Chapter 8 - Energy, Enzymes and Metabolism

Chemical Reaction

The change in the composition or distribution of atoms of a substance with consequent alterations in properties

A chemical reaction has the following two components:

• Reactants

• Products

Sucrose + H2O reacts to form ____ and ____

Glucose and fructose

* This is a hydrolysis reaction. Water is added to sucrose in order to break it down into glucose and fructose.

Metabolism

Sum total of all chemical reactions occurring in a biological system at a given time

Metabolism involves changes in _______

Energy

Energy is the capacity to do ______, or the capacity for change

Work

What are the two forms of energy?

• Kinetic

• Potential

Potential energy is energy stored as _______, _______, or ________

• Chemical bonds

• Concentration gradients

• Charge imbalance

Kinetic energy is the energy of _______

Movement

First Law of Thermodynamics states that energy is neither _____ nor ______

Neither created nor destroyed

* You can only change the form of the energy. The total energy before and after the conversion is the same.

Second Law of Thermodynamics states that when energy is converted from one form to another, some of that energy becomes __________

Unavailable to do work

The second law of thermodynamics states that some energy becomes unavailable to do work when energy is converted from one form to another. Some energy is lost to ______

Disorder

Entropy (S) is a measure of the ______ in a system

Disorder

The amount of disorder tends to increase because of _____________

Energy transformations

In a biological system, the total amount of energy is called ________

Enthalpy (H)

In a biological system, ________ is the usable energy that can do work.

Free energy (G)

In a biological system, usable energy is called free energy (G). Unusable energy is represented by the product of ____ and ____

Entropy (S) and Absolute temperature (T)

* Enthalpy = Free energy + Absolute Temp x Entropy

* H = G + TS

What’s the equation for enthalpy in terms of free energy, entropy, and absolute temperature?

H = G + T(S)

* You can rearrange this formula in order to solve for each individual variable.

What part of this formula is missing?

G (reactants)

Change in energy can be measured in ______ or ______

* A picture of the formula for free energy was attached

• Calories

• Joules

If ΔG is a positive value, then this indicates that energy is _______

Required

If ΔG is a negative value, then this indicates that energy is _______

Released

If ΔG is zero, then this indicates ___________

No reaction is occurring

Endergonic reactions are reactions that ______ free energy. This reaction is represented by a positive ΔG value.

Consume

Endergonic reactions are represented by a _______ ΔG value

Positive

Exergonic reactions are reactions that ______ free energy. This reaction is represented by a negative ΔG value.

Release

Exergonic are represented by a ______ ΔG value.

Negative

Helpful Info - How to remember that Endergonic reactions consume free energy:

Match the word endergonic with the word enter. Something is being consumed or entering into

Helpful Info - How to remember that Exergonic reactions release free energy:

Match the word exergonic with the word exit. When something exits, it is also being released.

Anabolism results in more _____ but less ______

More complexity, but less disorder

Catabolism results in less_____ but more______

Less complexity, but more disorder

Chemical Equilibrium is when the rate of a reaction forward is equal to the rate of the _______ reaction.

Reverse

At chemical equilibrium there is no net change. ΔG is equal to ______ at chemical equilibrium.

Zero

Food is broken down by ______ reactions

Catabolic

The components of food are used in ______ reactions

Anabolic

ATP

Adenosine triphosphate

ADP

Adenosine Diphosphate

AMP

Adenosine Monophosphate

ATP captures and ______ free energy

transfers

ATP can be hydrolyzed to _____ and _____, releasing a lot of energy for endergonic reactions.

ADP and Pi

ATP can also ____ other molecules, which gain some energy

Phosphorylate

Phosphorylation

Donation of a phosphate group to a molecule

Is the formation of ATP endergonic or exergonic?

Endergonic

The formation and hydrolysis of ATP couple _____ and _____ reactions

Endergonic and exergonic

Is cell respiration endergonic or exergonic?

Exergonic (releases energy)

Is active transport endergonic or exergonic?

Endergonic (requires energy)

Is cell movement endergonic or exergonic?

Endergonic (requires energy)

The synthesis of ATP from ADP and Pi requires _______

Energy

ATP ______ energy to endergonic reactions

Releases

Catalysts _____ rates of chemical reactions

Increase

Are catalysts altered by the reactions?

No

Most biological catalysts are ______, that act as a framework in which reactions can take place

Enzymes

Which type of RNA can be catalytic?

Ribozymes

Catalysts speed up reactions by ____________

Providing space for the reactants to bond

Activation Energy (E_a) is the amount of energy required to ______ the reaction

start

Activation energy puts the reactants in a reactive mode called the _________

Transitive state

Activation energy changes the reactants into _________ with higher free energy—transition state intermediates.

unstable forms

Enzymes lower the energy barrier by bringing the _______ together

reactants

Enzymes are highly specific in the reactions with substrates. The part of the enzyme that interacts with the substrate is called the ________

Active site

* Substrate molecules bind to this part

Reactants are called ______. These molecules bind to the active site of the enzyme

Substrates

The ______ of the enzyme determines specificity

3D shape

What are the 6 categories of enzymes

• Oxidoreductases (oxidization)

• Hydrolases (hydrolysis)

• Transferases (transfer functional groups)

• Isomerases (make isomers)

• Lyases (break bonds)

• Ligases (forms bonds)

The _________ is held together by hydrogen bonds, electrical attraction, or covalent bonds

Enzyme-substrate complex (ES)

An uncatalyzed reaction has greater ______________ than a catalyzed reaction

activation energy

There is no difference in __________ between catalyzed and uncatalyzed reactions

free energy

Enzymes can increase reaction rates by __________

1 million to 10^17

Enzymes do not change ________ and _______

• Final equilibrium

• Energy released as a result of the reaction

Enzymes reduce ________ and increase ________

• Reduce energy barrier

• Increase rate of reactions

3 Ways for Enzymes to Catalyze a Reaction

• Orient substrates to fit each other

• Induce substrates (stretching the substrate)

• Temporarily add chemical groups

Enzymes can catalyze a reaction by temporarily adding a chemical group. Acid Base Catalysis is an example of this. Define this:

Add/Remove H+ in order to destabilize covalent bonds

Enzymes can catalyze a reaction by temporarily adding a chemical group. Metal Ion Catalysis is an example of this. Define this:

Add/Remove electrons

Enzymes can catalyze a reaction by temporarily adding a chemical group. Covalent Catalysis is an example of this. Define this:

Form covalent bonds

What 3 features determine an enzymes function?

• Specificity

• Shape

• Induced fit (change in enzyme shape when binding to substrate, which also changes active site shape)

Induced Fit

A change in the shape of the enzyme when binding to a substrate. The shape of the active sit is changed.

Ribozymes

RNA molecules that act as biological catalysts

Some enzymes require “partners” or additional groups. What is a Prosthetic group?

Non-amino acid groups permanently bound to enzymes

Some enzymes require “partners” or additional groups. What is a inorganic cofactor?

Ions permanently bound to the enzyme

Some enzymes require “partners” or additional groups. What is a Coenzyme?

Temporarily-bound small carbon containing molecules (Ex: vitamins)

Rate of a catalyzed reaction depends on ________

Substrate concentration

The concentration of an enzyme is usually _____ than the substrate

Much lower

At low substrate concentration, the presence of an enzyme _______ the reaction rate

Greatly increases

At __________, all enzyme is bound to substrate; it is working at maximum rate.

Saturation

Turnover Number

# of substrate molecules converted to product per unit time (ranges from 1 to 40 million molecules per second)

One of two ways of controlling enzyme activity is Regulation of Gene Expression. What does this do?

Regulates how many enzyme molecules are made

One of two ways of controlling enzyme activity is Regulation of Enzyme Activity. What does this do?

Can block or change the shape of enzymes

Chemical reactions in cells are organized in metabolic pathways that are interconnected. Enzymes help organize and regulate ___________

Metabolic pathways

What are enzyme inhibitors?

Molecules that bind to the enzyme and slow reaction rates

Enzyme inhibitors bind to the enzyme and slow reaction rates. They can be naturally occurring or artificial. What is the purpose of naturally occurring inhibitors?

Regulate metabolism

Enzyme inhibitors bind to the enzyme and slow reaction rates. They can be naturally occurring or artificial. What is the purpose of artificial inhibitors?

• Treat disease

• Kill pest

• Study how enzymes work

What type of bond occurs in reversible inhibitors and what is the effect on the enzyme?

• Noncovalent bonds

• Reversible (prevents substrates from binding)

What type of bond occurs in irreversible inhibition and what is the effect on the enzyme?

• Covalent bonds

• Permanently inactivate enzyme

Competitive inhibitors compute with the _______ for binding sites

Natural substrate

* The degree of inhibition depends on concentrations of substrate and inhibitor

Methotrexate

• Anti-cancer drug

• Binds to the enzyme that catalyzes formation of a coenzyme for purine formation

Purine

• Needed for DNA replication and cell division

Allosteric Regulation is when a non-substrate molecule binds the enzyme at __________, which ____________

A site different from the active site, which changes enzyme shape

Active Form of Enzyme

• Enzyme has the proper shape to bind substrate

Inactive Form of Enzyme

• Enzyme cannot bind substrate

Non-substrate molecules may be an ________ or _______

Inhibitor or an activator

Most allosteric enzymes are proteins with _______ structure

Quaternary

The active site of allosteric enzymes is located on the __________

Catalytic subunit