Chapter 5-6, 8

Consider the following oligopeptide sequence below. At a pH of 7.4, what would be the overall charge on this species?

-2

Which graph best represents competitive inhibition?

A

Consider the following mRNA strand below and presume the following mutation (bold, underlined) occurs during transcription (uh oh!). What new amino acid (if any) would be incorporated, and is this a conservative or non-conservative mutation?

Aspartate, non-conservative

The interactions that stabilize multi-subunit protein structures are identical to those interactions seen in tertiary structures.

True

The term Kcat/Km is

a convenient measure of catalytic efficiency and substrate specificity of an enzyme

The various "folding classes" discussed in lecture include all of the following EXCEPT:

alpha-beta

The graph in panel B indicated that Km is ________, and Vmax is ___________ in the presence of inhibitor.

decreasing, decreasing

Protein folding is thermodynamically favorable process under physiological conditions because:

of the large negative change in enthalpy associated with many non-covalent (as well as covalent) interactions

The bond between the alpha-carboxylic acid group of one amino acid and the alpha- amino group on another is called a "________"

peptide bond

The peptide bond is __________ due to electron delocalization and resonance structures

planar

Consider the following dipeptide of Gln-Lys (with the structure shown at physiological pH of ~7.4). The individual residues are boxed and labeled. Calculate the pI of this dipeptide.

9.96

Which of the following statements about inhibitors of enzyme -catalyzed reactions is TRUE?

A competitive inhibitor will always binds at the active site.

Which of the following is considered FALSE?

A decrease in temperature can result in an increased reaction rate.

In consideration of protein secondary structure, which of the following is INCORRECT?

A network of main-chain hydrogen bonds connects parallel B- strands into anti B-sheets.

Anfinsen's experiment contends that at biological standard conditions, the native tertiary structure of a protein will:

All the above (have a unique structure, be thermodynamically stable, have a kinetically accessible minimum free energy state)

Enzymatic activity can be regulated via:

All the above (substrate level control, feedback inhibition, reversible covalent modification)

What post-translational modification prevents a charge C terminus and increases the half-life of hormonal peptides?

Amidation

Which 3D representation of protein tertiary structure is best utilized for showing various secondary structures?

Cartoon

Which letter best represents the transition state of the catalyzed reaction?

D

A competitive inhibitor will increase catalytic efficiency

False

At a pH below the pI of a specific protein, the overall surface charge will be negative.

False

Collagen is an abundant, elastic protein that incorporates the use of several post-transitionally modified residues, such as hydroxyarginine

False

Electrostatic catalysis proceeds via covalent bonding interactions

False

Prosthetic groups represent cofactors that bind tightly to their respective enzymes and travel with the enzyme

False

Protein biosynthesis uses only L-amino acids during transcription.

False

Protein folding is a random process, whereby a vast number of possible conformations are tested to find the desired most stable state.

False

The catalytic mechanism of lysozyme requires that both the active site glutamate and aspartate be protonated for activity.

False

Which letter best represents the change in free energy for the overall reaction?

G

Which of the following amino acids would most likely be found on the interior of a protein?

Glycine

Which amino acid has a pI near to physiological pH (~7.4)?

Histidine

Which of the following amino acid residues are often involved in acid-base catalysis in enzyme catalyzed reactions?

Histidine, aspartate and glutamate

____________ between amide (or amine) protons and carbonyl oxygens is necessary to stabilize a regular folding of protein secondary structure.

Hydrogen bonds

The enzyme pyruvate decarboxylase (which catalyzes the reaction below) best represents what major class of enzymes?

Lyase

The basic amino acids include _________, __________, and ___________

Lysine, Arginine, Histidine

Calculate the Kcat using the graph below:

More information is needed.

Which of the following is INCORRECT when considering the tertiary structure of globular proteins?

None of the above

"Turns" are categorized by the number of _______ they contain.

Peptide bonds

Looking at the general amino acid structure (below, right), which group is boxed?

Thats not an amino acid

Which of the following statements about a-keratin is FLASE?

There are three a-helix polypeptide chains in the quaternary structure.

A decrease in a protein's Tm indicates a decrease in protein (thermal) stability

True

At physiological pH (~7.4), the carboxylic acid group of a free cysteine will be deprotonated, while the amino group will be protonated, yielding the neutral zwitterion form.

True

Conservative amino acid mutations can affect stability or function of a protein.

True

Disulfide bonds form between two cysteine residues to increase protein stability

True

Glutathione is a unique tripeptide molecule whose function includes regulating the cellular redox state and preventing damage by ROS.

True

In a bi-substrate, ping pong type enzyme mechanism, the first product must dissociate from the enzyme before the binding of a second substrate

True