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Combination of the most recent oldies questions from amino acids to Enzymes I,II lectures.

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Biochemistry Exam 1

Biochemistry Exam 1

Question 1 of 44

1

An individual molecule of glycine possesses ________ carbon(s), and an individual molecule of alanine possesses _______ carbon (s).

Select one of the following:

  • 2,2

  • 1,2

  • 2,1

  • 2,3

  • 3,2

Explanation

Question 2 of 44

1

A recent study found that polyQ aggregation can interfere with the clearance of misfiled proteins in the cytosol. PolyQ is a serial repeat of _____________ residues.

Select one of the following:

  • Arginine

  • Glycine

  • Glutamate

  • Ubiquitin

  • Glutamine

Explanation

Question 3 of 44

1

With the exception of glycine, all the standard proteinogenic amino acids __________

Select one of the following:

  • Contain an optically inactive alpha carbon

  • Do not exhibit chirality

  • Are found in biological systems in equal ratios of the two superimposable stereoisomeric conformations

  • All of the above are true

  • None of the above are true

Explanation

Question 4 of 44

1

_______________ is formed by post-translational modification of the collagen molecule.

Select one of the following:

  • Proline

  • Hydroxyproline

  • Pyrrolysine

  • Selenocysteine

  • Gamma-carboxyglutamate

Explanation

Question 5 of 44

1

Phosphates cannot normally be attached to ________________ .

Select one of the following:

  • Asparagine

  • Serine

  • Threonine

  • Phosphates cannot be attached to any of the above

  • Phosphates can be attached to all of the above

Explanation

Question 6 of 44

1

At neutral pH, the side chains of __________ are charged.

Select one of the following:

  • Lysine

  • Arginine

  • Aspartic acid

  • The side chains of all of the above are charged

  • The side chains of none of the above are charged

Explanation

Question 7 of 44

1

Which of the following bonds in a peptide exhibits the greater amount of free rotation?

Select one of the following:

  • The bond between the carbonyl carbon and the nitrogen of the peptide bond

  • The bond between the alpha carbon and the alpha-amino (the amino group attached to the central carbon of an amino acid)

Explanation

Question 8 of 44

1

A decapeptide (peptide composed of 10 amino acids) contains ______ peptide bonds. _____________ of these peptide bonds possess polarity and also partial double bond character.

Select one of the following:

  • Two, None

  • Nine, Nine

  • Ten, None

  • Eleven, Ten

  • Nine, None

Explanation

Question 9 of 44

1

A disulfide bond can be formed by the _________ of two _________

Select one of the following:

  • Reduction, selenocysteines

  • Oxidation, selenocysteines

  • Reduction, cystines

  • Oxidation, cystines

  • None of the above

Explanation

Question 10 of 44

1

Serotonin is synthesized from an amino acid precursor. This amino acid is ____________.

Select one of the following:

  • Tyrosine

  • Histidine

  • Cysteine

  • Tryptophan

  • Threonine

Explanation

Question 11 of 44

1

An alpha-helix is stabilized by __________________.

Select one of the following:

  • Hydrogen bonding between peptide-bond carbonyl oxygens and amide hydrogens

  • Disulfide bond formation between cysteine residues located 4 amino acids away from each other

  • Hydrophobic interactions between non polar side chains

  • All of the above

  • None of the above

Explanation

Question 12 of 44

1

A(n) _______________ can be formed from two or more separate polypeptide chains (or segments of polypeptide chains) arranged either in a parallel or in an anti-parallel manner relative to each other.

Select one of the following:

  • Alpha-helix

  • Beta-sheet

  • Both alpha and beta

  • Neither alpha nor beta

Explanation

Question 13 of 44

1

_________ structure can be possibly stabilized by covalent bonds, hydrophobic interactions, hydrogen bonds, or ionic interactions

Select one of the following:

  • Tertiary

  • Quaternary

  • Both T and Q

  • Neither T nor Q

Explanation

Question 14 of 44

1

A monomeric protein is denatured by exposure to a chaotropic agent. This act of denaturation can result in the unfolding and disorganization of the protein's ____________.

Select one of the following:

  • Secondary

  • Tertiary

  • Both

  • Neither

Explanation

Question 15 of 44

1

Which of the following statements about beta-amyloid is (are) true?

Select one of the following:

  • It is a highly denatured peptide that consists of many different random conformations

  • It is associated with the deposition of plaques inside certain key neurons

  • It always results from a genetically encoded amino acid substitution

  • All of the above are true

  • None of the above are true

Explanation

Question 16 of 44

1

Which of the following statements about prions is (are) true?

Select one of the following:

  • The prion genome consists of a single molecule of RNA

  • The prion genome codes for an inherently unstable peptide

  • Both statements are true

  • Neither statement is true

Explanation

Question 17 of 44

1

One is comparing the noninfectious, normal PrP in a healthy brain to the infectious PrP. The infectious PrP ___________ relative to the normal PrP

Select one of the following:

  • Exhibits less resistant to proteolytic degradation

  • Exhibits a greater tendency to form insoluble aggregates of fibrils

  • Both

  • Neither

Explanation

Question 18 of 44

1

The reaction A-B + water ---> A-OH + B-H is enzymatically mediated by a(n) ___________.

Select one of the following:

  • Isomerase

  • Ligase

  • Transferase

  • Hydrolase

  • None of the above

Explanation

Question 19 of 44

1

An enzyme binds its substrate under optimal conditions. Upon this binding, which of the following will subsequently occur?

Select one of the following:

  • An enzyme-substrate complex is produced

  • Binding of the substrate causes a conformational change in the enzyme

  • Enzyme-substrate complex is converted to an enzyme-product complex

  • All statements are true

  • None are true

Explanation

Question 20 of 44

1

An enzyme functions by ______________

Select one of the following:

  • Increasing the free energy of activation

  • Decreasing the free energy of the reactants

  • Increasing the free energy of the product

  • All statements are true

  • None of the statements are true

Explanation

Question 21 of 44

1

Which of the following statements about the tau protein is (are) true?

Select one of the following:

  • The normal version of tau helps in the assembly and stabilization of the intracellular micro tubular structure

  • The abnormal tau results from the substitution of a valine to a glutamate

  • The abnormal tau is hypophosphorylated (fewer phosphates than normal) and is highly soluble

  • All are true

  • None are true

Explanation

Question 22 of 44

1

Protein X is a large and complex polypeptide. X's secondary and tertiary structure would be potentially altered the most by the substitution of a single ______ for a single ________

Select one of the following:

  • arginine, lysine

  • alanine, valine

  • glutamate, aspartate

  • serine, proline

  • glutamine, asparagine

Explanation

Question 23 of 44

1

Which of the following statement(s) about amino acids is (are) correct?

Select one of the following:

  • Certain amino acids can function in neurotransmission

  • Certain neurotransmitters are derived from amino acids

  • Certain hormones are derived from amino acids

  • Certain amino acids are not incorporated into proteins (non-proteogenic)

  • All are correct

Explanation

Question 24 of 44

1

Which of the following statements is (are) correct?

Select one of the following:

  • Glycine is not a chiral molecule

  • Glycine can be found in both an L and D form in many human proteins

  • Glycine has an asymmetric center at the alpha carbon

  • All are correct

  • None are correct

Explanation

Question 25 of 44

1

Which of the following amino acids would be least likely to be found on the outside surface of a protein buried inside of a hydrophobic environment?

Select one of the following:

  • Tyrosine

  • Phenylalanine

  • Leucine

  • Tryptophan

  • Alanine

Explanation

Question 26 of 44

1

The formation of a disulfide bond by the oxidation of two ______ residues can contribute to the stability of proteins

Select one of the following:

  • Methionine

  • Proline

  • Cysteine

  • Histidine

  • All options

Explanation

Question 27 of 44

1

Which of the following statements about amino acids is (are) correct?

Select one of the following:

  • The side chains of certain amino acids contain a carboxylate group

  • The side chains of certain amino acids contain an amide group

  • The side chains of certain amino acids contain polar hydroxyl groups, which can serve as sites of attachment for compounds that are not amino acids

  • All are correct

  • None are correct

Explanation

Question 28 of 44

1

Which one of the following statements about protein structure is correct?

Select one of the following:

  • Proteins consisting of one polypeptide can have quaternary structure

  • The formation of a disulfide bond in a protein requires that the two participating cysteine residues by adjacent to each other in the primary sequence of the protein

  • The stability of quaternary structure in proteins is mainly a result of covalent bonds among the subunits

  • The denaturation of proteins always leads to irreversible loss of secondary and tertiary structure

  • The information required for the correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain

Explanation

Question 29 of 44

1

Which one of the following statements is correct?

Select one of the following:

  • The alpha-helix can be composed of more than one polypeptide chain

  • B-sheets exist only in the anti-parallel form

  • There are 3.6 amino acids in each turn of an alpha helix

  • Domains are a type of secondary structure

  • The alpha-helix is stabilized primarily by ionic interactions between the side chains of amino acids

Explanation

Question 30 of 44

1

Which of the following statements about the normal form of PrP is (are) correct?

Select one of the following:

  • It has a different gene sequence relative to the infectious form

  • It has a different amino acid sequence relative to the infectious form

  • It has fewer B-sheets and more A-helices than the infectious form

  • It is more resistant to proteolytic degradation than the infectious form

  • It plays a significant role in the development of Alzheimer disease

Explanation

Question 31 of 44

1

A peptide bond:

Select one of the following:

  • Has partial double bond character

  • Is ionized at physiological pH

  • Is cleaved by agents that denature proteins, such as organic solvents and high concentrations of urea

  • Is stable to heating in strong acids

  • Most commonly in the cis configuration

Explanation

Question 32 of 44

1

Which of the following statements about the alpha-helix is (are) correct?

Select one of the following:

  • The sequence of amino acids in the alpha-helix always shows a predictable pattern of specific amino acids throughout the length of the entire helix

  • The formation of the alpha-helix is always mediated by the enzymatic activity of enzymes known as alpha-helicases

  • Approx. 50% of the alpha-helices are found in a parallel configuration, while about 50% are in anti-parallel configuration

  • All are correct

  • None are correct

Explanation

Question 33 of 44

1

Which of the following interactions can cooperate in the stabilization of the tertiary structure:

Select one of the following:

  • Ionic interactions between negatively charged and positively charged side chains

  • Hydrophobic interactions between different non polar side chains

  • Disulfide covalent linkages between two noncontiguous cysteine residues

  • All cooperate

  • None of the options cooperate

Explanation

Question 34 of 44

1

Which of the following statements about the neurofibrillary tangles associated with Alzheimer disease is (are) correct?

Select one of the following:

  • The neurofibrillary tangles are extra-cellular aggregates that tend to accumulate both in the brain and other regions of the central nervous system

  • There is significant evidence that these neurofibrillary tangles are usually caused by the ingestion of a pathogenic protein known as tau

  • The neurofibrillary tangles are generally intertwined with the intra-cellular amyloid plaque

  • All are correct

  • None are correct

Explanation

Question 35 of 44

1

Which of the following is the least likely to be disrupted by denaturation of a protein?

Select one of the following:

  • Disulfide bonds

  • Hydrophobic interactions

  • Peptide bonds

  • Weak noncovalent interactions

  • Hydrogen bonds

Explanation

Question 36 of 44

1

The addition of a hydroxyl to __________ produces tyrosine

Select one of the following:

  • Valine

  • Tyrosine

  • Phenylalanine

  • Glycine

  • Proline

Explanation

Question 37 of 44

1

This is an optically inactive amino acid

Select one of the following:

  • Valine

  • Tyrosine

  • Phenylalanine

  • Glycine

  • Proline

Explanation

Question 38 of 44

1

This is the precursor of dopamine, epinephrine, and norepinephrine

Select one of the following:

  • Valine

  • Tyrosine

  • Phenylalanine

  • Glycine

  • Proline

Explanation

Question 39 of 44

1

An example of an imino acid

Select one of the following:

  • Valine

  • Tyrosine

  • Phenylalanine

  • Glycine

  • Proline

Explanation

Question 40 of 44

1

Branched chain amino acid

Select one of the following:

  • valine

  • tyrosine

  • phenylalanine

  • glycine

  • proline

Explanation

Question 41 of 44

1

Protein P is a protein found inside a lipid environment. Which of the following amino acids would be most likely to be found on the outside surface of P

Select one of the following:

  • Aspartic acid

  • lysine

  • isoleucine

  • asparagine

  • arginine

Explanation

Question 42 of 44

1

Drug D has one ionizable group, an amino group, with a pKa of 9.0. This drug can pass through cell membranes most readily when uncharged. Theoretically, passage of the drug would occur most readily at pH ___________.

Select one of the following:

  • 2.5

  • 4.5

  • 6.5

  • 7.5

  • 9.3

Explanation

Question 43 of 44

1

Which of the following amino acids participates the most in protein buffering of blood?

Select one of the following:

  • histidine

  • proline

  • alanine

  • tryptophan

  • phenylalanine

Explanation

Question 44 of 44

1

PrP(Sc) is the causative agent of transmissible spongiform encephalopathies because of:

Select one of the following:

  • A single point mutation in the gene coding for the PrP(Sc)

  • The ability of the PrP(Sc) to complex with an infectious molecule of nucleic acid

  • A higher proportion of alpha-helical structures in the PrP(Sc)

  • All are correct

  • None are correct

Explanation

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