CH. 3 Prokaryote Cell Structure & Function Flashcards
What are the basic chemical composition of a bacterial cell and the proportions of chemicals? What are the features all prokaryotic cells possess? Which are variable characteristics?
Water - 70%
Proteins - 16%
RNA - 6.7%
Cell Envelope - 5% (peptidoglycan, membrane phospholipids, etc.)
DNA - 1%
What is the role of hopanoids in prokaryotic cell membranes?
Stabilizes membranes by controlling fluidity and permeability and strengthen the bacterial cell envelope
What is group translocation and ABC transporters? What form of transport is this?
ABC transporters transport amino acid and carbohydrate transport; expends ATPs to transport
Group translocation: modification of substrate during transport; the source substrate is continually moving down its gradient
They are both ACTIVE transport
What are active transport, passive transport, and osmosis?
Active Transport: requires energy to move molecules against their gradient concentration
Passive Transport/Diffusion: simple/facilitated; molecules move based on their concentration (high to low)
Osmosis: diffusion of water; water molecules move towards area of high SOLUTE concentration (bacteria maintain a hypertonic cell interior; water diffuses in)
How do the membrane lipids of Archaea differ from typical prokaryotes?
Archaea
- hydrocarbon chains are terpenoids (from isoprene)
- ether link (C-O-C) hydrocarbons to glycerol
Typical Prokaryotes
- phospholipid head group
- saturation/unsaturation of fatty acids
- cyclization of fatty acids
How does the cell envelope structure of Mycobacteria species differ from that of Gram‐negative and Gram‐positive bacteria?
Mycobacteria contains mycolic acids in addition to the peptidoglycan layers
Describe the structure of a prokaryotic cell wall (what is its chemical composition?)
Made of peptidoglycan (murein) -> a polymer of disaccharides, glycan, cross-linked with peptide tetramers
Compare and contrast the differences/similarities in the cell envelopes of Gram‐negative and Gram‐positive bacteria.
Gram-Positive:
- thick cell wall (multiple peptidoglycan layers and teichoic acids)
- s-layer (made of glycoprotein and is in-between the peptidoglycan and glycosyl)
Gram-Negative:
- thin cell wall (1-2 peptidoglycan layers) and is bridged to the outer membrane via murein lipoprotein
- lipoproteins connected with peptidoglycan and outer membrane
- lipopolysaccharide layer (LPS)
What is the nucleoid? How is DNA organized in here? How would you describe a bacterial chromosome?
A single, circular, double-stranded DNA; organized in loops (bacterial chromosome)
DNA is organized by supercoiling (DNA gyrase)
What does polysome or polyribosome formation refer to? What are the components required for this process?
It refers to transcription and translation
Some components required are DNA, RNA, proteins, and ribosomes
What is a replisome?
A protein complex that is responsible for carrying out DNA replication at the ori site
How is a bacterial chromosome copied? Describe the basic steps of the DNA replication process, starting with where replication is initiated.
DNA replication begins at the ori site where 2 replication forks and replisomes forms
Bidirectional replication continues where the replisomes synthe4size the DNA at each fork
Z-ring forms by FtsZ -> septation and cell division
What is septation?
The partition (a septum) that splits the envelope into two daughter cells
What element comprises the bacterial cytoskeleton? How does these function in bacteria? How is the cytoskeleton involved in cell division & septation?
FtsZ Protein - determines the cell diameter and forms a “z-ring” for cell division
MreB Protein - guides cell wall synthesis
CreS Protein (crescentin) - curves the inner side of crescent-shaped bacteria
To what does “polar aging” refer? How would you describe this? Of what significance is it?
Refers to two cell poles that differ in their origin and age which signifies that cells of different polar ages may differ in resistance to antibiotics
What are specialized structures of phototrophic bacteria? What are their functions?
Thylakoids: inner cell membrane foldings packed with photosynthetic components
Carboxysomes: protein-covered bodies containing Rubisco (also chemoautotrophs)
Gas Vacuoles: to maintain proper depth
What are intracellular inclusions? List and describe the different types found in bacteria. Which are energy storage types?
Metachromatic granules: inorganic phosphate
Polysaccharide granules: glycogen, starch
Sulfur granules: oxidation of H2S (insoluble granules)
Lipid inclusions: PHB
What are the functions of pili/fimbriae?
Involved with bacterial conjugation and attachment to the surface and motility
Ex. biofilm formation
What is a sex pilus?
Where the male bacterium connects with the female bacterium for conjugation (transfer DNA)
What is twitching motility?
A type of bacterial movement where the pilus extends and retracts
What are nanotubules and what is their function?
They are cell envelope extensions that connect the cytoplasm between different cells
Function is to share proteins, mRNA between members of same/different species
How does bacterial motion occur via a flagellum (or flagella)?
Rotary motion (clockwise rotations = “tumbles”)
What is chemotaxis?
The ability of organisms to move toward or away from specific chemicals
How does a slime layer differ from a capsule? What does a capsule provide?
Capsules are more organized and tightly associated compared to slime layer
Capsules provide bacterial adhesion to surfaces
What is endotoxin?
They are lipopolysaccharides (LPS) where they are released when bacteria die
