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BI 234: Lecture Exam QUESTIONS WITH
VERIFIED ANSWERS NEW VERSION
UPDATE 2024-2025 GRADED A.
what is the slime layer?
- ANSWER loose, water-soluble glycocalyx
- Allows prokaryotes to attach to surfaces What are flagella?
- ANSWER - Responsible for movement What compose flagella?
- ANSWER - Filament, hook and basal body
- basal body anchors the filament and hook to cell wall what are the different orientations of flagella?
- ANSWER Monotrichous Amphitrichous Lophoptrichous Peritrichous How many rings are present in the basal body of gram negative flagella?
- ANSWER 4 How many rings are present in the basal body of gram positive flagella?
- ANSWER 2 what is the motion called that bacteria move?
- ANSWER run and tumble What are fimbriae? - ANSWER hairlike appendages that allow for attachment
- shorter than flagella what are pili?
- ANSWER - Special type of fimbriae
- Transfer DNA from one cell to another Purpose of cell wall?
- ANSWER - Provide shape and structure and protect from osmotic forces what composes cell walls of bacteria?
- ANSWER peptidoglycan
What are the characteristics of gram-positive cell walls?
- ANSWER - Thick layer of peptidoglycan
- Contain teichoic and lipteichoic acids What are the characteristics of gram-neg cell walls?
- ANSWER - Thin layer of peptidoglycan What is the bilayer membrane outside of the peptidoglycan of gram neg bacteria? - ANSWER - contains phospholipids, proteins and lipopolysaccharies What is significant about lipid A?
- ANSWER can cause fever, vasodilation, inflammation, shock and blood clotting What is the fluid mosaic model?
- ANSWER states that a membrane is a fluid structure with a "mosaic" of various proteins embedded in it
- phospholipid bilayer What are integral proteins?
- ANSWER penetrate the hydrophobic interior of the lipid bilayer What are peripheral proteins?
- ANSWER bound to the surface of the membrane what is the function of the cytoplasmic membranes? - ANSWER - Controls passage of substances into and out of the cell
- Harvests ligh energy in photosynthetic bacteria
- selectively permeable
- naturally impermeable to most substances
- Proteins allow substances to cross membrane
- Maintains concentration and electrical gradients What happens to a cell in a hypertonic solution?
- ANSWER cell shrinks What happens to a cell in a hypotonic solution - ANSWER cell swells What is a nucleoid?
- ANSWER A dense region of DNA in a prokaryotic cell. What is the structure/number of the bacterial chromosome? - ANSWER circular, double- stranded DNA molecule condensed into a structure called the nucleoid, which has no nuclear membrane What are plasmids?
What are the common arrangements of cocci?
- ANSWER Diplo Streptococci (chains) Tetrads Sarcinae Staphylococcus What are the different arrangements of bacilli?
- ANSWER - Single
- Diplobacilli: pair of cells with ends attached
- Streptobacilli: chain of several cells
- Palisades: cells of a chain remain partially attached by a small hinge region at the ends How do archaea differ from bacteria?
- ANSWER a. Archaea lack peptidoglycan in their cell walls, a substance that is found in the cell walls of most bacteria. b. Archaea can live in more extreme environments than most bacteria can tolerate. c. Even more metabolic diversity is seen within the archaea than in the bacteria. What are the common features of archaea?
- ANSWER - lack true peptidoglycan
- cell membrane lipids have branched hydrocarbon chains
- AUG codon codes for methionine
- reproduce by binary fission, budding or fragmentation
- not known to cause disease What are thermophiles?
- ANSWER heat loving microbes
- DNA RNA cytoplasmic membranes and proteins do not function properly below 45 degrees celcius
- Thermococcus and pyrodictium What are hyperthermophiles?
- ANSWER some Archaea that grow at temperatures above 80C, some over 100C. What are halophiles?
- ANSWER salt loving archaea What are methanogens? - ANSWER the largest group of archaea; produce methane gas from organic waste, which is useful in sewage treatment
- Some live in colons of animals
- One of primary sources of environmental methane What are photosynthetic lamellae?
- ANSWER contained within phototrophs
What is the G + C content? - ANSWER GC-content (or guanine-cytosine content) is the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C). What is nitrogen fixation?
- ANSWER Process of converting nitrogen gas into ammonia What is sporulation?
- ANSWER formation of endospores What are endospores? - ANSWER Stores genetic material in harsh conditions and facilitates survival. Once conditions are restored it goes back to beinga vegetative cell. ONLY PROKARYOTIC What are cyanobacteria?
- ANSWER - Gram neg photorophs
- Some species reduce nitrogen gas via nitrogen fixation what is endospore forming clostridium?
- Important in medicine and industry What is Epulopiscium?
- ANSWER huge bacteria
- Live birth
- Large genome What is Bacillus thuringiensis?
- ANSWER AKA "BT" Is a bacteria commonly used for a biological pesticide or toxin to insects to induce the health of plants and crops What is Listeria? - ANSWER - Contaminates milk and meat products
- Capable of reproducing under refrigeration
- Can cross the placenta in pregnant women What are mycobacterium ? - ANSWER - Aerobic rods that sometimes form filaments
- Slow growth partly due to mycolic acid in its cell walls What is Rhizobium and Azospirillum? - ANSWER - Nitrogen fixers
- Grow in association with the roots of plants What is Bdellovibrio?
polyhedral complex What are the types and arrangements of nucleic acids found in different viruses? - ANSWER - may be DNA or RNA
- Can be dsDNA, ssDNA, dsRNA or ssRNA
- May be linear sugmented or singel and circular What is the host range of a virus? - ANSWER the spectrum of host cells a virus can infect What is tissue tropism? - ANSWER tissue specificity within a host How are viruses classified and named? - ANSWER - Type of nucleic acid
- Presence of an envelope
- Shape
- Size What is a bacteriophage? - ANSWER A virus that infects bacteria What are the steps of lytic replication? - ANSWER 1. Attachment
- Entry
- Synthesis
- Assembly
- Release What are the steps of lysogenic replication? - ANSWER - Modified replication cycle
- Infected host cells grow and reproduce normally for generations before they lysepe of bacterium
- Can carry genes that alter phenotype Why is lysogenic conversion medically important? - ANSWER Because the phage can carry genes which are responsible for the pathogenicity of the organism. What are the steps of animal virus replication? - ANSWER 1. Adsorption/Attachment - virus attached to host cell by specific binding of its spikes to cell receptors
- Penetration/Entry - mechanism depends on presence or absence of viral envelope
- Uncoating - nucleic acid separates from capsid prior to replication
- Synthesis of DNA/RNA viruses of animals - diverse strategies for different families
- Assembly and Maturation
- Release - viruses bud off of the host cell membrane; virion
is ready to infect other cells
- Shedding from Host
- Transmission What are the different methods of entry for animal viruses? - ANSWER 1) Direct penetration
- Membrane fusion
- Endocytosis What are the different methods of release for animal viruses? - ANSWER 1) Enveloped viruses released via budding
- Naked viruses are released by exocytosis or lysis what is viral latency? - ANSWER When animal viruses remain dormant in host cells
- May be prolonged for year with no viral activity
- Incorporation of provirus into host DNA is permanent What is a provirus? - ANSWER a virus genome that is integrated into the DNA of a host cell What are prions? - ANSWER misfolded versions of normal protein that can cause disease What diseases do prions cause? - ANSWER Bovine spongiform encephalopathy (BSE), A.K.A. Mad Cow, Creutzfeldt-Jakob disease, scrapie, kuru, CWD What animals do prions infect? - ANSWER humans and other mammals How do prions cause disease? - ANSWER They cause changes in the shape of normal protein molecules that lead to accumulation of prion protein deposits in the brain. How do prions replicate? - ANSWER They cause normal proteins to misfold into infectious proteins. How do prions propagate? - ANSWER Prions convert normal proteins to misfolded proteins. Misfolded proteins aggregate and interfere with normal cell functions. How are prions transmitted? - ANSWER Inherited and transmissible by ingestion, transplant, and surgical instruments What are some issues with disinfection of prions? - ANSWER Cannot be deactivated via normal sterilization procedures
How does temperature affect enzyme activity? - ANSWER As the temperature increases, so does the rate of reaction How does the pH effect an enzyme? - ANSWER If the pH is too high or too low, it interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme. How does enzyme concentration affect enzyme activity? - ANSWER Increasing enzyme concentration will speed up the reaction, as long as there is substrate available to bind to. Once all of the substrate is bound, the reaction will no longer speed up, since there will be nothing for additional enzymes to bind to. How does substrate concentration affect enzyme activity? - ANSWER Increasing substrate concentration also increases the rate of reaction to a certain point. Once all of the enzymes have bound, any substrate increase will have no effect on the rate of reaction, as the available enzymes will be saturated and working at their maximum rate. What do competitive inhibitors do? - ANSWER block substrates from entering the active site and reduce an enzyme's productivity What do noncompetitive inhibitors do? - ANSWER bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective What is feedback inhibition? - ANSWER When the product of a reaction near the end of a chain of reactions inhibits the function of an enzyme in an earlier reaction of the chain. What is cellular respiration? - ANSWER Cellular respiration is the process that releases energy from food in the presence of oxygen. What is fermentation? - ANSWER Making ATP w/out oxygen What are the steps of glycolysis? - ANSWER The first part of glycolysis is the investment stage. 2 molecules of ATP are consumed for each molecule of glucose. Next, glucose is converted to fructose-1,6-bisphosphate.Glucose is trapped inside the cell and at the same time converted to an unstable form that can be readily cleaved into 3 - carbon units. Next is stage 2, cleavage. In stage 2, fructose-1,6-bisphosphate is cleaved into 2 3- carbon units of glycerladehyde- 3 - phosphate. The last stage is the harvesting stage. 4 molecules of ATP and 2 molecules of NADH are gained from each initial molecule of glucose. This helps to form the final product, pyruvate; which will the be shipped to the Krebs Cycle. What are the products of glycolysis? - ANSWER 2 pyruvate, 2 ATP, 2 NADH What is the role of acetyl CoA? - ANSWER Needed for the Krebs cycle
What happens in the Krebs Cycle? - ANSWER The acetyl coenzyme A combines with a C4 acceptor molecule to form a C6 molecule. The coenzyme A is then released and recycled in another link reaction. The C6 molecule undergoes oxidation (NAD+ - > NADH+H+) and decarboxylation (-CO2) to form a C5 molecule. The C5 molecule undergoes oxidation and decarboxylation to form a C4 molecule. This then undergoes substrate level phosphorylation (ADP + Pi - > ATP) and 2 oxidations (FAD - > FADH and NAD+ - > NADH + H+) to form another C4 molecule. What happens in the electron transport chain? - ANSWER An electron transport chain (ETC) couples electron transfer between an electron donor (such as NADH) and an electron acceptor (such as O2) with the transfer of H+ ions (protons) across a membrane. The resulting electrochemical proton gradient is used to generate chemical energy in the form of adenosine triphosphate (ATP) What is aerobic respiration? - ANSWER Aerobic respiration uses oxygen from the air to release energy from glucose. What is anaerobic respiration? - ANSWER Anaerobic respiration is the release of energy from glucose without using oxygen. This produces lactic acid. What is the final electron acceptor during anaerobic respiration? - ANSWER NO3, SO4, CO What happens in fermentation? - ANSWER NADH is converted into NAD+ by passing high-energy electrons back to pyruvic acid What to lipids and proteins get converted to? - ANSWER Precursor metabolites that can serve as substrates in glycolysis and the krebs cycle How are catabolism and anabolism related? - ANSWER The interaction between catabolic and anabolic reactions is called a "coupled" reaction because catabolism breaks bonds that release energy that are used in anabolic reactions to build new bonds. what are the two groups of organisms based on source of carbon? - ANSWER - Autotrophs
- Heterotrophs What are two groups of organisms based on source of energy? - ANSWER - Chemotrophs
- Phototrophs What are obligate anaerobes? - ANSWER cannot survive with oxygen What are obligate aerobes? - ANSWER bacteria that require oxygen for metabolism
How does osmotic pressure control microbial growth? - ANSWER - Pressure exerted on a semipermeable membrane by a solution containing solutes that cannot freely cross the membrane How does hydrostatic pressure effect microbial growth? - ANSWER - Water exerts pressue in proportion to its depth
- Barophiles live under extreme pressure --Membranes and enzymes depend on pressure to maintain 3 dimensional, functional shape What are neutrophiles? - ANSWER those that grow best in a narrow range around neutral pH; 6.5 - 7.5; most bacteria and protozoans. What are acidophiles? - ANSWER bacteria that grow in acidic environments what are alkalinophiles? - ANSWER grow at extreme alkaline pH What are halophiles? - ANSWER salt loving bacteria What is a biofilm? - ANSWER a thin, slimy film of bacteria that adheres to a surface. How do biofilms form? - ANSWER Form as a result of quorum sensing What is quorum sensing? - ANSWER the ability of bacteria in a biofilm to communicate with each other and coordinate their activities How are pure cultures obtained? - ANSWER streaking to isolation What is the streak plate method? - ANSWER A small droplet of culture or sample is spread across the surface of a medium with an inoculating loop The pattern used to inoculate gradually thins out the sample and separates the cells in order to encourage the growth of discrete colonies What is a colony forming unit (CFU)? - ANSWER A colony forming unit is a live (viable) cell or small group of cells that gives rise to a colony. Arrangement, capsules and other cellular features influence how bacteria spread and are deposited on the surface of a plate. what is a defined media? - ANSWER precise chemical composition is known what is a complex media? - ANSWER nutrient rich but poorly defined (TSA) what is a selective media? - ANSWER contains one or more agents that inhibit growth of some microbes and encourage growth of the desired microbes
what is a differential media? - ANSWER allows growth of several types of microbes and displays visible differences among those microbes what is an anaerobic media? - ANSWER Thioglycollate broth what is TSA? - ANSWER trypticase soy agar What is TSB? - ANSWER Trypticase Soy Broth What is MSA used for? - ANSWER It selects for the growth of salt-tolerant organisms and differentiates mannitol fermenters from non-mannitol fermenters What is MacKonkey Agar? - ANSWER - Selective for gram neg organisms
- Differentiates between lactose and non lactose fermentors What is PEA media? - ANSWER Selective for gram positive organism what is a thioglycolate broth? - ANSWER a special broth where there is an oxygen gradient in it. More oxygen at the top and no oxygen at the bottom What is a serial dilution? - ANSWER used to obtain a series of solution whose concentrations differ by known amounts What are some methods of preserving cultures? - ANSWER Agar Slant Cultures: Agar Slant Culture Covered with Oil (Parafin Method): Saline Suspension: Preservation at Very Low Temperature: Preservation by Drying in Vacuum: Preservation by Freeze Drying (Byophilization) What is microbial growth? - ANSWER increase in number of cells What is binary fission? - ANSWER A form of asexual reproduction in which the parent divides into two approximately equal parts What is exponential growth? - ANSWER growth that occurs as a constant percentage of the existing amount What is the typical bacterial growth curve? - ANSWER Define genetics - ANSWER the study of heredity Define genome - ANSWER the complete set of genes or genetic material present in a cell or organism Define gene - ANSWER a heritable factor that controls a specific characteristic
- Termination OCCURS IN NUCLEOID OF PROKARYOTES Define sterilization? - ANSWER The process that completely destroys all microbial life, including spores. Define aseptic - ANSWER free of contamination What is disinfection? - ANSWER destruction of many pathogenic microorganisms on inanimate objects only. What is antisepsis? - ANSWER removal of pathogens from living tissue what is sanitation? - ANSWER reducing the microbial population to safe levels What is pasturization - ANSWER Disinfectant Heat (under boiling temp) applied to kill potential agents of infection and spoilage without destroying the food flavor or value kills non-spore-forming pathogens and lowers overall microbe count; does not kill endospores or many nonpathogenic microbes 63°C-66°C for 30 minutes (batch method) 71.6°C for 15 seconds (flash method) What does the suffix - cide/-cidal mean? - ANSWER to kill What does the suffix - stasis/-static mean? - ANSWER stopping, standing still What are the factors that affect the efficacy of various antimicrobial treatments? - ANSWER - Site to be treated
- Relative susceptability of microorganisms
- Environmental conditions (temp, pH, organic materials) How does moist heat kill microbes? - ANSWER - Denatures proteins
- Destorys cytoplasmic membranes How does dry heat sterilization work? - ANSWER oxidizes cell constituents and denatures proteins How does dessication control microorganisms? - ANSWER inhibits growth and disrupts metabolism due to removal of water How does lyophilization prevent food spoilage? - ANSWER - Prevents formation of damaging ice crystals
How does osmotic pressure suppress microbial growth? - ANSWER - High concentrations of salt or sugar in foods inhibit growth How does filtration effect microbial growth? - ANSWER physically separates microbes from air and liquids How does radiation prevent microbial growth? - ANSWER - Destroys DNA (ionizing radiation)
- Formation of thymine dimers inhibits DNA transcription and replication (non ionizing radiation) How does an autoclave work? - ANSWER It is a pressure chamber used to sterilize equipment and supplies by subjecting them to high pressure saturated steam at 121 °C (249°F) for 20 minutes How does refrigeration preserve foods? - ANSWER Inhibits metabolism How does freezing preserve food? - ANSWER By slowing or stopping metabolism and effectiviness of enzymes required by the bacteria. How do phenol and phenolics work? - ANSWER - Denature proteins
- Disrupt cell membranes
- Remain active for a prolonged time How does alchohol work for microbial control? - ANSWER - Denature proteins and disrupts cytoplasmic membrane
- not effective against fungal spores How do halogens work as disinfectants? - ANSWER - Damage enzymes by denaturation How do oxidizing agents work? - ANSWER kill by oxidation of microbial enzymes How do surfactants work? - ANSWER by disrupting phospholipid membrane integrity How do heavy metals disinfect? - ANSWER denature proteins How are enzymes used for disinfection? - ANSWER antimicrobial enzymes act against microorganisms How do anitbiotics work:? - ANSWER Act on cell walls, cell membranes, protein synthesis, and DNA transcription and replication How are antimicrobial agents tested for effectiveness? - ANSWER - phenol coefficient
- use-dilution test
- kelsey-sykes capactiy test
- In-use test
Which of the following statements is NOT true? a. Decomposition (degradation, catabolic) reactions are usually endergonic b. Enzymes increase the probability that a chemical reaction will take place by lowering the activation energy c. Chemical reactions in living cells are catalyzed by enzymes d. The energy required to cause a chemical reaction to occur is called the activation energy e. None of the above (all of these statements are true) - Ans - A. Decomposition reactions are usually exergonic, releasing energy If a bacterial cell is placed in a hypertonic (hyperosmotic) solution: a. Water moves through the plasma membrane into the cell b. The cell undergoes osmotic lysis c. Water moves through the plasma membrane out of the cell, causing plasmolysis d. There is no net movement of water either into or out of the cell e. None of the above describes what happens in a hypertonic solution - Ans - C. All of the following are correctly matched and can be found in bacteria EXCEPT: a. Ribosomes - site of protein synthesis b. Cell (plasma) membrane - encloses cytoplasm; phospholipid bilayer with proteins c. Cell wall - contains peptidoglycan d. Nucleus - membrane-bound organelle containing multiple chromosomes e. None of the above (all are correctly matched and can be found in bacteria) - Ans - D. Bacteria are prokaryotes which do not have a nucleus In the Gram stain, gram-positive bacteria are dark purple for all the following reasons EXCEPT: a. The counterstain (safranin) causes the purple color to develop b. Thick peptidoglycan in the gram-positive cell wall prevents decolorization by alcohol c. Crystal Violet is fixed inside the cell as a CV-iodine complex once iodine is added d. The primary stain, Crystal Violet, is dark purple e. None of the above (All are reasons that gram-positive bacteria are purple in the Gram stain) - Ans - A. Safranin is a counterstain that is used to color the gram-negative bacteria that lose their color after decolorization Which of the following is NOT true about chemoheterotrophs? a. Use organic compounds as a source of both carbon and energy b. Can use light for energy and CO2 as a source of carbon c. They are ultimately dependent on autotrophs to provide their carbon and energy d. Oxidize organic compounds (e.g., glucose) to generate ATP e. None of the above (All are true of chemoheterotrophs) - Ans - B Chemoheterotrophs are unable to utilize carbon dioxide to form their own organic compounds Which of the following is NOT true of photosynthesis?
a. The light-independent ("dark") reaction makes glucose from carbon dioxide (CO2) and water, using energy trapped by the light-dependent reaction b. Light-excited electrons in chlorophyll provide the energy for ATP production c. The light-independent ("dark") reaction converts light energy to chemical energy stored in ATP d. The light-dependent reaction captures electrons in NADPH, which are used for glucose synthesis in the light-independent ("dark") reaction e. None of the above (all are true of photosynthesis) - Ans - C In biological systems, anabolic and catabolic reactions are "coupled" (or linked) by: a. Krebs cycle b. Glycolysis c. Photosynthesis d. Adenosine Triphosphate (ATP) e. The Electron Transport Chain - Ans - D In the diagram below, which of the following is TRUE? a. The NAD+ becomes reduced b. The organic molecule becomes reduced c. Neither molecule is oxidized or reduced d. The NAD+ becomes oxidized e. None of the above are true (Image is an organic molecule that includes two hydrogen atoms. Arrows pointing from the hydrogen atoms to NAD+ coenzyme (electron carrier) then arrow to organic molecule with no hydrogen next to an illustration of NADH + H+) - Ans - A. Reduction is addition of electrons to a molecule The complete aerobic respiration of glucose yields far more energy stored in ATP than glycolysis alone for all of the following reasons EXCEPT: a. Krebs cycle generates some additional ATP through substrate-level phosphorylation b. Glycolysis only partially oxidizes the glucose molecule to pyruvic acid c. Electron transport chain (terminal respiratory pathway) produces many ATPs through oxidative phosphorylation using electron carrier molecules (NADH and FADH2) d. Krebs cycle generates reduced electron carrier molecules (NADH and FADH2) e. None of the above (All are reasons that aerobic respiration yields more energy than glycolysis alone) - Ans - E Bacteria that grow best (optimally) at very high temperatures are called: a. Mesophiles b. Hyperthermophiles c. Capnophiles d. Halophiles e. Psychrophiles - Ans - B In the diagram at right, enzyme action has been stopped (prevented) by binding of what to the active site? a. noncompetitive inhibitor b. coenzyme c. competitive inhibitor d. substrate e. none of the above (Diagram shows a something blocking a substrate from entering the active site of an enzyme) - Ans - C. Competitive inhibitors compete with the normal substrate for the active site of an enzyme
