Biochemistry II: Energy Changes and Metabolism
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Questions and Answers

In the context of biochemical reactions, what is the primary role of a tetrahedral intermediate?

  • To stabilize the transition state, lowering the activation energy required for the reaction (correct)
  • To destabilize the transition state, increasing the reaction's activation energy
  • To act as a catalyst by directly participating in the reaction
  • To prevent the conversion of substrates into products

Which type of biochemical reaction commonly involves the transfer of acyl, glycosyl, or phosphoryl groups?

  • Free-radical reactions
  • C-C bond making or breaking reactions
  • Oxidation-reduction reactions
  • Group-transfer reactions (correct)

In the activity of chymotrypsin, what is formed during the acylation step?

  • An unstable oxonium ion
  • A tetrahedral acyl-enzyme intermediate (correct)
  • A free radical intermediate
  • A stable carboxylate anion

What is the purpose of attaching a good leaving group to a metabolic intermediate in some group-transfer reactions?

<p>To 'activate' the intermediate for subsequent reactions (D)</p> Signup and view all the answers

Which of these is NOT directly mentioned as a type of biochemical reaction in the provided content?

<p>Peptide bond formation (A)</p> Signup and view all the answers

According to the law of conservation of energy, what is the relationship between energy intake and its expenditure?

<p>Energy intake is equal to the sum of internal heat produced, work done, and energy stored. (B)</p> Signup and view all the answers

Which of the following correctly describes the difference in ATP production between aerobic and anaerobic respiration for each glucose molecule?

<p>Aerobic respiration is much more efficient, producing about 36-38 ATP, while anaerobic respiration produces only 2 ATP. (C)</p> Signup and view all the answers

In the context of metabolism, which statement accurately differentiates between catabolism and anabolism?

<p>Catabolism releases energy through oxidation, while anabolism requires energy through reduction. (C)</p> Signup and view all the answers

What might an athlete experience due to an imbalance favoring catabolism over anabolism?

<p>Muscle breakdown and fatigue due to insufficient energy reserves and inadequate recovery. (A)</p> Signup and view all the answers

Which of the following options is NOT a general category of biochemical reactions mentioned?

<p>Hydration reactions. (C)</p> Signup and view all the answers

What is the primary function of stored chemical energy with respect to endergonic reactions?

<p>To drive energy-requiring (endergonic) reactions. (C)</p> Signup and view all the answers

If a biochemical reaction involves the transfer of electrons, what type of process is primarily involved?

<p>Redox reaction. (D)</p> Signup and view all the answers

Which of the following best describes the energy flow in a biological system?

<p>Energy is neither created nor destroyed but it is transferred and transformed. (D)</p> Signup and view all the answers

What is the primary role of ATP in cellular processes?

<p>It acts as an energy currency linking catabolism and anabolism. (B)</p> Signup and view all the answers

Which chemical species are typically produced from the hydrolysis of ATP?

<p>ADP and Pi (A), AMP and 2Pi (C)</p> Signup and view all the answers

Why does the hydrolysis of ATP release energy?

<p>The charge separation relieves electrostatic repulsion. (D)</p> Signup and view all the answers

What is the key difference between energy transfer from ATP and simple hydrolysis?

<p>Simple hydrolysis involves the direct release of energy, while energy transfer from ATP involves group transfers. (D)</p> Signup and view all the answers

How can an unfavorable reaction sequence be made favorable, using ATP?

<p>By coupling it with the hydrolysis of a sufficient number of ATP molecules. (A)</p> Signup and view all the answers

What is one of the roles of ATP hydrolysis in cellular activities?

<p>It provides energy for biochemical reactions. (B)</p> Signup and view all the answers

Which of the following processes does ATP hydrolysis drive?

<p>Thermodynamically unfavorable processes. (C)</p> Signup and view all the answers

What is the primary reason fats are a more efficient fuel source than carbohydrates?

<p>Fats have more reduced carbon compared to carbohydrates. (D)</p> Signup and view all the answers

Which coenzymes are known for carrying electrons in redox reactions?

<p>NAD+, NADP+, FMN, and FAD. (A)</p> Signup and view all the answers

What is the oxidation potential of glucose generally expressed as?

<p>ΔG'° = -2,840 kJ/mol. (D)</p> Signup and view all the answers

What occurs during the adenylylation process?

<p>Nucleophilic attack at the α-position of ATP transfers adenylate. (A)</p> Signup and view all the answers

What happens to the released electrons from glucose oxidation?

<p>They are donated to coenzymes for transport. (C)</p> Signup and view all the answers

How is the energy release from fats compared to carbohydrates during oxidation?

<p>Fats release more energy due to higher carbon reduction. (C)</p> Signup and view all the answers

What is the primary role of NADPH in cellular metabolism?

<p>Providing reducing power for anabolic reactions (C)</p> Signup and view all the answers

What does the recycling of coenzymes like NAD+ and NADH indicate about their function?

<p>They act catalytically without net change in concentration. (B)</p> Signup and view all the answers

How does a decrease in NAD+ and an increase in NADH affect the metabolic state of a cell?

<p>Indicates an increase in anaerobic respiration activities. (A)</p> Signup and view all the answers

What is the role of FAD and FMN in flavoproteins?

<p>Serve as prosthetic groups participating in redox reactions. (A)</p> Signup and view all the answers

Which statement accurately describes the function of NADH?

<p>It generates ATP through oxidative phosphorylation. (A)</p> Signup and view all the answers

What dietary deficiency can lead to Pellagra?

<p>Niacin deficiency (A)</p> Signup and view all the answers

What is the principal function of ATP in cellular activities?

<p>To serve as the main energy currency of the cell. (B)</p> Signup and view all the answers

What distinguishes NADH from NADPH?

<p>NADH primarily generates ATP, while NADPH is used for biosynthesis. (A)</p> Signup and view all the answers

Flashcards

Tetrahedral Intermediate

A temporary, unstable structure formed during a reaction, where the reactant molecule is partially bound to the enzyme.

Oxidation-Reduction Reactions

Chemical reactions involving the transfer of electrons between molecules, resulting in changes in oxidation states.

C-C Bond Making or Breaking

Breaking or forming carbon-carbon bonds within molecules.

Internal Rearrangements, Isomerizations, and Eliminations

Reactions involving internal rearrangements, isomerizations, and eliminations within a molecule.

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Group-Transfer Reactions

Reactions involving the transfer of specific groups, like acyl, glycosyl, or phosphoryl, from one molecule to another using enzymes.

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What is metabolism?

The sum of all biochemical reactions that occur within an organism. It encompasses both catabolism and anabolism.

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What is catabolism?

A metabolic pathway that breaks down complex molecules into simpler ones, releasing energy. It involves oxidation reactions.

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What is anabolism?

A metabolic pathway that builds complex molecules from simpler ones, requiring energy. It involves reduction reactions.

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What's the Law of Conservation of Energy?

The law stating that energy cannot be created or destroyed, only transformed from one form to another.

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Stored chemical energy is used for what?

The chemical energy stored within molecules, specifically ATP, that can be used to drive endergonic reactions.

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What is aerobic respiration?

A metabolic process that involves the breakdown of glucose in the presence of oxygen, generating ATP.

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What is anaerobic respiration?

A metabolic process that involves the breakdown of glucose without oxygen, generating only a small amount of ATP.

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What does ATP hydrolysis produce?

The process where ATP is hydrolyzed into ADP and inorganic phosphate, releasing energy for cellular work.

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What is the role of ATP in cells?

ATP is the primary energy currency in cells, facilitating energy transfer between catabolic and anabolic processes.

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What happens during ATP hydrolysis?

ATP hydrolysis involves breaking down ATP into ADP and inorganic phosphate (Pi), releasing energy. This process is often coupled with unfavorable reactions to drive them forward.

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How does ATP provide energy for reactions?

ATP provides energy for reactions through group transfers, not simply by hydrolysis.

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What is the nature of ATP conversion to ADP?

The conversion of ATP to ADP and Pi is often presented as a single step, but it usually involves two distinct steps.

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Why is ATP hydrolysis energetically favorable?

ATP hydrolysis releases energy because it relieves electrostatic repulsion between four negative charges on the ATP molecule.

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What is ATP Hydrolysis?

The process of breaking down ATP into ADP and a phosphate group, releasing energy that can be used for cellular processes.

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What are thermodynamically unfavorable processes?

Reactions that require energy input to proceed, such as building complex molecules. ATP hydrolysis provides the energy needed for these processes.

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How does ATP hydrolysis affect electrostatic repulsion?

ATP is a charged molecule, and its hydrolysis helps reduce the electrostatic repulsion between phosphate groups, making it more stable.

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How does ATP hydrolysis contribute to protein synthesis?

ATP hydrolysis provides the energy necessary for building proteins from amino acids, a fundamental cellular process.

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What happens to ADP and phosphate after ATP hydrolysis?

The products of ATP hydrolysis, ADP and phosphate, can be recycled and reused to regenerate ATP through various metabolic pathways.

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What is adenylylation?

A reaction in which a nucleophile attacks a phosphate group in ATP. The α-position of ATP is where this usually occurs.

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What is the flow of electrons in biological systems?

The movement of electrons through a series of molecules, often involving redox reactions, driving cellular energy production.

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What is biological oxidation?

The process of removing electrons from a molecule (oxidation). This release of electrons is often captured by coenzymes for later use in energy production.

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What are FAD and FMN?

FAD and FMN are non-protein molecules that bind to enzymes called flavoproteins. They help these enzymes participate in redox reactions, which involve the transfer of electrons.

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What are the roles of NADH and NADPH?

NADH is primarily used in oxidative phosphorylation, a process that generates ATP, the cell's main energy currency. NADPH, on the other hand, is mainly involved in reductive biosynthesis, which involves building complex molecules.

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How do NADH and NADPH act as electron carriers?

Both NADH and NADPH act as shuttle buses for electrons. They carry electrons from one molecule to another, working in conjunction with enzymes called dehydrogenases.

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What does a decrease in NAD+ and an increase in NADH indicate about the cell?

A decrease in NAD+ levels and an increase in NADH levels indicates that the cell is actively generating energy through glycolysis and the citric acid cycle, which produce NADH. This state is metabolically active.

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What is the role of NADH in the electron transport chain?

NADH transfers electrons to the electron transport chain, a series of protein complexes that generate a proton gradient for ATP synthesis.

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How does NAD+ accept electrons?

The oxidized form of a nucleotide cofactor, like NAD+, accepts a hydride ion, which is a hydrogen atom with two electrons. The second proton released during the reaction is released into the surrounding solution.

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What is the significance of the recycling of NAD+ and NADH?

The conversion of NAD+ to NADH and vice versa is a key process in metabolism. There's no net production or consumption of these coenzymes, just a continuous cycle of oxidation and reduction.

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What happens when there is a niacin deficiency?

A deficiency in niacin, a precursor to NAD+ and NADPH, can lead to pellagra, characterized by skin, digestive, and nervous system problems. This is because many enzymes require NAD+ and NADPH for their activity.

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Study Notes

Unit II: Importance of Energy Changes and Electron Transfer in Metabolism

  • This unit explores the importance of energy changes and electron transfer in metabolism, specifically within the context of Biochemistry II (CHEM 141).

Firefly Bioluminescence Cycle

  • Fireflies (Lampyridae family) use a bioluminescence cycle.
  • Luciferin (a chemical) reacts with oxygen
  • A chemical reaction with the enzyme luciferase produces light.
  • The reaction regenerates oxyluciferin.
  • ATP supplies energy for the cycle.

Topic Outline

  • A. Energy Balance: The law of conservation of energy applies to metabolism; energy intake = internal heat + work + storage.
  • B. The Nature of Metabolism:
    • Living things are unique thermodynamic systems.
    • Catabolism is an oxidative process releasing energy.
    • Anabolism is a reductive process requiring energy.
    • Catabolism and anabolism are separate pathways, not simply reversals of each other.
  • C. Biochemical Reactions: Five general categories:
    • C-C bond making or breaking.
    • Internal rearrangements, isomerizations, and eliminations.
    • Free-radical reactions.
    • Group transfers.
    • Oxidation-reductions (redox).
  • D. Adenosine Triphosphate (ATP): Essential molecule for energy transfer in cells.
  • E. ATP Hydrolysis: Breakdown of ATP releases energy.
  • F. Nucleophilic Reactions of ATP: ATP's phosphate groups are vulnerable to nucleophilic attack.
  • G. Firefly Bioluminescence Cycle: Details of the firefly light-producing process.
  • H. Flow of Electrons in the Biological System: Electrons drive cellular processes.
  • I. Biological Redox: Redox reactions involve electron transfer/oxidation and reduction.
  • J. Coenzymes in Biological Redox Reactions: NAD, NADP, FMN, and FAD are essential coenzymes for electron transfer.
  • K. Coupling of Production and Use of Energy: How ATP production and use are linked within a cellular system.

ATP Hydrolysis

  • The hydrolysis of ATP involves a release of stored energy.
  • Charge separation in ATP hydrolysis alleviates electrostatic repulsion within the molecule.
  • The reaction often occurs to drive unfavorable reactions in the cell.

Nucleophilic Reactions of ATP

  • Any of the three phosphate groups (α, β, or γ) can be a site for electrophilic attack.
  • Adenylylation is a nucleophilic attack on the α-phosphate of ATP leading to the transfer of AMP to another molecule.

Biological Redox

  • Fats have reduced carbon atoms and are more efficient fuel sources than carbohydrates.
  • The transfer of electrons from glucose oxidation to O2 is driven by electron affinity differences (EMF).
  • Oxidation of glucose produces ATP, water, and carbon dioxide.
  • Coenzymes like NAD+ and FAD+ are vital to facilitate electron transfer during cellular respiration.

Coenzymes in Biological Redox Reactions

  • Coenzymes facilitate redox reactions by carrying electrons.
  • NAD and NADP are readily transferred between enzymes.
  • FMN and FAD are tightly bound to enzymes, serving as prosthetic groups.
  • NADH and NADPH act as electron carriers in cellular respiration and biosynthesis.

Coupling of Production and Use of Energy

  • ATP molecules store energy in their phosphate bonds.
  • ATP is produced in the mitochondria, then transported into the cell for its use elsewhere.
  • ATP releases energy during cellular processes and its phosphates are recycled.

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Description

This quiz delves into the significance of energy changes and electron transfer in metabolic processes, as covered in Biochemistry II (CHEM 141). Explore the bioluminescence cycle of fireflies and the concepts of catabolism and anabolism in living organisms. Test your understanding of these critical biochemical reactions!

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