Chapter 3: Cell Structure And Function Flashcards
In the early 20th century, the cell was envisioned as a…
Bag of soup full of floating ribosomes and enzymes
3 shared bacterial traits:
- Thick, complex outer envelope
- Compact genome
- Tightly coordinated cell functions
________ consists of a gel-like network
Cytoplasm
______ encloses the cytoplasm
The cell membrane
______ covers the cell membrane
Cell wall
What is the non-membrane bound area of the cytoplasm that contains the chromosome in the form of looped coils?
The nucleoid
External helical filament whose rotary motor propels the cell
Flagellum
What must first take place in order to isolate and study cell parts?
Cell fractionation
4 types of cell fractionation
- Mild detergent
- Sonication
- Enzymes
- Mechanical disruption
A key tool of subcellular fractionation is the….
Ultracentrifuge
What does centrifugation do?
Separates particles by size
Chemical components shared by all cells:
- Water
- Essential ions
- Small organic molecules
- Macromolecules
The structure that defines the existence of a cell is the…
Cell membrane
Membranes have approximately equal parts of…
Phospholipids and proteins
A phospholipid consists of…
Glycerol with ester links to two fatty acids and a phosphoryl head group
The two layers of phospholipids in the bilayer are called…
Leaflets
Membrane protein function:
- Structural support
- Detection of environmental signals
- Secretion of virulence factors and communication signals
- Ion transport and energy storage
Small molecules such as ___ and ___ easily permeate the membrane by _______.
O2; CO2; diffusion
Osmosis
The diffusion of water across a membrane
Protein transporters are needed to…
Transport polar and charged molecules across the cell membrane
Molecules move along their concentration gradient in
Passive transport
Molecules move against their concentration gradient in
Active transport
In eukaryotic membranes, the reinforcing agents are ______, such as ______.
Sterols; cholesterol
Hopanes/hopanoids
Membrane-reinforcing agents in bacteria
Ether links between glycerol and fatty acids are in…
Archaea
In Archaea, hydrocarbon chains are branched…
Terpenoids
The most common structural support is the
Cell wall
The bacterial cell wall, or ______, consists of…
Sacculus; a single interlinked molecule
Most bacterial cell walls are made of…
Peptidoglycan (or murein)
Peptidoglycan consists of:
- Long polymers of two disaccharides
2. These are bound to peptides of 4 to 6 amino acids
Why are the enzymes responsible for peptidoglycan biosynthesis excellent targets for antibiotics?
Peptidoglycan is unique to bacteria
How does penicillin work?
It inhibits the transpeptidase that cross-links the peptides
How does vancomycin work?
It prevents cross-bridge formation by binding to the terminal D-Ala-D-Ala dipeptide
How does the widespread use of antibiotics effect microbes?
It selects for evolution of resistant strains
The _____-______ bacteria have multiple layers of peptidoglycan
Gram-positive
Composition of the capsule:
- Polysaccharides
2. Glycoproteins
Function of the capsule:
Protects cell from phagocytosis
Is the capsule found in gram-p or gram-n cells?
Both
An additional protective layer commonly found in free-living bacteria and archaea
S-layer
S-layer composition:
Crystalline layer of thick subunits consisting of protein or glycoprotein
How much peptidoglycan is in a gram-negative cell?
Thin layer of 1 or 2 sheets
What are lipopolysaccharides?
Lipids in the outer facing leaflet of gram-n cells that are toxic when released from the cell membrane
Where are the lipoproteins in gram-n bacteria?
On the inner leaflet
What does the outer membrane do in gram-n bacteria?
It confers defensive abilities and toxigenic properties on many pathogens
What is FtsZ?
A protein that gives bacteria the z-ring
MreB
Forms a coil inside rod-shaped cells
CreS
“Crescentin” - forms a polymer along the inner side of a crescent-shaped bactera
In bact. that appear superficially symmetrical, polar differences may appear at…
Cell division
Extensively folded intracellular membranes used for photosynthesis
Thylakoids
Bacterial structures that help control buoyancy
Gas vesicles
Carboxysomes
Polyhedral bodies packed with the enzyme Rubisco for CO2 fixation
What do bacteria use sulfur for?
Oxidation
What are glycogen, phb, and pha used for and where are they stored?
Energy; in the storage granules
Orient the swimming of magnetotactic bacteria
Magnetosomes
Straight filaments of pilin protein
Pili or fimbriae
Membrane-embedded extensions of the cytoplasm
Stalks
What do stalks do?
Secrete adhesion factors called holdfasts
Intercellular connections that pass material from one cell to the next
Nanotubes
The type of cell that has flagella randomly distributed
Peritrichous
Have a single flagella
Monotrichous
Have flagella at the ends
Lophotrichous
Each flagellum is a spiral filament of protein monomers called..
Flagellin
The flagellum is rotated by a motor driven by…
The proton motive force
The movement of a bacteria in response to chemical gradients
Chemotaxis
Repellents cause ____ rotation
CW
Attractants cause _____ rotation
CCW
Alternating runs and tumbles cause a
Random walk
