Biochemistry Final Exam Practice Questions

The central dogma of molecular biology teaches us that:
a. RNA replicates itself and DNA is translated into protein
b. RNA is typically the genetic material
c. RNA contains information, which is translated into amino acid sequences
d. Proteins are not nee

c. RNA contains information, which is translated into amino acid sequences

Cell membranes are...
a. ...aqueous partitions to keep the outside out and the inside in
b. ...entirely greasy bilayers that allow proteins to be localized to particular compartments
c. ...composed of amphipathic molecules with hydrophilic surfaces facing

c. ...composed of amphipathic molecules with hydrophilic surfaces facing outside and inside

Hydrogen bonds are
a. Weak associations in which protons are donated from a polar group to a hydrophobic group
b. Irreversible associations in which hydronium maximizes its entropy
c. Found in fluid water but not in DNA base pairs
d. Donated, for example,

e. Donated, for example, from the amide proton of an amino acid to the carbonyl oxygen of another amino acid

At pH 4
a. There are 4000 hydronium molecules per liter of solution
b. There are 1000 times more hydronium molecules per liter than at neutral pH
c. There are 3 times more hydronium molecules per liter than at neutral pH
d. There are 1000 times more hydro

b. There are 1000 times more hydronium molecules per liter than at neutral pH

At neutral pH, tyrosine has
a. A protonated amino group, a deprotonated alcohol group, and a deprotonated carboxylic acid group
b. A deprotonated amino group, a deprotonated alcohol group, and a protonated carboxylic acid group
c. A net charge of -1
d. A

d. A net charge of zero

The missing amino acid in the series Gly, ___, Ser is
a. Met, because all have sulfur
b. Ala, because it is a size series
c. Asn, because the amino acids are carboxamides
d. Lys, because they are the positively charged amino acids
e. Arg, because they are

b. Ala, because it is a size series

Alpha helices
a. Are the gene-rich regions of DNA
b. Are always double-stranded
c. Have their side chains on the inside
d. Are glycine and proline-rich
e. Have 3.6 amino acid residues per turn

e. Have 3.6 amino acid residues per turn

Beta sheets have all of the properties below EXCEPT
a. The property of twisting rather than lying in a flat plane
b. Strands that can run either parallel or anti-parallel
c. Location of side chains on alternating sides of the strand
d. Regular patterns of

d. Regular patterns of backbone hydrogen bonding between residues in the same strand

The fact that ribonuclease can refold after it is denatured indicates that
a. A protein sequence encodes its three dimensional structure
b. All sequences can form stable three dimensional structure
c. Free thiol reagents only disrupt incorrect disulfide b

a. A protein sequence encodes its three dimensional structure

Lactate dehydrogenase (LDH), purified to homogeneity from a cellular extract, had its specific activity increased by 200-fold. This suggests that
a. The yield of LDH was 0.5%
b. LDH might have constituted 0.5% of total protein in the cellular extract
c. I

b. LDH might have constituted 0.5% of total protein in the cellular extract

Gel filtration chromatography works by
a. Converting all proteins to detergent complexes with SDS
b. Using a gel to link sugar to the target protein
c. Native size separation
d. Increasing salt concentration to elute proteins off columns
e. Electrophoresi

c. Native size separation

Antibodies have a variable region to recognize antigens that is
a. made up of part of the heavy chain and part of the light chain
b. entirely derived from the heavy chain
c. entirely derived from the light chain
d. all helical
e. impossible to direct to a

a. made up of part of the heavy chain and part of the light chain

Which of the following is a TRUE statement?
a. Enzymes force reactions to proceed in only one direction
b. Enzymes alter the equilibrium of the reaction
c. Enzymes alter the standard free energy of the reaction
d. Holoenzymes are functional without a cofa

e. None of the above is true

Which statement best describes the relationship between ?G�?and ?G?
a. They are both determined only by the temperature of the reaction
b. They are described by changes in Keq
c. They account for differences between the standard state and the physiologica

c. They account for differences between the standard state and the physiological or actual concentrations of reactants and products

Which statement about an enzyme-substrate interaction is FALSE?
a. It is a reversible interaction
b. Specificity is due to the three dimensional structure of the enzyme
c. It promotes formation of the transition state
d. The "Lock-and-key" model best desc

d. The "Lock-and-key" model best describes enzyme-substrate interaction

Which of the following is CORRECT about the Michaelis constant (Km):
a. It is unique for each enzyme and is dependent on enzyme concentration
b. It varies for enzymes and substrates
c. K. = k-1 / k1
d. It is a measure of the rate of catalysis for a partic

b. It varies for enzymes and substrates

In the Lineweaver-Burk (double-reciprocal) plot, the x-intercept is equal to:
a. -1/Km
b. 1/Km
c. Km/Vmax
d. 1/Vmax
e. -1/Vmax

a. -1/Km

A critical feature of the Michaelis-Menten model of enzyme catalysis is:
a. Increasing the probability of product formation
b. Shifting the reaction equilibrium
c. The formation of an intermediate ES complex
d. Reactants have a lower energy than products

c. The formation of an intermediate ES complex

How is substrate specificity determined by chymotrypsin?
a. By binding a hydrophobic amino acid into a deep pocket in the enzyme
b. By the interaction of the catalytic amino acids with the substrate
c. By binding of the N-terminus at the active site
d. Th

a. By binding a hydrophobic amino acid into a deep pocket in the enzyme

An enzyme has an optimal pH of 8 that is entirely due to two amino acid residues in the active site. What two amino acids are most likely responsible for this observation?
a. Glycine and alanine
b. Aspartate and histidine
c. Glutamate and alanine
d. Argin

b. Aspartate and histidine

An inhibitor changes the Km and Vmax values of an enzyme reaction to the same extent. What statement below best describes the results of a double-reciprocal plot when comparing the enzyme alone to the enzyme plus inhibitor?
a. 1/Vmax values are identical

d. The plot of 1/V0 vs 1/[S] for the two cases results in lines with identical slopes

Which of the following statements is CORRECT for hemoglobin and oxygen transport?
a. The oxygen binds to the proximal histidine residue of the globin chain
b. Bonding of carbon dioxide to hemoglobin molecules increases the binding of oxygen
c. Hemoglobin

e. The binding of each O2 molecule to hemoglobin increases its affinity for the next O2 molecule

Which of the following describes the Bohr effect?
a. Lowering the pH and increasing the partial pressure of CO2 results in the release of O2 from oxyhemoglobin
b. Increasing the pressure of CO2 results in the release of O2 from oxyhemoglobin
c. Binding of

a. Lowering the pH and increasing the partial pressure of CO2 results in the release of O2 from oxyhemoglobin

Which of the following statements BEST describes the following equilibrium? CO2 + H2O <--> H2CO3
a. An increase in the pressure of CO2 will result in a decrease of pH
b. This reaction is catalyzed by carbonic anhydrase
c. The H2CO3 dissociates to H+ and b

e. All of the above correctly describe the equilibrium

Which of the following statements about sugars is FALSE?
a. Sucrose, lactose, and maltose are disaccharides
b. Disaccharides consist of two sugars joined by an O-glycosidic bond
c. Blood groups illustrate the effects of glycosyltransferases
d. Monosacchar

e. Cellulose is a polysaccharide of fructose

Which of the following statements is FALSE?
a. Milk sugar is cleaved by lactase
b. Glycogen is a polysaccharide that serves as a glucose storage in animal cells
c. Mucins are glycoproteins that act as lubricants
d. The N-linkage of glycoproteins is formed

d. The N-linkage of glycoproteins is formed by attaching carbohydrates to the amine group of any amino acid

Choose the answer that BEST describes glycolipids.
a. They serve as hormones
b. They are derived from glycerol
c. They contain phosphorylchlorine
d. They are oriented in membranes with the sugar residue always on the extracellular side
e. They are not amp

d. They are oriented in membranes with the sugar residue always on the extracellular side

Which of the following statements about mammalian triacylglycerols is TRUE?
a. They are stored in the nucleus of mammalian cells
b. They are a storage form of fatty acids
c. They contain a glucose molecule
d. They are energy rich, oxidized and hydrophobic

b. They are a storage form of fatty acids

Membrane fluidity in animals depends on:
a. Chain length of its lipids
b. Extent of unsaturation of constituent fatty acids
c. Cholesterol content
d. Number of cis double bonds of constituent fatty acids
e. All of the above play a role in membrane fluidit

e. All of the above play a role in membrane fluidity

Which of the following statements is FALSE?
a. Integral membrane proteins are embedded in the membrane
b. Integral membrane proteins can be released by changing the pH of the membrane's environment
c. Peripheral membrane proteins are bound to membranes by

b. Integral membrane proteins can be released by changing the pH of the membrane's environment

Select the statement that is TRUE
a. Glucose is transported into animal cells by a symporter
b. Pumps require energy to move molecules with their concentration gradient
c. Channels move molecules against their concentration gradient
d. Active transport th

a. Glucose is transported into animal cells by a symporter

Which of the following BEST completes the following statement to make it TRUE? cGMP, inositol 1,4,5-triphosphate (IP3), diacylglycerol (DAG) are all
a. primary messengers
b. second messengers
c. membrane receptors
d. effectors
e. found in the cell membran

b. second messengers

Pick the ending to the following statement that makes it TRUE. ?-adrenergic receptor is
a. a dimeric receptor that recruits protein kinases
b. a dimeric receptor that is a protein kinase
c. a seven-transmembrane-helix receptor
d. activated by binding of t

c. a seven-transmembrane-helix receptor

Which of the following steps does NOT contribute to insulin-induced uptake of glucose?
a. Phosphatidylinositide 3-kinase converts PIP2 to PIP3 (3,4,5)
b. PIP3-activated kinase activates Akt
c. Akt inhibits Ca2+ release activating GLUT4 transporter
d. PIP3

c. Akt inhibits Ca2+ release activating GLUT4 transporter

Which of the following statements about digestion is TRUE?
a. ?-amylase is the first enzyme to start digesting starch
b. The first step of protein digestion is trypsin hydrolyzing proteins in the stomach
c. Lipases convert fatty acids to triacylglycerol
d

a. ?-amylase is the first enzyme to start digesting starch

Pick the BEST ending for the following statement: Zymogens are
a. synthesized in the liver
b. inactivated by protease digestion
c. active enzymes
d. active only in low pH
e. inactive proteases

e. inactive proteases

Which of the following hypothetical drug treatments could cause weight gain by disrupting caloric homeostasis after eating?
a. A drug that inhibits growth hormone receptor activation
b. A drug that inhibits the release of zymogens from the pancreas
c. Tak

e. A drug that reduces the release of cholecystokinin (CCK)

Which of the following statements is TRUE?
a. ATP must be constantly regenerated to keep the body supplied with energy
b. ATP has the highest phosphoryl-transfer potential of phosphorylated compounds
c. ATP hydrolysis is endergonic
d. ATP contains one pho

a. ATP must be constantly regenerated to keep the body supplied with energy

Choose the correct statement about carbon oxidation:
a. The energy for ATP generation is primarily provided by oxidation of glucose and fats
b. Creatine phosphate is the major immediate donor of free energy in biological systems
c. Oxidation of carbons re

a. The energy for ATP generation is primarily provided by oxidation of glucose and fats

Which of the following compounds is primarily involved as an electron carrier in biosynthetic reactions (anabolism)?
a. ATP
b. NAD
c. FAD
d. NADP
e. CoA

d. NADP

Which two 3-carbon molecules are generated by the cleavage of fructose-1,6-bisphosphate?
a. glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
b. glyceraldehyde-3-phosphate and 3-phosphoglycerate
c. pyruvate and phosphoenolpyruvate
d. enolase and 2

a. glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

Oxidation in glycolysis converts NAD+ to NADH. Which of the following is a FALSE statement about the mechanisms used by living organisms to regenerate NAD+ for glycolysis?
a. Pyruvate is converted to ethanol
b. Microorganisms regenerate NAD+ without oxyge

d. NAD+ is generated during gluconeogenesis for use in glycolysis

Pick the BEST ending for the following statement: Glycolysis helps pancreatic beta cells regulate glucose through
a. The increase of ATP concentration
b. Closing of K+ channels
c. Influx of Ca2+
d. Insulin secretion
e. All of the above

e. All of the above

A key step of gluconeogenesis is conversion of pyruvate to phosphoenolpyruvate. Which of the following statements about this conversion is true?
a. Pantothenate is a required cofactor for pyruvate carboxylase
b. Malate is an intermediate of this conversio

b. Malate is an intermediate of this conversion

Which of the following reactions in glycolysis or gluconeogenesis is NOT regulated?
a. Conversion of fructose-6-phosphate to fructose-1,6-phosphate by phosphofructose kinase
b. Conversion of glucose to glucose-6-phosphate by hexokinase
c. Conversion of 3-

c. Conversion of 3-phosphoglycerate to 1,3-biphosphoglycerate by phosphoglycerate kinase

Which of the following statements about the Cori cycle is TRUE?
a. It is used to regenerate reducing potential for muscles
b. It allows lactate generated in muscle to be used to generate glucose
c. It generates amino acids to rebuild muscles damaged durin

b. It allows lactate generated in muscle to be used to generate glucose

Cellular reverse transcriptase describes the enzymatic activity of which of the following enzymes?
a. DNA polymerase
b. Exonuclease
c. Telomerase
d. Primase
e. Topoisomerase

c. Telomerase

Which of the following activities is NOT shared by E. coli DNA polymerase I and DNA polymerase III?
a. A proofreading activity
b. A 5' to 3' polymerase activity
c. A progressive and fast rate of DNA synthesis
d. A 5' to 3' exonuclease activity
e. A 3' to

d. A 5' to 3' exonuclease activity

Which of the following statements BEST describes lagging strand synthesis in DNA replication?
a. Is coordinated with leading strand synthesis
b. Involves DNA polymerization in the 5' to 3' direction
c. Uses an RNA primer
d. Requires DNA ligase
e. All of t

e. All of the above are characteristics of lagging strand synthesis

In growing cells, unrepaired spontaneous determination of cytosine is associated with:
a. No change in DNA sequence because base pairing is unaltered
b. A change in DNA sequence from a CG base pair to a TA base pair
c. A change in DNA sequence from a CG b

b. A change in DNA sequence from a CG base pair to an TA base pair

Base excision repair involves:
a. Cleavage of both strands of the DNA
b. Repair by DNA polymerase III
c. The action of the ABC exinuclease
d. Formation of an apurinic or apyrimidic site
e. All of the above

d. Formation of an apurinic or apyrimidic site

Which of the following statements about genetic mutations and DNA repair is TRUE?
a. Errors in DNA replication can cause mutations
b. Pyrimidine dimers are repaired using the mismatch repair pathway
c. The Ames test identifies mutagens that cause double-s

a. Errors in DNA replication can cause mutations

Which of the following mutations in the cis-elements of the lac operon will be associated with the HIGHEST level of transcription, when E. coli is grown in the presence of lactose but not glucose?
a.Mutation of the Repressor binding site so Repressor bind

e. Mutation of the -35 region to change the sequence to match consensus

Which of the following statements about E. coli RNA polymerase is FALSE:
a. Binds DNA using the ? subunit
b. Binds DNA using the ? subunit
c. Initiates RNA synthesis without a primer
d. Uses the coding strand as a template
e. Synthesizes RNA in the 5' to

d. Uses the coding strand as a template

Which of the following statements about transcription in E. coli is TRUE?
a. Transcriptional regulation is coordinated by organizing protein coding regions into operons
b. Catabolite activator protein (CAP) links transcriptional regulation with glucose le

e. All of the above

Acetylation of the histone tail _____.
a. inactivates transcription of the target gene
b. enhances histone tail-DNA interactions
c. enhances histone tail-general transcription factor interactions
d. neutralizes the positive charge on histone
e. does not a

d. neutralizes the positive charge on histone

RNA Polymerase III:
a. Transcribes mRNA
b. Transcribes the 28S RNA
c. Transcribes tRNAs
d. Does not require a promoter for initiation of transcription
e. All of the above

c. Transcribes tRNAs

Which of the following best describes Tata binding protein (TBP)?
a. Binds the Initiator element in RNA polymerase II promoters
b. It is required for transcription initiation of RNA polymerase II
c. Is required for double-strand break repair
d. It is part

b. It is required for transcription initiation of RNA polymerase II

In eukaryotes, the following enzyme(s) play(s) a role in tRNA processing:
a. RNase P
b. CCA-adding enzyme
c. Endonuclease
d. Ligase
e. All of the above

e. All of the above

Which snRNP is required for branchpoint recognition?
a. the U1 snRNP
b. the U2 snRNP
c. the U6 snRNP
d. the 5.5S RNA
e. None of the above

b. the U2 snRNP

The carboxyl-terminal domain of the largest subunit of RNA polymerase II:
a. Contains the RNA polymerase II active site
b. Undergoes acetylation during initiation
c. Coordinates transcription with RNA processing
d. Contains a repeat of basic amino acids t

c. Coordinates transcription with RNA processing

Which of the following is NOT a characteristic of the genetic code?
a. It is degenerate
b. It is universal
c. It has no punctuation between codons
d. It is non-overlapping
e. It is read in triplets

b. It is universal

Amino acyl

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