biology Chapter 7

Each enzyme has an optimum ___________ range. Changing the ______________ outside of this range will slow enzyme activity.

pH

Enzymes are most effective at optimal conditions. Factors that affect enzyme activity include ____________ and ________________.

pH temperature

ATP donates energy through the transfer of a phosphate group. Phosphate bonds in ATP are transferred by the process known as ________.

phosphorylation

In an endergonic reaction, free energy has a ________ value.

positive

Chemical energy in molecules is:

potential energy stored in chemical bonds released in a chemical reaction

Compliance with the second law of thermodynamics presumes that:

-entropy is increasing -maintaining order in a system requires input of energy -during any energy transformation, some energy is converted into an unusable form -disorder is increasing

The second law of thermodynamics states that

-supports the observation that energy available for doing work is decreasing -explains why heat is generated by a moving car -describes what happens when energy is converted from one form to another

Enzymes are inhibited:

-when an inhibitor competes for the active site on the enzyme - by specific drugs - when they bind weakly with an inhibitor - either competitively or noncompetitively - allosterically

ATP links exergonic and endergonic reactions. Exergonic reactions are generally part of ______________ pathways and endergonic reactions are generally part of __________________ pathways.

catabolic / anabolic

Entropy

A measure of disorder or randomness.

________________, the energy currency of the cell, has a structure that easily allows it to perform its vital function.

ATP

What type of reaction: results in a negative value for delta G releases energy is a "downhill" reaction reduces total free energy can be spontaneous

An exergonic reaction

metabolic pathway

Begins with a specific molecule, which is then altered in a series of defined steps, resulting in a certain product.

Plants convert radiant energy to _________ energy.

chemical

In the metabolism of living things, some _____________ occur spontaneously, releasing free energy that is then available to perform work.

chemical reactions

________ inhibition occurs when the inhibitor competes with the normal substrate by binding to the active site of the enzyme.

Competitive

According to the first law of thermodynamics:

Energy cannot be created or destroyed

lower the required activation energy are coded for by genes speed up biological chemical reactions

Enzymes

______________ reactions are spontaneous and they release energy that can perform work.

Exergonic reactions

_________________ pH values can cause enzymes to denature.

Extreme

Explain what is meant by G (free energy) and relate it to changes in entropy

Gibbs free energy is the energy associated with a chemical reaction that can do useful work. It equals the enthalpy minus the product of the temperature and entropy of the system. ... If ΔG is positive, then the reaction is non-spontaneous....

________ is sometimes described as a constant struggle against the second law of thermodynamics.

Life

Catabolism

Metabolic pathways that break down molecules, releasing energy.

Anabolism

Metabolic pathways that construct molecules, requiring energy.

The most common acceptor molecule in cellular oxidation reduction reactions is ________.

NAD+ nicotinamide adenine dinucleotide

________ inhibition occurs when the inhibitor binds to the enzyme at a site other than the active site.

Noncompetitive

Which has the most energy, the oxidized form of a substance or its reduced form?

Oxidation occurs when a molecule loses an electron or increases its oxidation state. When a molecule is oxidized, it loses energy. In contrast, when a molecule is reduced, it gains one or more electrons. As you might have guessed, the molecule gains energy in the process. Confused? Think about it like this. Electrons orbit the atomic nucleus, giving it electrical and kinetic energy. If you have more electrons, you have more energy. Keep in mind, however, energy input may be required (activation energy) to get a molecule to change its oxidation state.

_____________________ is "stored energy"

Potential energy

________________temperature generally speeds up a reaction, and _________________ temperature slows down a reaction. However, extreme high ______________ can cause an enzyme to lose its shape (denature) and stop working.

Raising / lowering / temperatures

________________________ reactions: -may use NAD as a hydrogen/electron acceptor -occur because every oxidation reaction must be coupled to a reduction reaction -often occur in a series -are part of aerobic respiration and photosynthesis -transfer energy stored in electrons

Redox

__________________________ explain why organisms cannot produce energy but must continuously capture it from somewhere else

The laws of thermodynamics

How do organisms succeed in this struggle without violating the second law?

The second law of thermodynamics states that all spontaneous processes increase the entropy, or disorder, of the universe. Living organisms are highly organized, and therefore it seems that as they maintain order they defy the second law of thermodynamics. Although the second law of thermodynamics always produces a trend towards disorder, living organisms can maintain order by releasing heat energy into the environment. This increases the net entropy of the universe even as the entropy of the organism itself decreases.

spontaneous reaction

a reaction that favors the formation of products at the specified conditions; spontaneity depends on enthalpy and entropy changes

The substance that gives up electrons is _______________ and the substance that receives the electrons is ______________________.

oxidized / reduced

The energy barrier in a chemical reaction necessary to start a reaction is the energy of:

activation

All noncompetitive inhibition is allosteric inhibition, but not all allosteric inhibition is noncompetitive inhibition because certain forms of allosteric inhibition can prevent the substrate from binding to the _______________ site. It can thus either be noncompetitive or competitive.

active

A substrate binds to an enzyme at the ________.

active site

Enzymes are specific because the shape of the ________ is closely related to the shape of the substrate.

active site

The part of the enzyme where the substrate binds is called the ____________. Here, the enzyme changes shape slightly, fitting tightly with the substrate and forming the enzyme/substrate complex.

active site

The three main parts of the ATP molecule are

adenine ribose three phosphates

An __________________ inhibitor binds to the enzyme, inducing it to assume an inactive form.

allosteric

Molecules that turn off enzymes are called ___________ inhibitors.

allosteric

Substances that bind to an enzyme at a specific site other than the active site and alter enzyme activity are called ________.

allosteric regulators

Metabolism is the sum of all ________________ and _________________ that occurs in an organism.

anabolism catabolism

Most enzyme names end in ________.

ase

All reactions have a required energy of activation. The activation energy of a reaction begins the reaction by using energy to ________.

break existing bonds

An organic non-polypeptide cofactor is called a ________.

coenzyme

Enzyme activity may be affected by:

cofactors temperature genes phosphorylation pH

The total energy in the universe does not change. The first law of thermodynamics states that energy can be neither ______________ nor ___________ , however, it can be ______________ from one form to another

created destroyed transformed / converted

Free energy ______________ during an exergonic reaction.

decreases

The mathematical/chemical symbol for change in free energy is ________.

delta G

The function of a biochemical pathway is to drive a sequence of reactions in a particular _________________.

direction

The term entropy refers to the ________ in the universe.

disorder randomness

The effectiveness of some _________ is due to their ability to inhibit _____________ that are critical to the normal functioning of certain pathogenic organisms.

drugs / enzymes

________________is the capacity to do work.

energy

G (free energy)

energy available to do work

Kinetic energy is:

energy of motion, doing work

bond energy

energy required to break a bond

Thermodynamics is the study of _______________

energy transformations

Free energy is available to do cell work. An increase in ________ leads to a decrease in the amount of free energy.

entropy

Enzymes lower activation energy by forming an unstable intermediate called the ________.

enzyme-substrate complex

Chemical reactions in organisms are regulated by _____________, substances that lower the amount of energy needed to activate reactions.

enzymes

Diffusion is an ________________ process.

exergonic

The cell regulates enzymatic activity. If a product in a series of reactions inhibits an earlier reaction in the pathway, the enzymatic activity is being regulated by a process called _______.

feedback regulation

In every energy transaction, some energy is dissipated as ___________.

heat

The entropy of the universe is increasing. The second law of thermodynamics states that in every energy conversion or transfer some energy is dissipated as ________.

heat

Diffusion is an exergonic process. In a concentration gradient, energy moves from a _____________ region of concentration to a region of ________________ concentration.

high / low

Redox reactions in cells usually involve the transfer of a ________ rather than just an electron.

hydrogen atom hydrogen

Free energy _____________ during an endergonic reaction.

increases

When the substrate binds to the enzyme molecule, it causes a change in the shape of both molecules, known as the ________.

induced fit

is the energy of motion

kinetic energy

The cell maintains a very high ratio of ATP to ADP. The cell cannot store ________ quantities of ATP.

large

ATP+ H2O ⟶ ADP+ P ΔG = -7.3 kcal/mol This reaction: a. loses free energy b. is anabolic c. hydrolyzes ATP d. is exergonic e. is endergonic

loses free energy hydrolyzes ATP is exergonic

The required energy of activation of a reaction can be _____________ by a specific enzyme.

lowered

Enzymes are organized into teams in _____________ pathways.

metabolic

A series of reactions can be illustrated as A → B → C... etc. where each reaction (→) is carried out by a specific enzyme. Such a series is referred to as a ________.

metabolic pathway

The sum of all chemical activities in an organism is known as:

metabolism

In the reaction C ⟶ D, where the value of ΔG is negative, the reactant has ________ (more or less) free energy than the free energy of the product.

more

A spontaneous reaction is one in which the change in free energy has a ________ value.

negative

A _______________ inhibitor inhibits the action of an enzyme by binding to the enzyme somewhere other than the active site.

noncompetitive

Allosteric inhibitors change how the active site is shaped and ____________ it from binding, or attaching, to the substrate. If the enzyme can't attach to the substrate, it can't do its job! These molecules and the allosteric site to which they bind are like the 'off switch' for the enzyme.

prevents

When enzymes work in teams, the ______________ from one enzyme-substrate reaction becomes the _________________for the next enzyme-substrate reaction.

product / substrate or reactant

Energy transfers often occur in cells through _______________ utilizing electron carrier molecules.

redox reactions

Cells drive endergonic reactions by coupling them to exergonic reactions. Exergonic reactions _____________ (release or require input of) free energy; endergonic reactions ________________ (release or require input of) free energy.

release require input of

Enzymes can be inhibited by certain chemical agents. Inhibition is ________ when the inhibitor-enzyme bond is weak.

reversible

Enzymes lower the activation energy to ________ the rate of the reaction.

speed up

potential energy

stored energy

competitive inhibition

substance that resembles the normal substrate competes with the substrate for the active site

Enzymes lower the activation energy of a reaction - that is the required amount of energy needed for a reaction to occur. They do this by binding to a _____________ and holding it in a way that allows the reaction to happen more efficiently.

substrate

"Induced fit" means that when a substrate binds to an enzyme's active site the _______________ and ______________ undergo conformational changes

substrate / enzyme

The total potential energy of a chemical reaction (enthalpy) equals the ________ of the reactants and products.

total bond energies

Cells are able to function because they have mechanisms that _________ energy from the _____________ into useful forms

transform / environment