!Chapter 8: Metabolism and Energy

Metabolism

Total system of all chemical reactions in a living being

What is a metabolic pathway?

Step-by-step changes a specific molecule undergoes to form a final product, with each step catalyzed by an enzyme.

What are catabolic pathways?

Metabolic pathways that break down complex molecules into simple compounds, releasing energy.

What are anabolic pathways?

Metabolic pathways that build complex molecules from simple compounds, consuming energy.

How do catabolic and anabolic pathways relate?

Catabolic pathways release energy that powers the 'uphill' reactions of anabolic pathways.

What is energy?

The capacity of a system to cause change in its surroundings, existing in various forms.

What is kinetic energy?

The energy of motion, enabling objects to perform work by imparting motion onto others.

What is thermal energy?

Kinetic energy at the atomic level; when transferred, it is called heat.

What is potential energy?

The energy of location or structure that can be transformed into kinetic energy.

What is chemical energy?

Potential energy stored in chemical bonds, released through chemical reactions.

What is thermodynamics?

The study of how a system transforms and exchanges energy with its surroundings.

What is the first law of thermodynamics?

Energy can be transferred or transformed, but never created or destroyed (principle of conservation of energy).

What is the second law of thermodynamics?

During energy transfer or transformation, some energy is always converted to thermal energy and lost as heat.

What is entropy?

A measure of how disordered a system is, indicating how much energy cannot be used to do work.

What are spontaneous processes?

Processes that increase the entropy of the universe without energy input.

What are nonspontaneous processes?

Processes that decrease entropy, requiring a dedicated input of energy.

What is free energy (G)?

A measure of how much energy in a system can do work.

How is the change in free energy (ΔG) calculated?

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

What does a negative ΔG indicate?

The reaction is spontaneous and requires no energy input.

What does a positive ΔG indicate?

The reaction is nonspontaneous and requires energy input.

What is equilibrium in a system?

The state of maximum stability where forward and reverse reactions occur at the same rate.

What are exergonic reactions?

Reactions that release free energy to the surroundings and are spontaneous (negative ΔG).

What are endergonic reactions?

Reactions that absorb free energy from the surroundings and are nonspontaneous (positive ΔG).

What is the relationship between free energy and stability?

The level of free energy is inversely related to stability; systems tend to move towards lower free energy (higher stability).

How do living beings maintain energy flow?

Through step-by-step metabolic pathways that prevent them from reaching equilibrium.

What is the significance of free energy calculations?

They help determine whether a reaction is spontaneous or nonspontaneous and assess energy requirements.

What happens in exergonic chemical reactions?

Energy is released, and products store less free energy than reactants.

What happens in endergonic chemical reactions?

Energy is absorbed, and products store more free energy than reactants.

What is metabolism?

The process by which living beings transform and transfer energy to sustain life.

What are the types of energy involved in metabolism?

Kinetic, thermal, potential, and chemical energy.

What determines if a reaction is spontaneous or non-spontaneous?

Free energy calculations.

What are exergonic reactions?

Reactions that release energy and are spontaneous.

What are endergonic reactions?

Reactions that require energy input and are non-spontaneous.

What is energy coupling?

The process where energy released from an exergonic reaction drives an endergonic reaction.

What type of work do cells perform to sustain life?

Chemical work, transport work, and mechanical work.

What is ATP?

Adenosine triphosphate, an energy storage molecule used in almost every cellular reaction.

What are the components of ATP?

Ribose (sugar), adenine (nitrogenous base), and three phosphate groups.

How is energy released from ATP?

By hydrolysis, which breaks the terminal phosphate bond.

What is the significance of phosphorylated intermediates?

They have higher free energy and are more reactive than their original form.

How do cells replenish ATP?

By adding a phosphate group to adenosine diphosphate (ADP) using energy from exergonic reactions.

What is activation energy?

The energy required for a reactant molecule to absorb in order to break its bonds.

What role do catalysts play in chemical reactions?

They speed up reactions by lowering the activation energy barrier.

What are enzymes?

Protein-based catalysts that speed up specific reactions.

What is the enzyme-substrate complex?

The interaction formed when an enzyme binds to its specific substrate.

What is the induced-fit model?

The concept that enzymes change shape to better fit the substrate during catalysis.

How do enzymes lower activation energy?

By orienting substrates, straining bonds, or providing a favorable microenvironment.

What happens when an enzyme is saturated?

Adding more substrate won't increase the reaction rate; adding more enzyme will.

What is the ATP cycle?

The process of replenishing ATP by coupling energy-yielding processes to energy-consuming processes.

What is the transition state?

An unstable state that reactants must reach for a reaction to proceed.

Why is thermal energy not the best way to speed up reactions?

It can denature proteins and is a nonspecific agent that speeds up all reactions.

What types of work do cells perform using ATP?

Transport work and mechanical work.

What is the relationship between endergonic and exergonic reactions?

Endergonic reactions are driven by the energy released from exergonic reactions.

What is the role of enzymes in cellular metabolism?

They facilitate reactions by binding to substrates and lowering activation energy.

What are some examples of reactions that enzymes speed up?

Photosynthesis, solute transport, and cargo transport.

What is the significance of the active site on an enzyme?

It is highly specific to one substrate and facilitates the catalytic process.

What is the role of ATP in cellular metabolism?

ATP is involved in energy coupling, balancing endergonic and exergonic reactions.

What types of work do cells perform to sustain life?

Cells perform chemical, transport, and mechanical work.

How do enzymes facilitate chemical reactions?

Enzymes bind to substrates and help them reach the transition state, lowering the activation energy barrier.

What happens to enzyme activity as temperature approaches its optimal level?

The reaction rate increases until the enzyme denatures at temperatures beyond the optimal level.

What is the optimal temperature range for human enzymes?

The optimal temperature for human enzymes is typically between 30-40°C.

How does pH affect enzyme activity?

Each enzyme has an optimal pH for activity, which is dependent on its environment.

What are cofactors in enzyme activity?

Cofactors are nonprotein helpers that can bind to enzymes or substrates to assist in catalysis.

What are the two types of cofactors?

Inorganic cofactors (e.g., metal ions) and organic cofactors (coenzymes).

What are inhibitors in enzyme regulation?

Inhibitors are chemical agents that can reduce or block enzyme activity by preventing substrate binding.

What is the difference between competitive and noncompetitive inhibitors?

Competitive inhibitors resemble the substrate and bind to the active site, while noncompetitive inhibitors bind elsewhere, altering enzyme shape.

How do mutations affect enzyme function?

Mutations can change the amino acid composition of enzymes, potentially altering their structure and activity.

What is the role of natural selection in enzyme evolution?

Beneficial mutations that enhance enzyme function may be favored by natural selection, while harmful mutations are not.

Why is enzyme regulation important?

Enzyme regulation prevents chaos in metabolism, allowing for controlled metabolic pathways.

What is allosteric regulation?

Allosteric regulation occurs when a regulatory molecule binds to an enzyme at one site, affecting activity at another site.

What happens when an allosteric activator binds to an enzyme?

It stabilizes the enzyme's shape, allowing functional active sites.

What is feedback inhibition in metabolic pathways?

Feedback inhibition is when the end-product of a pathway shuts down the activity of key enzymes, preventing resource waste.

How do cells utilize compartmentalization for enzyme function?

Cells compartmentalize enzymes in specialized locations to ensure they are present where needed.

What is cooperativity in enzyme activity?

Cooperativity occurs when substrate binding to one active site stabilizes other active sites for increased response.

What is the transition state in enzyme-catalyzed reactions?

The transition state is a high-energy state that substrates must reach for a reaction to proceed.

What is the significance of the activation energy barrier?

The activation energy barrier is the energy required to initiate a reaction; enzymes lower this barrier.

What can happen to enzymes if they are exposed to extreme pH levels?

Extreme pH levels can denature enzymes, leading to loss of function.

What is the effect of temperature on enzyme denaturation?

Excessive temperature can denature enzymes, reducing their catalytic effectiveness.

How do enzymes interact with substrates?

Enzymes bind to substrates at their active sites, facilitating the conversion to products.

What is the role of chemical agents in enzyme regulation?

Chemical agents can enhance or inhibit enzyme activity by binding to enzymes or substrates.

What is the impact of enzyme mutations on substrate recognition?

Mutations can allow enzymes to recognize new substrates or develop new activities.

How do enzymes contribute to metabolic pathways?

Enzymes catalyze reactions that are essential for metabolic pathways, regulating the flow of metabolites.

What is the relationship between enzyme structure and function?

The specific structure of an enzyme determines its function and the types of reactions it can catalyze.