Bio 211 Chapter 8

CNU

What is bioluminescence?

The conversion of chemical energy to light energy by organisms.

Which organism uses bioluminescence to attract termites in its larval stage?

Pyrophorus nyctophanus (click beetle)

What is the first law of thermodynamics?

Energy can be transferred and transformed, but it cannot be created or destroyed.

What is the second law of thermodynamics?

Every energy transfer or transformation increases the entropy of the universe

In the context of bioluminescence, what do click beetle larvae use to produce light?

Energy stored in organic molecules

What happens to some energy during every energy transformation?

It is converted to thermal energy and released as heat.

Which of the following is an example of the first law of thermodynamics?

Light from the sun is transformed into chemical energy in plants.

Which of the following processes increases the entropy of the universe?

A click beetle larva digesting termites and emitting light

Entropy

A measure of the disorder or randomness in a system.

What is the role of enzymes in metabolic reactions?

Enzymes speed up metabolic reactions by lowering energy barriers.

What is the totality of an organism's chemical reactions called?

Metabolism

What is the main function of catabolic pathways?

Breaking down complex molecules to release energy

Which of the following is an example of an anabolic pathway?

Synthesis of a protein from amino acids

What type of energy is associated with the random movement of atoms or molecules?

Thermal energy

What is the term for energy that matter possesses because of its location or structure?

Potential energy

According to the first law of thermodynamics, what can happen to energy?

It can be transferred and transformed but not created or destroyed

What is the measure of molecular disorder or randomness?

Entropy

What happens to the entropy of the universe during every energy transfer or transformation?

It increases

What type of process leads to an increase in entropy and can proceed without requiring an input of energy?

Spontaneous process

What is a metabolic pathway?

A series of chemical reactions in a cell where a specific molecule is altered in defined steps to produce a certain product.

What role do enzymes play in metabolic pathways?

Enzymes catalyze each step of the metabolic pathway, speeding up the chemical reactions.

Metabolism

The totality of an organism’s chemical reactions.

Catabolic Pathways

Metabolic pathways that release energy by breaking down complex molecules into simpler compounds.

Anabolic Pathways

Metabolic pathways that consume energy to build complex molecules from simpler ones.

Kinetic Energy

Energy associated with the relative motion of objects.

Potential Energy

Energy that matter possesses because of its location or structure.

Chemical Energy

The potential energy available for release in a chemical reaction.

Second Law of Thermodynamics

Every energy transfer or transformation increases the disorder (entropy) of the universe.

What role do enzymes play in metabolic pathways?

Enzymes catalyze each step of the metabolic pathway, speeding up the chemical reactions.

Catabolic Pathways

Metabolic pathways that release energy by breaking down complex molecules into simpler compounds.

Anabolic Pathways

Metabolic pathways that consume energy to build complex molecules from simpler ones.

Kinetic Energy

Energy associated with the relative motion of objects.

Potential Energy

Energy that matter possesses because of its location or structure.

Chemical Energy

The potential energy available for release in a chemical reaction.

First Law of Thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed.

What is a metabolic pathway?

A series of chemical reactions in a cell where a specific molecule is altered in defined steps to produce a certain product.

Catabolic Pathways

Metabolic pathways that release energy by breaking down complex molecules into simpler compounds.

Anabolic Pathways

Metabolic pathways that consume energy to build complex molecules from simpler ones.

Kinetic Energy

Energy associated with the relative motion of objects.

Potential Energy

Energy that matter possesses because of its location or structure.

Chemical Energy

The potential energy available for release in a chemical reaction.

Catabolic Pathways

Metabolic pathways that release energy by breaking down complex molecules into simpler compounds.

What is Gibbs free energy?

The portion of a system’s energy that can perform work when temperature and pressure are uniform throughout the system.

Which equation is used to calculate the change in free energy (ΔG) of a system?

ΔG = ΔH - TΔS

For a process to be spontaneous, what must be true about ΔG?

ΔG must be negative

What does a negative ΔG indicate about a process?

The process is spontaneous and energetically favorable

What does ΔH represent in the free energy equation?

The change in the system’s enthalpy (total energy)

What does ΔS represent in the free energy equation?

The change in the system’s entropy

What is the relationship between free energy (G) and stability of a system?

Lower free energy (G) indicates a more stable system

What happens to the free energy of a system at equilibrium?

G is at its lowest possible value

What type of reaction is characterized by a net release of free energy?

Exergonic reaction

What type of reaction absorbs free energy from its surroundings?

Endergonic reaction

Who defined the Gibbs free energy of a system?

J. Willard Gibbs

Gibbs Free Energy (G)

The portion of a system’s energy that can perform work when temperature and pressure are uniform throughout the system.

Spontaneous Process

A process that occurs without an input of energy, characterized by a negative ΔG.

Exergonic Reaction

A chemical reaction that proceeds with a net release of free energy and has a negative ΔG.

Endergonic Reaction

A chemical reaction that absorbs free energy from its surroundings and has a positive ΔG.

Equilibrium

A state of maximum stability where the forward and reverse reactions occur at the same rate, and ΔG is zero.

What are the three main types of work performed by cells?

Chemical, transport, and mechanical work

What is the immediate source of energy that powers cellular work?

ATP

What does ATP stand for?

Adenosine triphosphate

Which part of the ATP molecule is responsible for its high energy?

The triphosphate group

What is the result of ATP hydrolysis?

ADP, inorganic phosphate, and energy release

What is the free energy change (ΔG) for ATP hydrolysis under standard conditions?

-7.3 kcal/mol

What is the term for the transfer of a phosphate group from ATP to another molecule?

Phosphorylation

What is the role of a phosphorylated intermediate in cellular reactions?

It is more reactive and less stable than the original molecule.

How does ATP drive mechanical work in the cell?

By binding to motor proteins and causing shape changes

What is the ATP cycle?

The continuous process of ATP being consumed and regenerated

What is energy coupling in cellular processes?

The use of an exergonic process to drive an endergonic one

ATP (Adenosine Triphosphate)

A molecule that contains the sugar ribose, the nitrogenous base adenine, and a chain of three phosphate groups; it mediates most energy coupling in cells

Phosphorylated Intermediate

A molecule that has received a phosphate group from ATP, making it more reactive

What is the role of enzymes in metabolic reactions?

They speed up reactions by lowering the activation energy.

What is activation energy?

The energy required to start a reaction by contorting the reactant molecules so the bonds can break.

What is the transition state in a chemical reaction?

An unstable condition where reactants have absorbed enough energy for bonds to break.

How do enzymes affect the activation energy (EA) of a reaction?

They lower the activation energy.

What is the effect of temperature on enzyme activity?

Enzyme activity increases with temperature up to an optimal point, then decreases sharply.

What is the optimal pH for the enzyme pepsin

Approximately 2

What is the optimal temperature for most human enzymes?

35–40°C

What is a competitive inhibitor?

A molecule that mimics the substrate and competes for the active site of an enzyme.

What is a noncompetitive inhibitor?

A molecule that binds to a different part of the enzyme, changing its shape and reducing its effectiveness.

What is the function of the enzyme sucrase?

It catalyzes the hydrolysis of sucrose into glucose and fructose.

Activation Energy

The initial investment of energy required to start a chemical reaction, abbreviated as Eₐ.

Catalyst

A chemical agent that speeds up a reaction without being consumed by the reaction.

Transition State

An unstable condition of reactants that occurs when they have absorbed enough energy for bonds to break.

Induced Fit

The change in shape of an enzyme's active site to fit the substrate more snugly after the substrate binds.

Substrate

The reactant on which an enzyme acts.

Noncompetitive Inhibition

A type of enzyme inhibition where the inhibitor binds to a site other than the active site, causing a change in enzyme shape and function.

Coenzyme

An organic cofactor required for enzyme activity, often derived from vitamins.

What is allosteric regulation in enzymes?

Regulation of an enzyme's function by binding of a regulatory molecule to a site other than the active site

How does an activator affect an allosterically regulated enzyme?

It stabilizes the shape that has functional active sites

What is the role of ATP in the regulation of catabolic enzymes?

ATP binds allosterically to catabolic enzymes, lowering their affinity for substrate and inhibiting their activity

What happens when ADP accumulates in a cell?

It activates enzymes that speed up catabolism to produce more ATP

What is feedback inhibition in metabolic pathways?

A process where the end product of a pathway inhibits an enzyme involved early in the pathway

How does cooperativity in enzymes work?

Binding of one substrate molecule to an active site increases the catalytic activity at other active sites

What is the effect of an allosteric inhibitor on an enzyme?

It stabilizes the inactive form of the enzyme