Chapter 3 Flashcards
What are three fundamental traits that most bacteria share?
- Thick, complex outer envelope
- Compact genome
- Tightly coordinated cell functions
What is the cytoplasm?
consists of a gel-like network
What is the cell membrane?
encloses the cytoplasm
What is the cell wall?
encloses the cell membrane
What is the nucleoid?
non-membrane-bound area of the cytoplasm that contains the chromosome in the form of looped coils
What is the flagellum?
external helical filament whose rotary motor propels the cell
What four chemical components do all cells share?
- Water
- Essential ions
- Small organic molecules
- Macromolecules
What is cell fractionation?
how we separate cellular components such as membranes, ribosomes, and flagella.
What is a key tool for cell fractionation?
ultracentrifuge
What is genetic analysis?
an approach that is complementary to cell fractionation
What structure defines the existence of a cell?
The cell membrane
What is a phospholipid?
consists of glycerol with ester links to two fatty acids and a phosphoryl head group
What are the functions of the cell proteins?
- Structural support
- Detection of environmental signals
- Secretion of virulence factors and communication signals
- Ion transport and energy storage
What is diffusion?
Small uncharged molecules easily permeate the membrane
What is osmosis?
When water permeates the membrane
Why are membrane-permeant weak acids and weak bases important?
They can diffuse across the membrane and increase or decrease, respectively, the H+ concentration within the cell.
What type of transport moves along its concentration gradient?
Passive Transport
What type of transport moves against its concentration gradient and requires energy?
Active Transport
In prokaryotes, what structure protects the cell membrane?
Cell wall
What consists of a single interlinked molecule?
Sacculus or bacterial cell wall
What are most bacterial cell walls made up of?
Peptidoglycan
What is the difference between Gram-positive, gram-negative and mycobacteria?
- Gram-Positive: thick cell wall
- Gram-Negative: thin cell wall
- Mycobacteria: complex, multilayered cell wall
What is the S-layer?
- an additional layer often found in free-living bacteria and archaea
- May contribute to cell shape and help protect the cell from osmotic stress
What is the inward facing protein in a Gram-negative bacteria?
lipoprotein
What is the outward facing protein in a Gram-negative bacteria?
lipopolysaccharides
porins
What type of shape does a FtsZ form?
forms a “Z-ring” in spherical cells
What type of shape does a Mreb form?
forms a coil inside rod-shaped cells
What type of shape does a CreS “crescentin form?
forms a polymer along the inner side of crescent-shaped bacteria
What is different about the nucleus in eukaryotes and prokaryotes?
- Eukaryotes have a well-defined nucleus delimited by a nuclear membrane.
- Prokaryotes have a nucleoid region that extends throughout the cytoplasm
Transcription
- RNA polymerase transcribes DNA into a single strand of RNA (mRNA)
- mRNA immediately binds to a ribosome for translation into a polypeptide.
- This is aided by transfer RNA (tRNA), which brings the amino acids to the ribosome
- Lightly coupled with Translation
What requires highly coordinated growth and expansion of all the cell’s parts?
Cell division or cell fission
What is unique of prokaryotes during cell division?
Prokaryotes synthesize RNA and proteins continually while the cell’s DNA undergoes replication
What is Bacterial DNA replication coordinated with?
the cell wall expansion and ultimately the separation of the two daughter cells.
What happens to a circular chromosome at the start of cell division in prokaryotes?
It begins to replicate at its origin, or ori site.
What happens in cell division after the circular chromosome replicates at its origin?
Two replications forks are generated, which proceed outward in both directions
What happens at each replication fork during cell division?
- At each fork, DNA is synthesized by DNA polymerase with the help of accessory proteins (protein complex is called the replisome)
- As the termination site is replicated, the two forks separate from the DNA
What triggers the growth of the dividing partition, or septum.?
Replication of the termination site
What does the septum ultimately do?
The septum grows inward, at last constricting and sealing off the two daughter cells
What has a key role in determining the shape and arrangement of cocci?
The spatial orientation of septation
What is the spatial orientation of parallel planes called?
Streptococci
What is the spatial orientation of random planes called?
Staphylococci
What is the spatial orientation of perpendicular planes called?
Tetrads or Sarcinae
What is polar aging?
two cell poles differ in their origin and age
What are the two possible kinds of daughter cells that can be generated by a bacterial cell?
stationary and mobile
How has bacterial cell differentiation been studied?
via Genetic analysis
What is a landmark protein that correctly marks the site of a new cell pole and the polar placement of flagella?
TipN
True or False. Cell development involves many such proteins working together.
True
What determines that the poles of each daughter cell differ chemically from each other?
The actual process of cell division itself
What are thylakoids?
extensively folded intracellular membranes
What are Carboxysomes?
polyhedral bodies packed with the enzyme Rubisco for CO2 fixation
What are Gas Vesicles?
increase buoyancy
What are storage granules?
- Glycogen- for energy
2. Sulfur globules- for oxidation
What are pili or fimbriae?
- They are straight filaments of pilin protein.
2. Used in attachment
What are sex pili?
- Pili that are used in conjugation
What are stalks?
- They are membrane-embedded extensions of the cytoplasm.
2. The tips secrete adhesion factors called holdfasts
What are nanotubes?
They are intercellular connections that pass materialfrom one cellto the next.
How do prokaryotes move around?
rotary flagella
What are the different types of flagella?
- Peritrichous cells have flagella randomly distributed around the cell
- Lophotrichous cells have flagella at the end(s).
- Monotrichous cells have a single flagellum.
What is flagellin?
Each flagellum is a spiral filament of protein monomers
Rotary Flagella
The filament is rotated by a motor driven by the proton motive force.
The motor possesses an axle and rotary parts, all composed of specific proteins.
MotB - Forms part of the proton channel
FliG - Forms part of device that generates torque
Note: flagella rotate either clockwise (CW) or counterclockwise (CCW) relative to the cell
What is chemotaxis?
the movement of a bacterium in response to chemical gradients.
What are attractants?
- CCW Rotation
- Flagella bundle together
- Push cell forward
- “Run”
What are Repellants?
- CW Rotation
- Flagellar bundle falls apart.
- “Tumble”
3a. Bacterium briefly stops, then changes direction
