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Bacterial Physiology and Biochemistry - First Exam Questions | MICR 425, Exams of Biology

Material Type: Exam; Professor: Clark; Class: Biochem Phsl Microorgnsms; Subject: Microbiology; University: Southern Illinois University Carbondale; Term: Fall 2003;

Typology: Exams

2009/2010

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MICRO 425 Name_____________________________
First Exam 22 September 2003
PART I: MULTIPLE CHOICE (80 points; two points per question)
Circle the letter next to the single correct answer.
1. The function of capsular polysaccharides is to:
a) store surplus carbohydrate
b) anchor bacterial cells to the intestinal lining
c) protect against dehydration
d) keep the periplasmic space inflated at low osmotic pressure
e) keep out molecules of greater than 1,000 molecular weight
2. By weight, cells contain more of:
a) ribosomal RNA
b) messenger RNA
c) phospholipid
d) peptidoglycan
e) lipopolysaccharide
3. An organotroph uses organic molecules as:
a) source of reducing power
b) carbon source
c) source of energy
d) all of the above
e) none of the above
4. Prokaryotes differ from eukaryotes as follows:
a) prokaryotes have ribosomes made of 60S plus 40S subunits
b) eukaryotes have a single linear chromosome
c) prokaryotes have several linear chromosomes
d) eukaryotes have a single intron in each gene
e) prokaryotes have a single circular chromosome
5. The phospholipids found in biological membranes differ from fats as follows:
a) phospholipids have three fatty acids plus phosphate
b) phospholipids have three fatty acids plus glycerol
c) fats have three fatty acids plus glycerol
d) fats have two fatty acids, glycerol and glucosamine
e) fats have two fatty acids and two glycerols
6. Isoprenoids differ from the typical fatty acids found in membranes as follows:
a) isoprenoids usually have even numbers of carbon atoms
b) fatty acids are branched
c) isoprenoids are made from five carbon units
d) fatty acids usually have double bonds
e) fatty acids are long enough to cross the whole width of a typical biological
membrane
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MICRO 425 Name_____________________________

First Exam 22 September 2003

PART I: MULTIPLE CHOICE (80 points; two points per question) Circle the letter next to the single correct answer.

  1. The function of capsular polysaccharides is to: a) store surplus carbohydrate b) anchor bacterial cells to the intestinal lining c) protect against dehydration d) keep the periplasmic space inflated at low osmotic pressure e) keep out molecules of greater than 1,000 molecular weight
  2. By weight, cells contain more of: a) ribosomal RNA b) messenger RNA c) phospholipid d) peptidoglycan e) lipopolysaccharide
  3. An organotroph uses organic molecules as: a) source of reducing power b) carbon source c) source of energy d) all of the above e) none of the above
  4. Prokaryotes differ from eukaryotes as follows: a) prokaryotes have ribosomes made of 60S plus 40S subunits b) eukaryotes have a single linear chromosome c) prokaryotes have several linear chromosomes d) eukaryotes have a single intron in each gene e) prokaryotes have a single circular chromosome
  5. The phospholipids found in biological membranes differ from fats as follows: a) phospholipids have three fatty acids plus phosphate b) phospholipids have three fatty acids plus glycerol c) fats have three fatty acids plus glycerol d) fats have two fatty acids, glycerol and glucosamine e) fats have two fatty acids and two glycerols
  6. Isoprenoids differ from the typical fatty acids found in membranes as follows: a) isoprenoids usually have even numbers of carbon atoms b) fatty acids are branched c) isoprenoids are made from five carbon units d) fatty acids usually have double bonds e) fatty acids are long enough to cross the whole width of a typical biological membrane
  1. The long carbohydrate chains of peptidoglycan consist of alternating residues of: a) N-acetyl-heptosamine and N-acetyl-muriatic acid b) N-acetyl-glucosamine and N-acetyl-muramic acid c) N-acetyl-muramic acid and N-acetyl-galactose d) N-acetyl-glucosamine and N-acetyl-maltose e) N-acetyl-glucose and N-acetyl-mycolic acid
  2. Bacteria differ from eukaryotes as follows: a) bacteria do not use ATP for transporting nutrients b) bacteria sometimes use the proton motive force directly for transporting nutrients, but eukaryotes do not c) eukaryotes use the proton motive force directly for motility d) eukaryotes use ATP for sugar transport whereas bacteria use UTP e) bacteria can interconvert ATP and the proton motive force but eukaryotes cannot
  3. Escherichia coli possesses approximately how many genes of which approximately how many are expressed at any one time? a) 5000 genes of which 1000 are expressed at a time b) 6000 genes of which 2000 are expressed at a time c) 3000 genes of which 500 are expressed at a time d) 4000 genes of which 1000 are expressed at a time e) 3000 genes of which 1000 are expressed at a time
  4. Which of the following is used as the activated precursor for synthesis of phospholipids in bacteria? a) fatty acyl-CoA b) ADP-serine c) UDP-ethanolamine d) CDP-ethanolamine e) CDP-diglyceride
  5. When the temperature changes, bacteria regulate the fluidity of the cytoplasmic membrane by changing: a) the proportion of unsaturated fatty acids b) the proportion of hydroxylated fatty acids c) the ratio of phosphatidyl glycerol to phosphatidyl choline d) the proportion of cyclopropane fatty acids e) the ratio of phosphatidyl glycerol to phosphatidyl ethanolamine
  6. Penicillin is an analog of: a) Phosphoenol pyruvate b) D-glutamic acid c) Diaminopimelic acid d) D-Ala-D-Ala e) N-acetyl glucosamine
  7. Vancomycin inhibits cell wall synthesis by binding to: a) bactoprenol carrier lipid b) UDP-N-acetyl-glucosamine c) D-Ala-D-Ala

d) is made by E. coli to kill competing fungi which steal iron e) none of the above is true

  1. The porin proteins of E. coli a) are found in the cytoplasmic membrane b) are energized by the proton motive force c) form phosphorylated intermediates d) exclude molecules greater than about 700 in molecular weight e) have four subunits
  2. During protein export the SecA protein acts to: a) initiate translocation and consumes ATP b) guide proteins to the outer membrane c) remove the signal sequence d) prevent premature folding e) provide energy from the proton motive force
  3. During protein export the chaperonin, SecB, acts to: a) insert the signal sequence into the membrane b) guide proteins to the outer membrane c) carry proteins across the periplasmic space d) prevent premature folding of exported proteins e) provide energy for protein export by using the PMF directly
  4. The signal sequence for protein export has: a) a positively charged N-terminus b) a specific amino acid sequence c) a stretch of about 40 hydrophobic amino acids d) covalently attached fatty acids, including hydroxymyristic acid e) a binding site for ATP
  5. Choline: a) is converted to ethanolamine when E. coli grows at low osmotic pressure b) carries both a positive and a negative charge c) is found in bacterial lipids during stationary phase d) is transferred from phospholipids to membrane derived oligosaccharides when E. coli grows at low osmotic pressure e) is converted to glycine betaine when E. coli grows at high osmotic pressure
  6. When bacteria such as E. coli are shifted to high osmotic pressure the earliest response is: a) EnvZ protein phosphorylates OmpR protein b) the TolAB proteins energize the porins c) trehalose synthesis increases d) cyclic AMP is excreted e) potassium uptake increases
  7. The term sodium antiport means that: a) Both sodium and potassium are transported together b) Sodium uptake is coupled to uptake of a nutrient

c) The same transport protein moves sodium in one direction and another molecule in the opposite direction d) Sodium export is coupled to the excretion of a waste product e) Sodium is transported due to osmotic forces without the need for energy

  1. During the transport of lactose: a) ATP is used as an energy source b) phosphoenolpyruvate supplies energy c) the proton motive force is used directly as an energy source d) both ATP and the proton motive force are used as energy sources at different stages of uptake e) the TonB protein provides energy
  2. The sugar trehalose: a) is an isomer of lactose that consists of glucose plus galactose b) is synthesized by E. coli via UDP-glucose c) cannot be made by E. coli but is taken up at high osmotic pressure d) is made by degrading membrane derived oligosaccharides at high osmotic pressure e) is a longer analog of maltose that contains three glucose subunits
  3. The sensor in a two component regulatory system usually: a) binds cyclic AMP b) is located in the cytoplasmic membrane c) phosphorylates DNA using ATP d) splits GTP to GDP when it receives a signal e) binds to DNA upstream of RNA polymerase
  4. Transport of potassium into E. coli a) is controlled by OmpR and cyclic AMP b) is induced at low osmotic pressure c) is prevented by membrane derived oligosaccharides d) is due to binding of potassium by putrescine e) is controlled by a two component regulatory system
  5. Membrane derived oligosaccharides consist of: a) glucosamine chains with short fatty acids attached b) galactose chains with phosphoglycerol side chains c) glucose chains with phosphoglycerol side chains d) glucose residues attached to bactoprenol carrier lipid e) glucosamine chains with attached ethanolamine groups
  6. During the operation of the simple version of the phosphotransferase system: a) High energy phosphate is transferred from ATP to HPr via enzyme I b) High energy phosphate is transferred from HPr to enzyme II to the sugar c) An ADP group is transferred from HPr to enzyme II to the sugar d) High energy phosphate is transferred from PEP to HPr by enzyme II e) A UDP group is transferred from HPr to enzyme II to the sugar
  7. Inducer exclusion is the result of: a) inhibition of transport proteins by enzyme III (= IIA)

PART II: ESSAY QUESTIONS (20 points per question) Choose any ONE question. Answer by notes and diagrams. Remember that one diagram is worth a thousand words. Use only one side of the paper provided.

  1. Explain how the following nutrients get across the outer membrane of gram negative bacteria: a) glucose b) phosphate c) iron
  2. Describe the structure of the lipopolysaccharide (LPS) of gram-negative bacteria. How are LPS molecules held together? Where is the LPS located in the cell? What effect does bacitracin have on LPS assembly?
  3. Describe how a newly synthesized outer membrane protein, such as a porin is transported to its correct location in the cell. At what stage is ATP used and at what stage is the proton motive force used?
  4. Explain how (a) glucose and (b) lactose are transported across the cytoplasmic membrane of bacteria such as Escherichia coli. What are the major differences between these two systems?
  5. What is the difference between osmotic pressure and ionic strength? Explain how E. coli adapts itself to growing in medium of low osmotic pressure.
  6. Explain how glucose-6-phosphate is converted to pyruvate. Where are ATP and NADH produced? What are the two main controlling steps and how are they regulated?

MICRO 425 2nd Exam 2003 Name

Monday 27th October

PART I: MULTIPLE CHOICE (60 points) Circle the letter next to the single best answer. Two points per question.

  1. The most important factor in protection against oxygen toxicity is: a) superoxide dismutase b) peroxide dismutase c) catalase d) peroxide degradation by flavoproteins e) carotenoids trapping hydroxyl radicals
  2. During fermentation in E. coli an ATP is made: a) during conversion of pyruvate to formate b) during conversion of pyruvate to acetaldehyde c) during conversion of pyruvate to lactate d) during conversion of acetyl-CoA to alcohol e) during conversion of acetyl-CoA to acetate
  3. During anaerobic growth of E. coli pyruvate is split into: a) carbon dioxide and acetaldehyde by pyruvate dehydrogenase b) acetyl-CoA and formate by pyruvate formate lyase c) carbon dioxide and acetyl-CoA by pyruvate dehydrogenase d) lactate and formate by pyruvate formate lyase e) acetyl-CoA and carbon dioxide by pyruvate decarboxylase
  4. Pyruvate dehydrogenase and -ketoglutarate dehydrogenase both: a) convert NADP+^ to NADPH b) are regulated by attaching a phosphate group to the enzyme c) produce acetyl-CoA d) have lipoamide dehydrogenase as their third subunit e) are induced by their substrates
  5. The correct equation for the reduction of NADP is: a) NADP + 2H+^  NADPH+^ + H+ b) NADP+^ + H+^ + [H]  NADPH 2 c) NADP+^ + 2[H]  NADPH + H+ d) NADP + 2[H+] + 2e–^  NADPH 2 e) None of the above is correct
  6. In the Krebs cycle, citrate is made by condensing: a) Acetyl-CoA with oxaloacetate b) Acetyl-CoA with cis -aconitate c) Malonyl-CoA with pyruvate d) Malonyl-CoA with oxaloacetate e) Acetyl-CoA with glyoxylate
  7. The glyoxylate cycle is used to provide:

a) the proton channel of the ATP synthase supplies protons to the basal body of the flagellum instead of using them to make ATP b) protons are bound by acceptor groups on a rotating ring of protein found at the base of the flagellum in the cytoplasmic membrane c) protons are bound by acceptor groups on a stationary protein ring at the base of the flagellum which is embedded in the cell wall d) sodium ions are used to operate the flagellum and later they are exchanged for protons by a separate transport protein e) protons move from the basal body down the inside of the flagellum and exit into the culture medium

  1. When the ATP synthase makes ATP by using the proton motive force: a) protons go through a channel in the F 0 subunit b) ADP is bound by the F 0 subunit c) two phosphate groups are added to AMP by the  and  subunits d) the F 1 subunit expels sodium ions across the membrane e) the F 0 subunit releases the ATP on the inside of the cytoplasmic membrane
  2. The transmembrane charge potential () may be measured using: a) an NMR machine and phosphate b) a weak acid c) a pH meter and a giant E. coli cell d) an uncoupler plus potassium ions e) a lipophilic cation
  3. Valinomycin: a) is an uncoupler b) blocks the proton channel of the ATP synthetase c) exchanges Na+^ for K+ d) allows chloride ions to exit from cells e) none of the above is true
  4. The ArcAB regulatory system: a) induces pyruvate dehydrogenase in the presence of air b) represses most Krebs cycle enzymes in the absence of air c) induces nitrate and fumarate reductase in the absence of air d) represses nitrate and fumarate reductase in the presence of air e) induces the cytochrome d complex in the presence of air
  5. When the electron transport chain to nitrate is operating, electrons flow from the quinone to: a) FeS groups  cytochrome b  molybdenum  nitrate b) cytochrome b  FeS groups  molybdenum  nitrate c) cytochrome b  molybdenum  FeS groups  nitrate d) cytochrome b  cytochrome c  molybdenum  nitrate e) FeS groups  cytochrome b  cytochrome c  nitrate
  6. Selenium takes part in anaerobic respiration as follows: a) selenium is found in a tetrapyrrole ring in nitrite reductase b) selenium is found as selenomethionine in hydrogenase

c) formate dehydrogenase contains selenium as selenocysteine d) nitrate reductase contains selenium bound to molybdenum in its active site e) none of the above is true

  1. During anaerobic respiration E. coli can convert: a) nitrate to nitrogen b) succinate to fumarate c) formate to succinate d) TMAO to trimethyl amine e) TMAO to trimethyl acetate
  2. The tetrapyrrole ring of chlorophyll has: a) an Fe atom in the center b) a Ni atom in the center c) a Co atom in the center d) an isoprenoid tail, unlike heme e) an FeS group in the center
  3. The main difference in the mechanism of photosynthesis between cyanobacteria and purple bacteria is: a) cyanobacteria use rhodopsin and only generate PMF b) cyanobacteria use light to reduce NAD instead of NADP c) purple bacteria have both rhodopsin and halorhodopsin d) purple bacteria use their purple membrane for respiration e) cyanobacteria release oxygen during photosynthesis
  4. The reaction centre complex of purple photosynthetic bacteria contains: a) bacteriochlorophyll, phylloquinone and bacteriopheophytin b) bacteriochlorophyll, ubiquinone and bacteriopheophytin c) bacteriochlorophyll, cytochrome c and bacteriopheophytin d) bacteriopheophytin, ubiquinone and cytochrome b e) bacteriopheophytin, phylloquinone and cytochrome b
  5. Oxygen release during photosynthesis by chloroplasts is due to: a) the S protein, which has two Mn atoms b) the D protein, which has two Mo atoms c) cytochrome f plus plastocyanin d) cytochrome oxidase working backwards e) carbon dioxide reductase plus coenzyme B
  6. When retinaldehyde absorbs a photon: a) it is released from the protein to which it was bound b) it transfers an electron to a quinone c) it changes from the trans to the cis isomer d) it transfers an electron to cytochrome b e) it changes from the disulfide form to the sulfhydryl form
  7. In archebacterial membranes, an ether linkage connects glycerol to: a) isoprenoid hydrocarbon chains b) the phosphate of phospholipids c) fatty acids
  1. What is anaerobic respiration? Give three examples of compounds that may be used as alternative electron acceptors by bacteria such as E. coli. What are they converted into when used? Show the electron transport chain for one of your chosen electron acceptors. How does Fnr protein regulate anaerobic respiration?
  2. Explain how Halobacterium generates the proton motive force using light as an energy source. Where does Halobacterium live and what does Halobacterium do with the excess energy it gets from light?
  3. Explain how the proton motive force is converted into ATP. Explain how the proton motive force is used to drive the flagella in bacteria.
  4. Describe how cyanobacteria and chloroplasts generate the proton motive force from light energy. How is NADPH made? How is oxygen released?
  5. Outline the pathways by which Escherichia coli converts pyruvate to carbon dioxide and NADH when growing in air. Outline how these pathways are regulated.
  6. What happens to pyruvate when Escherichia coli is growing by fermentation in the absence of oxygen? Why are different enzymes used to split pyruvate anaerobically and aerobically?

MICRO 425 FINAL EXAM Thursday 11th Dec 2003

SECTION I MULTIPLE CHOICE (150 points)

  1. Some bacteria possess alternative nitrogenase systems in which: a) iron is replaced by cobalt b) molybdenum is replaced by tungsten c) nitrogen is replaced by acetylene d) iron is replaced by manganese e) molybdenum is replaced by vanadium
  2. Leghemoglobin is synthesized by: a) Cyanobacteria that make oxygen, in order to protect their nitrogenase b) Jointly by Rhizobium , which makes the globin, and the plant, which makes the heme c) Jointly by Rhizobium , which makes the heme, and the plant, which makes the globin d) Klebsiella when it respires anaerobically using nitrate e) All nitrogen fixing bacteria when oxygen is present
  3. In nitrogen fixing root nodules, the plant provides the bacteria with: a) amino acids b) glucose and fructose c) starch d) succinate, oxaloacetate and malate e) purines and pyrimidines
  4. The role of iron in the active site of nitrogenase is to: a) pass electrons to the molybdenum b) bind oxygen by its triple bond c) receive reducing equivalents from ferredoxin d) hydrolyze ATP to increase reducing power e) weaken the nitrogen triple bond
  5. Nitrogenase consumes ATP because: a) ATP regulates nitrogen fixation b) energy is consumed to generate a more powerful redox potential c) conversion of nitrogen to ammonia consumes energy d) the above statement is untrue: nitrogenase uses GTP not ATP e) ATP is used to protect the cells against ammonia toxicity
  6. Nitrogenase is usually assayed by measuring the conversion of: a) nitrogen to ammonia b) ethylene to methane c) carbon monoxide to methane d) nitrate to nitrite e) acetylene to ethylene
  7. The NifLA regulatory system operates as follows: a) NifA responds to lack of ammonia by phosphorylating NifL b) NifL switches off the nif genes in the presence of oxygen c) NifA acts as a repressor for the nif genes d) NifL acts as a sensor for glutamine levels in the cell e) none of the above is true
  8. Genes involved in nitrogen metabolism are usually controlled as follows: a) They are switched off by a repressor that binds ammonia b) They are switched on by an activator that binds ketoglutarate c) They require an alternative sigma factor, RpoN or NtrA for expression d) They are switched off in the presence of oxygen e) none of the above is true

d) certain clay minerals e) magnesium or molybdenum ions

  1. Some stony meteorites contain organic material from outer space. This generally includes: a) RNA containing L-ribose b) a mixture of D- and L-amino acids c) derivatives of DNA with unusual bases d) L-glucose-phosphate e) silicon analogs of amino acids
  2. When phospholipids vesicles are used to illustrate primeval metabolism with trapped enzymes: a) C16-C18 fatty acids are needed to keep enzymes trapped but will allow small molecules in and out b) C14 fatty acids are needed to keep enzymes trapped but will allow small molecules in and out c) positively charged proteins must be added to the phospholipids to prevent soluble enzymes getting out d) negatively charged RNA must be added to the phospholipids to prevent soluble enzymes getting out
  3. Colicin tolerant mutants: a) have lost the receptor for the colicin b) are defective in energizing uptake of the colicin c) possess an immunity protein d) inactivate colicin by adding ADP-ribose e) inactivate the colicin by adding an acetyl group
  4. Colicin resistant mutants: a) have lost the receptor for the colicin b) possess an immunity protein c) are defective in energizing uptake of the colicin d) inactivate colicin by adding ADP-ribose e) inactivate the colicin by adding an acetyl group
  5. Chromosomal mutations tfor resistance to streptomycin and other aminoglycoside antibiotics often result in: a) alteration of the ribosome b) inhibition of antibiotic uptake c) adding a phosphate group to the antibiotic d) cleavage of bonds in the antibiotic molecule e) any of the above - depending on the mutation
  6. The two anthrax toxins: a) act by degrading cyclic AMP and cyclic GMP b) are neutralized by ciprofloxacin c) both use the same recognition subunit, the PA protein d) inactivate elongation factor EF2 and cleave ribosomal RNA e) are encoded by genes on a lysogenic bacterial virus that only infects a few strains of Bacillus
  7. When cholera toxin binds to the target cell: a) its A subunit recognizes a protein on the eukaryotic cell surface b) its B subunit binds to ganglioside GM1 in the eukaryotic cell membrane

c) the B subunits make a channel through the membrane of eukaryotic cells that allows the A subunit to enter d) four B subunits are left outside and one enters bound to the A subunit by a disulfide bond e) none of the above is true

  1. Pathogenicity islands: a) contain the genes for cholera toxin and diphtheria toxin b) often have a different percentage GC from the rest of the chromosome c) are zones on the host cell membrane involved in attaching pathogenic bacteria to host cells d) are usually found on plasmids or bacteriophages e) are regions of specialized lipopolysaccharide on the bacterial cell surface involved in attaching pathogenic bacteria to their host cells
  2. Cholera toxin and diphtheria toxin both act by inactivating: a) a GTP binding protein by adding ADP-ribose b) a UTP binding protein by adding GDP-ribose c) a CTP binding protein by removing AMP d) a CTP binding protein by adding ADP-ribose e) a GTP binding protein by removing AMP
  3. Plasmid encoded resistance to tetracycline is due to: a) acetylation of ribosomal proteins b) acetylation of the antibiotic c) phosphorylation of the antibiotic d) pumping antibiotic out e) hydrolysis of tetracycline into two fragments
  4. Plasmid encoded resistance to chloramphenicol is due to: a) alteration of the ribosome b) inhibition of antibiotic uptake c) adding an acetyl group d) adding ADP-ribose e) any of the above - depending on which plasmid
  5. Antibiotic resistance plasmids: a) usually exist in multiple copies b) only encode enzymes which are secreted into the periplasmic space c) only carry resistance to a single antibiotic on each type of plasmid d) can often transfer themselves from cell to cell e) are often induced by UV light
  6. The enzyme beta-lactamase attacks penicillin derivatives as follows: a) it breaks open the C-N bond in the four membered ring b) it removes the side chain from the penicillin nucleus c) it removes the sulfur from the five membered ring d) it splits the four membered ring off from the rest of the penicillin nucleus e) none of these is the correct mechanism
  7. Mobilizable plasmids are those which can: a) transfer themselves from one bacterial cell to another b) mobilize the host cell chromosome c) mobilize transposons to jump from chromosome to plasmid d) move toxic proteins from bacterial cells to animal cells e) move from cell to cell if helped by a transferable plasmid
  1. Which of the following amino acids have hydrophobic side chains? a) isoleucine and glycine b) methionine and lysine c) serine and phenylalanine d) leucine and threonine e) valine and tryptophan
  2. The maximum velocity of an enzyme is: a) the rate when all of the active sites are saturated with substrate b) the rate when the substrate concentration is half the Km c) the rate when the enzyme is working at its optimum pH d) the rate when the reaction has reached a steady state e) none of the above
  3. Beta-mercaptoethanol helps denature proteins by: a) disrupting hydrogen bonds b) disrupting disulfide bonds c) providing negative charges d) solubilizing hydrophobic groups e) none of the above is correct
  4. Allosteric enzymes are those which: a) obey Michaelis Menten kinetics b) possess multiple identical subunits c) can use both the D- and the L-form of their substrate d) change shape upon binding a small molecule e) are only stable inside a cell, away from molecular oxygen
  5. A racemase is an enzyme that: a) interconverts cis and trans isomers b) possesses multiple identical subunits c) can use both the D- and the L-form of the substrate d) interconverts the D- and the L-form of the substrate e) opens or closes the ring of a sugar
  6. A kinase is an enzyme that: a) interconverts cis and trans isomers b) obeys Michaelis Menten kinetics c) adds a phosphate group to the substrate d) acts by concerted acid base catalysis e) uses a histidine residue at the active site
  7. A mutase is an enzyme that: a) interconverts cis and trans isomers b) interconverts the D- and the L-form of the substrate c) adds a sulfate group to the substrate d) interconverts sugar isomers e) moves a phosphate group from one site to another on the substrate
  8. The lower the Km of an enzyme for its substrate a) The lower the affinity of the enzyme for that substrate b) The higher the concentration of a competitive inhibitor needed to reduce the reaction rate by 2-fold c) The slower the reaction proceeds when the substrate concentration is high d) The more the equilibrium constant is shifted in favor of the product
  1. The signal sequence a) has a negative charge at the very end b) consists of mostly hydrophilic amino acids c) is recognized by the SecB protein d) is found at the carboxyl end of proteins to be exported e) is cleaved off by the leader peptidase
  2. Lipopolysaccharide is found a) only in gram-positive bacteria b) only in the outer half of the inner membrane c) only in the inner half of the outer membrane d) in both halves of the outer membrane e) only in the outer half of the outer membrane
  3. Penicillin is an analog of: a) D-Ala-D-Ala b) N-acetyl muramic acid c) Diaminopimelic acid d) Phosphoenol pyruvate e) N-acetyl glucosamine
  4. The porin proteins of E. coli a) are found in the cytoplasmic membrane b) are energized by the proton motive force c) form phosphorylated intermediates d) exclude molecules greater than about 700 in molecular weight e) form tetramers
  5. The TonB protein: a) provides energy for iron transport b) removes the signal sequence from exported proteins c) senses the osmotic pressure in the culture medium d) recognizes and binds to siderophores e) protects cells against colicins
  6. The cross-linking of two peptidoglycan chains requires: a) hydrolysis of GTP b) the proton motive force c) the outer membrane lipoprotein d) cleavage of the signal sequence e) breaking the D-Ala-D-Ala linkage
  7. Bactoprenol phosphate is involved in the assembly of: a) iron transport systems in the outer membrane b) peptidoglycan c) outer membrane lipoprotein d) membrane derived oligosaccharides e) none of the above
  8. The sugar trehalose: a) is an isomer of lactose that consists of glucose plus galactose b) is synthesized by E. coli via ADP-glucose c) is made by E. coli only at high osmotic pressure d) is made by degrading membrane derived oligosaccharides at high osmotic pressure e) is a longer analog of maltose that contains three glucose subunits
  9. Membrane derived oligosaccharides are: