Cell Structure and Function Flashcards
Diplococci
-remain in pairs
-divide in one plane
Streptococci
-forms chains
-divide in one plane
Tetrads
-forms groups of 4
-divide in two plans
Sarcinae
–forms cubes
-divide at right angles in 3 planes
Staphylococci or Micrococci
-forms irregular “bunches”
-divides irregularly in many planes
Factors affecting evolution of cell shape and size
-surface area and volume
-motility
-attachment to surface
Factors affecting evolution of cell shape and size: Surface Area
-Sphere has the lowest surface to volume ratio
-adding appendages gives increased surface for nutrient
Surface Area to Volume Ratio Can Affect:
- Rate of nutrient uptake and thus rate of growth
-high S/V = faster rate of uptake
-Growing faster allows you to outcompete your neighbors - Number of cells produced per unit of nutrients available
-smaller and less DNA per cell (Prokaryotic vs eukaryotic) means more generations per unit of nutrient, faster growth, more generation, faster evolution
Factors affecting evolution of cell shape and size: Motility
-Rods have a greater capability for movement in specific direction
-Spirilla and spirochetes seem to have the greatest capability of moving through highly viscous media
Factors affecting evolution of cell shape and size: Attachment to Surface
-Stalked bacteria tend to adhere to surface via their stalks
-Stalks provide a high surface to volume ratio for nutrient exchange
What are the structure s of the Cytoplasmic membrane?
-phospholipid bilayer
-amphipathic
-hydrophilic and hydrophilic
Structure of Cytoplasmic membrane
- Membrane Fluidity
- ~50% protein + 50% Lipid
- Integral and transmembrane proteins
- Peripheral membrane proteins
- Lipoproteins
- Asymmetric (In vs Out, patches, domains)
Structure of Cytoplasmic membrane: Integral and transmembrane proteins
-some are integral - significantly embedded in at least ne face of the membrane
-some are transmembrane - embedded and exposed on both faces
Structure of Cytoplasmic membrane: Peripheral membrane proteins
-some are peripheral-associated with one face of the membrane, but not buried in the hydrophobic region
Structure of Cytoplasmic membrane:
Lipoproteins
-some proteins are covalently attached to lipids and remain membrane associated by this
Structure of Cytoplasmic membrane: Asymmetric (In vs Out, patches, domains)
-the inside and the outside of the membrane are different
Variation in Cytoplasmic Membranes
-Glycerol diether
-diglycerol tetraethers
-crenarchaeal
-lipid bilayer membrane = phytanyl
-lipid monolayer membrane = bi-phytanyl or crenarchaeal
Functions of Cytoplasmic membranes
- Permeability barrier = prevents leakage and functions as a gateway for transport of nutrients into, and waste out of, the cell
- Protein anchor: site of many proteins that participate in transport, bio energetics, and chemotaxis.
- Energy Conservation: site of generation and use of the protein motor force.
Archaeal Cytoplasmic Membrane
-Bilayer (diether with 20-carbon phytanyl) glycerol diether
OR
-Monolayer (tetraether with 40-carbon bi-phytanyl) diglycerol tetraethers
Transport across cytoplasmic membranes
-Passive
-Active
Passive Transport
-movement with/DOWN the concentration gradient.
-movement from high to low concentration
-Requires no energy
Active Transport
-movement against/UP the concentration gradient
-movement from low to high concentration
-Requires Energy
Passive Mechanisms
-Simple diffusion
-Facilitated diffusion
Simple diffusion
-small non-polar and uncharges polar molecules
Facilitated Diffusion
-requires channel proteins or carrier proteins
-selective for specific chemicals
-can be regulated by cell, turned on and off
Types of Active Transport
-simple
-group translocation
-ABC transport
Simple Transport
-driven by the energy in the proton motive force
-depends on ion concentration gradients
Group Translocation
-Chemical modification of the transported substance driven by phosphenopyruvate
-example is the phosphotransferase system (PTS)
-Energy comes from phosphenolpyruvate (PEP)
-The transported molecule gets phosphorylated. This energy is actually conserved, as the glucose is now activated for further metabolism
ABC Transport
-Periplasmic binding proteins are involved and energy comes from ATP
-three proteins
-a periplasmic binding protein outside the cell brings the substance to the channel
-the channel
-a cytoplasmic protein hydrolyzes ATP to provide energy
Protein Secretion is a transport system
-SEC SYSTEM - at least seven protein components
-cells must place proteins on the surface of the membrane, in the cell wall, and into the medium
-getting a large protein across the membrane is more complex than transporting a small ion, sugar, or amino acid
-essentially a transport system
-Energy from ATP and PMF
Structure of bacteria cell envelops
-The cell envelope refers to all layers surrounding the cell, including any membrane and wall material
-The cell wall refers only to the peptidoglycan layer
-Gram negative = thin peptidoglycan layer and outer membrane
-Gram Positive = thick peptidoglycan layer and NO outer membrane
Cell Wall = Peptidoglycan = Murein
-Glycan tetrapeptide
-N-Acetylglucosamine (G) and N-Acetylmuramic acid (M)
-Peptide (amino acids)
Structure of bacterial cell wall
-crosslinking
Insertion of New Cell Wall Material
-peptidoglycan synthesis
-Transglycosylase
-Transpeptidase
-Autolysins
-Bactoprenol
-PBPs: Penicillin-Binding Proteins catalyze BOTH the glycosyl transferase and transpeptidase activities
How to insert a new cell wall?
-transpeptidation involves cleavage of the terminal D-ala from one peptide side chain, with formation of a new peptide bond with the di-amino acid in another peptide side chain
-cleavage of the terminal D-ala provides the energy for formation of new bond in the cross-link
Gram-Positive Cell Wall
-contain teichoic acid (attach to PG) and lipoteichoic acid (in membrane)
-These produce a negatively charged cell surface
-and many buffer the PMF in the absence of an outer membrane
Degradation of bacterial cell walls
-lysozyme cleaves the B(1,4) glycosidic bond between NAG and NAM
-Antibiotics like penicillin prevent cross-linking of the peptide side chains
-Mycoplasma (bacteria) and Thermoplasma (archaea) are prokaryotes that can live without a cell wall (always live on animal)
Structure of Gram-negative cell envelope (Big picture)
- Thin peptidoglycan wall
- Outer membrane a lipid bilayer like the cytoplasmic membrane, but:
Structure of Gram-negative cell envelope (Small picture)
A. Lipid A makes up much of the outer leaflet of the membrane, Lipopolysaccharide is attached to lipid
B. Porins (NOT IN GRAM POSITIVE BACTERIAL)
C. Lipoproteins (linked to PG and to lipid in outer membrane, anchors OM to PG)
D. Periplasm site of PG and site of PMF
Structure of Gram-Negative outer membrane
-Lipopolysaccharide (LPS), outer leaflet of the membrane
-Lipid A (endotoxin) -> shock
-Core Polysaccharide
-O-specific polysaccharide (variable)
Archaeal Cell Wall
-Pseudomurein is in “some” archaeal walls
-N-acetyl-talosaminuronic acid
-B(1,3) glycosidic bonds
-no PG
-N-Acetylglucosamine
Other Cell Surface Structure and Appendages
-S-layers (paracrystalline surface)
-Glycocalyx/capsule/slime layer/extracellular polysaccharide
-Phili
-Fimbriae
-Flagella
S-Layer
-paracrystalline surface layer
-protein or glycoprotein
-common in archaea
-can resist osmotic pressure like a peptidoglycan wall
-also found in some bacteria, along with peptidoglycan, as the outermost layer
Capsule/Slime layer/extracellular
-attachment of cell surface
-biofilm formation
-protection from immune cells: phagocytosis
Fimbriae and Phili
-Protein structures
-Fimbriae are abundant, shorter, and involved in adherence
-Phili are longer, generally fewer per cell RETRACTABLE
How do Phili function?
-adherence
-motility
-exchange of DNA by conjugation
Twitching motility
-Type IV (4) Phili
attach and retract
important in pathogenesis in some species
Flagella and Swimming Motility
-Organization
polar=one or both pole of cell
-lophotrichous = one pole of cell
-Amphitrichous=both pole
Peritrichous=all around the cell
Flagella and Motility
-swimming motility
Flagella (flagellum)
Flagella (flagellum)
-basal body, hook, filament
-synthesis
bottom up, hollow filament grows at tip
many genes/gene products involved
-MANY copies of flagellin protein in the rigid, helical filament
Chemotaxis
-Swimming motility (flagellar) is a random walk
-in the presence of attractants or repellents, it becomes a “biased random walk”
-other taxes (phototaxis, aerotaxis, osmotaxis)
Methods to study motility and taxes
-capillary assay
-phototaxis to specific light wavelength
Intracellular Structure/inclusions
-carbon storage polymers
poly-B-hydroxybutyric acid (PHB)
Polyhydroyalkanotes
-(PHAs)
polyphosphate
elemental sulfur(sulfur oxidizing bacteria)
Gas Vesicles (aquatic phototrophs)
Buoyancy
