Bio chapter 6- energy and metabolism

Select the true statements about the ATP cycle in cells.

ATP hydrolysis is an exergonic reaction. ATP synthesis is an endergonic reaction.

Which of the following is true about spontaneous energy transformations?

They proceed to convert matter from a more ordered to a less ordered form.

What occurs during a redox reaction?

When an atom or molecule is oxidized, the electron that is removed is transferred to another atom or molecule, which is thereby reduced.

_________ energy is the energy required to destabilize existing chemical bonds and initiate a chemical reaction.

activation

In order to be initiated, all chemical reactions, even exergonic ones, need _______

activation energy

The ______________ ____________ for an exergonic reaction is lower in the presence of a catalyst for the reaction.

activation energy

Enzyme-mediated chemical reactions take place when the substrate molecules bind to the ___________ ___________ of an enzyme

active site

A reaction that requires an input of energy is said to be a(n) ________ reaction.

endergonic

During the ATP cycle, energy is consumed as well as released. ATP synthesis is a(n)______ step, while ATP hydrolysis is a(n) ______ step.

endergonic; exergonic

The first law of thermodynamics states that the total amount _______ of in the universe remains constant.

energy

Work in the cell or in the physical world can only be done with expenditure of ; ------ it is defined as the capacity to do work.

energy

_________ stored in the chemical bonds of a molecule can be used to make new bonds in a different molecule.

energy

__________ stored in the chemical bonds of a molecule can be used to make new bonds in a different molecule.

energy

The hydrolysis of ATP has ______.

negative ΔG

Exergonic reactions have a(n) _________ change in free energy, and endergonic reactions have a(n) _________ change in free energy.

negative, positive

How many different kinds of enzymes are known?

thousands

Phosphate bonds in ATP are high energy bonds, because they are ______.

unstable

In a chemical reaction, an electron is transferred from molecule X to molecule Y. Which of the two molecules is oxidized in this reaction?

x

RNA molecules that have catalytic properties are called

ribozymes

Order the steps in enzyme catalysis starting at the top.

1. )Substrate binds to enzyme. 2.) Amino acids from enzyme interact with substrate. 3.) Bonds in substrates are broken and/or created; products form. 4.) Products dissociate from the enzyme.

How much energy is released when the outermost phosphate bond of ATP is hydrolyzed under standard conditions?

7.3 kcal/mol

The optimum pH of most enzymes is 6 to

8

From the list below, select the three components of ATP.

A chain of three phosphates Ribose Adenine

What is a substrate?

A reactant molecule that forms a temporary association with an enzyme before being converted to a product.

Which of the following statements about chemical reactions are true?

A reaction that is exergonic in the forward direction will be endergonic in the reverse direction. Chemical reactions are reversible.

Select the events that must occur before bonds in the substrate are broken during an enzyme catalyzed reaction.

A substrate-enzyme complex must form. Amino acids in the enzyme must interact with the substrate. The substrate must bind the enzyme.

The two main steps in the ATP cycle are the synthesis of ATP from _______ and Pi, and the subsequent hydrolysis of ATP, which releases _______ that drives endergonic reactions.

ADP, energy

All cells use a molecule called to carry and release energy cyclically

ATP

Cells _____ use hydrolysis to drive endergonic reactions.

ATP

What molecule is a common energy source for living organisms?

ATP

Which nitrogenous base is a component of ATP?

Adenine

Which of the following is the best description of the fit between an enzyme and its substrate?

As the substrate binds to the enzyme, the shape of the active site changes to accommodate the reaction.

In the following chemical reaction, which molecule(s) is(are) reduced? Ae− + B → A + Be−

B

Select the ways in which catalysts affect chemical reactions.

Catalysts accelerate both the forward and reverse reactions by the same amount. Catalysts reduce activation energy.

The activation energy is a barrier to the formation of products. How can this be overcome?

Catalysts can be used to lower the activation energy.

How can catalysts increase the rate of a chemical reaction?

Catalysts stabilize the transition state in a reaction.

Select the true statements about cellular enzymes.

Different cells contain different sets of enzymes. Each enzyme in a cell catalyzes one or a few specific reactions.

Which statement about energy conversion is true?

During any type of energy conversion, some of the energy is lost into the environment as heat.

Select the true statements about endergonic reactions.

Endergonic reactions have a positive change in free energy. The products have a higher free energy than the reactants. Endergonic reactions are not spontaneous.

What is the first law of thermodynamics?

Energy cannot be created or destroyed

Which of the following describe how energy is used in chemical reactions?

Energy stored in certain chemical bonds can be used to make new bonds.

What is kinetic energy?

Energy that is in motion

What is produced by the binding of enzyme and substrate?

Enzyme-substrate complex

Select the characteristics of enzymes.

Enzymes lower the activation energy required for new bonds to form in a chemical reaction Enzymes are not changed or consumed in reactions. Enzymes may be used more than once in a cell.

What is the second law of thermodynamics?

Every energy transfer or transformation increases the entropy of the universe.

How does the change in free energy differ between exergonic and endergonic reactions?

Exergonic reactions have a negative change in free energy whereas endergonic reactions have a positive change in free energy.

Select two ways to increase the rate of reactions.

Lower the activation energy Increase energy of reactants

Select the steps in the ATP cycle.

Hydrolysis of ATP to release energy that can be used to drive endergonic reactions. Synthesis of ATP using energy released from exergonic reactions.

Select the true statements about the effect of temperature on an uncatalzyed chemical reaction.

Increased temperature increases the rate of the reaction. Increased temperature increases random molecular movements which increases stress on bonds.

Which statement accurately describes the fate of chemical potential energy in living things?

It can be shifted and stored into different molecules, or it can be converted into other forms, such as kinetic energy, electricity, or light.

Which of the following describes the active site of an enzyme?

It is the part of the enzyme where the substrate fits.

Which of the following describes the major difference between kinetic and potential energy?

Kinetic energy is the energy of motion while potential energy is stored energy.

Most enzymes only function in a narrow range of temperatures and have an optimum temperature at which they work best. Why?

Lower temperatures prevent the formation of the substrate-enzyme complex while higher temperatures can denature the enzyme.

During a chemical reaction, which molecules become oxidized?

Molecules that have an electron removed

During a chemical reaction which molecules become reduced?

Molecules that have one or more electrons added

Which of the following statements about the size and turnover rate of the ATP pool in a typical cell are true?

Most cells have a few seconds' supply of ATP. Most cells have to produce more ATP constantly.

Hydrolysis of which covalent bonds in ATP releases a considerable amount of energy?

Phosphate-phosphate bond

What are enzymes?

Proteins that speed up chemical reactions (biological catalysts) Proteins or RNA molecules that act as catalysts.

Which of the following statements, that describe catalysis of protein synthesis in ribosomes, are true?

Ribosomal RNA functions as a catalyst. Ribosomes are essentially large ribozymes.

Most enzymes in the human body work best at neutral pH. Select the reasons why changing the pH of the fluid in which a human enzyme is dissolved (for example to a pH of 3) will affect the enzyme's ability to function.

The balance between positively and negatively charged amino acids in the enzyme is shifted. Enzymes cannot maintain their three-dimensional shape at extreme pHs, such as a pH of 3.

Which of the following statements about ATP is true?

The high energy phosphate bonds in ATP are unstable and, therefore, not used by cells for long-term energy storage.

Which characteristic of ATP is responsible for its high energy bonds?

The repulsion of the negative phosphate groups

When two reactions are coupled in a cell, what determines if they will both proceed spontaneously?

The sum of ΔG of the two coupled reactions (the overall ΔG) should be negative

Which of the following statements about oxidized molecules is true?

They have fewer electrons and less energy than reduced molecules.

Select the true statement about enzymes.

They lower the activation energy of a reaction by binding to the substrates.

Is any energy released during ATP hydrolysis and if so, how much?

Yes, a considerable amount of energy is released.

What is entropy?

a measure of the disorder of a system

The rate of an exergonic reaction can be increased by lowering the _________ energy required to destabilize chemical bonds in the reactants

activation

The process of influencing chemical bonds to lower the activation energy of a reaction is called ________.

catalysis

The process of influencing chemical bonds to lower the activation energy of a reaction is called______.

catalysis

Any agent that speeds up the rate of a chemical reaction without being permanently changed or consumed by it is known as a(n)

catalyst

In photosynthesis, energy absorbed from sunlight is used to ______.

combine small inorganic molecules into larger organic molecules

What is potential energy?

energy that is stored

According to the second law of thermodynamics, _________ increases when energy is transferred from one form to another and some energy is lost as heat in the process.

entropy

_______ are proteins or RNA molecules that act as catalysts to speed up reactions in living organisms.

enzymes

When a reactant binds to the active site of an enzyme, a(n) _________ - ________ complex forms.

enzymes and substrate

A reaction is said to be ________ when it releases excess free energy and tends to proceed spontaneously.

exergonic

What type of reaction or process releases free energy?

exergonic

During each energy conversion that happens in a living organism, some of the energy dissipates as

heat

In general, energy transformations can proceed spontaneously when disorder

increased

When a physical system becomes more disordered, the entropy

increases

The binding of a substrate usually produces a slight change in the enzyme's shape resulting in a better enzyme-substrate fit; this is called fit

induced

When a cheetah eats an antelope,______.

it transfers some of the potential energy stored in the tissues of the antelope to its own body

_________ energy is associated with movement, while _________ energy is stored energy.

kinetic and potential

What are the two main states of energy?

kinetic and potential energy

Living organisms can convert the potential energy stored in chemical bonds into what other forms of energy?

kinetic energy potential energy in the bonds of new molecules light energy electrical energy (electricity)

In broad terms, energy can exist in two states:------ energy and ----- energy.

kinetic, potential

What causes the rate of some chemical reactions to be very slow?

large activation energy

Which of the ATP's phosphate bonds is hydrolyzed in most cellular reactions?

outermost

Redox reaction is a term used to describe a(n) _________ - _________ reaction.

oxidation, reduction

A fraction of the energy from the Sun is captured by plants, algae, and some bacteria through the process of

photosynthesis

Green plants, certain bacteria, and algae can all perform the process of ------- during which the energy of light is used to synthesize molecules.

photosynthesis

As living organisms consume other living organisms, ______.

potential energy is transferred from one organism to another

For a molecule that participates in a redox reaction, the _________ form of the molecule has a higher level of potential energy than the __________ form.

reduced, oxidized

Chemical reactions are , _________ which means that they can proceed in either direction (reactants to products or products to reactants).

reversible

catalyst

substance that speeds up the rate of a chemical reaction

_________ ,or reactants, are molecules that bind to an enzyme and are converted to products in chemical reactions.

substrates

The energy that flows through most biological systems on Earth ultimately comes from which source?

sun