Prokaryotic Cell Structure Flashcards
Q: The shape of a bacteria may determine its …
A: Nutrient uptake, motility, reproduction & interaction with hosts or surfaces.
Q: The size of a bacteria may determine its …
A: Nutrient uptake, growth rate, survival/defense & metabolic efficiency
Q: What are the advantages of larger bacteria?
A: Greater capacity for nutrient storage, resistance to phagocytosis, contain more genetic material, may compartmentalize functions resulting in more efficient metabolism, better resilience in harsh environments.
Q: What are the disadvantages of larger bacteria?
A: Slower nutrient uptake, slower growth, slower reproduction, higher energy requirements, difficulty in diffusion-based processes.
Q: What are the advantages of smaller bacteria?
A: Efficient nutrient uptake, rapid growth and reproduction, lower energy requirements, quick adaptation to novel environments, greater mobility, harder to detect by “predators”
Q: What are the disadvantages of smaller bacteria
A: Limited nutrient storage, lacking structural complexity, vulnerability to environmental stress, lower antibiotic resistance, easy target in phagocytosis
Q: What are the characteristics of a membrane in the gel phase?
A: Low chain disorder, crystal packing, thick bilayer
Q: What are the characteristics of a membrane in the fluid phase?
A: High chain disorder, irregular packing, thin bilayer.
Q: What three types of glycerolipids commonly make up the bacterial membrane?
A: PG (glycerophosphatidylglycerol), PE (glycerophosphatidylethanolamine) , CL (cardiolipins)
Q: Which three types of lipids can form bacterial membranes, and which of these is most common?
A: Saccharolipids, Glycerophospholipids & Glycerolipids. Of these, glycerolipids are the most common.
Q: What is the function of hopanoids (bacterial steroids)?
A: Regulate membrane rigidity & mark microdomain boundaries
Q: Why do bacteria benefit from lipid diversity?
A: Lipid diversity aids in membrane fluidity & stability, regulating permeability, biofilm formation & resistance to toxins
Q: What is the structure of peptidoglycan in Gram (-) bacteria?
A: Single layer with a hexagonal structure & direct cross- links. Fewer connections than in Gram (+).
Q: What is the structure of peptidoglycan in Gram (+) bacteria?
A: Multiple layers with dense peptide cross-linking.
Q: Why do bacteria need cell walls?
A: Bacteria have a high internal solute concentration that creates osmotic pressure, which would cause the bacteria to burst in the absence of a cell wall.
Q: What is the Gram (-) outer membrane composed of?
A: The gram (-) bacterial membrane is an asymmetric bilayer composed of an outer and inner leaflet. The outer leaflet is composed of lipopolysaccharides (LPS). The inner leaflet is composed of phospholipids (PE/PG/CL).
Q: What is the main difference between the inner and outer layer of the Gram (-) bacterial membranes?
A: The presence of lipopolysaccharides in the outer leaflet.
Q: What are the components of a lipopolysaccharide?
A: Lipid A, core polysaccharides, O-specific polysaccharides (O-antigens)
Q: What is Lipid A?
A: A saccharolipid anchored in the outer membrane
Q: What is a core polysaccharide?
A: A polysaccharide with 10-20 sugar subunits and sometimes a phosphate side group. Connects Lipid-A to O-antigen (O-specific polysaccharide)
Q: What is an O-antigen (O-specific polysaccharide)
A: Chain of repeating sugars which influence membrane permeability & immune system recognition.
Q: Outer membrane proteins are formed by …
A: β-sheets
Q: Inner membrane proteins are formed by …
A: α-helixes
Q: What are the four main types of outer membrane proteins (OMPs)?
A: Outer membrane protein F (OmpF), unspecific porins, substrate specific porins, TonB dependent transporters
Q: What is the function of Outer membrane protein F (OmpF)?
A: OmpF acts as a molecular sieve, allowing smaller molecules to pass through the outer membrane while blocking larger ones.
Q: What is the function of unspecific porins?
A: Unspecific porins allow for passive diffusions without binding any specific substrate
Q: What is the function of substrate specific porins?
A: Substrate specific porins facilitate the passage of specific molecules through the outer membrane by binding to these
Q: What is the function of TonB dependent transporters?
A: TonB dependent transporters are “mechano-activated” transporters that rely on the TonB system to actively transport complex molecules like iron or vitamin B12, by using energy from the inner membrane.
Q: Does active transport occur in the outer membrane layer?
A: No, never.
Q: What is the ratio of proteins to lipopolysaccharides in the outer membrane layer?
A: ~ 1 : 1
Q: What is the periplasm?
A: The aqueous space between the inner and outer membrane in Gram (-) bacteria
Q: What are S-layers and where are they located?
A: S-layers are crystalline layers that form a protective lattice around some bacterial and archaeal cells. They also act as a molecular sieve and provide support for the cell. In Gram (+) bacteria S-layers are found outside the thick peptidoglycan layer. In Gram (-) bacteria S-layers are found outside the outer membrane layer.
Q: What are capsule slime layers and where are they located?
A: Capsule slime layers are layers composed of sugars and sometimes proteins. They surround some bacterial cells and prevent dehydration and are important for biofilm formation.
Q: What subunits are bacterial ribosomes divided into?
A: Bacterial ribosomes are 70S ribosomes, divided into a 50S larger subunit and a 30S smaller subunit.
Q: What are the two types of DNA in bacteria?
A: DNA in the bacterial chromosome & plasmid DNA.
Q: What are the functions and traits of plasmid DNA?
A: Plasmid DNA is DNA in small, circular form that is replicated independently from the rest of the genome. Plasmid DNA typically confers a selective advantage such as antibiotic resistance and can easily be transferred between bacteria.
Q: What are inclusions in bacterial cells?
A: Any non-native materials clustered up inside the cell such as PHAs or PHB which serve as carbon- and energy storage or gas vesicles which increase buoyancy in certain bacteria.
Q: What is the function of flagella in bacteria?
A: Flagella enable movement for bacteria in aqueous environments
Q: How do flagella enable a bacteria to change direction?
A: Through flagellar rotation which happens through an alteration in conformation of the C-ring
Q: What is the function of pimbriae (sometimes called pili) in bacteria
A: Pimbraes primary function is attaching the bacterial cell to other surfaces. They have specific adhesion proteins in their tips which aid in this.
Q: What is the function of conjugation pili?
A: Transfering genetic information, mostly plasmid DNA, between bacterial cells.
