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Microbiology Test 3 |Questions with 100%
Correct Answers | Updated & Verified | 2024
What is microbial growth? - ✔✔increase in the number of cells What are the two general requirements for microbial growth? - ✔✔physical: temperature, pH, osmotic pressure chemical: types of nutrients, growth factors A bacterium has just encountered a new environment. What are its three basic choices with respect to growth in this new environment? - ✔✔Adapt- allows growth to continue Tolerate- survive without growth DIE What are a bacterium's cardinal temperatures? Do all bacteria have the same cardinal temperatures? - ✔✔the minimal, optimal, and maximal growth temperatures as a microbe, not all the microorganisms grow in the same temp range Define psychrophiles - ✔✔cold-loving microbes
- cannot grow above room temperature Define psychotrophs - ✔✔-cannot grow above 30 degrees but can grow at temperatures between 4C(fridge temp) and room temperature
- food spoilage microbes
define mesophiles - ✔✔moderate temperature loving microbes
- optimal growth 25-40 degrees celcius
- many pathogenic microbes are mesophiles (including strep throat) Define thermophiles - ✔✔Heat loving microbes
- optimal growth 50-70 degrees celcius
- cannot live below 40 degrees Celsius define hyperthermophiles - ✔✔optimal growth of temperatures above 80 degrees Celsius What category do most human pathogens fall into? - ✔✔mesophiles Define neutrophiles, acidophiles, and alkaliphiles. What category do most human pathogens fall into? - ✔✔acidophiles: can survive and grow under acidic conditions ph < 5. Alkaliphiles: can survive and grow under basic conditions ph 8- 10 neutrophiles: most pathogenic bacteria that cause disease in humans With respect to osmotic pressure, what type of environment will most bacteria encounter and what happens under this condition? - ✔✔most environments bacteria will be ISOTONIC (a solute concentration equal to the solute concentration in the cytoplasm) or HYPOTONIC (solute concentration slightly lower than the solute concentration in cytoplasm)
superoxide, hydrogen peroxide, hydroxyl radical Define and explain how obligate aerobes handles the presence and absence of oxygen - ✔✔-require oxygen for growth and survival Presence of O
- aerobic respiration includes oxidation of organic compounds to produce energy ATP, only has cellular pathways that can produce energy in the presence of O2, have enzymes necessary to break down toxic forms of oxygen Define and explain how facultative anaerobes handles the presence and absence of oxygen - ✔✔Absence of O
- facultative anaerobes have cellular pathways that can produce energy in the presence or absence of O2, have the enzymes necessary to break down toxic forms of oxygen, prefers O2 since more energy produced define and explain how obligate anaerobes handle the presence and absence of oxygen. - ✔✔-only have cellular pathways that can produce energy in the absence of O
- do not have the enzymes necessary to break down toxic forms of oxygen
- can only grow in the absence of O Define and explain how an aerotolerant anaerobe handles the presence and absence of oxygen - ✔✔- only has cellular pathways that can produce energy in the absence of O
- only has one of the two enzymes necessary to break down toxic forms of oxygen
- can only grow in the absence of O2 but will tolerate and not be killed by presence of O
What is a microaerophilic organism and a capnophilic microorganism? - ✔✔-can only survive and grow under lower O2 concentrations
- some microbes require less O2 but more CO What are trace elements, why are they important and how are thy generally obtained by a microbe? give an example of a trace element - ✔✔They are essential elements, needed in much smaller amounts, important for enzyme function and maintaining protein structure, micronutrients. They are obtained from minerals in soil, many micronutrients are also present in water but as unusable concentrations EX: iron, copper, zinc, calcium, sodium What are growth factors and what is a fastidious microorganisms? - ✔✔-organic compounds that must be provided to a microbe as a nutrient
- those microbes that require numerous growth factors What is a microbe's nutritional pattern based on? - ✔✔based on their source of ENERGY (source of electrons for transfer) and CARBON (type of compounds used) Define chemotroph, phototroph, heterotroph, and autotroph and indicate what the energy and carbon source is for these types of microorganisms. - ✔✔chemotrophs (chemical energy source)-electron transfers through the breaking of the chemical bonds phototroph (light energy source)- electron transfers from light heterotroph(organic carbon source- complex organic compounds supplied by others autotroph (inorganic carbon source)- inorganic compounds converted into organic compounds in order to feed themselves
What is a generation time? Are the generation times of all bacteria the same? Under optimal environmental conditions a bacterium will show logarithmic growth, what does this mean? - ✔✔-time required for a cell to divide generation time depends on bacterial species and the environmental conditions yes exponential or logarithmic growth How can you calculate the size of bacterial population over time? - ✔✔Nn = (No) 2n Nn= # of cells present at generation n No= initial # of cells n= the # of generations Explain what a closed growth system is. Diagram the four phases that occur when a bacterium is grown in a closed growth system and explain what is happening at/during each phase. - ✔✔-growth in a system in which no nutrients are added and no waste products are removed
- LAG phase: adjustment time to get used to new environment, bacteria are metabolically active but not growing at this time (straight horizontal line)
- LOG phase: maximum rate of cell division, exponential growth will continue as long as an adequate supply of nutrients is available (diagonal line)
- STATIONARY phase: growth rate equals death rate (straight horizontal line), fewer nutrients available and build up of waste products
- DEATH phase: no nutrients remain and waste products at toxic levels, growth stops and exponential death begins (diagonal line - negative?) List four direct methods for measuring microbial growth and provide one advantage and one disadvantage for using this method. - ✔✔1) serial dilutions and plate counts
Pro- samples that contain large quantities of bacteria Con-time consuming, contamination risk
- Filtration and plate Counts P- sample contains very small quantities of bacteria C- selective growth
- Most Probably Numbers (MPN method) P- samples contain very small quantities of bacteria or when bacteria will not grow on solid media C-limited precision
- Bacterial cell counts P-easy and inexpensive, no need to be incubated C- tedious and inaccurate What is metabolism? - ✔✔all chemical reactions within a living organism How can metabolism be used to help identify bacteria? - ✔✔knowing a bacteria's metabolic pathways useful because not all bacteria utilize the same metabolic pathways so knowing them can be used to identify Define anabolism. What does anabolism require and what types of reactions, in general, are associated with it? - ✔✔-building up from small molecules to make more complex compounds
- usually involves dehydration reactions
- requires energy so endergonic reactions
What three things can increase the reaction rate and which of these is most feasible/practical in a biological system? - ✔✔concentration, temperature, or adding a biological catalyst ENZYME
- most practical adding enzyme What are enzymes? What is the region of an enzyme that interacts with a specific substrate called? What gives an enzyme its specificity? - ✔✔-proteins that increase the rate of a chemical reaction
- Active site: region of the enzyme that a specific chemical substrate binds to
- enzyme is specific and binds to and acts only on a specific substrate What is an apoenzyme, a cofactor, a coenzyme and a holoenzyme? - ✔✔apoenzyme: need nonprotein helper molecules cofactor: inorganic ion coenzyme: organic molecule holoenzyme: apoenzyme combined with cofactor or coenzyme Briefly explain how any enzyme works - ✔✔A substrate binds to an active site. Enzyme changes shape slightly as substrate binds. Substrates are converted to products then leaves the active site and is released. After reaction enzyme remains unchanged and can be recycled for another reaction. enzymes aren't part of products, aren't consumed, and don't create they just speed things up. How can you tell that an oxidase, catalase and an aldolase are all enzymes? - ✔✔based on their ability to catalyze specific chemical reactions
Explain how temperature, pH and substrate concentration can influence theactivity of an enzyme - ✔✔1) Temperature: at a very low temp molecules move slower, high energy collisions are less likely, at high temps enzymes will denature and active site is destroyed
- pH: acids and bases can alter the 3D structure of an enzyme, strong acids and bases can cause enzyme to denature and active site destroyed
- substrate concentration: at high concentration substrate the active site will be constantly occupied and the maximum rate of enzyme activity will be reached Describe how competitive and noncompetitive inhibitors can influence an enzyme's activity. - ✔✔A) competitive inhibitors: imposter that is similar in structure to normal substrate. if competitive inhibitor gets to active site first the reaction is blocked. B) noncompetitive inhibitors: binds at allosteric site, which causes enzyme to change its shape and this alters the active site so that normal substrate cannot bind Explain how feedback inhibition can influence an enzyme's activity - ✔✔-the final product of a metabolic pathway can be a noncompetitive inhibitor to an enzyme early in the pathway and allows pathway to be shut off if necessary What are exoenzymes and endoenzymes? - ✔✔-enzymes that work outside the cell (extracellular enzymes)
- enzymes that work inside the cell (intracellular enzymes) Explain why bacterial enzymes can be important in infectious diseases - ✔✔Microbial toxins are enzymes. This can cause damage or destroy a cell, tissue invasion, host attachment etc. How is energy produced, passed on and stored in prokaryotic and eukaryotic cells? - ✔✔Prokaryotic
Which macromolecule do most microbes use as their primary source of energy? - ✔✔carbohydrates Where does glycolysis occur, and does it require the presence of oxygen? In general, what does glycolysis involve? - ✔✔metabolic process that occurs in cytoplasm of a cell and does not use oxygen and involves splitting of glucose. it involves atp, reduced electron carriers, precursor molecules for further cellular metabolism Name the three glycolysis pathways that may be present in bacteria. Of these three pathways which is the most common? - ✔✔1) EMP
- most common pathway used by microbes for production of energy
- PPP
- shared by all prokaryotic and eukaryotic organisms, parallels the EMP glycolysis pathway
- ED
- only possessed by certain bacteria, completely independents pathways Name the two phases that constitute the EMP glycolysis pathway - ✔✔Energy Investment Energy Payoff n the first phase of the EMP pathway, what molecule goes into the pathway and how many carbons does it contain? What are the final products of this phase and how many carbons does each of these molecules contain? - ✔✔IN: one glucose (6 carbon sugar) OUT: two phosphorylated (3 carbon compound) What is required to complete the first phase of the EMP pathway and how many of these molecules are required? - ✔✔2 ATP
What are the final products of the second phase of the EMP pathway and how many carbons do each of these molecules contain? What else is generated from the second phase of this pathway? - ✔✔ENERGY: generated 4 ATP, 2 NADH OUT: 2 pyruvate (3 carbon compounds) What is the net gain of energy if a bacterium uses the EMP pathway? - ✔✔2 ATP Is the pentose phosphate glycolysis pathway specific to prokaryotes or eukaryotes or is it a pathway common to both? In general, when and why would an organism use this pathway? - ✔✔-shared by ALL prokaryotic and eukaryotic organisms
- used when cell REQUIRES nucleotides, amino acids and fatty acids since intermediate molecules generated by this pathway used in nucleic acid, protein and lipid biosynthesis Is the ED glycolysis pathway common to all eukaryotes and prokaryotes? If a bacterium were to use this pathway what would be the final products generated and how much energy would the organism gain? - ✔✔-possessed only by certain bacteria OUT: 2 molecules of ethanol GAIN: 1 ATP Why is pyruvate considered a critical intermediate metabolite in carbohydrate catabolism? - ✔✔Because it is the final product of glycolysis, to capture more energy through respiration or fermentation
6 NADH
Where does the Krebs cycle reactions occur in a prokaryote and where do these reactions occur in a eukaryote? - ✔✔prokaryotic: cytoplasm eukaryotic: mitochondrial matrix The Krebs cycle does not directly produce a large quantity of ATP, but it is still critical to energy production in a cell, why? - ✔✔the release of protons H+ loads a total of 8 energy carriers Are the intermediate compounds produced during the Krebs cycle useful to the cell and if so, what can these compounds be used to generate? - ✔✔yes, can be used for macromolecule synthesis in general what is the electron transport chain and where is it located in prokaryotic organisms and in eukaryotic organisms? - ✔✔prokaryotic: inner plasma membrane eukaryotic: inner mitochondrial membrane What are the four general classes of electron carrier molecules used in the electron transport chain? - ✔✔1) cytochromes (proteins that contain heme)
- flavoproteins
- iron-sulfur proteins
- quinones (non-protein organic molecules) What is the overall goal of these electron carrier molecules in the ETS? - ✔✔to release energy as an electron flows down the chain
Where do the electrons that enter the ETS come from? - ✔✔from NADH and FADH Name the six electron carrier molecules/complexes that are used by the ETS in bacteria. Which of these 6 carriers simple absorb a little energy during the transfer of electrons and what is the second "job" of the other 3 carriers? - ✔✔1) succinate dehydrogenase
- uniquinone
- cytochrome C carriers absorb little energy
- Complex 1 NADH dehydrogenase
- Complex 2 bc1 cytochrome
- Complex 3 cytochrome oxidase
- these three are proton pumps, use energy from electron to pump H+ across membrane What are protons, what is the proton motive force and why does this form? - ✔✔-energy build up H+ protons cannot cross plasma membrane, causing proton motive force a ton of energy buildup. To get protons across phospholipid bilayer a membrane bound enzyme is used called ATP synthase. What is chemiosmosis and describe the enzyme that is critical to chemiosmosis? If this enzyme was not present what would happen? - ✔✔-flow of hydrogen ions across membrane through ATP synthase
- ATP synthase: F0 complex and the F1 complex F0 complex forms protein channel and F1 complex contains catalytic sites for ATP
- without ATP cells struggle to produce ATP efficiently, production impaired, significant reduction in energy availability for various cellular processes
What is the final electron acceptor in fermentation and how much energy is produced from fermentation? - ✔✔Organic molecule accepts electron 2 ATP per glucose molecule What would the end products be if one molecule of glucose was used in the lactic acid fermentation pathway? What is the final electron acceptor in the lactic acid fermentation pathway? - ✔✔OUT: 2 molecules of lactic acid 2 ATP Pyruvate is the final electron acceptor in lactic acid fermentation What would the end products be if one molecule of glucose was used in the alcohol fermentation pathway? What is the final electron acceptor in the alcohol fermentation pathway? - ✔✔OUT: 2 molecules ethanol 2 molecules of CO 2 molecules of ATP Acetaldehyde is the final electron acceptor in alcohol fermentation Compare and contrast aerobic respiration, anaerobic respiration and fermentation in terms of the amount of ATP produced by each and the final electron acceptors used - ✔✔Aerobic
- O2 is needed
- O2 is electron acceptor 38 ATP made per glucose Anaerobic
- no O2 needed
- inorganic molecule final electron acceptor
- 5 - 36 ATP made per glucose Fermentation
- no O2 needed
- organic molecules final electron acceptor
- 2 ATP made per glucose What are lipases and phospholipases? When lipids are broken down what pathway does the glycerol molecule enter and what pathway do the fatty acids enter? What occurs during beta-oxidation? Overall is a large or small amount of energy obtained from lipid catabolism? - ✔✔Lipases are enzymes that break down triglycerides, phospholipases are enzymes that break down phospholipids.
- When lipids are broken down, the glycerol molecule enters the glycolytic pathway and converted to glycerol- 3 - phosphate. The fatty acids go down the beta oxidation pathway.
- In Beta oxidation, fatty acids are broken down into two carbon acetyl-CoA units that undergo enzymatic reactions. These acetyl-CoA units then enter krebs cycle.
- gains a lot of energy compared to other macronutrients because fats are highly energy dense molecules What are proteases, deamination reactions and decarboxylation reactions? What pathways can the amino acids of a protein enter after the protein has been broken down? Overall is a large or small amount of energy obtained from protein catabolism? - ✔✔1. proteases: enzymes that hydrolyze peptide bonds in proteins by cleaving the bonds between amino acid residues, releasing individual amino acids
- Deamination reaction: removal of amino acid group from an amino acid. amino acids removed at NH or NH4+ and converted into a less toxic substance to be excreted
