MICROBIO 2 Flashcards
(90 cards)
1
Q
What is a virus?
A
Genetic element that replicates only in a living (host) cell
Viruses are considered not living and do not belong on the tree of life.
2
Q
Define obligate intracellular parasite.
A
Needs host for energy, metabolic intermediates, and protein synthesis.
3
Q
What is a virion?
A
Extracellular virus particle that facilitates transmission between host cells.
4
Q
What are the two types of viral infections?
A
- Virulent (lytic) infection
- Lysogenic infection
5
Q
What happens during a virulent (lytic) infection?
A
Virus replicates and destroys host cell.
6
Q
What is a lysogenic infection?
A
Host genome altered by integration of viral genome.
7
Q
How are viruses classified?
A
By host: * Bacterial (bacteriophage)
* Archaeal
* Animal
* Plant
* Protozoan
* Others
8
Q
What are naked viruses?
A
Viruses with no additional layers.
9
Q
What are enveloped viruses?
A
Viruses with an outer phospholipid bilayer (from host) + viral proteins.
10
Q
What is a capsid?
A
Protein shell surrounding virus genome.
11
Q
What is the function of virion surface proteins?
A
Important for host cell attachment and may include enzymes for infection/replication.
12
Q
What does the titer measure?
A
Number of infectious virions per volume.
13
Q
What is a plaque assay?
A
Method to count clear zones of cell lysis where viral infection occurs.
14
Q
What is the major difference in nucleic acid entry between prokaryotic and eukaryotic viruses?
A
Nucleic acid entry in prokaryotes vs. virion entry in eukaryotes.
15
Q
List the five steps of viral replication.
A
- Attachment (adsorption) to host cell
- Penetration (entry) of viral nucleic acid
- Synthesis of viral nucleic acid and proteins
- Assembly of capsids and genome packaging
- Release of new virions from host cell
16
Q
What is lysogenic conversion?
A
Acquisition of new traits by a host cell harboring a temperate virus.
17
Q
What are viroids?
A
Infectious RNA molecules that lack a protein component.
18
Q
What is the size range of most viruses?
A
0.02–0.3 μm.
19
Q
True or False: Enveloped viruses are easier to release from host cells.
A
True.
20
Q
What are prions?
A
Infectious proteins whose extracellular form contains only protein, no nucleic acid.
21
Q
What is a wild-type strain?
A
Isolated from nature; can also refer to a single gene.
22
Q
What is a mutant?
A
Cell or virus derived from wild type that carries a nucleotide sequence change.
23
Q
Fill in the blank: Mutations can lead to a change in organism properties, some beneficial, some detrimental, most _______.
A
neutral.
24
Q
What is the role of horizontal gene transfer in bacterial genetics?
A
Generates larger genetic changes than mutation.
25
What is the eclipse phase in the one-step growth curve?
Genome replication and protein translation.
26
What is the definition of plating efficiency?
Number of plaque-forming units (PFUs) is lower than direct electron microscopy counts.
27
What is hisC related to?
Histidine biosynthesis
## Footnote
Mutations designated as hisC1, hisC2, etc.
28
How are observable properties (phenotype) designated?
By a capital letter and two lowercase letters, then +/−
## Footnote
Example: His+ indicates histidine production.
29
What is the difference between selectable and nonselectable mutations?
Selectable mutations confer advantage; nonselectable mutations do not
## Footnote
Example of selectable: antibiotic resistance. Example of nonselectable: pigment loss.
30
What is an auxotroph?
A mutant that requires additional nutrient for growth compared with prototroph/wild-type strain
## Footnote
Auxotrophs are identified through methods like replica plating.
31
Define spontaneous mutations.
Mutations that occur without external intervention
## Footnote
Often result from DNA polymerase replication errors.
32
What are induced mutations?
Mutations caused environmentally or deliberately
## Footnote
Examples include those caused by radiation or DNA-modifying chemicals.
33
What are point mutations?
Mutations that change only one base pair
## Footnote
Can occur via single base-pair substitution.
34
What are the types of base-pair substitutions?
Missense, nonsense, and silent mutations
## Footnote
Silent mutations have no effect on polypeptide sequence.
35
What is a nonsense mutation?
A mutation that creates a stop codon
## Footnote
Typically results in a truncated protein with lost function.
36
Differentiate between transitions and transversions.
Transitions: purine to purine or pyrimidine to pyrimidine; Transversions: purine to pyrimidine or vice versa
## Footnote
Both are types of base-pair substitutions.
37
What are frameshift mutations?
Mutations caused by single base-pair deletions or insertions shifting the reading frame
## Footnote
Scrambles the entire polypeptide sequence downstream.
38
What is the role of RecA in homologous recombination?
Essential recombination protein found in all Bacteria, Archaea, and most Eukarya
## Footnote
It facilitates the exchange of DNA between homologous sequences.
39
What is a revertant?
A strain where the original phenotype is restored
## Footnote
Can be a same-site or second-site revertant.
40
Define mutation frequency.
Varies depending on mutation rate and selection pressure
## Footnote
Influenced by factors like environmental stresses.
41
What is horizontal gene transfer?
Movement of genes between non-descendant cells
## Footnote
Enhances metabolic diversity in bacteria.
42
What are the three mechanisms of bacterial genetic exchange?
Transformation, transduction, conjugation
## Footnote
These processes allow for the acquisition of new traits.
43
What is the significance of the fluctuation assay?
Demonstrates that mutations occur independently of selection conditions
## Footnote
Used by Luria and Delbrück to study resistance in E. coli.
44
What is the basic reproduction number (R₀)?
Defined as R₀ ≡ R_eff(1) = β/γ
## Footnote
Used to assess the potential for disease spread.
45
What is the role of ATP in metabolism?
Stores energy and fuels cellular processes
## Footnote
ATP formation requires a specific change in free energy.
46
What are phototrophs?
Microorganisms that obtain energy from light
## Footnote
Includes those that perform oxygenic and anoxygenic photosynthesis.
47
What is the difference between chemoorganotrophs and chemolithotrophs?
Chemoorganotrophs obtain energy from organics; chemolithotrophs obtain energy from inorganics
## Footnote
Both groups derive reducing power from their respective energy sources.
48
What is metabolic coupling?
Links catabolic and anabolic reactions for energy conservation
## Footnote
Catabolism drives ATP synthesis while anabolism consumes ATP.
49
What is the significance of redox reactions?
Involve transfer of electrons between electron donors and acceptors
## Footnote
Essential for energy conservation and metabolic processes.
50
What type of bond does Acetyl-CoA contain?
Thioester bond
## Footnote
Acetyl-CoA is involved in energy metabolism.
51
What type of bond does Acetyl phosphate contain?
Anhydride bond
## Footnote
Anhydride bonds are high-energy bonds important for energy transfer.
52
What type of bond does Glucose-6-phosphate contain?
Ester bond
## Footnote
Ester bonds are common in biochemical compounds.
53
What is NAD⁺?
A redox coenzyme that undergoes oxidation-reduction and is freely diffusible.
54
What is the structure of NAD⁺?
Composed of an ADP molecule, ribose, and nicotinamide.
55
What happens when 2H⁺ and 2e⁻ attach to NAD⁺?
It becomes NADH with an additional hydrogen on the ring.
56
What is activation energy?
Minimum energy required for a chemical reaction to begin.
57
What is a catalyst?
A substance that facilitates a reaction without being consumed.
58
What is the role of enzymes in reactions?
Lower the activation energy barrier, facilitating the reaction.
59
What are the two stages of glycolysis?
Preparatory stage and redox stage.
60
What is produced from one glucose molecule in glycolysis?
2 pyruvate, ATP, and NADH.
61
What is the Citric Acid Cycle (CAC)?
Pathway by which pyruvate is oxidised to CO₂.
62
What are the products formed per oxidised pyruvate in the CAC?
* 2 CO₂
* 3 NADH
* 1 FADH₂
* 1 ATP
63
What is substrate-level phosphorylation?
Directly synthesising ATP from ADP and a phosphate group.
64
What is oxidative phosphorylation?
Production of ATP using energy from electron transport.
65
What does the glyoxylate cycle allow?
Net synthesis of four-carbon compounds from acetyl-CoA.
66
What is the main purpose of fermentation?
To conserve energy and maintain redox balance.
67
What are the end products of yeast fermentation of glucose?
2 ethanol and 2 CO₂.
68
What do lactic acid bacteria produce from glucose?
2 lactic acid.
69
What is the role of NADH and FADH₂ in respiration?
They must be reoxidised for redox balance.
70
What is the function of ATP synthase?
Uses energy from the proton motive force to synthesize ATP.
71
What is the composition of ATP synthase?
* F₁: catalytic complex in the cytoplasm
* F₀: membrane-integrated proton-translocating complex
72
How many ATP are produced for every full rotation of the F₀ c-ring?
3 ATP.
73
True or False: Oxidative phosphorylation conserves more energy than lactic acid fermentation.
True.
74
What is the H⁺ requirement for ATP synthesis in Escherichia coli?
Approximately 3.3 H⁺ are required per ATP
75
How does the number of c subunits affect H⁺ requirements?
The number of c subunits varies between organisms, affecting H⁺ requirement
76
What is the energy conservation comparison between oxidative phosphorylation and lactic acid fermentation?
Oxidative phosphorylation conserves more energy: 38 ATP in aerobic respiration vs 2 ATP in lactic acid fermentation
77
What is the role of ATP synthases in cellular respiration?
ATP synthases are reversible; ATP hydrolysis can reverse ATPase activity to pump protons out of the cytoplasm, generating pmf
78
What is the primary function of ATPases in strict fermenters?
ATPases generate pmf for motility and transport by hydrolysing ATP from substrate-level phosphorylation
79
What is the net reaction of lactic acid fermentation?
Glucose + 2 ADP + 2 Pi yields 2 lactate + 2 ATP
80
What is the net reaction of aerobic respiration?
Glucose + 6 O₂ yields 6 CO₂ + 12 H₂O + 34 ATP
81
What are the two types of respiration based on oxygen availability?
* Aerobic respiration (requires O₂) * Anaerobic respiration (uses alternative terminal electron acceptors)
82
What characterizes anaerobic respiration?
Anaerobic respiration uses alternative terminal electron acceptors and generates ATP by oxidative phosphorylation
83
How do fermentation and anaerobic respiration differ in electron acceptor requirements?
Fermentation does not require an external electron acceptor; anaerobic respiration does
84
How does Escherichia coli grow in different respiratory conditions?
Grows by aerobic respiration, fermentation, and anaerobic respiration with nitrate
85
What are the components of the basic organization in Escherichia coli respiration?
* Complexes * Quinones * Terminal reductases
86
What happens in Complex I during aerobic respiration in Escherichia coli?
When FMNH₂ reduces an iron–sulphur protein, 4 H⁺ are translocated
87
What is the energy conservation difference between Escherichia coli and Paracoccus denitrificans?
Escherichia coli conserves less energy, exchanging only 8 H⁺ per 2 electrons compared to Paracoccus denitrificans
88
What is the fermentation reaction equation for glucose?
C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂
89
How much CO₂ is produced from 35 liters of wort with 12% fermentable glucose?
1045 liters of CO₂
90
What is the height of CO₂ accumulation in an 8 m² room if 1045 liters of CO₂ is produced?
130 mm or 13 cm
