CHAPTER 6

the first law of thermodynamics states that the total disorder of a system always increases

FALSE- the second law of thermodynamics

The potential energy in a chemical bond is defined as chemical energy

TRUE

At Equilibrium , the concentrations of the reactants equals that of the products

FALSE- Rate of Formation

Reactions that reach an equilibrium point are reversible 

TRUE

ATP synthesis is exergonic

FALSE Endergonic

Enzymes alter the equilibrium point of a reaction

FALSE- activation energy 

Enzymes dont change the DG of a reaction

TRUE

The rate of catalyst is proportional to the concentration of the enzyme

TRUE

If an enzyme is bound by an allosteric activator, the enzyme will convert from a low-affinity state to a high affinity state

TRUE

Ribozymes are enzymes

FALSE - biological catalysts

The term that best describes all of the chemical reactions of a cell, incluing acquisition and use of molecules and energy, is ______ 

Metabolism 

The removal of a phosphate group during an enzyme catalyzed reaction takes

About 10 milliseconds

A child swinging on a swing utilizes which type of energy

Kinetic, potential, and chemical energy

The ultimate fate of the energy used by organisms is

Conversion into heat

In molecules, the constant motion of the atoms is an example of ______ energy, while the arrangement of atoms and bonds is an example of ____ energy 

Kinetic; potential

Which system is considered a closed system

Earth

Which system is considered an open system

Human

According to the first law of thermodynamics

Energy only changes form

Which statement is a part of the first law of thermodynamics

Energy can be neither created or destroyed

What is the ultimate source of energy for almost all organisms 

The Sun

During every energy transformation, it can be said that

the entropy of the universe increases

Which example would have a negative charge in entropy

water freezing

Which equation is used to calculate the free energy associated with a reaction

G= H-TS

Although energy cannot be created or destroyed, energy transformation are not 100% . WHY?

Energy is lost as an increase in entropy 

If a reaction is endergonic, what can we infer about the reaction

G must be positive

Which two factors determine whether a reaction is spontaneous

Enthalpy and entropy

If a reaction is spontaneous then G is ___ and the reaction is ____

Negative; exergonic

what can be inffered from the graph 

this reaction is endergonic with a positive G

In an exothermic reaction

the products have less potential energy than the reactants

Reversible reactions in a cell rarely reach equilbrium because

the products are generally reactants in other reactions and are thus immediately used

When an enzyme catalyzed reaction reaches equilibrium

the rate of the forward and reverse reaction are equal

Identify the exergonic reaction in the list below

Burning wood for a campfire

Which statement is true for exergonic reactions

The products have less free energy than the reactants

Which reaction is most likely to have more products than reactants when it reaches equilibrium

-100 kcal the most negative one 

An exergonic reaction will have a 

negative change in enthalphy

Eating and digesting a candy bar for energy during a sports event is a good example of 

catabolism 

the breakdown of glucose into carbon dioxide ,water, and ATP is an example of a

catabolic pathway

Energy from ATP is trasnferred to the reactant of an endergonic reaction by addition of a _______ to that molecule

Phosphate

How does energy coupling allow chemical reactions that are not spontaneous to proceed

the energy from the exergonic reaction is transferred to the substrate to destabilize it 

How do cells overcome the erngy requiremnt of endergonic reactions

coupling endergonic and exergonic reactions

Where does energy for ATP synthesis come from 

catabolism of complex molecules into simpler molecules 

Approximately how many ATP molecules are hydrolyzed and resynthesized each second in a typical cell

10 million

answer the question using the graph. Which portion of the graph shows the activation energy in the absence of an enzyme

A

Which portion of the graph shows the activation energy in the presence of enzyme 

B

Which portion of the graph shows the free energy of the reaction

C

The conversion of a diamond into graphite is a spontaneous reaction. Why are most women walking aorund with diamond rings and not graphite rings

the energy of activation is very high

Enzymes aid in metabolism by

stabilizing the transition state

Enzymes

change the rate of a reaction

What is the primary determinant of the function and specificity of an enzyme 

The enzymes conformation 

enzymes function primarily by

increasing the probability that the reactants will come into close proximity to each other in the proper orientation for forming the transition state molecule

Enzymes are ____ catalysts

Protein

You modify the primary sequnce of an enzyme in a region that will be the active site when the protein is properly folded. What is the predicted outcome of this change>>??

the enzyme will not bind to the substrate properly

What is the difference between cofactors and coenzymes

Cofactors can be inorganic or organic, coenzymes are organic cofactors

What is the name of the specific region of an enzyme responsible for catalysts 

Active site 

Coenzymes that bind tightly to enzymes are called

prosthetic groups

What happens to an enzyme after it has catalyzed a reactions

it returns to its original state

What is the purpose of ionic groups in the active sites of enzymes

to alter the substrate in a way that favors catalysts

If an enzyme is saturated

the reaction is being catalyzed at the maximum rate

you do an experiments adding increasing amounts of substrate to a solution containig an enzyme and a ph buffer. If you graph the results with substrate concentrations on the x axis and reaction rate on the y what wil you find over time 

the rate of the reaction will increase rapidly then level off as it reaches saturation.

In competive inhibition

inhibitor binds to and directly blocks the active site of the enzyme

How does the cell overcome inhibition from irreversible inhibitors 

by degrading the enzyme inhibitor complex and generating new enzymes

In order to prevent hair loss in men an inhibitor of the enzyme that converts test to a different androgen DHT is used. The inhibitors are steroids similar to test . what would you classify this inhibition

Competitive

Allosteric inhibition are often

products of the reactions that they regulate

What happens when an enzyme is bound by an allosteric activator 

the enzyme transitions form a low affinity state to a high affinity state 

Why does the cruve sharply drop after 45 C instead of mirroring the slop of the linge goin from 0-40 C

The enzyme begins to denature above a certain temperature eliminating all cataltic activity of the protein 

If an enzymes optimal temp is 37 C then the enzyme

activity will drop at temperature above 37 C and likely be eliminated by 60 C

the optimal ph for enzyme 1 is ?

3 

The optimal pH for enzyme 2 is 

7 

if all three enzymes catalyze the same reaction and your experimental conditions require a ph of 8 which enzyme would you choose 

Enzyme 3

What is the optimal ph of most enzymes

7

Is a ribozyme a true enzyme

no because it is not a protein 

Zhang and CECE’s experiments confrimed which feature of ribozyme activity

Ribozymes catalyze formation of bonds between amino acids in protein synthesis

Ribozymes are 

RNA catalysts 

How did Zhang and Cech puring the RNA molecules that were able to catalyze the linkage between two amino acids 

passing the reaction mixture through a column that binds biotin 

The discovery of ____ suggested that nucleic acdis likely existed prior to proteins 

ribozymes 

Because of some of the problems with explaining how the first RNA organisms originated, an alternative possibility has been proposed in which 

a different form of life existed before the RNA world 

Coupled reaction

The linking of an exergonic reaction with an endergonic reaction that allows a cell to drive a nonspontatneous reaction to completion

equilibrium point

a state in which the rate of the forward reaction equals the rate of the reverse reaction 

Metabolic pathway

A series of chemical reactions where the products of one reaction are the reactants for a subsequent reaction 

Catalyst 

A substance that facilitates a chemical reaction without itself being consumed by the reaction 

Activation Energy

A series of chemical reaction where the products of one reaction are the reactants for a subsequent reaction

Active site 

the portion of the enzume that binds to a reactant or reactants

Substrate

the reactant molecules that binds to an enzyme

Transition state

An intemrediate arrangement of unstable bonds between atoms that can proceed towards either the reactants or products of a reaction

Allosteric regulation

the product of the reaction interacts with an enzyme in a noncompetitive way to inhibit or enhance enzyme activity 

Protein synthesis

Endergonic

Digestion of a candy bar

exergonic

A dead cell

Equilibrium

reactions where DG is negative

Exergonic

A reaction where DG is positive

endergonic

the rate of synthesis equals the rate of degradation

Equilibrium