MCB 151 EXAM 1 2023 with 100% correct questions and answers

Lab Skills: convert .2 ml to microliters 200 ul Lab Skills: This type of molecule cannot form hydrogen bonds with water molecules and it repels water molecules. characteristics of hydrophobic molecules Lab Skills: Your total magnification on a light microscope if you are using the 100X objective 1000X Lab Skills: 0.0001 expressed in scientific notation 1.0 * 10^-4 Lab Skills: Formula used to make single step dilutions C1V1 = C2V2 Bacteria: cocci, bacilli, spirochete bacterial cell shapes Bacteria: A visible cluster of cells on the surface of solid medium a colony Bacteria: Culture containing only one type of microorganism pure culture Bacteria: The type of plate used to generate countable colonies from a diluted culture spread plate Bacteria: Probability that a single cell will form a colony EOP (Efficiency of plating) Enzymes: Lowers the activation energy of chemical reactions A catalyst Enzymes: An activated intermediate that must be formed for a chemical reaction to occur. the transition state Enzymes: The enzyme that catalyzes the hydrolysis of lactose to glucose and galactose B-galactosidase Enzymes: A structural analog of lactose ONPG Enzymes: raises the pH of the reaction to 11 and inactivates the enzyme (B-galactosidase) Na2CO3 DNA: The restriction enzymes used in this exercise EcoRV and PstI DNA: The types of cuts produced by restriction enzymes. staggered and blunt DNA: Covalent joining of two DNA molecules. ligation DNA: An enzyme that cuts within a nucleic acid sequence. endonuclease DNA: The purpose of the following reagents in chromosomal DNA prep: Sodium dodecyl sulfate Proteinase K 95% Ethanol EDTA lyses of the cell membrane degradation of proteins precipitation of the DNA protects from contaminating nucleases Electrophoresis: The charge of DNA negative Electrophoresis: A planar molecule that inserts itself between the stacked bases in the DNA double helix. ethidium bromide Electrophoresis: The plasmid used in this exercise pBR322 Electrophoresis: Standard used on your gel lambda DNA Electrophoresis: A physical map of DNA showing the relative positions of restriction sites and the distance in kb between the restriction sites. a restriction map True or false? When observing bacteria with brightfield microscopy, dyes are usually needed because bacteria cells have a high water content and lack pigments. TRUE The correct sequence of steps for observing a bacterial cell slide under the microscope is: bacterial cells slide on stage the objective from the side the stage using coarse focus knob using coarse focus knob e nosepiece so that 10X objective is over the slide using fine focus knob A) 2,6,1,3,4,7,5 B) 1,2,6,3,4,5,7 C) 2,6,1,3,4,5,7 D) 1,2,6,3,4,7,5 E) 1,2,3,4,5,6,7 B) 1,2,6,3,4,5,7 What are the three basic shapes of most bacteria? A) Sphere, staphylococci, streptococci B) Spiral, sphere, streptococci C) Rod, spiral, staphylococci D) Rod, spiral, sphere E) Rod, spiral, streptococci D) Rod, spiral, sphere This week in lab we will be (Bacteria Lab): (pick all that apply) A) Isolating single colonies of E. coli by spread plating B) Proving that the lab space is free of microorganisms C) Identifying areas of the lab space with microbial contamination D) Isolating single colonies of S. aureous by streak plating E) Isolating single colonies of E. coli by streak plating F) Determining the types of bacterial contamination found in the lab space based on the metabolic testing we will be performing C) Identifying areas of the lab space with microbial contamination E) Isolating single colonies of E. coli by streak plating In nature, β-galactosidase catalyzes conversion of lactose to galactose and glucose. What does β-galactosidase do in our lab? A) Converts ONPG to galactose and o-nitrophenol B) Converts lactose to galactose and o-nitrophenol C) Converts lactose to galactose and o-nitrophenolate D) Converts ONPG to glucose and o-nitrophenol E) Converts lactose to galactose and glucose A) Converts ONPG to galactose and o-nitrophenol Why is it important to raise the pH during the experiment? A) This is required for visibility of the substrate. B) This inactivates the enzyme, allowing us to stop the reaction. C) This is required for the enzyme to catalyze the reaction. D) It is not important to raise the pH during the experiment. E) This is required for stability of the reaction product. B) This inactivates the enzyme, allowing us to stop the reaction. Which of the following statements about enzymes is most correct? A) Enzymes effectively double the product concentration for specific reactions. B) Enzymes are required for biological reactions. C) Enzymes effectively halve the substrate concentration for specific reactions. D) Enzymes decrease the reaction time for specific reactions. E) All of the above statements are correct. D) Enzymes decrease the reaction time for specific reactions. True or false? The color of galactose helps us determine the level of completion of the reaction in this lab. (enzyme lab) FALSE True or false? In the procedures for purifying chromosomal DNA from E.Coli, EDTA is used to chelate divalent cations which are required by DNases. TRUE Which of the following operations is not done for the purpose of preventing DNA from being contaminated with nuclease? A) Add chloroform into DNA/protein mixture. B) Wear gloves during the experiment period to prevent contaminating tubes with our own endonucleases on our skin. C) Use sterile TE buffer. D) Sterilize 5M NaCl solution before use. E) Use a new sterile micropipette tip each time when removing restriction enzyme from tube. A) Add chloroform into DNA/protein mixture. Which of the following statements is incorrect? A) When moving supernatant after centrifuging the water-chloroform-isoamyl alcohol mixture, be careful to avoid the white interphase. B) In part I, all mixing procedures before adding ethanol have to be done by gently inverting the tube. C) You must be present for both Exercises 4 and 5 in order to turn in the LNA for credit. D) In part II, the restriction enzymes must be kept on ice until use. E) In part II, tubes should be centrifuged for 5mins after adding restriction enzymes. E) In part II, tubes should be centrifuged for 5mins after adding restriction enzymes. Choose the correct statement(s) about plasmids and restriction enzymes below. A) All plasmids carry antibiotic resistance genes thus bacteria can be killed by antibiotic. B) Only one plasmid can be found in each bacterium. C) Plasmids can carry gens that have nothing to do with plasmid replication. D) For most restriction enzymes, each recognition sequence has a palindrome structure. E) The shortest sequence that can be recognized by restriction enzymes is 10bp. C) Plasmids can carry gens that have nothing to do with plasmid replication D) For most restriction enzymes, each recognition sequence has a palindrome structure. n DNA of which of the following base pair lengths will migrate the fastest? A) 300 bp B) 1,250 bp C) 135 bp D) 790 bp E) Speed of migration does not depend on base pair length. C) 135 bp If a plasmid has three restriction enzyme digestion sites and is cut with those enzymes, how many bands will you see after running this digested plasmid on an agarose gel? A) 5 B) 3 C) 4 D) 2 E) 1 B) 3 Why do we add ethidium bromide to the gel? A) To denature the DNA, allowing it to run through the gel B) To give DNA a charge, allowing it to run through the gel C) To aid in visualization of the DNA D) To give the gel an appropriate pH for DNA migration E) To neutralize the charge of DNA C) To aid in visualization of the DNA True or false? DNA will not migrate through an agarose gel unless it is in linear form. FALSE Which of the following is not an appropriate action to take when handling bacteria? A) Reuse pipette tips when dealing with the same culture. B) Wear gloves at all times. C) Refrain from eating in the laboratory space. D) Pipette using equipment only and refrain from mouth pipetting. E) Sterilize glassware and equipment that has contacted bacteria. A) Reuse pipette tips when dealing with the same culture. Which of the following is not likely to cause injury in the laboratory? A) Bacteria B) Ultraviolet light C) Electricity D) Chemicals E) All of the above may cause injury in the laboratory. E) all of the above Which of the following numbers is incorrectly converted to scientific notation? A) .0045 4.5 x 10-3 B) 1. x 106 C) .1894 1.894 x 10-1 D) 305 3.05 x 102 E) 22000 2.2 x 105 E) 22000 2.2 x 105 Which of the following would be the correct setting for pipetting 4.5 μL with a 20 μL pipette? A) 4 0 5 B) 4 5 0 C) 0 5 4 D) 0 4 5 D) 0 4 5 Which of the following is not a valid reason for using a centrifuge? A) To collect a cell pellet. B) To spin down small volumes from the sides of tubes. C) To collect supernatant. D) To mix a cell suspension. E) All of the above are valid reasons for using a centrifuge. D) to mix a cell suspension If a solution of cells has 3.5 x 105 cells per mL in a volume of 3 mL, what is the new concentration of those cells in a 12 mL volume? A) 3.5 x 1012 cells/mL B) 3.5 x 108.75 cells/mL C) 8.75 x 104 cells/mL D) 8.75 x 103 cells/mL E) 8.75 x 105 cells/mL C) 8.75 x 104 cells/mL What is not a main reason for the high specific heat of water? A) The structural strength of water molecule interactions. B) The strength of hydrogen bonds. Incorrect: The polarity of water molecules. C) The surface tension of water. D) All of the above contribute to the high specific heat of water. C) The surface tension of water. True or false? Buffers allow us to easily change the pH of a solution. FALSE True or false? For oil immersion objective lens, oil is used because it has a refractive index similar to glass that enables more light to go through the objective lens. TRUE Which of the following cannot be seen by a brightfield light microscopy due to the resolution limit? A) Ribosome B) Human hair C) Plant cell wall D) Staphylococcus E) Nucleus A) ribosome Which of the following combination of objective lens and ocular lens will give the maximum magnification? A) 40X, 60X B) 60X, 60X C) 100X, 10X D) 40X,10X E) 80X, 40X B) 60X, 60X When doing plate counts using agar plates, no more than ____ ml of cell suspension should be spread on a plate, and only _____ to _____ cells should be spread on a plate. A) 2; 30; 300 B) 0.2; 300; 3000 C) 0.2; 3; 30 D) 2; 30; 300 E) 0.2; 30; 300 E) 0.2; 30; 300 Which of the following pictures shows the correct way to incubate an agar plate? see pictures on desktop one with foil which one is not a picture of bacteria see pics on desktop one on bottom right of desktop screen What is the difference between viable cell count and total cell count? A) Is measured by turbidity B) Depends on the optical density C) Only counts the cells that can replicate D) Can only be measured in cultures where at least 2 organisms are present E) None of the above C) Only counts the cells that can replicate What plate was streaked by a pure culture the one that is below the bacteria How many cells were streaked on plate A to obtain 1 colony? A) 2 B) 4 C) 1 D) 3 E) 5 C) 1 Which of the following statements about competitive inhibitors is incorrect? A) They can bind the enzyme active site. B) They do not change the maximum velocity of the reaction. C) They change the concentration of substrate necessary to reach maximum velocity. D)The substrate and the inhibitor bind the enzyme simultaneously. E) They can resemble the substrate structure. D)The substrate and the inhibitor bind the enzyme simultaneously. Which of the following statements about noncompetitive inhibitors is incorrect? A) They change the maximum velocity of the reaction. B) They cannot change the enzyme conformation. C) They do not normally bind the enzyme active site. D) They do not normally resemble the substrate. E) They are frequently heavy metal ions. B) They cannot change the enzyme conformation. Why does temperature increase a given reaction rate? A) It removes noncompetitive inhibitors from allosteric sites. B) It increases the kinetic energy of the substrates. C) It lowers the activation energy of the reaction. D) It removes competitive inhibitors from the active site. E) All of the above. B) It increases the kinetic energy of the substrates. Why do we add Na2CO3 to the blank cuvette? A) Na2CO3 is essential to the enzymatic reaction. B) Na2CO3 decreases background absorbance. C) Na2CO3 absorbs light at a wavelength of 420 nm. D) Na2CO3 inactivates the enzyme, allowing for background reading. E) Na2CO3 may contribute to background absorbance in the samples. E) Na2CO3 may contribute to background absorbance in the samples. Which of the following is left unchanged by the addition of an enzyme to a reaction? A) The final product concentration after complete use of substrate B) The final state of the reactants C) The overall free energy change of the reaction D) The initial state of the reactants E) All of the above. E) all of the above After enzyme saturation, which of the following stops increasing? A) [P] B) ΔG C) V E) Ea F) Keq C) V Which of the following describes ONPG in the conversion of lactose to galactose and glucose? A) Reaction intermediate B) Catalyst C) Cofactor D) Competitive inhibitor E)Noncompetitive inhibitor D) competitive inhibitor True or false? Adding more substrate does not always increase the rate of the reaction. TRUE What did you add to the restriction enzyme reactions to stop the reaction? A) Ethidium bromide B) Buffer C) DNA D) Blue loading solution E) Water D) Blue loading solution Match the pairs of DNA that can be successfully ligated to each other. A) B and I B) C and G C) D and H D) B and F E) E and G SEE PHOTO ON DESKTOP B) C and G C) D and H D) B and F Complete the following statement: Of the DNA fragments listed in Question 2, Fragment A contains _______ ends and Fragment B contains ________ ends. A) Blunt, sticky B) Cohesive, sticky C) Staggered, sticky D) Sticky, staggered E) Sticky, blunt SEE PHOTO ON DESKTOP E) sticky, blunt SEE PHOTO OF PBR322 What is the size of pBR322? A) 2.7 kb B) 2867 kb C) 4361 kb D) 1249 kb E) 4.3 kb E) 4.3 kb Which pair of restriction enzymes would produce fragments of 1920 and 2441 bp? A) Eco321, AatII B) XagI, MlsI C) HindIII, PvuII D) ScaI, SspI E) BamHI, NdeI E) BamHI, NdeI What did the DNA look like after you precipitated it? A) White fiber B) Green fibers C) Red clump D) Red fibers E) Blue stings A) white fiber What function does EDTA serve? A) Precipitates DNA B) Degrades RNA C) Prevents DNase activity D) Removes cell membrane E) Disrupts lipid bilayer C) Prevents DNase activity What would happen if we ran the agarose gel for too long a time? A) The ethidium bromide would dissociate from the DNA, preventing visualization. B) It is not possible to run the gel for too long a time. C) The DNA would melt. D) The DNA would run off of the gel. E) We would not get good separation of DNA bands. D) the DNA would run off the gel What would happen if we ran the agarose gel for too short a time? A) The ethidium bromide would not intercalate with the DNA, preventing visualization. B) The DNA would run off the gel. C)The DNA would not linearize, making size determination inaccurate. D) We would not get good separation of DNA bands. E) It is not possible to run the gel for too short a time. D) We would not get good separation of DNA bands. Why is it important to have an undigested pBR233 control DNA lane? A) This allows us to determine the sizes of the digested fragments. B) This lets us know if there is any DNA contamination. C) This allows us to identify any undigested pBR233 in other lanes. D) This allows us to determine the size of the E.coli chromosomal DNA. E) The control lane is used as a ladder. C) This allows us to identify any undigested pBR233 in other lanes. Why is it important to have an empty lane? A) It is not important to have an empty lane. B) This lets us know if there are any contaminating restriction enzymes. C) This lets us know if there is any DNA contamination. D) This allows us to see if the buffer is conducting properly. E) An empty lane is necessary for proper migration of DNA in adjacent lanes. C) This lets us know if there is any DNA contamination. What may happen if the tracking dye moved more slowly than the DNA? A) The dye would not intercalate with the DNA, preventing visualization. B) The ethidium bromide would not intercalate with the DNA, preventing visualization. C) The DNA would run into the tracking dye, preventing proper migration. D) The DNA may run off the gel. E) The ladders would not properly separate, preventing size determination. D) the DNA may run off the gel Why does chromosomal DNA move differently from digested plasmid DNA on an agarose gel? A) The chromosomal DNA is double-stranded. B) The plasmid DNA has not been linearized. C) The plasmid DNA is double-stranded. D) The chromosomal DNA is much smaller than the plasmid DNA. E) The chromosomal DNA has not been linearized. E) The chromosomal DNA has not been linearized. True or false? DNA is negatively charged, so it moves from the red electrode toward the black electrode. FALSE moves towards the red electrode Why is it important to wear gloves while handling ethidium bromide? A) Ethidium bromide can indirectly cause DNA mutations. B) Ethidium bromide may interfere with DNA replication. C) Ethidium bromide may cause cancer. D) Ethidium bromide is a DNA-intercalating agent. E) All of the above. E) all of the above MASS: A)mg B) ug C)ng A) 10^3 milligrams B) 10^6 micrograms C) 10^9 nanograms VOLUME A) ml B) ul C) 1 ml= A) 10^3 milliliters B) 10^6 microliters C) 1ml= 1 cubic centimeter LENGTH A) mm B) um C) nm A) 10^3 millimeters B) 10^6 micrometers C) 10^9 nanometers properties of water: high surface tension -at the air water interface, all the H bonds face downward as the water molecules at teh surface are hydrogen bonded to other water molecules below -explains why a container can be filled to slightly above its rim without overflowing and why small insects can walk on water properties of water: ice floats in water solid water is less dense than liquid water, explains why ice flats properties of water: high specific heat can be traced by hydrogen bonding -hydrogen bonds release heat when they form -heat must be absorbed to break hydrogen bonds and heat is released when hydrogen bonds form hydrophillic substances with an affinity for water -salt sugar, cottom hydrophobic substances that repel water acids= base= -acids donate protons -base: accepts protons ph is dependent on -H and OH concentration buffers -2 sets of molecules that allows the solutions to resist changes in the hydrogen ion concentration artifacts -apparent structures that are not biological in origin -staining with a dye provides contrast but may introduce artifacts proper way of looking at a sample under a microscope -selection of objective lens: start at lower magnification -focus: start with the coarse focus knob then fine focus difference between a prokaryote and an eukaryote -prokaryote: lack a nuclear membrane -eukaryote: organism possessing a nuclear membrane (nucleus, etc) sterilization -autoclaving (heating by steam under pressure) at 15 pounds per square inch or 15 to 60 min -bacteriological transfer loops are sterilized by heating the loop in the flame of the burner -glass spreaders are sterilized by flaming the alcohol -heat sensitive solutions are passed through a filter with pores that are smaller than the diameter of almost all bacterial cells aseptic technique -tools used to transfer bacteria: the inoculating loop. serological pipettes, and microliter pipettors -transfers made from bacteria growing in either solid media (usually on agar plates), or in liquid media (usually in tubes) to either solid or liquid media -may be from one tube to another tube, from a tube to a plate, from a plate to a plate or from a plate to a tube pure culture -a culture that contains only 1 type of microorganism lawn when all the cells run together as they divide forming a confluent layer of growth on the surface of the plate called a "lawn" -CONFLUENT LAYER OF GROWTH- Minimal/Defined media vs. complex media -A complex medium is one in which the exact chemical constitution of the medium is not known. -complex media usually contain complex materials of biological origin such as blood or milk or yeast extract or beef extract, the exact chemical composition of which is obviously undetermined. -Defined media are usually composed of pure biochemicals off the shelf; A defined medium is a minimal medium if it provides only the exact nutrients (including any growth factors) needed by the organism for growth. efficiency of plating (EOP) -the probability that a single cell will form a colony shapes of bacteria -sphere (cocci) -rod (bacilli) -spiral (spirilla and spirochetes) beers law A=Ecl absorbance=E(concentration)(length) catalyst increase the rate of the reaction by lowering the activation energy -enzymes are catalysts transition state -an activated intermediate that must be formed for a chemical reaction to occur activation energy -the amount of energy required to produce the transition state intermediate enzyme, substrate, product -enzyme is the catalyst which lowers the Ea of the reaction -substrate: the enzyme acts on the substrate -if high substrate concentration the reaction rate will not increase because the enzyme will not have enough of an effect -product: what is produced What factors may influence an enzyme's rate of catalysis? -temperature, the amount of substrate -competitive inhibition, noncompetitive inhibition (doesn't bind to active site but prevents the enzyme from being effective) What is enzyme kinetics study of chemical reactions that are catalyzed by enzymes Km -a constant that is inversely proportional to the affinity of an enzyme for its substrate Vmax -the maximal rate of an enzymatic reaction that is observed when the enzyme is saturated with substrate ∆G -free energy change during a reaction. a negative delta g indicated that its an exothermic reaction (energy is released), pos delta g indicated that energy input is required for the reaction (endothermic) initial velocity -the rate of a reaction before significant consumption of the substrate or production of the product that could alter the reaction kinetics zero order -conditions where the rate of a chemical reaction is independent of the concentration of the substrate b galactosidase catalyzes the hydrolysis of lactose to glucose and galactose --- genome -all of the genetic material of an organism, virus, or organelle (mitochondria or chloroplast) -all of the DNA in an organism, DNA virus, or organelle plasmid an autonomous, self-replicating, DNA molecule cloning -generation of a hybrid DNA molecule by insertion of a DNA fragment in a replicon such as a plasmid or virus antibiotic resistance -bacteria become resistant to the antibiotic because one survives and reproduces -important because used in recombinant DNA to kill bacteria that do not contain the plasmid we want What are some applications of plasmids and recombinant DNA that are commonly used in biology? -Recombinant DNA is widely used in biotechnology, medicine and research. Today, recombinant proteins and other products that result from the use of rDNA technology are found in essentially every western pharmacy, doctor's or veterinarian's office, medical testing laboratory, and biological research laboratory. -Recombinant DNA is used to identify, map and sequence genes, and to determine their function. rDNA probes are employed in analyzing gene expression within individual cells, and throughout the tissues of whole organisms. Recombinant proteins are widely used as reagents in laboratory experiments and to generate antibody probes for examining protein synthesis within cells and organisms.[2] restriction enzyme -an endonuclease that recognizes a specific double stranded DNA sequence and makes a single cut in both strands of the DNA the cut sites may be directly opposite each other (resulting in blunt ends) or the cut sites may be staggered (resulting in sticky ends) palindromic DNA sequence -an inverted repeat in the DNA; the DNA sequence is the same when one strand is read from left to right as when the other strand is read from right to left DNA ligase DNA ligase is a specific type of enzyme, a ligase, that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond. -It plays a role in repairing single-strand breaks in duplex DNA in living organisms, but some forms (such as DNA ligase IV) may specifically repair double-strand breaks sticky ends -complimentary, single stranded DNA ends on double stranded DNA molecules (also called cohesive ends) blunt ends -the end of a double stranded DNA fragment where neither strand of the DNA extends past the other strand (also called flushed ends) double digest transformation when you treat DNA with 2 enzymes electrophoresis -the separation of molecules in an electrical gradient -allows you to make a restriction map Negatively charged DNA is pulled toward the anode Large pieces/fragments of DNA do not move as fast as smaller ones ethidium bromide -a chemical used to visualize nucleic acids by fluorescence; free ethidium bromide has little fluorescence but when it intercalates between double stranded nucleotides the fluorescence increases supercoil -over/unwinding of a DNA strand