmotic lysis
What is tensile strength ?
Resistance to lengthwise stress
What is peptidoglycan ?
It is an alternating copolymer of glucosamine and n-acetylmuramic acid crosslinked with short peptide chains which gives a 3D mesh and high tensile strength
How can you distinguish between gram positive and gram negative bacteria ?
Using peptidoglycan staining -
• in gram positive bacteria the cell wall has a thick layer of peptidoglycan so the bacteria stain purple
• in gram negative bacteria the cell wall has a thin layer of peptidoglycan and an outer cell membrane with lipopolysaccharides so the bacteria stain pink
What is a virus ?
An infectious nucleic acid surrounded by a protective protein coating
