Energy, Enzymes & Biological Reactions: Key Concepts for Biology

What is bioenergetics?

The study of energy flow through living systems.

What are the two main types of energy?

Kinetic and potential energy.

List four forms of energy.

Chemical, electrical, thermal, and radiant energy.

What are the three types of systems in energy flow?

Isolated, open, and closed systems.

What does the first law of thermodynamics state?

Energy can be transformed or transferred but cannot be created or destroyed.

What is the second law of thermodynamics?

The total disorder (entropy) of a system and its surroundings always increases.

What is entropy?

A measure of molecular disorder or randomness in a system.

What is free energy?

A measure of a system's instability and its tendency to change to a more stable state.

What does Gibbs free energy change (ΔG) indicate?

Whether a process can occur spontaneously.

What characterizes a spontaneous reaction?

It occurs without an input of energy.

What must ΔG be for a reaction to be spontaneous?

ΔG must be negative.

What is the equation for Gibbs free energy change?

ΔG = ΔH - TΔS.

What is an exergonic reaction?

A reaction that proceeds with a net release of free energy (ΔG is negative).

What is an endergonic reaction?

A reaction that absorbs free energy from its surroundings (ΔG is positive).

What is energy coupling?

The process of linking the exergonic reaction of ATP hydrolysis with endergonic reactions.

What role do enzymes play in biological reactions?

They act as biological catalysts that increase the rate of reactions by lowering activation energy (EA).

What is activation energy (EA)?

The initial investment of energy required to start a reaction.

What is the lock-and-key model of enzyme-substrate interaction?

The substrate's shape is complementary to the active site's shape, like a key fitting into a lock.

What is the induced-fit model of enzyme-substrate interaction?

The enzyme changes shape upon substrate binding, making the active site complementary to the substrate.

What factors can lead to enzyme denaturation?

Changes in pH and temperature.

What is reversible enzyme inhibition?

A process where enzyme activity can be temporarily reduced without permanently altering the enzyme.

What is kinetic energy?

The energy of an object in motion, associated with the relative motion of objects.

What is potential energy?

Stored energy within a system due to an object's position, arrangement, or state.

Define entropy.

A measure of disorder or randomness in a system, often increasing during energy transformations.

What are exergonic reactions?

Reactions that release energy and are spontaneous according to the second law of thermodynamics.

What are endergonic reactions?

Reactions that require energy input and are not spontaneous.

How does energy coupling work?

Energy coupling allows endergonic reactions to occur by using the energy released from exergonic reactions.

What is the role of ATP in energy coupling?

ATP serves as the primary energy currency of the cell, facilitating energy transfer for various biochemical processes.

Define activation energy.

The minimum energy required to initiate a chemical reaction.

What is the transition state in a chemical reaction?

A high-energy state that occurs during the conversion of reactants to products.

How do enzymes lower activation energy?

Enzymes provide an easier path to the transition state, thus lowering the activation energy required for reactions.

What is competitive inhibition?

A type of enzyme inhibition where an inhibitor competes with the substrate for the active site.

What is allosteric regulation?

A regulatory mechanism where an effector molecule binds to an enzyme at a site other than the active site, altering its activity.

How do pH and temperature affect enzyme activity?

Enzyme activity can increase or decrease based on pH and temperature, with each enzyme having optimal conditions.

What distinguishes enzymes from ribozymes?

Enzymes are proteins that catalyze reactions, while ribozymes are RNA molecules with catalytic activity.

What is metabolism?

The totality of chemical reactions occurring within a living organism, including catabolism and anabolism.

What are catabolic pathways?

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

What are anabolic pathways?

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

How is energy converted from one form to another in biological systems?

Energy transformations occur, such as chemical energy from food being converted to kinetic energy during movement.

What is the first law of thermodynamics?

Energy cannot be created or destroyed, only transformed from one form to another.

Give an example of kinetic energy.

A falling rock or moving water.

Give an example of potential energy.

Water behind a dam or a rock at the top of a hill.

What is chemical energy?

Potential energy available for release in a chemical reaction, often associated with molecular bonds.

What is an example of a high-energy molecule?

Glucose, which has a high amount of chemical energy due to its complex structure.

What happens during a catabolic reaction?

Bonds are broken, energy is released, and lower-energy products are formed.

What is the significance of thermal energy in reactions?

Thermal energy can be released as heat during chemical reactions, affecting the overall energy balance.

What do the laws of thermodynamics apply to?

All matter and all energy transformations in the universe.

What is the role of thermodynamics in biology?

It helps understand how organisms and cells harvest and transform energy to sustain life.

What is a system in thermodynamics?

The object under study; everything outside is considered its surroundings.

What are the three types of thermodynamic systems?

Isolated, closed, and open systems.

Describe an isolated system.

An isolated system cannot exchange either energy or matter with its surroundings.

What is a closed system?

A closed system can exchange energy (as heat or work) but not matter with its surroundings.

What is an open system?

An open system can exchange both energy and matter with its surroundings.

How do living organisms function as open systems?

They absorb energy and release heat and metabolic waste products to their surroundings.

What is another name for the first law of thermodynamics?

The principle of conservation of energy.

What is the ultimate source of energy for most organisms?

The sun (solar energy).

How do plants utilize solar energy?

Plants capture kinetic energy of light and convert it to chemical potential energy in organic molecules.

What does entropy measure?

Entropy measures molecular disorder or randomness.

What happens during every energy transfer or transformation?

Some energy is converted to thermal energy and released as heat, increasing the universe's disorder.

What is a spontaneous reaction?

A chemical or physical reaction that occurs without an input of energy.

What two factors determine if a reaction is spontaneous?

(1) The change in energy content of a system (ΔH) and (2) the change in entropy (ΔS).

What characterizes exergonic reactions?

They release energy; products have less potential energy than reactants.

What characterizes endergonic reactions?

They absorb energy; products have more potential energy than reactants.

How does heat energy affect chemical bonds?

Heat energy increases atomic motion, making it easier for atoms to pull apart.

What is the net effect of chemical bonding and heat on disorder?

Chemical bonding reduces disorder while heat increases it.

What is the free energy of a molecule?

The amount of energy available to break and subsequently form other chemical bonds.

What happens to energy absorbed by green plants?

Most is converted into heat energy and radiated into space.

What is the relationship between free energy and stability?

Unstable systems (higher G) tend to change to more stable states (lower G).

What is the significance of the change in entropy for spontaneous reactions?

For a reaction to be spontaneous, the entropy of the system should be positive.

What is the effect of energy transformations on the universe?

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

What is free energy in a chemical context?

Free energy is the amount of energy available to break and form chemical bonds.

How is free energy defined in a general sense?

Free energy is the portion of a system's energy that can perform work when temperature and pressure are uniform.

When do reactions tend to be spontaneous?

Reactions tend to be spontaneous when the products are less ordered (more random) than the reactants.

What does the term 'spontaneous' imply in chemical reactions?

Spontaneous implies that a reaction is energetically favorable, not necessarily that it occurs rapidly.

What happens to entropy in a system as time elapses?

Entropy tends to increase, leading to greater disorder.

What is a nonspontaneous process?

A process that leads to a decrease in entropy and requires energy input to occur.

What is an example of a spontaneous process?

Water flowing downhill is a spontaneous process.

What happens to energy during a nonspontaneous process?

Some energy is lost as heat, increasing the entropy of the surroundings.

How do living systems affect entropy?

Living systems increase the entropy of their surroundings as predicted by the second law of thermodynamics.

How do cells create ordered structures?

Cells take in organized forms of matter and energy, replacing them with less ordered forms.

What is the change in heat content during a spontaneous process?

The heat content or enthalpy decreases as the system releases heat.

What are the three variables that determine a spontaneous process?

1. Enthalpy change 2. Entropy change 3. Temperature

What is Gibbs Free Energy denoted as?

G (for Gibbs free energy).

How can the change in free energy (ΔG) be calculated?

ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, T is the absolute temperature, and ΔS is the change in entropy.

What must be true for a reaction to be spontaneous?

ΔG must be negative.

What dominates in making a reaction spontaneous in combustion?

A large loss of potential energy and negative enthalpy (ΔH) dominates.

What dominates in making the melting of ice at room temperature spontaneous?

An increase in entropy (ΔS increases) dominates.

What is the relationship between free energy and the ability to do work?

Free energy (G) is the portion of a system's energy available to do work.

What is the significance of the absolute temperature in the Gibbs Free Energy equation?

It is measured in degrees Kelvin (K).

What does the symbol ΔH represent?

The change in enthalpy.

What does the symbol ΔS represent?

The change in entropy.

What is the implication of a positive ΔH in a spontaneous process?

A positive ΔH can occur in spontaneous processes if the increase in entropy (ΔS) is sufficiently large.

What is the relationship between energy transformations and order?

Energy transformations tend to convert matter from a more ordered, less stable form to a less ordered, more stable form.

What is the role of catabolic pathways in living organisms?

Catabolic pathways break down complex molecules, releasing smaller molecules that possess less chemical energy.

How does the melting of ice relate to spontaneous processes?

Melting ice is a spontaneous process that absorbs heat, demonstrating that spontaneity does not always correlate with heat release.

What is required for life processes?

Free energy

What must a living cell take in to grow or replicate?

Free energy and raw materials

What happens to a cell when free energy consumption stops?

It decays toward chemical equilibrium and dies.

What is the equilibrium point in a reaction?

A state of balance between the opposing factors pushing the reaction in either direction.

What does a negative ΔG indicate about a reaction?

The reaction is spontaneous and can proceed toward completion.