Ch. 1 Flashcards
What are the differences between eukaryotes and prokaryotes?
- Eukaryotes have a membrane-bound nucleus and organelles
- Eukaryotes have linear DNA vs. prokaryotes have circular DNA
- Eukaryotes have multiple chromosomes while prokaryotes only have one
- Eukaryotes don’t have plasmids
- Eukaryotes have 80S ribosomes vs. prokaryotes have 70S ribosomes
What are the differences between bacteria and archaea?
- Membrane lipids of bacteria are fatty acids, esterlinked to glycerol vs. archaea are methyl-branched, isoprenoid alcohols, etherlinked to glycerol
- Archaea don’t have peptidoglycan
- Archaea have histones that resemble eukaryotic histones
- Archaeal RNA polymerase has 8-10 subunits, whereas bacterial RNA polymerase has 4 subunits, and are not sensitive to rifampin
- Some protein components of the archaeal protein synthesis machinery differ from the bacterial one
What are the similarities between archaea and eukarya?
- Have similar histones
- Similar genes/metabolic pathways
Give an overview of the structure of prokaryotes.
- Don’t have membrane-bound organelles
- Plasma membrane
- Gas vacuole
- Inclusions
- Nucleoid (like nucleus minus the membrane)
- Periplasmic space
- Cell wall
- Capsules and slime layers
- Fimbriae/pili
- Flagella
- Endospore
What is the importance of appendages on bacteria?
Motility (flagella) and adhesion (pili)
What are the two main classes of appendages?
- Flagella
- Pili
What is function of flagella?
Swimming in liquid and swarming (swimming on moist solid surfaces)
Describe the structure of flagella.
- Basal body
- Embedded in CM and surface
- 3 rings
- Motor complex rotates - Hook
- Connects basal body and filament
- Hook protein - Filament
- Made of single protein (flagellin)
- Tube shaped
- Growing tip
What is the function of fimbriae/pili?
- Help stick to surfaces
- Not usually involved in motility
- important for colonization in natural habitats
- Have adhesins at the tip –> can recognize and bind specific receptors
What is the medical significance of pili?
Attachment to host cells plays a key role in causing infection
- Ex. V. cholerae: mutants without Tcp pili don’t cause disease, therefore, pili of different types are specialized for attachment to specific receptors and can account for specificity of bacterial attachment to host and tissues
What is the glycocalyx?
All extracellular material that is external to the cell wall
- Made up of polysaccharides and/or proteins
- Surround bacteria in natural habitats
What are the 3 components of the glycocalyx?
- S layers
- Capsules (tightly integrated with cell)
- Slime layers (glycocalyx loosely associated with cell; can diffuse into medium)
What is the S layer?
Protein or glycoprotein layer found on the surface of prokaryotes
- Except mycoplasmas
- Can be lost in laboratory strains
What is the composition of the S layer?
- Repeating subunits of S layer proteins with attached carbohydrate moiety
- Form lattice structures
What are the functions of the glycocalyx?
- Adhesion and colonization - biofilm formation
- Protection from phagocytosis
- Prevention of dessication
What are the two major types of bacterial cell walls?
Gram-positive and gram-negative
What is the function of the cell wall?
To protect the cell from bursting from internal turgor pressure
Why does turgor pressure exist?
The turgor pressure exists because the bacteria generally live in environments that are more dilute than the cytoplasm
What is the main component of cell walls?
Peptidoglycan
What are the differences between gram-positive and gram-negative cell walls?
Gram-positive:
- Thick
- No OM, thicker CW
- Contains peptidoglycan, teichoic acid, lipoteichoic acid
Gram-negative:
- Structurally and chemically complex
- Outer membrane composed of LPS, phospholipid, protein, underlying peptidoglycan layer
- Periplasm between outer and inner membrane, where peptidoglycan lies
Draw the basic unit of peptidoglycan in E. coli.
Draw the structure of LPS.
