PSU BMB 211 EXAM 2

An electrostatic interaction might occur within a protein between what types of amino acid pairs at typical physiological pH?

+ and - charged

A hydrophobic interaction might occur within a protein between what types of amino acid pairs?

non polar and non polar

Secondary and higher orders of structure are not determined by

peptide bonds

If an aspartic acid residue were present in the interior of a globular protein, it would most likely be _________.

tightly associated with the R-group of a lysine residue

Alpha helices are stabilized primarily by what bonds between what

hydrogen bonds between main chain peptide bond component atoms

Tertiary structure is

the folding into a 3d piece

Fibrous proteins contain polypeptide chains ____ producing long fibers or large sheets

organized approximately parallel along a single axis

does a-keratin have polar amino acids?

no

In hemoglobin, a ____ protein, the space between the helices is filled efficiently and tightly with mostly amino acids with __side chains

globular, hydrophobic, polar

functional advantages of quaternary structures include

cooperativity, stability, bringing catalytic sites together, genetic economy and efficiency.

. In the tertiary structure of a protein, a hydrophobic interaction could form between the R-groups of which two amino acids? this question is essentialy asking for what

two non polar amino acids

The information needed for the structure of a protein is contained in

primary structure

. Hemoglobin differs from myoglobin because

hemoglobin is a tetramer, whereas myoglobin is a single polypeptide chain.

in allosteric interactions

changes that take place in one site of a protein cause changes at a distant site

what can denature proteins

heat, pH, detergents

. As catalysts, enzymes are

more effective than nonenzymatic cats

The substrate will only bind to the enzyme when the shapes fit together rigidly

false

In the induced-fit model of substrate binding to enzymes what happens

there is a conformational change in the enzyme when the substrate binds

The active site of an enzyme is the place where the following happen

The enzyme-substrate complex forms and the reaction occurs at the active site.

enzymes are flexible and can work well with different substrates?

Yes

The substrate-enzyme (E-S) complex

may break down to form free enzyme and substrate, or free enzyme and product (essentially may or may not work)

The rate of reaction depends on what

activation energy

catalizing a reaction does what

lowers the activation energy

does the catylist have an effect on delta g?

no

cofactors are what

a non-protein in chemical nature

Nicotinamide adenine dinucleotide is

. a coenzyme in oxidation-reduction reactions

. Which of the following statements about coenzymes is true?

a. They are commonly derived from vitamins.

b. They bind to the active site region on specific types of enzymes.

c. They can be metal ions, such as Zn(II).

d. NAD+, FAD and biotin are all examples of coenzymes.

e. All of these statements are true.

all of the above

which of the following is a mechanism of regulating enzyme activity?

a. Feedback inhibition by product.

b. Addition or removal of phosphate groups from of the enzyme.

c. Presence of activators.

d. Activation of zymogens.

e. All of these regulate enzyme activity

all of the above

Where do allosteric inhibitors bind on an enzyme?

they always bind at a site different from the active site

what type of inhibitor is most likely to inhibit regulatory subunits of an allosteric enzyme?

a competitive inhibitor

. For competitive inhibition is possible to overcome the effect of the inhibitor by increasing the concentration of substrate?

yes

A noncompetitive inhibitor binds where?

to the enzyme at a site other than the active site

does the Michaelis constant determine vmax?

no

What effect is seen on a Lineweaver-Burk graph when a competitive inhibitor is added?

the y intercept remains the same but the slope is changed

What effect is seen on a Lineweaver-Burk graph when a non-competitive inhibitor is added?

slope and y int are changes

Non-competitive inhibitors have what effect?

Changine the vmax

If an inhibitor changes the slope of the Lineweaver-Burk graph, but not the y-intercept, it is this type of inhibition:

competative

The rate of a zero-order reaction depends on the _____.

presence of a catalyst

Competitive Inhibition (what is it, vmax and km)

mimics the substrate and competes for the enzymes activation site, v max remains unchanged, km is higher

Non-Competitive Inhibition (what is it, vmax and km)

binds to the allosteric site (an additional site) on both the free enzyme and the e-s complex, decreases vmax, km unchanged

Un-Competitive Inhibition (what is it, vmax and km)

binds to the e-s complex, reduces vmax and kmax

competative graph

x

uncompetative graph

parallel

non- comp

touch at x axis and continue on

v=

vmax [s]/km+[s]

lineweaver burke the y intercept is what and the slope is what

y intercept is the km, slope is km/vmax

Name the positively charged amino acids

Lysine, Arginine, and Histidine

Name the negatively charged amino acids

Aspartatic acid and Glutamic acid

A polypeptide has a high pI value. What type of amino acids are likely to be present?

basic/negatively charged

Given that pK₁ = 2.35 and pK₂ = 9.69 for alanine. What is its isoelectric point?

6.02

Secondary and higher orders of structure are determined by all EXCEPT

 

hydrophobic interactions

 

ionic bonds

 

van der Waals forces

 

hydrogen bonds

 

peptide bonds

peptide bonds

An electrostatic interaction might occur within a protein between what type of amino acid pairs at typical physiological pH?

±

What remains intact when a protein is denatured

primary structure

The expression of the Michaelis constant is equal to

Where
K₁ = the rate constant for ES formation
K₂ = the rate constant for ES dissociation
K₃ = the rate constant for product formation

(K₂ + K₃)/K₁

In the Lineweaver-Burk double reciprocal plot the slope is equal to __________.

K_m/V_max

In the Lineweaver-Burk double reciprocal plot the vertical intercept is equal to __________.

1/V_max

In the Lineweaver-Burk double reciprocal plot the horizontal intercept is equal to __________.

-1/km

In the michaelis menten plot the x axis is equal to __________.

S

In the michaelis menten plot the y axis is equal to __________.

V0

In the lineweaver burk plot the x axis equal to __________.

1/s

In the lineweaver burk plot the y axis equal to __________.

1/v

In competitive inhibition, increasing the concentration of substrate __________

increases the overall rate of the reaction

The pKa values for tyrosine are as follows:

pK₁ 2.20

pK₂ 9.11

pK_R 10.07

What is the pI of tyrosine?

(choose the closest answer to the one you calculated)

 

 

9.59

 

5.65

 

6.14

 

9.11

5.65

A hydrophobic interaction might occur within a protein between what type of amino acid pairs?

polar/nonpolar

Alpha helices are stabilized primarily by:

 

electrostatic interactions between R-groups.

 

hydrogen bonds between the main chain peptide bond component atoms.

 

hydrophobic interactions between the α-carbons of the main chain.

 

hydrogen bonding between the R-groups.

hydrogen bonds between the main chain peptide bond component atoms.

In allosteric interactions

 

proteins that consist of a single polypeptide chain form aggregates.

 

disulfide bonds are broken.

 

changes that take place in one site of a protein cause changes at a distant site.

 

metal ions always bind to the protein.

changes that take place in one site of a protein cause changes at a distant site.

In competitive inhibition, Vmax remains unchanged but K_M increases.

 

True

 

False

true

Increasing the substrate concentration can overcome non-competitive inhibition.

 

True

 

False

false

In a Michaelis Menten Plot, decreasing [S] has what effect on V_o ?

 

 

Has no effect

 

Decreases Vo

 

Increases Vo

 

Cannot be determined

Decreases Vo

In a Michaelis Menten plot ______ is represented on X-axis and ______ is represented on Y-axis. 

[S], Vo

For an enzyme kinetics experiment, the Lineweaver-Burk plot of the data shows Y-intercept is 0.25. What is the Vmax of the enzyme under investigation.

4

In Michaelis–Menten kinetics, what does a low Km value indicate? Check all that apply

 

Low product formation

 

High reaction rate

 

High substrate affinity

 

Low enzyme concentration

 

Low substrate affinity

 

substrate concentration at Vmax

 

substrate concentration at Vmax/2

High reaction rate, High substrate affinity, substrate concentration at Vmax/2

In Michaelis Menten graph, the which of following hold true once the reaction reaches Vmax? Select all the answers that are correct. (select all that apply)

 

substrate concentration increases

 

Enzyme active sites are all saturated with substrate

 

No more substrate is available to bind to enzyme

 

Reaction follows first-order kinetics

 

reaction follows zero-order kinetics

 

The substrate concentration equals K_M

Enzyme active sites are all saturated with substrate, reaction follows zero-order kinetics

after pka1 what is deprotonated, what isn’t

COOH is deprotonated, NH3+remains protonated

Why should the core of most globular and membrane proteins consist almost entirely of α-helix and β-sheets?

 

Hydrogen bonded structures must be kept away from water solvent.

 

Highly polar N−H and C=O moieties of the peptide backbone must be neutralized in the hydrophobic core of the protein.

 

Hydrogen bonding only occurs in the core of proteins.

 

Trapped water stabilizes the helix and sheet structures.

 

None are true.

Highly polar N−H and C=O moieties of the peptide backbone must be neutralized in the hydrophobic core of the protein.

Vmax of a reaction is is 100 umol/min and Km is 5mM. What is the velocity of this reaction when [S] is 20 mM?

 

a) cannot be determined

 

b) 40

 

c) 80

 

d) both b and c are right

 

e) 20

80

Which of the following is a coenzyme?

 

NADP⁺

 

Zn⁺⁺

 

Cu⁺⁺

 

Mg 2+

 

Oxytocin

NADP⁺

Which of the following is not a type of oxidoreductase?

 

Peroxidase

 

Hydroxylase

 

Reductase

 

Dehydrogenase

 

Peptidase

Peptidase

what is competitive inhibition

an inhibitor molecule binds directly to the enzyme’s active site

what is noncompetitive inhibition

an inhibitor binds to an allosteric site (a location other than the active site), decreasing enzyme efficacy

what is uncompetitive inhibition

Binds exclusively to the enzyme-substrate (ES) complex, preventing product formation.

draw non competitive inhibition

draw un competitive inhibition

draw competitive inhibition

x shape (y intercept is same, x is changed)