Question

1. Why does E. coli need both DNA polymerase III and DNA polymerase I?

a. The DNA replication is bidirectional; one polymerase is used for each direction.

b. Each polymerase is specific for only one strand of DNA. DNA polymerase III acts only on the leading strand, and DNA polymerase I acts only on the lagging strand.

c. Only DNA polymerase I has proofreading ability.

d. DNA polymerase III lacks the 5' → 3' exonuclease activity needed to remove RNA primers.

2. The replication of DNA is ________ because ________.

a. semiconservative; one strand of parental DNA is retained in each daughter DNA.

b. semiconservative; each daughter molecule has two new strands copied from the parental DNA template

c. conservative; each daughter molecule has two new strands copied from the parental DNA template.

d. conservative; one strand of parental DNA is retained in each daughter DNA.

3. Active transport proteins in biological membranes are

a. always transporting Ca2+ ions.

b. never driven by concentration gradients.

c. never driven by ATP to ADP conversion.

d. sometimes driven by concentration gradients.

4. Why should it not be surprising that for many cells water requires a protein for its transport across a membrane?

a. The transport protein is needed to prevent the hydrolysis of the phospholipid chains as water crosses the membrane.

b. Water is very polar which inhibits its free diffusion across the membrane.

c. All molecules require transport proteins to cross a membrane.

d. There is never a concentration gradient for water across the membrane to drive its transport.

5. The conversion of pyruvate to lactate in muscles also causes the ________.

a. reduction of NAD+.

b. oxidation of NAD+

c. oxidation of NADH

d. reduction of oxygen to water.

6. ATP is a cosubstrate of the enzyme PFK-1. In most species ATP is also an inhibitor of PFK-1 at higher concentrations. Which statement below would provide a suitable explanation?

a. PFK-1 must be phosphorylated by ATP in the active site and the phosphorylated PFK-1 must be the less active form.

b. There are two sites on PFK-1 that bind ATP. One is the active site; the other is the regulatory site where inhibition occurs allosterically.

c. ATP actually activates the reverse of the reaction preceding the PFK-1 step in the pathway. It likely has no direct effect on PFK-1.

d. There must be another cofactor interacting with ATP at high concentrations to achieve inhibition of PFK-1.

7. Briefly describe two ways for deactivation of GPCR-signaling.

Answer 1

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. Why does E. coli need both DNA polymerase III and DNA polymerase I?

a. The DNA replication is bidirectional; one polymerase is used for each direction.

b. Each polymerase is specific for only one strand of DNA. DNA polymerase III acts only on the leading strand, and DNA polymerase I acts only on the lagging strand.

c. Only DNA polymerase I has proofreading ability.

d. DNA polymerase III lacks the 5' → 3' exonuclease activity needed to remove RNA primers.-answer

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The replication of DNA is ________ because ________.

Answer------*A. semiconservative; one strand of parental DNA is retained in each daughter DNA

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. The conversion of pyruvate to lactate in muscles also causes the ________.

a. reduction of NAD+.

b. oxidation of NAD+ .---------- oxidation of NAD+

c. oxidation of NADH-

d. reduction of oxygen to water.

6. ATP is a cosubstrate of the enzyme PFK-1. In most species ATP is also an inhibitor of PFK-1 at higher concentrations. Which statement below would provide a suitable explanation?

b. There are two sites on PFK-1 that bind ATP. One is the active site; the other is the regulatory site where inhibition occurs allostericall------------------ANSWER

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DNA replication is semi-traditionalist on the grounds that every helix that is made contains one strand from the helix from which it was duplicated. The replication of one helix brings about two little girl helices each of which contains one of the first parental helical strands.

replication of DNA is (A) semiconservative, one strand of parental DNA is held in every little girl DNA. The unfastening of twofold stranded DNA into two single strands permits polymerases to utilize every strand as a layout to manufacture new strands-the two new strands of DNA will each be assembled straightforwardly onto one of the strands from the first DNA. This is called semi-moderate on the grounds that the little girls each hold an unaltered strand of the mother DNA, additionally a completely recently incorporated strand of DNA. B is off base since it portrays a non-moderate replication-none of the first DNA is in the little girl atoms. C is mistaken hence

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Pyruvate is the terminal electron acceptor in lactic corrosive maturation

At the point when adequate oxygen is not present in the muscle cells for further oxidation of pyruvate and NADH delivered in glycolysis, NAD+ is recovered from NADH by decrease of pyruvate to lactic corrosive. Pyruvate is changed over to lactic corrosive by the compound lactate dehydrogenase. The standard free vitality change of the response is - 25.1 kJ/mol.

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Pol I

Prokaryotic family A polymerases incorporate the DNA polymerase I (Pol I) catalyst, which is encoded by the polA quality and pervasive among prokaryotes. This repair polymerase is included in extraction repair with both 3'- 5' and 5'- 3' exonuclease action and handling of Okazaki sections produced amid slacking strand amalgamation. Pol I is the most plenteous polymerase, representing >95% of polymerase movement in E. coli; yet cells lacking Pol I have been discovered recommending Pol I action can be supplanted by the other four polymerases. Pol I includes ~15-20 nucleotides for each second, in this way indicating poor processivity. Rather, Pol I begins including nucleotides at the RNA primer:template intersection known as the source of replication (ori). Around 400 bp downstream from the beginning, the Pol III holoenzyme is collected and assumes control replication at a profoundly processive speed and nature.

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Pol II

DNA polymerase II, a family B polymerase, is a polB quality item otherwise called DinA. Pol II has 3'- 5' exonuclease action and partakes in DNA repair, replication restart to sidestep injuries, and its phone nearness can bounce from ~30-50 duplicates for every phone to ~200-300 amid SOS acceptance. Pol II is additionally thought to be a reinforcement to Pol III as it can associate with holoenzyme proteins and expect an abnormal state of processivity. The primary part of Pol II is thought to be the capacity to direct polymerase movement at the replication fork and aided slowed down Pol III sidestep terminal jumbles.

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Pol III

DNA polymerase III holoenzyme is the essential chemical required in DNA replication in E. coli and has a place with family C polymerases. It comprises of three gatherings: the pol III center, the beta sliding clasp processivity calculate, and the brace stacking complex. The center comprises of three subunits: α, the polymerase action center point, ɛ, exonucleolytic editor, and θ, which may go about as a stabilizer for ɛ. The holoenzyme contains two centers, one for every strand, the slacking and driving. The beta sliding clasp processivity calculate is additionally present copy, one for every center, to make a cinch that encases DNA taking into account high processivity. The third get together is a seven-subunit (τ2γδδ′χψ) cinch loader complex. Late research has arranged Family C polymerases as a subcategory of Family X with no eukaryotic reciprocals.

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Pol IV

In E. coli, DNA polymerase IV (Pol 4) is a mistake inclined DNA polymerase required in non-focused on mutagenesis. Pol IV is a Family Y polymerase communicated by the dinB quality that is exchanged on through SOS enlistment brought on by slowed down polymerases at the replication fork. Amid SOS acceptance, Pol IV creation is expanded ten times and one of the capacities amid this time is to meddle with Pol III holoenzyme processivity. This makes a checkpoint, stops replication, and permits time to repair DNA sores by means of the proper repair pathway. Another capacity of Pol IV is to perform translesion blend at the slowed down replication fork like, for instance, bypassing N2-deoxyguanine adducts at a speedier rate than transversing undamaged DNA. Cells lacking dinB quality have a higher rate of mutagenesis brought on by DNA harming operators.

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Pol V:

DNA polymerase V (Pol V) is a Y-family DNA polymerase that is included in SOS reaction and translesion combination DNA repair mechanisms.Transcription of Pol V by means of the umuDC qualities is very controlled to create just Pol V when harmed DNA is available in the cell producing a SOS reaction. Slowed down polymerases causes RecA to tie to the ssDNA, which causes the LexA protein to autodigest. LexA then loses its capacity to quell the translation of the umuDC operon. The same RecA-ssDNA nucleoprotein posttranslationally changes the UmuD protein into UmuD' protein. UmuD and UmuD' frame a heterodimer that cooperates with UmuC, which thus actuates umuC's polymerase reactant movement on harmed DNA