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thermodynamics

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32 Questions

What type of reactions synthesize molecules with more bonds and higher free energy products?

Anabolic reactions

Which concept states that energy transformation always results in a loss of usable energy through entropy?

First and Second Laws of Thermodynamics

What is the function of enzymes in a reaction?

Reduce the activation energy

Which factor determines the specificity and function of enzymes?

The structure (shape) of the protein

In which type of reaction are molecules broken down to make lower free energy products?

Catabolic reactions

What does the difference in free energy, ∆G, between reactants and products determine in a reaction?

The direction of change in free energy

What is the role of allosteric effectors in enzyme regulation?

Bind to the allosteric site to inhibit enzyme function

How is ATP primarily involved in reaction coupling?

By using its hydrolysis to generate phosphorylated intermediate molecules

What process involves the loss of electrons from molecules?

Oxidation

In redox reactions, what is the role of NADH (or NADPH)?

Donate high energy electrons for cellular work

What is a common feature of catabolic reactions compared to anabolic reactions?

Positive change in free energy

When do negative feedback loops inhibit an enzyme in a metabolic pathway?

At the beginning of the pathway

Which type of reaction degrades molecules to make lower free energy products?

Catabolic

What is the function of enzymes in a reaction?

Reduce activation energy

Which concept involves the transformation of energy always resulting in a loss of usable energy through entropy?

Second Law of Thermodynamics

In an enzyme-substrate complex, substrates interact with enzymes at the:

Catalytic site

Which type of reactions synthesize molecules with more bonds and higher free energy products?

Anabolic

What determines the specificity and function of enzymes?

Shape and structure of the protein

What is the chemical energy available to do work and expressed as the difference between enthalpy and entropy?

Free Energy

When do negative feedback loops inhibit an enzyme in a metabolic pathway?

When the product concentration is high

What involves a change in free energy, delta G, between reactants and products in a reaction?

Gibbs Free Energy

Which factor indicates if a reaction is positive or negative delta G?

Free Energy Change

Which statement best describes the second law of thermodynamics?

Entropy always increases in a spontaneous process.

What is the primary role of ATP in reaction coupling?

To provide energy for endergonic reactions.

Which of the following statements about anabolic and catabolic reactions is correct?

Anabolic reactions are exergonic and require energy input.

Which of the following best describes the role of allosteric effectors in enzyme regulation?

They alter the shape of the enzyme to activate or inhibit its function.

Which of the following statements about free energy diagrams is correct?

The transition state has the highest free energy.

What is the primary role of NADH (or NADPH) in metabolic reactions?

To carry high-energy electrons for later energy extraction.

Which of the following statements about entropy is correct?

Entropy is a measure of disorder or randomness.

What is the primary function of negative feedback loops in metabolic pathways?

To inhibit enzymes at the beginning of the pathway.

Which of the following statements about oxidation and reduction is correct?

Oxidation and reduction always occur together.

Which of the following statements about enzymes is correct?

Enzymes lower the activation energy of reactions.

Study Notes

Regulation of Enzymes and Metabolic Pathways

  • Enzymes can be regulated by allosteric effectors that bind to the allosteric site, altering the shape of the protein to either inhibit or activate enzyme function.
  • Metabolic pathways can be regulated at different steps depending on the demands of the cell.
  • Negative feedback loops use the product of a pathway to inhibit an enzyme at the beginning of the pathway.

Thermodynamics and Energy Transformations

  • The First and Second Laws of Thermodynamics state that energy is transformed in many ways, but always at a cost of energy lost through entropy.
  • Free energy (G) is chemical energy available to do work and is expressed as the difference between enthalpy (total energy) and entropy.
  • Any reaction involves a change in free energy, ∆G, between reactants and products.
  • The direction of change in free energy tells if it is positive or negative ∆G (anabolic or catabolic).

Enzymes and Reaction Coupling

  • Enzymes are proteins that reduce the activation energy of a reaction.
  • Enzyme specificity and function are the result of the structure (shape) of the protein.
  • Substrates interact with enzymes at the active site, forming an enzyme-substrate complex with a close interaction through induced fit.
  • Reaction coupling combines a positive ∆G reaction with a negative ∆G reaction to give a new net negative ∆G for the combined reactions.
  • The most common means of reaction coupling is to use the hydrolysis of ATP, yielding a ∆G = -7.3 kcal/mole, to generate phosphorylated intermediate molecules of higher energy.

Redox Reactions and Energy Transfer

  • Oxidation is the loss of electrons and reduction is the gain of electrons by molecules.
  • NADH (or NADPH) is a commonly used high energy electron carrier in metabolism.
  • It captures high energy electrons from organic molecules and holds on to them for later when energy from those electrons can be extracted bit by bit using an electron transport chain to do work.

Anabolic and Catabolic Reactions

  • Anabolic reactions synthesize or "build" molecules with more bonds, making higher free energy products.
  • They use or store energy (endergonic), reduce entropy, and are non-spontaneous.
  • Catabolic reactions degrade or "break" molecules to make lower free energy products with fewer bonds.
  • They increase entropy and release energy (exergonic), and are spontaneous.

Metabolism and Cellular Processes

  • Metabolism is the sum of all anabolic and catabolic reactions in a cell, connected in a network of reaction pathways.
  • You should be able to define the first and second laws of thermodynamics and recognize energy transformations and changes in entropy in cellular processes.
  • Compare and contrast anabolic and catabolic reactions in terms of change in free energy, change in entropy, if they are spontaneous, and if they are endergonic and exergonic.
  • Recognize and explain free energy diagrams for negative and positive delta G reactions.
  • Explain the function of enzymes in relation to their structure and their role in negative delta G reactions, and discuss how enzymes are regulated in cells.

Learn about the fundamental concepts of metabolism, including anabolic and catabolic reactions, energy transformations, and the interconnected pathways within a cell.

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