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Biochemistry > Discussion 3 > Flashcards

Discussion 3 Flashcards

1
Q

Which statement is TRUE for RNA but not DNA?

RNA uses 2-deoxyribose sugar.

RNA uses uracil as a nitrogenous base.

RNA is created from DNA in a process known as translation.

RNA is the only nucleic acid that can be absorbed in the UV spectrum.

A

RNA uses uracil as a nitrogenous base.

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2
Q

RNA occurs primarily as single stranded molecules that can give rise to _______ structures.

diploid
stem-loop
parallel
tautomeric
haploid

A

stem-loop

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3
Q

Genomic DNA is _____, resulting in the production of _____.

transcribed; mRNA

translated; tRNA

transcribed; protein

translated; protein

translated; rRNA

A

transcribed; mRNA

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4
Q

Polypeptide synthesis proceeds from the _____ to the _____.

entrance site; exit site

50S subunit; 30S subunit

C-terminus; N-terminus

N-terminus; C-terminus

peptidyl site; aminoacyl site

A

N-terminus; C-terminus

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5
Q

a. Name these three types of RNA____________

A

rRNA, tRNA, mRNA.

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6
Q

_____________ moves genetic information from the nucleus to the ribosomes in the cytoplasm. ______________ decodes the genetic message; it matches sequences of three nucleotides to amino acids. __________________is involved in the catalysis of amide bond formation.

A

mRNA, tRNA, rRNA.

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7
Q

In bacteria, riboflavin can inhibit its own synthesis by binding to an mRNA element termed a _____________

A

riboswitch.

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8
Q

RNA interference is a mechanism of post-transcriptional RNA-dependent ______.

chromatin-remodeling

gene silencing

histone methylation

coactivation

apoptosis

A

gene silencing

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9
Q

What is the region immediately adjacent to the starting site for RNA polymerization called?

promoter

enhancer

initiator

consensus sequence

TF binding site

A

promoter

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10
Q

Two amino acids of the standard 20 contain hydroxyl-groups. They are:

cysteine and serine.

cysteine and threonine.

methionine and cysteine.

methionine and serine.

threonine and serine.

A

threonine and serine.

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11
Q

At a pH above its pKa, the phenol group of tyrosine is_______________

A

deprotonated.

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12
Q

A typical protein weighs ________ daltons.

50

500

5000

50,000

A

50,000

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13
Q

Which statement is most TRUE regarding peptide bonds?

They are amide linkages that connect amino acids.

They are flexible linkages that rotate around the sp2 bond in the carbonyl carbon.

They are composed of an electronegative carbonyl group and an electropositive nitrogen atom.

They are weaker than London dispersion forces.

A

They are amide linkages that connect amino acids.

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14
Q

In the tripeptide Lys-Pro-Ile, the C-terminal residue is____________

A

Ile.

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15
Q

The formation of a dipeptide from two amino acids involves

side-chain complementarity.
loss of water.
oxidation of the α-carbon.
reduction of the α-carbon.
base catalysis.

A

loss of water.

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16
Q

Which one of the following statements about peptide bonds is FALSE. Peptide bonds are:

rigid and planar, with partial double-bond character.

charged.

covalent.

involved in forming the primary structure of proteins.

amides.

A

charged.

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17
Q

Which of the following statements BEST describes a prosthetic group?

They are nonpeptide molecules or ions critical to a protein’s structure.

They are short peptide chains attached to a larger protein.

They are nonfunctional components of a protein.

They are the active part of an enzyme.

A

They are nonpeptide molecules or ions critical to a protein’s structure.

18
Q

Which of the following are methods of denaturing a protein?

pH changes

heat

mechanical agitation

all of the above

A

all of the above

19
Q

Why do detergents denature proteins?

The primary structure of the protein can cause alterations in the charges of the residues.

The secondary structure can be altered because of disruptions in the hydrogen bonding.

The forces stabilizing the tertiary structure are disrupted, changing the conformation of the protein.

The quaternary structure can be modified because of the deprotonation of prosthetic groups.

A

The forces stabilizing the tertiary structure are disrupted, changing the conformation of the protein.

20
Q

Two cysteine residues would most likely result in what type of bonding?

hydrogen bond

disulfide bond

dispersion forces

salt bridge

A

disulfide bond

21
Q

The simplest protein structure is __________ structure.

primary

secondary

tertiary

quarternary

A

primary

22
Q

The overall charge of the polypeptide His-Tyr-Lys-Met-Ile-Glu at pH 6.9 is ___?

–2

–1

0

+1

+2

A

0

23
Q

Which level of protein structure is defined as “the hydrogen bonded arrangement of the polypeptide backbone”?

Primary

Secondary

Tertiary

Quaternary

A

Secondary

24
Q

Why does a decrease in pH alter/disrupt the tertiary structure of an enzyme?

It reduces disulphide bonds.

It promotes proteolytic cleavage of peptide bonds.

It disrupts ion pairs/salt bridges.

It reduces hydrophobic interactions.

It deprotonates prosthetic groups.

A

It disrupts ion pairs/salt bridges.

25
Q

Zwitterions are _____.

amino acids

ionic molecules that are racemic

ions that bear both negatively and positively charged groups

side-chain carboxylate anions

delocalized ions

A

ions that bear both negatively and positively charged groups

26
Q

Which of the 20 standard amino acids is optically inactive?

Arg

Pro

Ile

Gly

Cys

A

Gly

27
Q

Which of the following amino acids has a charged polar side chain at pH 7.0?

Leu

Ala

Met

Trp

Glu

A

Glu

28
Q

Which of the following amino acids has a sulfur atom in its side chain?

Asn

Ser

Phe

Met

Tyr

A

Met

29
Q

At a pH above its pKa, the R-group of Asp is _____.

protonated and neutral

protonated and positively charged

deprotonated and neutral

deprotonated and negatively charged

none of the above

A

deprotonated and negatively charged

30
Q

Leucine has a ___________side chain; glutamate has a ____________ side chain.

A

Non-polar, charged.

31
Q

At physiological pH, all amino acids have at least _____ charged groups.

0

1

2

3

cannot be determined

A

2

32
Q

a. How many different amino acids can be incorporated into proteins during translation?

A

20

33
Q

b. Do ribosomes use L or D amino acids for protein synthesis?

A

L

34
Q

Choose amino acid(s) and amino acid derivative(s) that can act as neurotransmitter. Select all that apply.

glycine
glutamate
γ-aminobutyric acid (GABA)
proline
valine

A

glycine
glutamate
γ-aminobutyric acid (GABA)

35
Q

The peptide AYDG has an N-terminal _________ residue.

glycine

glutamic acid

glutamine

aspartic acid

alanine

A

alanine

36
Q

Which of the following tripeptides would be expected to be the most hydrophobic?

KYG

KYA

GYA

DYA

DYG

A

GYA

37
Q

The predominant noncovalent interaction seen in α helices and β sheets is _____.

electrostatic interaction

hydrogen bond

dipole–dipole interaction

hydrophobic interaction

all of the above

A

hydrogen bond

38
Q

Which of the following amino acids is generally absent from an α helix?

Trp

Ser

Ile

Pro

none of the above

A

Pro

39
Q

α helices and β sheets constitute _____ structure.

primary

secondary

tertiary

quaternary

none of the above

A

Secondary

40
Q

Which of the following best describes the peptide backbone in a β sheet?

coiled

compacted

highly extended

rigid

none of the above

A

highly extended

41
Q

In a protein, the most conformationally restricted amino acid is ______; the least conformationally restricted is ______.

Trp, Gly

Met, Cys

Pro, Gly

Ile, Ala

Ala, Pro

A

Pro, Gly

Biochemistry (32 decks)

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