more prac

Question 1

In DNA the phosphate groups are on the outside of the helix. Why does this stabilize the structure?

hydrogen bonding with itself

ionic interactions with the solvent

covalent binding to the solvent

It does not stabilize the structure.

Answer 1

ionic interactions with the solvent

Question 2

What is the cause of the overall negative charge of a molecule of DNA?

hydrogen bonding between base pairs

the sugars

the phosphate backbone

the antiparallel orientation of the DNA

Answer 2

the phosphate backbone

Question 3

Cell signaling and cell membranes are examples of functions performed by which biomolecule?

amino acid

nucleotide

simple sugar

fatty acid

Answer 3

fatty acid

Question 4

If the equilibrium constant (Keq) is greater than 1, which direction will the reaction proceed?

spontaneously to reactants

neither direction

spontaneously to products

Not enough information is given to determine the direction of reaction.

Answer 4

spontaneously to products

Question 5

Under what conditions could a biological reaction spontaneously proceed to reactants if the mc028-1.jpg?

Reactant concentrations are greater than product concentrations.

Product concentrations are greater than reactant concentrations.

Reactant concentrations are equal to product concentrations.

There are no conditions where this could happen.

Answer 5

Product concentrations are greater than reactant concentrations.

Question 6

The interaction between an amino group and a carboxylate group is best characterized as

hydrogen bonds.

ionic interactions.

van der Waals interactions.

a covalent bond.

Answer 6

ionic interactions.

Question 7

The K+ ion concentration in a DNA sample is increased from 50 mM to 100 mM. The Tm will

increase.

remain the same.

decrease.

vary unpredictably.

Answer 7

increase.

Question 8

During eukaryotic DNA condensation, nucleosomes are packed together to form

histones.

chromatin.

chromosomes.

genes.

Answer 8

chromatin.

Question 9

Polycistronic genes that contain a coding sequence for proteins that are only involved in one biochemical process are called

exons.

introns.

promoters.

operons.

Answer 9

operons.

Question 10

In the eukaryotic cell, the coding sequences on a gene are referred to as

exons.

operons.

introns.

promoter.

Answer 10

exons.

Question 11

When a gene sequence is cloned using mRNA, which enzyme is used to seal the single-strand gaps left behind in the second strand of DNA?

DNA methylase

restriction endonucleases

reverse transcriptase

DNA ligase

Answer 11

DNA ligase

Question 12

When DNA is sequenced, which analytical technique is used to separate the chain-terminated DNA fragments?

blue-white screening

gel electrophoresis

antibiotic resistance

fluorescent labeling

Answer 12

gel electrophoresis

Question 13

This method of analyzing RNA transcripts relies on a predetermined collection of complementary DNA sequences.

plasmid cloning

viral transduction

RNA-seq

gene-expression microarrays

Answer 13

gene-expression microarrays

Question 14

Which method of analyzing RNA transcripts is considered to be an unbiased approach because it does not use a predetermined collection of complementary DNA sequence?

plasmid cloning

viral transduction

RNA-seq

gene-expression microarrays

Answer 14

RNA-seq

Question 15

Use the table below to determine how many possible RNA sequences could code for the dipeptide Pro-Ala.

1

16

8

64

Answer 15

16

Question 16

All of the following are types of protein secondary structure EXCEPT

B-sheets.

a-helixes.

B-helixes.

B-turns.

Answer 16

B-helixes.

Question 17

Which statement regarding protein secondary structures is correct?

B-strands allow a-helices to interact with one another.

Protein a-helices alternate with B-strands in stabilizing protein structure.

Protein a-helices and B-strands differ in that a-helices are stabilized by intrahelical hydrogen bonds, whereas B-strands are stabilized by hydrogen bonds across adjacent strands.

Protein a-helices are left handed, whereas B-sheets are right handed in arrangement.

Answer 17

Protein a-helices and B-strands differ in that a-helices are stabilized by intrahelical hydrogen bonds, whereas B-strands are stabilized by hydrogen bonds across adjacent strands.

Question 18

What is the minimum number of amino acids needed to make one turn of an a-helix?

3

4

6

7

Answer 18

4

Question 19

How many B-turns or B-loops are required to construct a B-sheet composed of four antiparallel strands?

0

3

4

5

Answer 19

3

Question 20

The protein fold known as the Rossman fold is found in proteins that commonly bind

a-helices.

nucleotides.

cytochromes.

membranes.

Answer 20

nucleotides.

Question 21

At the interface between subunits of a protein with quaternary structure, which of the following interactions between amino acid side chains would contribute to the stability of the dimer?

glutamate–aspartate.

leucine–aspartate.

glutamate–lysine.

phenylalaninelysine.

Answer 21

glutamate–lysine.

Question 22

In multi-subunit proteins, such as hemoglobin, the different subunits are usually bound to one another by all of the following EXCEPT

hydrogen bonds.

electrostatic interactions.

hydrophobic interactions.

peptide bonds.

Answer 22

peptide bonds.

Question 23

Which gives rise to a favorable enthalpic (delta S) driving force for protein folding?

The lining up of hydrogen bonds as the protein folds.

The limiting of possible conformations as the protein folds.

The decrease in ordered water molecules as hydrophobic amino acids pack together.

The stabilization caused by favorable electrostatic interactions of amino acid side chains.

Answer 23

The decrease in ordered water molecules as hydrophobic amino acids pack together.

Question 24

After centrifugation, there is a 10% decrease in activity and a 75% decrease in total protein. What is purification of the target protein?

0. 28-fold
1. 3-fold
2. 6-fold
3. 5-fold

Answer 24

3.6-fold

Question 25

In tandem mass spectrometry, the first mass spectrometer determines the nuclear spin of the atoms. determines the mass of peptide subfragments. uses bioinformatics to compare the masses of the peptides. uses electrospray ionization to select peptide fragments.

Answer 25

uses electrospray ionization to select peptide fragments. FIRST = spray

Question 26

In tandem mass spectrometry, the second mass spectrometer determines the nuclear spin of the atoms. determines the mass of peptide subfragments. uses bioinformatics to compare the masses of the peptides. uses electrospray ionization to select peptide fragments.

Answer 26

determines the mass of peptide subfragments. SECOND = "sub"(fragments)

Question 27

During the production of polyclonal antibodies, how are the antigen-specific antibodies purified? dialysis gel electrophoresis size exclusion chromatography affinity chromatography

Answer 27

affinity chromatography

Question 28

In monoclonal antibody generation, the cells that produce the antibody in the animal are located in __________ cells. heart spleen liver red blood

Answer 28

spleen

Question 29

The part of the Western blot that contains the protein-specific recognition and facilitates the antigen-antibody interactions is the SDS-PAGE gel. primary antibody. tertiary antibody. filter membrane.

Answer 29

primary antibody.

Question 30

An enzyme that requires the coenzyme nicotinamide adenine dinucleotide belongs to which enzyme class? transferases isomerases ligases oxidoreductases

Answer 30

oxidoreductases

Question 31

All of the following are common catalytic reaction mechanisms in enzyme active sites EXCEPT __________ catalysis. acid–base covalent metal ion van der Waals

Answer 31

van der Waals

Question 32

When a nucleophile present in the enzyme attacks an electrophilic substrate to form an enzyme-substrate intermediate, this is an example of __________ catalysis. covalent acid–base metal ion hydrophobic

Answer 32

covalent

Question 33

The regulation of a biomolecule through the addition or removal of a molecular tag involves __________ reactions. coenzyme-dependent redox metabolite transformation isomerization reversible covalent modification

Answer 33

reversible covalent modification

Question 34

Which type of reaction does not change the molecular formula of the product compared with that of the substrate? isomerization condensation reduction hydrolysis

Answer 34

isomerization iso = does not change

Question 35

Which type of interaction is more likely to be found between an enzyme and an irreversible inhibitor? covalent bond hydrogen bond ionic interaction van der Waals interaction

Answer 35

covalent bond

Question 36

A mixture of enzyme and inhibitor is run through a size-exclusion chromatography column. The activity of the enzyme is assessed before and after the chromatography. The enzyme has more activity after the chromatography step. Which of the following is true? The enzyme was not eluted fully from the column. The enzyme was denatured during chromatography. The inhibitor is a reversible inhibitor. The inhibitor is an irreversible inhibitor.

Answer 36

The inhibitor is a reversible inhibitor.

Question 37

An inhibitor that binds only to the ES complex and not free enzyme is known as a(n) __________ inhibitor. irreversible competitive uncompetitive mixed

Answer 37

uncompetitive

Question 38

A Lineweaver–Burk plot displays parallel lines for an enzyme in the absence and presence of increasing amounts of an inhibitor. The inhibitor in this experiment binds both the free enzyme and the ES complex. is competitive. alters the Km but not the vmax. is uncompetitive.

Answer 38

is uncompetitive.

Question 39

Which protein is part of the TNF receptor–activated programmed cell death signaling pathway? FADD TRAF2 NFκB-inducing kinase IKK

Answer 39

FADD

Question 40

Phosphorylation of which of the following is necessary for the increased expression of antiapoptotic genes? RIP TNF receptor FADD IKK

Answer 40

IKK

Question 41

Which of the following is an energy conversion pathway? urea cycle citrate cycle nitrogen fixation and assimilation fatty acid degradation and synthesis

Answer 41

citrate cycle

Question 42

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change (delta G) of 23.8 kJ/mol. Under what conditions (encountered in erythrocytes) will the free-energy change (delta G) be negative, enabling the reaction to proceed to products? The free-energy change will be negative if the concentrations of the two products are high relative to that of fructose 1,6-bisphosphate. The reaction will not go to the right spontaneously under any conditions because the delta G is positive. Under standard conditions, enough energy is released to drive the reaction to the right. The free-energy change will be negative when there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products.

Answer 42

The free-energy change will be negative when there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products.

Question 43

In two turns of the citrate cycle, how many electrons are transferred from the citrate cycle intermediates to NAD+ and FAD? 4 8 12 16

Answer 43

16

Question 44

The primary function of the citrate cycle is to oxidize glucose. pyruvate. acetyl-CoA. citrate.

Answer 44

acetyl-CoA.

Question 45

Which of the following is a reactant in the net reaction of the citrate cycle? CO2 H2O GTP CoA

Answer 45

H2O

Question 46

Which molecule in the net reaction of the citrate cycle contributes to the inhibition of pyruvate dehydrogenase? FAD H2O H+ NADH

Answer 46

NADH

Question 47

Coenzyme A is derived from which of the following vitamins? thiamine pantothenic acid riboflavin niacin

Answer 47

pantothenic acid

Question 48

Which vitamin is the precursor to the coenzyme that functions as a reductant in the pyruvate dehydrogenase complex in the final step of the reaction? thiamine pantothenic acid riboflavin niacin

Answer 48

riboflavin

Question 49

How would a high NADH to NAD+ ratio be expected to affect the pyruvate dehydrogenase reaction? The pyruvate dehydrogenase kinase enzyme activity would increase, resulting in an increase in pyruvate dehydrogenase activity. The last step of the pyruvate dehydrogenase reaction is blocked, resulting in a decrease in activity. The E1 subunit is phosphorylated by pyruvate dehydrogenase kinase, and the catalytic activity of pyruvate dehydrogenase decreases. The pyruvate dehydrogenase phosphatase-1 enzyme would increase, resulting in pyruvate dehydrogenase activation at an accelerated rate.

Answer 49

The last step of the pyruvate dehydrogenase reaction is blocked, resulting in a decrease in activity.

Question 50

How would an increased level of acetyl-CoA be expected to affect the pyruvate dehydrogenase reaction? The pyruvate dehydrogenase kinase enzyme activity would increase, resulting in an inhibition of pyruvate dehydrogenase activity. The last step of the pyruvate dehydrogenase reaction would be blocked, resulting in a decrease in activity. The E1 subunit would be phosphorylated by pyruvate dehydrogenase kinase, and the catalytic activity of pyruvate dehydrogenase would decrease. The pyruvate dehydrogenase phosphatase-1 enzyme would increase, resulting in pyruvate dehydrogenase activation at an accelerated rate.

Answer 50

The pyruvate dehydrogenase kinase enzyme activity would increase, resulting in an inhibition of pyruvate dehydrogenase activity.

Question 51

The reaction catalyzed by __________is the most endergonic reaction in the citrate cycle. fumarase succinate dehydrogenase malate dehydrogenase aconitase

Answer 51

malate dehydrogenase

Question 52

The reaction catalyzed by __________ is likely to be reversible under cellular conditions according to the delta G. malate dehydrogenase citrate synthase succinate dehydrogenase a-ketoglutarate dehydrogenase

Answer 52

succinate dehydrogenase REVERSIBLE SUCC

Question 53

A high concentration of which molecule would inhibit citrate synthase in the citrate cycle? AMP ADP NAD+ ATP

Answer 53

ATP

Question 54

Which anaplerotic reaction balances the input of oxaloacetate with acetyl-CoA in the citrate cycle by converting pyruvate into oxaloacetate? pyruvate carboxylase malate dehydrogenase malic enzyme pyruvate kinase

Answer 54

pyruvate carboxylase

Question 55

The anaplerotic reaction catalyzed by pyruvate carboxylase requires which coenzyme? niacin biotin riboflavin thiamine

Answer 55

biotin

Question 56

Which citrate cycle intermediate is siphoned off the citrate cycle during starvation? succinyl-CoA malate a-ketoglutarate fumarate

Answer 56

malate

Question 57

Which citrate cycle metabolite is used as a precursor for heme biosynthesis? succinyl Co-A oxaloacetate a-ketoglutarate malate

Answer 57

succinyl Co-A heme bio succ

Question 58

Predict the fate of a-ketoglutarate when it is not used in the citrate cycle. cholesterol synthesis heme synthesis gluconeogenesis amino acid synthesis

Answer 58

amino acid synthesis

Question 59

What is the location of the electron transport system protein called cytochrome c? cytoplasm mitochondrial matrix inner mitochondrial membrane intermembrane space

Answer 59

intermembrane space cyto to space

Question 60

What would happen to a mutated ATP synthase enzyme where the proton binding aspartate residue on the c subunits was mutated to an alanine? The enzyme would make ATP as normal in the presence of a proton gradient. The enzyme would not make ATP in the presence of a proton gradient. The enzyme would make ATP without the need for a proton gradient. The rotor would rotate in response to a proton gradient, but no ATP would be made.

Answer 60

The enzyme would not make ATP in the presence of a proton gradient.

Question 61

What is the cellular location of eukaryotic thermogenin (or uncoupling protein)? mitochondrial inner membrane mitochondrial matrix cytoplasm both cytoplasm and mitochondrial matrix

Answer 61

mitochondrial inner membrane