Bbmb 316 Exam 2

Front 1

In what class of enzymes does alcohol dehydrogenase belong?

Back 1

oxidoreductase

Front 2

Reaction-progress curves for two different reactions are shown below. Which of the following statements is true?

Back 2

Reaction A is exergonic.

Reaction B is endergonic.

The activation energy for B is greater than that of A

(all)

Front 3

Which of the following is INCORRECT

Back 3

Enzymes typically act under milder conditions of temperature and pH than chemical catalysts.

Enzymes typically catalyze reactions at much higher rates than chemical catalysts.

Enzymes catalyze reactions in the forward direction only.

Enzymes are often very specific for their substrates.

Enzyme activities can often be regulated.

Front 4

An enzyme will bind its substrate with high specificity due to

Back 4

a large number of weak interactions at the active site

Front 5

The x-intercept of a Lineweaver-Burk plot is

Back 5

-1/KM

Front 6

Use the velocity plot provided below to estimate values of KM and Vmax for an enzyme-catalyzed reaction

Back 6

The Vmax is approximately 30 μM/s and the KM is approximately 5μM

Front 7

All simple enzyme-catalyzed reactions yield a hyperbolic velocity curve. The shape of the curve suggests

Back 7

an enzyme-substrate (ES) complex is formed

Front 8

Data recorded for a kinetic analysis of the MEK5 kinase and its substrate ERK5 is shown in the table below. Based on this data, determine the VMAX and KM for the MEK5 enzyme

Back 8

VMAX = 61 μM/minute and KM = 5 μM

Front 9

Enzymes assist in the formation of a transition state intermediate by

Back 9

Preventing interference by water molecules.

Positioning substrates precisely in spatial relation with one another and with specific amino acid side chains.

Binding the substrate with high affinity and the product with low affinity.

Playing a direct role in the reaction mechanism

Front 10

Enzymes that show allosteric regulation

Back 10

show regulation by other molecules

Front 11

As shown below, two pathways cooperate to form a single product. What type(s) of feedback mechanism(s) is/are depicted

Back 11

positive and negative feedback regulation

Front 12

What is the physiological significance of cooperativity in sigmoidal kinetics

Back 12

allosteric enzymes display a threshold effect

below a certain substrate concentration there is very little enzyme activity for allosteric enzymes allosteric enzymes are mostly either ON (R state) or OFF (T state)

Front 13

For Michaelis-Menten enzymes, this type of inhibitor binds only to the ES (enzyme-substrate) complex

Back 13

uncompetitive inhibitor

Front 14

Succinylcholine is a fast acting, short duration muscle relaxant that is used when a tube (bronchoscope) is inserted into a patient's trachea and bronchi to look for signs of cancer. Within seconds of the administration of succinylcholine, the patient experiences muscle paralysis and is placed on a respirator while the examination proceeds. Succinylcholine is a competitive inhibitor of acetylcholinesterase, and this inhibition causes paralysis. However, succinylcholine is hydrolyzed by blood-serum cholinesterase, thus, paralysis lasts until the succinylcholine is hydrolyzed by the serum cholinesterase, usually several minutes later. Some patients have a mutant form of the serum cholinesterase that displays a KM of 10 mM, rather than the normal 1.4 mM. What will be the effect of this mutation on the patient?

Back 14

The patient will clear the drug at a much slower rate, and paralysis time will be extended

Front 15

An enzyme is assayed in the presence of an inhibitor (red and green lines) or absence of an inhibitor (black line), and v is measured as a function of [S]. The double reciprocal plot obtained is shown in the figure below.Where is the inhibitor likely to bind on the enzyme?

Back 15

At a regulatory site

Front 16

The active site of acetylcholine esterase contains a powerful nucleophile reactive group that becomes temporarily covalently modified in the course of catalysis. Which catalytic strategy does acetylcholine esterase employ?

Back 16

covalent catalysis

Front 17

The effect of pH on the activity of an enzyme was examined. At its active site, the enzyme has an ionizable group that must be negatively charged in order for substrate binding and catalysis to take place. The ionizable group has a pKa of 6.0. The substrate is positively charged throughout the pH range of the experiment. At which pH will the velocity equal one-half of the maximal velocity attainable under these conditions?

Back 17

pH 6

Front 18

Chymotrypsin uses the following mechanism(s) to catalyze the cleavage of a peptide bond

Back 18

covalent and acid-base catalysis

Front 19

In conducting an experiment with a new drug, you find that regardless of the concentration of substrate, the drug is able to inhibit the enzyme activity. From these data you know that the inhibitor is NOT

Back 19

competitive

Front 20

For the chymotrypsin enzyme, predict the effect of mutating the active site aspartate residue to a tyrosine

Back 20

It is likely that the mutant chymotrypsin enzyme will lose all activity

Front 21

Both myoglobin and hemoglobin can be classified as

Back 21

globular proteins

Front 22

The structure of normal hemoglobin can be best described as

Back 22

a tetramer composed of two αβ dimers

Front 23

What is the Bohr effect?

Back 23

the regulation of hemoglobin binding by hydrogen ions and carbon dioxide

Front 24

The binding of 2,3-bisphosphoglycerate to hemoglobin increases its affinity for oxygen.

Back 24

False

Front 25

In the naturally occurring D series of aldoses, the carbonyl group is found on carbon number

Back 25

one

Front 26

At equilibrium in solution, D-glucose consists of a mixture of its anomers. Which statement most accurately describes the solution?

Back 26

The β-anomer is more stable and predominates over the α-anomer by a ratio of approximately 2:1

Front 27

For the sugars shown below, the enatiomer of sugar C is

Back 27

None of them

Front 28

Lactose is a reducing sugar

Back 28

True

Front 29

Proteins that have covalently bonded carbohydrate units attached to them are called glycoproteins. A functional group in proteins that may serve as a glycosylation site is

Back 29

hydroxyl group

Front 30

The storage form of glucose in animals is

Back 30

glycogen

Front 31

In plants glucose is stored as

Back 31

B) amylose, a linear polymer of glucose units joined by α-1,4-glycosidic bonds.

C) amylopectin, a branched polymer with glucose molecules joined by α-1,4-glycosidic bonds that are linked at approximately every 30 glucose units with α-1,6-glycosidic bonds.

Front 32

Glycogen and amylopectin have the same chemical structure but different architectures

Back 32

True

Front 33

Identify palmitate from the following chemical representations

Back 33

Structure B

Front 34

The longer the fatty acid, the

Back 34

higher the melting point of the fatty acid

Front 35

Identify the molecular structure depicted below

Back 35

Triacylglycerol

Front 36

Why are triacylglycerides well suited as energy storage compounds?

Back 36

A) Fatty acids are ionized at physiological pH and large quantities could disrupt cellular pH.

B) Fatty acids can be cleaved from triacylglycerols by lipases, and then utilized to generate energy.

Front 37

Why can phosphoglycerides form membranes, while triacylglycerols cannot?

Back 37

triacylglycerols are completely nonpolar and hydrophobic

triacylglycerols will aggregate together in an aqueous environment

phosphoglycerides are amphiphilic, with polar heads and nonpolar tails.

phosphoglycerides spontaneously arrange in bilayers, with tails aggregating, and the polar heads interfacing with the aqueous environment

(all)

Front 38

Fatty acids aggregate to form spherical structures called

Back 38

micelles

Front 39

Which of the following concerning sphingolipids and phospholipids is (are) correct

Back 39

A) The backbone of phosphoglycerides is glycerol.

B) The backbone of sphingolipids is sphingosine.

Front 40

Why are lipids a more efficient storage form than glycogen?

Back 40

A) Lipids are stored in an anhydrous from.

B) Lipids are more reduced than glycogen.