Unit 2 Section 5 Enzymes Homework & Study Guide

What are the two laws of thermodynamics?

1. Energy can change form but cannot be destroyed or created (law of conservation). 2. Energy transfers or transformations increase disorder, or entropy, with some energy being lost as heat.

What's the difference between competitive and noncompetitive inhibitors?

A competitive inhibitor competes with the substrate for the active site. A noncompetitive inhibitor alters an enzyme's function by binding elsewhere on the enzyme and changing the active site shape.

What is entropy?

A measure of disorder or randomness.

Which of these is exhibiting kinetic energy?

A space station orbiting Earth. Kinetic energy of motion.

What is an exergonic reaction?

A spontaneous reaction that releases energy.

Which of the following substances could be a cofactor?

A zinc atom

In cells, what is usually the immediate source of energy for an endergonic reaction?

ATP. The hydrolysis of ATP provides the energy needed for an endergonic reaction.

Which of the following statements regarding thermodynamics is false?

An automobile engine is a closed system because it does not exchange energy and matter with its surroundings.

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?

Cellular respiration. This is the name given to the process by which the body converts food energy to energy stored in ATP.

How does inhibition of an enzyme-catalyzed reaction by a competitive inhibitor differ from inhibition by a noncompetitive inhibitor?

Competitive inhibitors bind to the active site of the enzyme; noncompetitive inhibitors bind to a different site.

Enzymes:

DO: interreact with specific substrates, speed up reactions, and can be slowed or halted using inhibitors. DO NOT: change shape after a reaction occurs. One enzyme can be used for many different types of chemical reactions.

What does heating the enzyme too much cause?

Denaturing. This means it changes the 3-dimensional shape.

A child is brought to the hospital with a fever of 107°F. Doctors immediately order an ice bath to lower the child's temperature. Which of the following statements offers the most logical explanation for this action?

Elevated body temperatures may denature enzymes. This would interfere with the cell's abilities to catalyze various reactions.

"Conservation of energy" refers to the fact that ___.

Energy cannot be created or destroyed but can be converted from one form to another. This is what is meant by conservation of energy.

What is the correct label for "A"?

Energy of activation. The energy of activation must be overcome in order for a reaction to proceed.

What is used to overcome an energy barrier?

Enzymes

Which of the following statements regarding enzyme function is false?

Enzymes are used up when they catalyze a chemical reaction so must be synthesized for reach new chemical reaction.

How does an enzyme catalyze a reaction?

Enzymes speed up the cell's chemical reactions by lowering energy barriers. They are protein catalysts that decrease the activation energy needed to begin a reaction.

What is the basic difference between exergonic and endergonic reactions?

Exergonic reactions release energy; endergonic reactions absorb it.

Which of these are by-products of cellular respiration?

Heat and water. These are the by-products of cellular respiration.

What is the fate of the phosphate group that is removed when ATP is converted to ADP?

It is acquired by a reactant in an endergonic reaction. By acquiring by the phosphate group the reactant acquires energy.

What is the advantage of feedback inhibition to the cell? (short answer)

It regulates metabolism so you are not wasting energy and resources.

What is feedback inhibition? Know how it works

It regulates metabolism.

What is an endergonic reaction?

It requires energy and yields products rich in potential energy.

Name & define the two types of energy.

Kinetic energy is the energy of motion (moving object). Potential energy is energy stored in the location or structure of matter.

Labeling:

Last page of the notes

Substrate:

Molecule fits in the active site.

Is an enzyme used up or changed? Can it be reused?

No, an enzyme is not used up or changed. It can be reused.

Can the same enzyme be used by multiple reactions? Why or why not?

No, because there are specific enzymes for specific reactions. A specific enzyme catalyzes a specific reaction. An enzyme's substrate fits specifically in its activation sight. A specific enzyme catalyzes each cellular respiration.

Which type of energy is chemical energy an example of?

Potential Energy

Most enzymes are ___.

Proteins

What type of macromolecule are enzymes?

Proteins (catalyst)

Two major ways enzyme inhibitors work.

Reversible (weak bonds)- Prescription drugs Irreversible (covalent/strong bonds)- Pesticides, herbicides, and warfare

What does the active site of an enzyme attach to?

Substrate

What is the (activation) energy barrier of a reaction?

The activation energy barrier protects the molecules in your cells from spontaneously breaking down.

What happens to the chemical energy that is extracted from molecules by cellular activities but that is not used for cellular work?

The energy contributes to the entropy of the system. The second law of thermodynamics states that in any energy transformation, the overall disorder of the universe increases. Most often, this disorder comes in the form of thermal molecular motion (heat), which is a form of energy that is not lost but cannot be harnessed for work.

What are the two major conditions that affect the rate of enzymatic activity?

The pH and temperature (optimal).

In the reaction A--> B + C heat,

The potential energy of the products is less than that of the reactant.

What happens to the rate of an enzyme catalyzed reaction when the pH or the temperature is too high or low?

The rate decreases

What happens to the rate of an enzyme catalyzed reaction when substrate increases?

The rate increases

What happens to the rate of an enzyme catalyzed reaction when enzyme increases?.

The rate increases.

Active site:

The region of an enzyme that attaches to a substrate.

Does an enzyme change shape during a reaction? Is it the same shape after a reaction?

The shape changes slightly due to induced fit. Induced fit is used to weaken bonds in reaction molecules so that they can break bonds and new bonds form. The shape is not changed after the reaction.

Table sugar, or sucrose, is quite stable, and left on its own at room or even human body temperature, breakdown occurs very slowly. The breakdown of sucrose into the simple sugars fructose and glucose is an exergonic reaction. Sucrase, an enzyme, can increase the reaction rate at least one-million-fold. How does the net amount of energy released during the breakdown of sucrose compare between a spontaneous reaction and one catalyzed by sucrase?

The sucrase-catalyzed reaction releases the same amount of energy as the spontaneous reaction. The net yield of any quantity is the difference between what's gained and what's put in. In the case of the surcease-catalyzed reaction and spontaneous (noncatalyzed) reactions, the trip up to and down from the activation energy barrier yields nothing, no matter how far the journey; all that matters is the difference in energy between product and reactant, something that remains constant, regardless of the rate of the reaction.

Which of the following processes is classified as a metabolic pathway?

The synthesis of a protein.

What is energy coupling?

The use of energy released from an exergonic reaction to drive an endergonic reaction. This is energy coupling.

Which of the following processes is endergonic?

They synthesis of glucose from carbon dioxide and water.

Which of the following is a coenzyme?

Vitamin B6

Induced fit:

When the enzyme will hold the substrate that allows bonds to break.

When is enzyme inhibition irreversible and reversible?

When there are weak bonds formed, the inhibition is reversible. When the bonds are strong (covalent), it is reversible.

Does an enzyme's function rely on its shape and remaining intact?

Yes, an enzyme's function depends on its 3-dimensional shape that remains intact.

Cells store energy that they use for work in the ___.

arrangement of atoms within molecules. The bonds holding atoms together also contain potential energy, energy the cell harnesses when the bonds are broken during metabolism.

Heating inactivates enzymes by

changing the enzyme's three-dimensional shape.

Inhibition of an enzyme is irreversible when

covalent bonds form between inhibitor and enzyme.

To "inhibit" means to ___, ___, or ___ the action or function of something.

decrease; limit; block

The reaction ADP + P--> ATP is a(n) ___ reaction.

endergonic. Energy has been acquired from the surroundings.

This graph illustrates a(n) ___ reaction.

endergonic. The products contain more potential energy than the reactants.

Which of these reactions requires a net input of energy from its surroundings?

endergonic. The products of endergonic reactions have more potential energy than the reactants.

Cells transform ___ and ___ as they preform work.

energy; matter

The reaction A--> B + C + heat is released in a(n) ___ reaction.

exergonic. Energy has been released.

A(n) ___ reaction occurs spontaneously.

exergonic. In exergonic reactions, the products have less potential energy than the reactants.

The energy for an endergonic reaction comes from a(n) ___ reaction.

exergonic. The energy released by an exergonic reaction can be used to drive an endergonic reaction.

Select the INCORRECT association.

exergonic... uphill. Exergonic reactions release energy.

The cell uses energy released from ___ reactions to drive ___ reactions.

exergonic; endergonic

Part B: In this reaction ___.

heat has been released to the environment. The potential energy of the products is less than that of the reactants.

What happens to the rate of an enzyme catalyzed reaction when the pH or the temperature is optimal? The rate of the reaction ___.

increases

An enzyme ___.

is an organic catalyst. Enzymes are proteins that behave as catalysts.

As a result of its involvement in a reaction, an enzyme ___.

is unchanged. Enzymes are not changed as a result of their participation in a reaction.

When an enzyme catalyzes a reaction,

it lowers the activation energy of the reaction.

Which part of the ATP molecule breaks free of the rest when an ATP molecule releases energy?

part D

The transfer of a phosphate group to a molecule or compound is called

phosphorylation

Chemical energy is a form of ___ energy.

potential. Chemical energy is a form of stored energy.

An energy barrier

prevents the spontaneous breakdown of molecules in the cell.

Most of a cell's enzymes are

proteins

Enzymes work by ___.

reducing activation energy. Enzymes work by reducing the energy of activation.

Enzymes ___ ___ the cell's chemical reactions by ___ ___ ___.

speed up; lowering energy barriers

A covalent bond is a...

strong bond

What name is given to the reactants in an enzymatically catalyzed reaction?

substrate. This is the name given to the reactants in an enzymatically catalyzed reaction.

In this reaction ___.

the products have less potential energy than the reactants. This is what is shown by the graph.

The active site on an enzyme is

the region of an enzyme that attaches to a substrate.

Denatured:

unraveled enzyme, meaning it doesn't work. The structure affects the function.