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Biochem Exam 2
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Perguntas do quiz (31)
1The chirality of an amino acid results from the fact that its alpha carbon:
- Ahas a net charge
- Bhas both amino and carboxyl groups
- Cis bonded to four different chemical groups
- Dis in the L absolute configuration in naturally occurring proteins
- Eis symmetric
2Of the 20 standard amino acids, only ___________ is not optically active. The reason is that its side chain __________.
- Aalanine; is a simple methyl group
- Bglycine; is a hydrogen atom
- Cglycine; is unbranched
- Dlysine; contains only nitrogen
- Eproline; forms a covalent bond with the amino group
3For an amino acid, at any pH above the pI of the amino acid, the population of the amino acid in solution will have:
- Aa net negative charge
- Ba net positive charge
- Cno charged groups
- Dno net charge
- Epositive and negative charges in equal concentration
4The peptide GVFDQHK has
- Aa disulfide bridge
- Bseven peptide bonds
- Csix peptide bonds
- Dno free carboxyl group
- Etwo free amino groups
5Amino acids are ampholytes because they can function as either a(n):
- Aacid or a base
- Bneutral molecule or an ion
- Cpolar or a nonpolar molecule
- Dstandard or a nonstandard monomer in proteins
- Etransparent or a light-absorbing compound
6Titration of serine by a strong base, for example NaOH, reveals two pK's. The titration reaction occurring at pK1(=2.21) is:
- A-COOH + OH- -> -COO- + H2O
- B-COOH + -NH2 -> -COO- + -NH2+
- C-(COO-) + -NH2+ -> -COOH + -NH2
- D-(NH3+) + OH- --> -NH2 + H2O
- E-NH2 + OH- --> -NH- + H2O
7At pH 7.0, replacing a Glu with a Val will have what effect on the overall charge of the protein containing it?
- AIt will become more negative
- BIt will become more positive
- CIt will stay the same
- DThere is not enough information to answer the question
8An octapeptide composed of four repeating Lys - Asp units has:
- Aone free amino group and one carboxyl group
- Btwo free amino groups and one carboxyl group
- Ctwo free amino groups and two carboxyl groups
- Dfour free amino groups and four carboxyl group
- Efive free amino groups and five carboxyl groups
9In a conjugated protein, a prosthetic group is:
- Aa fibrous region of a globular protein
- Ba nonidentical subunit of a protein with many identical subunits
- Ca part of the protein that is not composed of amino acids
- Da subunit of an oligomeric protein
- Esynonymous with "protomer"
10A naturally occurring hindrance to the formation of an alpha helix is the presence of:
- Aa negatively charged Arg residue
- Ba nonpolar residue near the carboxyl terminus
- Ca positively charged Lys residue
- Da Pro and Gly residues
- Etwo Ala residues side by side
11Amino acid residues commonly found in the middle of Beta turn are:
- AAla and Gly
- Bhydrophobic
- CPro and Gly
- Dthose with ionized R-groups
- Etwo Cys
12A sequence of amino acids in a certain protein is found to be Ser-Gly-Pro-Gly. The sequence is most probably part of a(n):
- Aantiparallel beta sheet
- Bparallel beta sheet
- Calpha helix
- Dalpha sheet
- EBeta turn
13The alpha-keratin chains indicated by the diagram below have undergone one chemical step. To alter the shape of the alpha-keratin chains - as in hair waving - what subsequent steps are required?
- AChemical oxidation and then shape remodeling
- Bchemical reduction and then chemical oxidation
- Cchemical reduction and then shape remodeling
- DShape remodeling and then chemical oxidation
- Eshape remodeling and then chemical reduction
14Which of the following refers to particularly stable arrangements of amino acid residues in a protein that give rise to patterns?
- APrimary structure
- BSecondary structure
- CTertiary structure
- DQuaternary structure
- ENone of the above
15In the mixture of the five proteins listed below, which should elute second in size exclusion (gel filtration) chromatography
- Acytochrome c Mr=13,000
- Bimmunoglobulin G Mr=145,000
- Cribonuclease A Mr=13,700
- DRNA polymerase Mr=450,000
- Eserum albumin Mr=68,500
16Asn has ______ pKa's
- A1
- B1.5
- C2
- D2.5
- E3
17At pH 7.0, replacing an Arg with a Glu will have what effect on the overall charge of a peptide containing it?
- AIt will become more negative
- BIt will become more positive
- CIt will stay the same
- DThere is not enough information to answer the question
- Ethe answer depends on the salt concentration
18A hexpeptide composed of three repeating Lys-Glu units has:
- Aone free amino group and one carboxyl group
- Btwo free amino groups and one carboxyl group
- Ctwo free amino groups and two carboxyl groups
- Dthree free amino groups and three carboxyl group
- Efour free amino groups and four carboxyl groups
19In a conjugated protein, a prosthetic group is:
- Aa fibrous region of a globular protein
- Ba nonidentical subunit of a protein with many identical subunits
- Ca subunit of an oligomeric protein
- Da part of the protein that is not composed of amino acids
- Esynonymous with "protomer"
20In a mixture of the five proteins listed below, which should elute first in size exclusion (gel filtration) chromatography?
- Acytochrome c Mr = 13,000
- Bimmunoglobulin G Mr = 145,000
- Cribonuclease A Mr = 13,700
- DRNA Polymerase Mr=450,000
- Eserum albumin Mr = 68,500
21Kendrew's studies of the globular myoglobin structure demonstrated that:
- A"corners" between alpha-helical regions invariably lacked proline residue
- Bhighly polar or charged amino acid residues tended to be located interiorally
- Cmyoglobin was completely different from hemoglobin, as expected
- Dthe structure was very compact, with virtually no internal space available for water
- Ethe alpha helix predicted by Pauling and Corey was not found in myoglobin
22Determining the precise arrangement of atoms within a large protein is possible only throuhg the use of:
- Aelectron microscopy
- Blight microscopy
- Cmolecular model building
- DRamachandran plots
- EX-ray diffraction
23Proteins often have regions that show specific, coherent patterns of folding or function. These regions are called:
- Adomains
- Boligomers
- Cpeptides
- Dsite
- Esubunits
24When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe2+ are occupied by
- Aone O atom and one amino acid atom
- Bone O2 molecule and one amino acid atom
- Cone O2 molecule and one heme atom
- Dtwo O atoms
- Etwo O2 molecules
25In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as:
- Ahyperbolic
- Blinear with a negative slope
- Clinear with a positive slope
- Drandom
- Esigmoidal
26An allosteric interaction between a ligand and protein is one in which:
- Abinding of a molecule to a binding site affects binding of additional molecules to the same site
- Bbinding of a molecule to a binding site affects binding properties of another site on the protein
- Cbinding of the ligand to the protein is covalent
- Dmultiple molecules of the same ligand can bind to the same binding site
- Etwo different ligands can bind to the same binding site
27The fundamental cause of sickle cell disease is a change in the structure of:
- Ablood
- Bcapillaries
- Chemoglobin
- Dred cells
- Ethe heart
28Arg has ________ pka's
- A1
- B1.5
- C2.5
- D3
29Titration of Lys by a strong base reveals three pka's. The titration reaction occurring at pKa3 is:
- A- COOH + OH- --> - COO- + H2O
- B- COOH + NH2 --> - COO- + -NH2+
- C- COOH + -NH2+ --> - COOH + NH2
- D- NH3+ + OH- --> - NH2 + H2O
- E- NH2 + OH- --> - NH- + H2O
30A tetrapeptide composed of two repeating Asp-Arg units has:
- Aone free amino group and one carboxyl group
- Btwo free amino groups and one carboxyl group
- Ctwo free amino groups and two carboxyl groups
- Dthree free amino groups and three carboxyl groups
- Efour free amino groups and four carboxyl groups
31In a mixture of the five proteins listed below, which should elute last in size-exclusion (gel filtration) chromatography?
- Acytochrome c Mr=13,000
- Bimmunoglobulin G Mr=145,000
- Cribonuclease a Mr=13,700
- DRNA polymerase Mr=450,000
- ESerum albumin Mr=68,500
Informações
- Descrição
- Quiz sobre Biochem Exam 2 , criado por Alexis Sanders em 21-03-2015.
- Autor
- Alexis Sanders
- Idioma
- English
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