-
The bicarbonate/CO2 pair is a good buffer, in vivo, at pH 7.4 because?
The partial pressure of CO2 in the blood is maintained at about 40mm of Hg upon addition of acid or base.
-
Carbonic anhydrase?
Catalyzes the formation of CO2 from H2CO3 in the lungs
-
A weak acid can act as a buffer?
At pH values = pK ±1
-
What is the pH of a buffer solution (HA and A-)containing 0.5M HA and 0.5M A- (pKa of HA=6.8)?
6.8
-
The isoelectric point [pI] for alanine is (pK1=2.3; pK2=9.9)?
6.1
-
At pH 7.0, which of the following amino acid side chains will be positively charged?
Lysine, Histidine, Glutamate, Aspartate or Cysteine
Lysine
-
Decreasing the pH of a solution from pH 7 to pH 5 results in an increase in the hydrogen ion concentration, [H+], by?
100 times
-
The most important buffer in extracellular fluid is?
Bicarbonate
-
The enzyme, carbonic anhydrase, catalyses the reaction of carbon dioxide and water.What is the equation?
CO2 + H2O --Carbonic anhydrase--> H+ + HCO3-
-
The Henderson-Hasselbalch equation is written as?
pH = pK + Log [A-]/[HA]
-
What is the pH of a buffer solution (HA and A-)containing 0.5M HA and 0.05M A- (pKa of HA=6.8)?
5.8
-
Which of the following compounds is the strongest acid?
Hydrochloric acid
-
The main form of carbon dioxide in the blood is?
HCO3-
-
Which of the following groups of atoms is capable of forming hydrogen bonds?
N-H and H-N
O-H and H-S
C=O and O=C
N-C and O-H
N-H and O=C
N-H and O=C
-
Which of the amino acids could serve as the best buffer at pH 7.0?
Histidine
-
At its isoelectric point (pI), a protein will have?
Equal numbers of positive and negative charges
-
An acidic solution could have a pH of?
3
-
What is the conjugate base of HCO3–?
CO32-
-
Hydrophilic compounds are soluble in water owing to the formation of?
Hydrogen bonds
-
The concentration of hydrogen ions [H+] in a solution is expressed as the pH, which is numerically equivalent to?
-Log [H+]
-
For a weak acid, maximum buffering capacity occurs when?
pH = pK
-
The partial negative charge at one end of a water molecule is attracted to a partial positive charge of another water molecule. What is this attraction called?
A hydrogen bond.
-
For the following reaction, which of the following is a conjugate acid-base pair? H2PO4- (aq) + NH3 (aq) HPO42- (aq) + NH4+ (aq)
H2PO4- and HPO42-
-
Which of the following statements best describes the difference between a strong electrolyte and a weak electrolyte?
A strong electrolyte does not form a conjugate base, but a weak electrolyte does have a conjugate base
-
Determines blood H2CO3 concentration?
Alveolar CO2 tension
-
Which of the following best describes a titration curve?
It shows buffering of the change in pH near the pK of each dissociable group
-
In biochemistry, what is meant by the term "buffer"?
A compound or solution that resists change in pH.
-
Which of the following solutions has the greatest concentration of hydroxyl ions(OH)?
Sea water (pH 8)
Vinegar (pH 3)
Water (pH 7)
Tomato puree (pH 4)
Black coffee (pH 5.5)
- Sea Water (pH 8)
- The more basic it is the more OH ions it has.
-
Buffer solutions?
tend to maintain a relatively constant pH
-
A substance that is NOT a blood buffer anion is?
Chloride
-
A substance that is a blood buffer anion is?
- Proteinate
- Bicarbonate
- Phosphate
-
Polymerization of glucose units to form glycosides requires the formation of which type of bond?
Glycosidic bond
-
Which is most likely to increase the midpoint temperature of the melting curve for DNA?
Decreasing the number of A-T pairs
-
When lysine has a charge of +1?
Both amino groups are protonated
-
An amino acid with an ionic, polar side chain is?
Lysine
-
Which of the following statements concerning nucleotide structure is correct?
1)A purine or pyrimidine base is attached to the 3'-carbon position
2)Nucleotide polymerization proceeds via the 5'-carbon
3)The 4'-carbon position determines whether the nucleotide is a deoxyribonucleotide or a ribonucleotide
4)One or more phosphate groups is attached to the 5'-carbon
5)A purine or pyrimidine base is attached to the 1'-carbon
A purine or pyrimidine base is attached to the 1'-carbon
-
Which of the following amino acids contains an imidazole group?
Histidine
-
Reducing sugars are oxidized by Fehling's solution to produce a color reaction. What is NOT a reducing sugar?
Sucrose
-
Reducing sugars are oxidized by Fehling's solution to produce a color reaction. What is a reducing sugar?
- Glucose
- Galactose
- Lactose
- Fructose
-
In carbohydrate nomenclature, a triose contains how many carbon atoms?
3
-
What is NOT an L-amino acid in human proteins?
Glycine
-
Which amino acids contains an amide group?
Asparagine(N)(ASN) and Gluatmine(Q)(GLN)
-
Which amino acid pairs have side chains that carry a negative charge at pH 7.0?
Aspartate and Glutamate
-
Which fatty acids contains 18 carbon atoms and two double bonds in its structure?
Linoleic acid
-
Which of the following statements concerning the process of denaturation of DNA is correct?
Denaturation can be monitored by hyperchromicity (increased absorbance at 260 nm)
-
Medium chain fatty acids contain how many carbon atoms?
6-10
-
Standard Watson-Crick base-pairing requires that guanine always pairs with?
Cytosine
-
Naturally-occurring fatty acids always contain which of the following types of double bonds?
Only cis
-
Which of the following Greek symbols is used to designate the position of double bonds in a fatty acid structure?
Delta Δ
-
Which of the following is true for the double helical structure of DNA?
DNA double helices are more stable than RNA double helices
-
Which one of the following types of bonds or interactions is LEAST important in determining the tertiary structure of proteins?
Coordination bonds (to ligands)
-
Which of the following is true of the peptide bond?
It is a type of amide linkage
-
Because of the abundance of hydroxyl groups, sugar molecules can form several types of carbohydrate derivatives which include?
1)Sugar alcohols
2)All of the above
3)Deoxy sugars
4)Amino sugars
5)Sugar acids
All of the above
-
Which of the following statements concerning DNA is correct?
The B-form of DNA is the predominant natural form
-
Which of the following is true of lysine (pK1=2.2, pK2=9.0, pK3=10.5)?
It will migrate toward the cathode (negative electrode) during electrophoresis at pH 7.0
-
which of the following amino acids in involved in the formation of disulfide bonds?
Cysteine
-
Which carbohydrates is a ketose sugar?
Fructose
-
Which amino acids can exist in four optically-active isomers?
Threonine
-
What sugar alcohols is a derivative of glucose?
Sorbitol
-
Which bases is found only in RNA?
Uracil
-
What will increase the melting point of a fatty acid?
Increased Chain Length
-
What amino acids has three pK values between pH 2 and 12?
Cysteine
-
Which structural hierarchy corresponds to the linear amino acid sequence of a protein?
Primary
-
The proteolytic action of the enzyme chymotrypsin is specific to which amino acids?
Tyrosine
-
The "sickling" of erythrocytes in sickle cell hemoglobin is due to polymerization of the hemoglobin molecules under conditions of?
Increased concentrations of the deoxygenated form of HbS
-
Which of the following statements concerning the peptide bond is TRUE?
1)Peptide bonds are formed by a condensation reaction between the a-carboxy and a-amino groups of two amino acids
2)All of the above
3)The peptide bond has partial double bond character
4)The C, O, N and H atoms around the peptide bond are all coplanar
5)Peptide bonds can be cleaved by acid hydrolysis in the presence of concentrated HCL at 110 oC
All of the above
-
Whcih of the following statements is correct?
Amino acid R-groups or side chains point above and below the plane of b-sheets
-
Similarities between hemoglobin and myoglobin include which of the following?
Heme is a prosthetic group
-
A mutation is most likely to alter the three-dimensional conformation of a protein if?
It places a proline residue in the middle of an a-helix
-
Amino acid sequences are read in which direction?
Left to right
-
In the a-helix, the carbonyl oxygen in hydrogen-bonded to which amino nitrogen in the linear chain?
n+4
-
Hydolysis of the hexapeptide Glys-Arg-Cys-Met-Lys-Ala with the protease trypsin, would produce how many fragments?
3
-
Which one of the following correctly describes the expected products obtained when the polypeptide Arg-Gly-Phe-Leu-Met-Lys is treated as indicated?
Treatment with cyanogen bromide yields two products
-
Cooperativity in the binding of oxygen to hemoglobin compared to myoglobin is indicated by which shape of the oxygen saturation curve?
Sigmoidal
-
A negative allosteric effector, such as carbon dioxide, acts on the oxygen saturation curve of hemoglobin dispacing it in which direction?
right
-
Protein secondary structure is stabilized by which of the forces?
Hydrogen bonds
-
The b-sheet is an example of which type of structure?
Secondary
-
Which of the following statements concerning denaturation of proteins is CORRECT?
Denaturation results in the loss of secondary and tertiary structure
-
How many a-amino functional groups are present in the pentapeptide Gly-Arg-Lys-Cys-His?
1
-
Monitoring the formation or levels of HbA1c in a patients blood can be used to diagnose which of the following disease?
Diabetes mellitus
-
The Edman degration, performed using phenylisothiocyanate, is used to determine which of the following structural heirarchies?
Primary
-
Which of the following mutations is observed in sickle cell hemoglobin?
b6 Glu -> Val
-
Which of the following statements concerning the structure of heme is correct?
The proximal ligand is a histidine residue
-
All of the following statements about the a-helix are true EXCEPT?
1)It is stabilized by minimizing unfavorable R-group interactions
2)Prolyl and glycyl residues tend to interrupt a-helix structure
3)It is stabilized by intramolecular hydrogen bonds
4)It is one type of secondary structure found in proteins
5)It is stabilized by hydrophobic interactions
It is stabilized by hydrophobic interactions
-
All EXCEPT which of the following statements may characterize sickle cell anemia?
1)The disease can be diagnosed by restriction enzyme digestion
2)Sickling occurs when there is a high concentration of the deoxygenated form of hemoglobin S
3)HbS is caused by an alteration of a single amino acid in the b-chain
4)The clinical symptoms are much less severe when the mutation is only on one chromosome
5)HbS has the same electrophoretic mobility as normal hemoglobin
HbS has the same electrophoretic mobility as normal hemoglobin
-
he chemical cyanogen bromide cleaves peptide chains on the carboxyl side of which amino acid residue?
Methionine
-
Acid hydrolysis of a peptide reveals equimolar amounts of lysine, glycine and alanine. Following trypsin digestion of the peptide, only free glycine and a single dipeptide are observed upon analysis. What is the primary structure of the original peptide?
Ala-Lys-Gly
-
Which of the following is an allosteric effector of hemoglobin oxygen binding?
2,3-bisphosphoglycerate
-
Hemoglobin exhibits which of the following structural hiearchies?
- Secondary Quaternary Tertiary Primary
- All of the above is the answer on the quiz
-
Which of the following hemoglobin variants has a quaternary structure comprised of two alpha chains and two beta-2 glucose chains?
HbA1c
-
Which of the following treatments hydrolyzes all the peptide bonds in a protein regardless of specificity?
Acid hydrolysis
-
Which of the following best describes a drug that acts as a noncompetitive inhibitor?
It acts by removing active enzyme from the substrate pool
-
The Michaelis constant, Km, for enzyme-catalyzed reactions is?
The substrate concentration at v=1/2 Vmax
-
A purely noncompetitive inhibitor of an enzyme has which of the following kinetic effects?
Decreases Vmax without affecting Km
-
Captopril, a competitive inhibitor for angiotensin converting enzyme, can be used as a therapeutic agent for hypertension. Competitive inhibitors change?
The Km of the reaction
-
Which of the following statements concerning enzymes is CORRECT?
1)Enzymes use salt bridges and hydrogen bonds to bind ligands specifically
2)All of the above
3)Enzymes chiefly bind substrates by noncovalent interactions
4)Enzyme active sites ensure that two substrates come together in the correct orientation for chemical reaction to occur.
5)Changes in the specificity sub-site may change the type of substrate that is bound but not the chemistry that is catalyzed
All of the above
-
In biochemical energetics and thermodynamics, the change in free energy of a reaction is indicated by the symbol?
G
-
An enzyme that catalyzes the reaction A B changes the?
Rate of both the forward and reverse reactions
-
Which of the following statements concerning allosteric regulation of enzyme activity is CORRECT?
1)Positive allosteric effectors displace the sigmoidal reaction curve to the left
2)Positive cooperativity occurs when the binding of a ligand at one site increases the affinity at adjacent sites
3)Allosteric inhibitors generally have a greater effect on enzyme velocity than competitive inhibitors
4)The binding of allosteric effectors generally induce a change in the conformation of the enzyme
5)All of the above
All of the above
-
Which of the following is the correct form of the Michaelis-Menten equation?
v=Vmax[S]/Km+[S]
-
Which of the following statements concerning enzymes is CORRECT?
1)All proteins are enzymes
2)Enzymes require specific cofactors for activity
3)Enzymes have absolute specificity for their natural substrate
4)None of the above
5)Enzymes have only organic compounds as substrates
None of the above
-
The Michaelis constant, Km, for an enzyme-catalyzed reaction can be determined from?
Measuring reaction rates at different substrate concentrations
-
Which of the following statements concerning enzyme-catalyzed first order reactions is CORRECT?
1)Increasing substrate concentration has no effect on rate of reaction
2)Reaction rate is directly proportional to the amount of substrate added
3)Enzyme is saturated with substrate, no more will bind
4)None of the above
5)Reaction rate is proportional to the concentration of two substrates
Reaction rate is directly proportional to the amount of substrate added
-
Reaction rate is directly proportional to the amount of substrate added
An active site binds substrate, while an allosteric site binds a regulatory ligand
-
The presence of a noncompetitive inhibitor?
Leads to a decrease in the observed Vmax
-
A purely competitive inhibitor of an enzyme has which of the following kinetic effects?
Increases Km without affecting Vmax
-
The rate of an enzyme-catalyzed reaction was measured using several substrate concentrations that were much lower than Km. The dependence of reaction velocity on substrate concentration can best be described as?
Proportional to the substrate concentration
-
Regulation of enzyme activity by covalent modification occurs primarily through that action of protein kinases that phosphorylate specific amino acids such as?
Serine
-
In an intact cell, the free energy change (delta G) associated with an enzyme-catalyzed reaction is frequently different from the standard free energy change (delta Go) of the same reaction because in the intact cell the?
Reactants are not at 1M concentrations
-
Which of the following reactions is an example of an oxidation-reduction reaction?
Lactate + NAD+ -> Pyruvate + NADH + H+
-
What is not an enzyme prosthetic group?
NAD+
-
What is a enzyme prosthetic group?
- FAD
- Biotin
- CU
- Pyridoxal Phosphate
-
Vmax and Km can be derived from the Lineweaver-Burke plot of the Michaelis-Menten equation. When V is the reaction velocity at substrate concentration S, the x-axis experimental data are expressed as?
1/S
-
Which is NOT a property of enzymes?
Enzymes alter the reaction equilibrium
-
The Michaelis constant, Km, is?
Numerically equal to the substrate concentration that gives half-maximal velocity
-
Which of the following is NOT a common regulatory strategy for controlling the flux through a metabolic pathway?
Non-Competitive inhibition
-
An example of irreversible regulation of enzyme activities is?
Proteolytic conversion of digestive enzymes
-
Which of the following statements concerning simplifying assumptions governing Michaelis-Menten enzyme kinetics is CORRECT?
1)A single substrate (S) binds reversible to form the enzyme-substrate complex, ES
2)All or the above
3)The enzyme-substrate complex, ES, can break down to enzyme and substrate without reacting
4)E+S ES -> E + P
5)The enzyme-substrate complex, ES, can complete the reaction to form product, P
All of the above
-
Enzymes as classic catalysts accomplish which of the following energy effects?
Lower the energy of activation
-
In the study of enzymes, a sigmoidal plot of substrate concentration ([S]) versus reaction velocity (V) may indicate?
Cooperative binding
-
Which of the following statements concerning isoenzymes is CORRECT?
Isoenzymes catalyze the same chemical reactions but have different amino acid sequences
-
Captopril, a competitive inhibitor for angiotensin converting enzyme, can be used as a therapeutic agent for hypertension. Competitive inhibitors change?
The Km of the reaction
-
Which of the following is NOT one of the 6 IUB classes of enzymes?
Polymerase
-
Which of the following is one of the 6 IUB classes of enzymes?
Ligase Isomerase Transferase Hydrolase
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