Chapter 3: Cell Biology

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

polymerization

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

random, random

Select each of the statements which are related to the second law of thermodynamics:

* states events in the universe have direction
* is measured by entropy
* states that energy tends to proceed from a state of higher energy to a state of lower energy

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.

the total energy content of a system

Given the equation G = H - T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

entropy decreases and the reaction is endothermic

Which reaction below might be a suitable coupled reaction for the reaction A + B

C + F

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

irreversible

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

a dead organism

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

a permanent covalent bond

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.

They are required only in large amounts.

An enzyme inhibitor is a molecule that is able to ______ an enzyme and _____ its activity.

bind to; decrease

Tripling the concentration of enzyme will ______ the Vmax and _____ the KM.

triple, not change

When an enzyme is working as fast as it can because its active site is continually refilled with substrate, the condition is referred to as

saturation.

When an enzyme's activity is destroyed by heat or a change in pH, the enzyme is said to be

denatured.

Enzymes increase reaction rate by

lowering the activation energy of a reaction.

When a chemical reaction is in equilibrium,

there is no net change in the amount of substrates or products.

Energy is defined as

the capacity to do work.

Entropy

a measure of disorder

Bioenergetics

study of energy transformations

standard Free Energy Change

the free energy released when reactants are convert to products under standard conditions.

Free Energy

the energy available to do work

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 G of a reaction and thus speeding up the reaction.
d) lowering the G of a reaction and thus speeding up the reaction.
e) changing the free energy of the products and speeding up the reaction.

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

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

a permanent covalent bond

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

The Induced Fit model

Doubling the concentration of enzyme will ______ the Vmax and _____ the KM.

a) double, not alter
b) not alter, double
c) double, double
d) not change, not alter
e) halve, halve

double, not alter

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.

irreversible

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

increasing substrate concentration

What is the effect of a competitive inhibitor on an enzyme-mediated reaction?
a) Vmax stays the same, KM decreases
b) Vmax decreases, KM is unchanged
c) Vmax increases, KM is unchanged
d) Vmax stays the same, KM is unchanged
e) Vmax stays the same, KM increases

Vmax stays the same, KM increases

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

intrinsic and built-in

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

catabolism

The rate of product formation by an enzyme-catalyzed reaction would be increased by

adding more substrate molecules.

Lineweaver Burk Plot

linear graph \n 1/\[S\] vs 1/V

linear graph \n 1/\[S\] vs 1/V

Enzyme vs non enzyme catalyzed graph \n \[S\] vs Vmax/2

The Michaelis constant (KM) of an enzymatic reaction is

a measure of the substrate concentration at exactly one-half of Vmax.

The maximal velocity (Vmax) of an enzymatic reaction refers to ________.

The initial velocity at which the enzyme has attained its theoretical saturation point.

Coenzyme

Organic components used to help enzymes carry out their function

Activation Energy (EA)

A barrier of sufficient kinetic energy necessary for chemical transformations

Transition State

A point when reactants will soon be converted to products

Enzyme

Usually proteins which act as catalysts for specific reactions

Substrate

Reactants abound by an enzyme

Cofactor

Inorganic components of enzymes

Select each of the common mechanisms of enzyme catalysis.

Substrate orientation \n Inducing strain in the substrate \n Changing substrate reactivity

The binding sites of enzymes are

regions of an enzyme that are involved in bringing substrates together.

A molecule that loses electrons during a reaction is

oxidized.

The general term that describes energy stored in chemical bonds is

potential energy

A competitive inhibitor binds to

the active site

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.

reduction

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

cytoplasm, mitochondria, cytoplasm

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

protein kinases

Equilibrium constant

a ratio of the product concentration to the reactant concentration

Enthalpy

total energy content of a system

Which of the following is an example of potential rather than kinetic energy?

A molecule of glucose

Which of the following statements is representative of the second law of thermodynamics?

Cells require a constant input of energy to maintain their high level of organization.

According to the induced fit hypothesis of enzyme catalysis, _____.

the binding of the substrate changes the shape of the enzyme's active site

A number of systems for pumping ions across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases, although they do not often hydrolyze ATP unless they are simultaneously transporting ions. Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a resting muscle cell's cytosol has a free calcium ion concentration of 10-7 while the concentration in the SR is 10-2, then how is the ATPase acting?

ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.

A noncompetitive inhibitor decreases the rate of an enzyme reaction by _____.

changing the shape of the enzyme's active site

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?

catabolism (catabolic pathways)

Catabolic pathways _____.

supply energy, primarily in the form of ATP, for the cell's work

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction?

\-20 kcal/mol

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?

competitive inhibition

When ATP releases some energy, it also releases inorganic phosphate. What happens to the inorganic phosphate in the cell?

It may be used to form a phosphorylated intermediate.

You have discovered an enzyme that can catalyze two different chemical reactions. Which of the following is most likely to be correct?

Either the enzyme has two distinct active sites or the reactants involved in the two reactions are very similar in size and shape.

Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as _____.

a cofactor necessary for enzyme activity

Which of the following is true when comparing an uncatalyzed reaction to the same reaction with a catalyst?

The catalyzed reaction will have the same ∆G.

When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?

It is lost to the environment.

The lock-and-key analogy for enzymes applies to the specificity of enzymes _____.

Binding to their substrate

The active site of an enzyme is the region that _____.

is involved in the catalytic reaction of the enzyme

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's _____.

activation energy

Which of the following statements is a logical consequence of the second law of thermodynamics?

Every chemical reaction must increase the total entropy of the universe.

Which of the following is true of metabolism in its entirety in all organisms?

Metabolism consists of all the energy transformation reactions in an organism.

Which of the following is a statement of the first law of thermodynamics?

Energy cannot be created or destroyed

Which of the following involves a decrease in entropy?

Condensation reactions

Most cells cannot harness heat to perform work because _____.

Temperature is usually uniform throughout a cell.

Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?

As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.

For living organisms, which of the following is an important consequence of the first law of thermodynamics?

The organism ultimately must obtain all of the necessary energy for life from its environment.

Anabloic pathways___

Consume energy to build up polymers from monomers

Reactions that gain heat from the surroundings are said to be __

endothermic.

For a reaction with a standard free energy change, ΔG°' = +7.3 kcal/mol, select each of the following statements which are true

* The reaction could not occur spontaneously.
* The reaction is endergonic.

The continual flow of oxygen and other materials into and out of cells allows cellular metabolism to exist in a steady state because

the concentrations of reactants and products remain relatively constant.

The ________ of glycogen from many glucose molecules is an ________ reaction

synthesis, endergonic

the addition of a phosphate group to a substrate is called ________. The enzyme that catalyzes this reaction is referred to as a ________.

phosphorylation, kinase

An allosteric modulator binds to

a region of the enzyme other than the active site.

According to the second law of thermodynamics,

the amount of entropy in living systems increases without the input of energy.

An exergonic chemical reaction

releases energy as the reaction progresses.

When a chemical reaction is at equilibrium, which of the following statements is always true?

The rate of the forward reaction is equal to the rate of the backward reaction.

Reactions that release heat into the surroundings are said to be ___

exothermic

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

protein kinases

Select each of the statements which are related to the first law of thermodynamics:

is the law of conservation of energy

The part of an enzyme which binds to substrate is called the __.

active site