Deck 3: Bioenergetics,enzymes and Metabolism

Question 1

Enzymes work by ___________.

A)raising the activation energy of a reaction and thus speeding up the reaction.
B)lowering the activation energy of a reaction and thus speeding up the reaction.
C)raising the $\Delta$ G of a reaction and thus speeding up the reaction.
D)lowering the $\Delta$ G of a reaction and thus speeding up the reaction.
E)changing the free energy of the products and speeding up the reaction.

Answer 1

lowering the activation energy of a reaction and thus speeding up the reaction.

Question 2

What kind of enzyme adds phosphate groups to enzymes for the purpose of activating or deactivating them?

A)phosphatases
B)protein kinases
C)flippases
D)glycosyltransferases
E)carboxypeptidase

Answer 2

B

Question 3

What kind of inhibitor binds very tightly to an enzyme often forming a covalent bond with an amino acid in the active site?

A)irreversible
B)reversible
C)uncompetitive
D)reversible and uncompetitive
E)None of these are correct.

Answer 3

A

Question 4

The presently accepted model of enzyme action was proposed by Daniel Koshland in the 1960s and suggested that the enzyme was a flexible structure with an active site roughly complementary to the substrate that binds it.After its initial interaction with the substrate,the enzyme alters its shape and thus improves the fit of the substrate in the active site)What is the name of this model?

A)The Induced Fit model
B)The Flexible Sponge model
C)The Lock and Key model
D)The Koshland model
E)The Flexible Fit model

Question 5

Entropy is associated with the _______ movement of particles of matter,which because they are _____ cannot accomplish a directed work process.

A)rapid,directed
B)random,random
C)rapid,random
D)slow,rapid
E)random,slow

Question 6

Proteins are dynamic molecules that are capable of ________ motion that can have important functional relevance.The existence of this type of motion has suggested that enzymes are capable - even in the absence of substrate - of many of the same movements that can be detected during their catalytic cycle.

A)extrinsic
B)intrinsic
C)instant
D)built-in
E)intrinsic and built-in

Question 7

Given the equation $\Delta$ G = $\Delta$ H - T $\Delta$ S,which set of conditions would result in a reaction that is unambiguously nonspontaneous?

A)entropy decreases and the reaction is endothermic
B)entropy increases and the reaction is exothermic
C)entropy stays the same and there is no change in enthalpy
D)entropy decreases and the reaction is exothermic
E)entropy increases and the reaction is endothermic

Question 8

The energy stored in ATP is converted to mechanical energy that moves organelles around within the cell.This is an example of __________.

A)being exothermic
B)being endothermic
C)energy transduction
D)polymerization
E)catheterization

Question 9

Doubling the concentration of enzyme will ______ the V_max and _____ the K_M.

A)double,not alter
B)not alter,double
C)double,double
D)not change,not alter
E)halve,halve

Question 10

What is the effect of a competitive inhibitor on an enzyme-mediated reaction?

A)V_max stays the same,K_M decreases
B)V_max decreases,K_M is unchanged
C)V_max increases,K_M is unchanged
D)V_max stays the same,K_M is unchanged
E)V_max stays the same,K_M increases

Question 11

What kind of interaction is not involved in the binding of a substrate to a normally functioning enzyme?

A)H bonds
B)a transient covalent bond
C)ionic bonds
D)a permanent covalent bond
E)hydrophobic interactions

Question 12

Glycolysis occurs in the ________; the Krebs (TCA)cycle occurs in the ______ of eukaryotes and the ______ of prokaryotes.

A)cytoplasm,cytoplasm,cytoplasm
B)mitochondria,cytoplasm,mitochondria
C)cytoplasm,mitochondria,cytoplasm
D)cytoplasm,photosynthesis,cytoplasm
E)cytoplasm,mitochondria,mitochondria

Question 13

Which reaction below might be a suitable coupled reaction for the reaction A + B <-> C + D ( $\Delta$ G = -8.7 kcal/mole)?

A)E + F <-> G + H ( $\Delta$ G = -5.4 kcal/mole)
B)B + F <-> G + H ( $\Delta$ G = -5.4 kcal/mole)
C)C + F <-> G + H ( $\Delta$ G = +8.3 kcal/mole)
D)C + F <-> G + H ( $\Delta$ G = +9.7 kcal/mole)
E)A + F <-> G + H ( $\Delta$ G = +10.2 kcal/mole)

Question 14

The effect of a competitive inhibitor can be reversed by _______.

A)increasing inhibitor concentration
B)increasing substrate concentration
C)heating the reaction mixture
D)changing the pH
E)massaging the enzyme

Question 15

A reaction involving the gain of one or more electrons is a(n)_________ reaction.

A)oxidation
B)reduction
C)inclusion
D)elimination
E)None of these are correct.

Question 16

Which property below is not a characteristic of enzymes?

A)They are required only in large amounts.
B)They can be altered reversibly during a reaction.
C)They do not alter the G of a reaction.
D)They are used over and over again.
E)They do not determine whether a reaction is exergonic or endergonic.

Question 17

You are observing a reaction and discover that the reaction vessel is warm to the touch.The reaction also results in an increase in entropy.Is the reaction spontaneous? How do you know?

Question 18

Metabolic pathways that make available raw materials from which other molecules can be synthesized and that provide chemical energy required for many cell activities are known as ______.

A)anabolism
B)catabolism
C)manabolism
D)allosterism
E)anabolism and catabolism

Question 19

Enthalpy is ________.

A)the energy available to do work
B)the total energy content of a system
C)named after J.Willard Gibbs
D)the energy available to do work and the total energy content of a system
E)All of these are correct.

Question 20

What kind of organism reaches equilibrium?

A)one that is actively metabolizing
B)one with a low metabolic rate
C)a dead organism
D)a eukaryote
E)a prokaryote

Question 21

The development of bacterial resistance to antibiotics is an example of what engine of evolution?

Question 22

You are studying metabolic pathways and discover that two pathways intersect so that the enzyme basinase participates in both of the intersecting pathways,in one case using substrate K and in the other using substrate M.When presented with substrate K in amounts significantly larger than M,basinase converts K to L which leads eventually to the production of the end product R.The activity of the second pathway is depressed simultaneously.In the presence of large amounts of substrate M and lower amounts of substrate K,the second pathway is activated and culminates in the production of that pathway's end product Y.The activity of the first pathway is depressed simultaneously.What are the alternative substrates K and M acting like?

Question 23

You isolate the enzyme that synthesizes folic acid in bacteria and conduct some enzyme kinetics experiments.You find,not surprisingly,that sulfa drugs inhibit the enzyme's activity.What happens to the Vmax and KM of this enzyme when it is treated with sulfa drugs? Why do sulfa drugs have no effect on human metabolism?

Question 24

Do the equations below represent coupled reactions? If not,why not?
A + B <-> C + D ( $\Delta$ G = +5.4 kcal/mole)
D + F <-> G + H ( $\Delta$ G = -4.4 kcal/mole)

Question 25

Below is a segment of a cell's collection of biochemical pathways.M is a product of one series of these reactions.It is also a regulatory molecule.Look at the pathway below and indicate the position(s)at which M is most likely to act as a feedback inhibitor when its concentration gets too high.

Question 26

If ATP is present in relatively high amounts,what is likely to happen to the rate of glycolytic activity in that cell?

Question 27

A number of antibiotics attack prokaryotic protein synthesis,but not eukaryotic protein synthesis.Name two common antibiotics that work this way.What is their site of action and why don't they affect eukaryotic protein synthesis?

Question 28

If a reaction vessel is cold to the touch and the reaction results in an increase in order in the reaction vessel,is the reaction spontaneous or nonspontaneous? Explain your answer.

Question 29

Penicillin is an irreversible inhibitor of the transpeptidases,enzymes that cross-link components of the bacterial cell wall.The cell wall is thus fragile and the bacteria die.Penicillin and its derivatives are structural analogs of the natural substrates of these enzymes.Why doesn't penicillin normally kill humans,unless a severe allergic reaction (anaphylaxis)develops? How does penicillin inhibit transpeptidase?

Question 30

An enzyme has a K_M of 20 µM and a V_max of 50 mmoles of product/minute/µg of enzyme.After exposure to an inhibitor and analysis on a Lineweaver - Burk plot the following values are obtained: -1/ K_M = - 0.05 liters/µmole and 1/ V_max = 0.04 (mmoles of product/minute/µg of enzyme)-1.What kind of inhibitor was used in the experiment?

Question 31

Why are alcoholic beverages often made in airtight containers?

Question 32

Why has the pharmaceutical industry drastically cut resources devoted to the development of new antibiotics?

Question 33

Do the equations below represent coupled reactions? If not,why not?
A + B <-> C + D ( $\Delta$ G = -5.4 kcal/mole)
E + F <-> G + H ( $\Delta$ G = +4.4 kcal/mole)

Question 34

What is the reason for treating a patient simultaneously with two antibiotics against the same bacterium?

Question 35

Where is S.aureus usually found in humans? What kind of hospitalized patients develop life-threatening S.aureus infections? Distressingly,instead of just showing up in hospitals,methicillin-resistant S.aureus (MRSA)is showing up in other places.What are some examples?

Question 36

What is unusual about the mechanism by which vancomycin inhibits transpeptidation of the bacterial cell wall? Why is it more difficult for bacteria to develop resistance to vancomycin than to other antibiotics?

Question 37

If an antibiotic were found to bind to a site on an essential bacterial enzyme other than the active site,what would its most likely mode of action be?

Question 38

In the reaction A + B <-> C + D,how might the reaction take place in the cell if the $\Delta$ G is very positive? How might the reaction occur if the $\Delta$ G is slightly positive?

Question 39

4 ATPs per glucose molecule are made during glycolysis.Why then is there a net production of only 2 ATPs for each glucose molecule in the pathway?

Question 40

You are observing an enzyme driven reaction.To the reaction mixture you add a chemical X which inhibits the reaction.If you add more substrate,the reaction rate approaches the V_max of the uninhibited reaction.Furthermore,the structure of X is similar to the natural substrate.What kind of inhibitor is X?

Question 41

There have been two new classes of antibiotics developed and approved since 1963.One of these antibiotics acts specifically on bacterial ribosomes.What is it? Another new group of antibiotics is the cyclic lipopeptides.What is a representative of this group and how does this group of antibiotics work?

Question 42

What appears to be the effect of reduced calorie intake on rhesus monkeys?

Question 43

Certain bacteria have an adaptation that allows them to render penicillin harmless; they have adapted due to their possession of an enzyme called penicillinase.How does it render them immune to the effects of penicillin?

Question 44

Many bacteria have acquired resistance to penicillin by picking up the gene for -lactamase.However,some have developed resistance without acquiring this gene.How do these bacteria escape the fatal effects of penicillin?

Question 45

If mice are maintained on very strict diets with reduced caloric intake,what happens to their life span as compared to littermates fed diets with normal caloric content? What is a possible explanation for the effect of this diet on these animals?

Question 46

What evidence suggests that lower blood levels of insulin may be important in promoting longevity?

Question 47

How are new compounds typically screened for their effectiveness as antibiotics?

Question 48

What are some ways that antibiotic resistance genes can be passed from bacterium to bacterium?

Question 49

What strategies are employed to combat the ability of the AIDS (HIV)virus to develop drug-resistant variants?

Question 50

Which antibiotic inhibits the enzyme DNA gyrase,which is required for bacterial DNA replication?

Question 51

If people are kept on diets containing about 25% fewer calories than would be required to maintain their initial body weight,what happens?

Question 52

Why was methicillin developed?

Question 53

How does the AIDS virus manage to avoid the effects of drugs that attack its enzymes so effectively?

Question 54

Penicillin fits into the active site of transpeptidases and thus acts as what kind of inhibitor? How is the effect of such an inhibitor usually able to be reversed? Why would this approach not work with penicillin?