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Microbiology 210 > Lecture Exam 2 SG > Flashcards

Lecture Exam 2 SG Flashcards

1
Q

What is the term for the sum of all chemical reactions in an organism?

Chapter 5

A

Metabolism

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2
Q

For both catabolism and anabolism, describe the following: (a) is it used to build or break down
molecules, (b) does it use a hydrolysis or dehydration reaction, and (c) are the reactions exergonic or endergonic?

A

Catabolism: Break down, Hydrolysis, Exergonic
Anabolism: Build, Dehydration, Endergonic

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3
Q

Describe an endergonic vs. an exergonic reaction. Give an example of each.

A

Endergonic: Cold, Absorbs energy, Photosynthesis
Exergonic: Hot, Releases energy, Explosion

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4
Q

When a chemical bond forms, does this release or store energy?

A

This stores the energy which can be released by breaking the bond

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5
Q

Does an exergonic or an endergonic reaction require a high amount of potential energy for the reaction to occur? Why?

A

An exergonic reaction requires more PE than an endergonic reaction because energy must be released as opposed to endergonic reactions which absorb energy

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6
Q

What are the three types of metabolic pathway patterns? Give an example for each.

A

Linear: Starch hydrolysis
Branched: Glycolysis
Circular: Kreb’s cycle

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7
Q

Why are some organisms able to carry out certain metabolic processes and while other organisms
cannot? For example, yeast perform alcoholic fermentation and humans cannot. Why is the human body physiologically unable to perform alcoholic fermentation?

A

Metabolic pathways are determined by enzymes and enzymes are encoded by genes. If humans do not have the gene required to make enzymes that are needed for processes such as alcoholic fermentation we cannot perform these processes

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8
Q

Why is it necessary for all organisms to possess some form of metabolism? Which class of
macromolecule provides the most cellular energy?

A

It is important for all organims to posses some form of metabolism because metabolism allows us to store and release energy using organic molecules. If this was not the case organims would need to constantly eat to survive. Carbohydrates provide the most cellular energy as they can be oxidized.

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9
Q

Which part of ATP’s structure allows it to store potential energy? What happens to ATP when its
stored energy is released?

A

The phosphate component is where the energy is held. When energy is released from ATP it becomes ADP and Pi due to the loss of energy showing that a phosphate that had energy has been shed.

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10
Q

Define the following terms: collision theory, activation energy, and reaction rate.

A

Collision Theory: Atoms/ molecules must collide to be able to react
Activation Energy: Minimum amount of energy required to make a reaction occur
Reaction Rate: Number of Products over seconds

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11
Q

What are the ways that a reaction rate can be increased?

A

Increase heat, increase enzyme/substrate, increase pressure, aggitate

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12
Q

A(n) ______________ is a type of protein that accelerates the rate at which a chemical reaction takes place in an organism.

A

Enzyme

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13
Q

Enzymes are usually made of which type of macromolecule?

A

Polypeptides

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14
Q

Does a specific enzyme usually catalyze one specific reaction or many types of reactions?

A

An enzyme usually catalyzes a specific reaction

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15
Q

Lactose is the _________________ of the enzyme ___________________.

A

Substrate
Lactase

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16
Q

How do enzymes work?

A

The globular protein has an activation site where a substrate can attach and this will induce a reaction that lowers the energy required to make a reaction occur. once the chemical reaction has occured, the product will be released and the enzyme can catalyze the reaction once more

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17
Q

Name the region of the enzyme that binds to the substrate.

A

Active Site

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18
Q

Define the following parts of an enzyme: apoenzyme, cofactors, holoenzyme, active site, and allosteric site.

A

Apoenzyme: Protein component of enzyme
Cofactor: Non protein component of enzyme
Holoenzyme: Apoenzyme + Cofactor (fully functional)
Active site: Location where substrate binds
Allosteric site: Molecular on/off switch for enzyme

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19
Q

Name and describe two types of cofactors. What is the role of an enzyme cofactor?

A

Cofactors: The non protein portion that helps a reaction occur. Often play a role in stabilizing the enzyme or catalyzing the enzymatic action
Inorganic: Iron in heme, Mg, Cu
Organic (coenzymes): NAD+, NADP+, FAD, CoA

NAD+, NADP+, FAD are all electron carriers

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20
Q

Describe the mechanism of enzymatic action (4 steps)

A
  1. Substrate makes contact with binding site
  2. Enzyme and substrate form complex (induced fit)
  3. Substrate is transformed and released
  4. Enzyme remains unchanged and available for further reactions
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21
Q

List the factors that influence enzymatic activity. Briefly describe how each factor affects enzymatic
activity.

A

Temperature - Increased molecular motion as temp increases
Pressure - Less space means more molecules bumping increasing reaction rate
pH - If pH is not ideal, the denatured enzyme can stop functioning
Concentration - More substrate or enzyme can increase reaction rate unless one factor is limited by the other
Inhibitors - Some inhibitors can either compete with substrates or turn off enzymes resulting in decreased reaction rates

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22
Q

What is the difference between competitive and noncompetitive inhibition? Which type of inhibitor
can be reversed by increasing the substrate concentration? Which type of inhibitor has a structure that is similar to the normal substrate?

A

Competitive: Competes with substrate to block activation site
Noncompetitive: Binds to allosteric site resulting in enzymatic shape change which makes enzyme inactive
- Competitive
- Competitive

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23
Q

How does sulfanilamide inhibit the synthesis of folic acid? Why is this important?

A

Sulfadrug is a competitive inhibitor that is analogous with PABA. Because bacteria such as S. aureus or E. coli rely on making folate it will inhibit bacteria by competing for active sites

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24
Q

Describe feedback (end-product) inhibition and how it works.

A
  • A pathway in which the end product inhibits enzyme activity
  • Excess product binds to allosteric site on the first enzyme in the pathway deforming activation site and shutting pathway down
  • As [end product] decreases activesites reform and pathway resumes
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25
For exoenzymes and endoenzymes, discuss the following: (a) where are these enzymes used (inside or outside the cell), (b) are the substrates usually large or small, and (c) what are those types of enzymes used for? (7)
Endoenzymes: - Found inside the cell - Typically smaller - **Used for metabolic enzymes and essential processes** Exoenzymes: - Found outside the cell - Typically larger - Often used to breakdown contents that is too big to go into the cell - **Used only when the need arises**
26
Compare constitutive and induced (adaptive) enzymes.
Constitutive: - Always present - Essential Induced (adaptive): - Not always present/produced - Only made when a substrate is present - Goal is to save energy
27
What are the RNA-based enzymes called in the nucleus that are responsible for splicing RNA?
Ribozymes: Catalytic RNA -> enzymatic function SnRNPs -> splicosome for RNA processing (small nuclear ribonuclear proteins)
28
For redox reactions, what type of reactions are used for the loss of electrons and what type of reactions are used for the gain of electrons?
Oxidation: Loss/removal of electrons Reduction: Gain of electrons Redox: Oxidation reaction paired with reduction reaction **Always occur together**
29
What are the reactants and products of cellular respiration? (Hint: Use the overall equation.)
Equation: C6H12O6 + 6O2 -> 6CO2 + 6H2O + E Reactants: Glucose and Oxygen Products: CO2, H2O, Energy
30
What is the source of electrons in cellular respiration? What reactant became oxidized and which reactant became reduced?
- The source of electrons is Glucose - Glucose is oxidized - Oxygen is reduced
31
Name the electron carriers involved in cellular respiration. Are the oxidized or the reduced, electron carriers energy-rich?
32
Define the term phosphorylation. Name and describe the three mechanisms of phosphorylation involved in ATP synthesis.
Phosphorylation is the process of adding a phosphate group to a molecule Ex. ADP + Pi ->ATP Substrate level: When a molecule donates a phosphate group to an ADP making ATP Oxidative Phosphorylation: A series of redox reactions release energy to form ATP in the ETC Photophosphorylation: Conversion of light energy to ATP and NADPH
33
Compare aerobic respiration, anaerobic respiration, and fermentation.
Note: Aerobic Respiration includes Glycolysis, Kreb's, and ETC
34
What are the four steps involved in aerobic respiration
Glycolysis: 1 Glucose + 2NAD+ + 2ADP -> 2 Pyruvate + 2NADH + 2ATP (Substrate level phosphorylation) Intermediate Step: 1 Pyruvate + CoA + NAD+ -> Acetyl-CoA + CO2 + NADH Krebs Cycle: Acetyl-CoA + 3NAD+ + FAD + ADP -> CoA + 3NADH + FADH2 + ATP+ 2CO2 (Substrate level phosphorylation) ETC: NADH( + H+) + FADH2 + 6 ADP + O2 -> NAD+ + FAD+ + 6 ATP + H2O (Oxidative phosphorylation)
35
What is the function of oxygen in aerobic cellular respiration? What happens when oxygen is not present?
- Oxygen is the final electron acceptor at the end of aerobic respiration which produces water - If no oxygen is present the hydrogens cannot be moved along the ETC which stops aerobic respiration
36
Glycolysis and the Kreb’s Cycle produce very little ATP compared to the Electron Transport Chain. Name the most important product of Glycolysis and the Kreb’s Cycle. Why is this product important?
NADH and FADH2 are electron carriers that pass electrons to the complexes in the ETC and power ATP synthesis
37
Describe what happens in the Electron Transport Chain and how the proton motive force is used to generate the bulk of the ATP during aerobic cellular respiration. (3)
1. When an electron is transported to plasma membrane it reaches the complexes of the ETC it travels through Complex I-IV. It is able to travel through th complexes due to increasing electronegativity 2. The electron's energy is used to pump protons across the plasma membrane into the periplasmic space which creates an electrochemical gradient 3. The proton motive force is what allows the energy of H+ traveling through ATP synthase to be used to make ATP from ADP. The protons will then be added to oxygen which makes water
38
What drives ATP synthase to produce ATP?
Proton Motive Force as protons move down their concentration gradient
39
Where do the steps of cellular respiration take place?
40
The reactions of fermentation function to produce ________________ molecules for use in glycolysis.
NAD+
41
True or False? Anaerobic respiration is also called fermentation. Explain your answer.
False - Fermentation is a pathway that produces minimal energy through incomplete oxidation of glucose - Anaerobic respiration is when a molecule other than oxygen is used as the FEA and fully breaks down a glucose generating more energy than in fermentation but slightly less than aerobic respiration
42
What are the two types of fermentation? What are the final electron acceptors in each type? What types of organisms do each type?
Lactic Acid Fermentation: 2 Pyruvate + 2NADH -> 2 Lactic Acid + 2NAD+ - Pyruvate is FEA - Animal cells and some bacteria Alcoholic Fermentation: 2 Pyruvate + 2NADH -> 2 Ethanol + CO2 + 2NAD+ - Acetaldehyde is FEA - Carried out by yeast and mold
43
During intensive exercise, what is responsible for “muscle burn”?
Build up of protons from ATP production
44
What does it mean to say that an organism is homolactic or heterolactic?
Homolactic: Lactic acid only is produced Heterolactic: Lactic acid and other acids are produced
45
Define the following terms: sterilization, disinfection, antisepsis, degerming, sanitization, bactericide, and bacteriostatic.
Sterilization:Killing/destroying all microbial life on an object Disinfection: Killing or inhibiting microbial populations on non-living surfaces Antisepsis: The process of killing or inhibiting microbial populations on living tissue Degerming: Removal of germs from a limited area Sanitization: Lowering microbial count to safe levels Bactericide: Kills bacteria Bacteriostatic: Inhibits bacterial growth
46
Washing your hands would be an example of which type(s) of microbial control? Why?
Degerminating - You are lowering the microbial population to a safe level
47
During sterilization, what pattern does the rate of microbial death show (ie. constant, logarithmic, sporatic, etc.)? What is the kill time of a chemical dependent on?
- Logarithmic decline - The time to kill is dependent on the number of cells
48
How does moist heat sterilization work? What is an autoclave, what is it used for, and what are the minimum operating conditions? If you tightly wrapped forceps in foil (and the steam could not contact the forceps), would the forceps be sterilized?
- Quickly denatures faster than dry heat - Sterilizes heat stable items at 121C and 15 PSI - No the steam must be in contact with the forceps to sterilize
49
If you set out to reduce spoilage organisms and potential pathogens in milk, juice, and wine, which physical control method would be the most practical? Why? Does this method sterilize the liquid?
- Pasteurization - Slowly heats liquid to greatly reduce the amount of bacteria (-cidal) making it safer for consumption while not compromising taste
50
Which is a more efficient sterilization technique, dry heat or moist heat? Explain your answer.
Moist heat denatures quicker. Dry heat could give endospores the opportunity for vegatative cells to become spores
51
For each of the following physical control methods, list the way that the method controls microbial growth: low temperature, high pressure, desiccation, and osmotic pressure. For each method, indicate whether it is bacteriostatic or bactericidal.
Low temp: - Bacteriostatic - Flash freeze High pressure: - Disrupts cell structure and function - Bacteriocidal Desiccation: - No moisture, but molds resist - Bacteriostatic Osmotic pressure: - Plasmolysis - Bacteriostatic
52
Which group of organisms are more resistant to osmotic pressure?
Molds and Yeast
53
How do surface tension depressants work?
They loosen contamination from surfaces
54
What is the best method to sterilize liquid solutions that may be damaged by heat (for example, medications)?
Filtration
55
How does filtration work?
Passing a substance through a physical barrier that ensures only the desired substance passes through
56
How does high energy/ ionizing radiation work to control microbial growth? What is high energy/ionizing reagent used for?
High Energy (ionizing): - Turns water into free radicals - Arrests fruit and veggie maturation - No exposure to consumers
57
How does UV radiation control microbial growth? Is it bacteriostatic or bactericidal? Can it be used to disinfect solutions inside a sealed glass bottle? Why or why not?
Low Energy (non-ionizing): - UV light - Causes T-T dimers in DNA - Disinfects surfaces only - Bacteriocidal - It cannot disinfect solutions
58
What are the factors influencing the effectiveness of control agents?(7)
- Bacterial Population - Age of cells - Species - Concentration (5% alcohol vs 50%) - Temperature - pH - Time of exposure
59
Do most chemical agents achieve sterility? Explain your answer.
No, it is hard to kill all spores, vegatative cells, fungi, viruses and more due to their protective mechanisms
60
List organisms from the most resistant to the least resistant to antimicrobial chemicals. For each one, explain why they would be resistant (or not resistant) to antimicrobial chemicals.
61
What is selective toxicity and why is it important?
- The property of an antimicrobial agent being toxic to a microorganism and less/non-toxic to the host - THis is important because you can target bacteria withou harming the host in the way many drugs target bacterial ribosomes since they are 70s and human ribosomes are 80s
62
What is the difference between a narrow spectrum drug and a broad spectrum drug?
A narrow spectrum drug is specialized at targetting a specific mechanism and avoids unwanted side effects more (gram + inhibition) - A broad spectrum drug is effective against many microbes but can also harm the natural flora (gram + and - inhibition)
63
What is a superinfection and how can it occur?
An infection following a previous infection by a microorganism that has become resistant Ex. methicillin resistant S. aureus (MRSA) vancomycin intermediate S. areus (VISA) Vancomycin resistant cocci (VRE)
64
Why is it difficult target a pathogenic virus, protozoan, fungus, or helminth without damaging the host’s cells?
- Virus do not have DNA and instead hijack host cells. They are not identified as living and re hard to target - Protozoan, Fungus, and Helminths are eukaryotes and it is difficult to find a mechanism to attack that will not harm human cells
65
Why are antibiotics with a very broad spectrum of activity not as useful as one might first think?
- They also harm the natural flora which can lead to an opportunistic infection of fungus if bacteria are wiped out. It can also lead to superinfections
66
What is the difference between antimicrobial agents that are bacteriostatic versus those that are bactericidal?
Bacteriostatic: These pause bacterial growth and give the body time to adapt and mount a response. Good for gram negative as the rapid death of G- could release excess lipid A which can induce shock and even death Bacteriocidal: Kills bacteria
67
If you have an infection with a Gram-negative organism, should you choose a drug that is bactericidal or bacteriostatic? Why?
Bacteriostatic. If all the bacteria are killed rapidly the release of toxic lipid A from cell walls may be too rapid for your body to adapt to leading to shock and death
68
Name and discuss the five modes of antimicrobial inhibition (Figure 20.2). For each of the 5 modes:
1. Inhibition of Cell Wall synthesis - Selectively toxic target cell wall - cidal 2. Inhibition of protein synthesis - Attacks 70s not 80s - static 3. Inhibition of nucleic acid replication and transcription - inhibits RNA/DNA synthesis (gyrase not in humans) - Static at low [] cidal at high[] 4. Injury to plasma membrane - Usually topical as human plasma membrane is too similar - cidal 5. Inhibition of metabolite synthesis - Humans do not make their own folic acid - static
69
Which class of antimicrobial drugs contain a β-lactam ring? How do these drugs inhibit microbial growth? Which group of organisms do those drugs target?
- Penicillins - B-lactam rings prevent crosslinking of PG interfering with cell wall construction - Gram positive bacteria
70
Which enzyme do bacteria produce that makes them to resistant to penicillin?
Penicillinase (B-lactamases)
71
What advantage do semi-synthetic penicillins have over natural penicillins?
- Their side chains make them resistant to penicillinases - Side chains may also extend spectrum
72
What do the following antimicrobial drugs have in common, in terms of their structure: penicillin, amoxicillin, cephalosporin, and ampicillin?
B-Lactam antibiotics that disrupt cell wall
73
What are two polypeptide antibiotics that inhibit cell wall synthesis? What is each one used for?
Bacitracin: - Good against some G+ bacteria - Topical only Vancomycin: - Good against G+ - Good against antibiotic resistant infections such as MRSA - VRE and VISA resist vancomycin
74
What disease is isoniazid and ethambutol used to treat?
Tuberculosis - Isoniazid inhibit mycolic acid over a long treatment - Ethambutol inhibits mycolic acid incorperation and synergizes with isoniazid (usually only for multidrug resistant TB)
75
How do streptomycin, tetracycline, and chloramphenicol all inhibit microbial growth?
They all target different parts of bacterial ribosomes Tetracycline: blocks tRAN-mRNA complex Streptomycin: denatures 30s subunit Chloramphenicol: binds 50S and inhibits formation
76
What drug is used topically, is combined with bacitracin and neomycin in nonprescription ointments, and works by injury to the cell membrane?
Neosporin
77
What is the term for the effect of two drugs together is greater than the effect of either alone?
Synergy
78
List desirable characteristics of antibiotics. (8)
- Selective toxicity (reduce side effects) - Means of administration (delivery) - Efficacy (How well it works) - Length of time and dosage - Cost - Availability - Synergy - Tissue solubility
79
What is the Kirby-Bauer method used for and how does it work? What would a plate look like if the organism is sensitive to the antibiotic? What would it look like if the organism is resistant to the antibiotic?
- Used to test drug sensitivity by dropping disks of drugs on a bacterial culture and comparing inhibition zones - If the bacteria is sensitive there will be a large zone of inhibition - The drug will not stop any of the bacterial growth
80
What are the advantages of using the Kirby-Bauer method?
- Can test multiple drug at the same time -Very cheap - Easy to interpret
81
If there is clearing around an antibiotic disk, does that mean that the bacteria is definitely dead in that area? Why or why not? How could you test if the bacteria in that area are dead?
- No, Some antibiotics are bacteriostatic - Swab the clear zone and see if it grows on a plate without the antibiotic. If it does then the antibiotic was bacteriostatic
82
What type of test would you use to determine the minimal inhibitory concentration (MIC) for an antibiotic? How does the test work?
Broth Dilution Test - The growth is monitored with respect to varrying drug concentrations - This allows the MIC to be determined E Test - A gradient diffusion method - Uses plastic strip (epsilometer) with increasing [] gradient of drug - Estimates MIC
83
What are the four mechanisms of resistance to antibiotics? Describe each one.
1. Blocking entry - Outer membranes, endospores, capsules, ect. 2. Inactivating Enzymes - Periplasmic space, penicillinases, B-lactamases 3. Alteration of target molecules - Mutation of target molecules 4. Efflux of antibiotic - Drug is pumped out of bacteria
84
What are the 3 ways that bacteria can acquire the genes needed for antibiotic resistance? Describe each method for how it works.
Conjugation (Sex pilus): - Sex pilus only possessed by gram negative bacteria Transformation (Naked DNA): - DNA obtained when bacteria takes in a dead bacteria's DNA (looting) Transduction (Phage transfer): - Defective virus takes up DNA from one bacteria and takes it into another
85
The duplication of a cell's DNA is called _________________________

Microbiology 210 (13 decks)

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