Metabolism: Energy Changes and Electron Transfer

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Questions and Answers

Which type of biochemical reaction involves the alteration of carbon atom oxidation states?

Free-radical reactions

Oxidation-reduction reactions (correct)

Group-transfer reactions

Internal rearrangements

What is the primary role of ATP in cellular processes?

Energy currency linking catabolism and anabolism (correct)

Structural component of cell membranes

Direct use as an enzyme

Storage of genetic information

In group-transfer reactions, which of the following are commonly transferred?

Carbon dioxide and water

Protons and electrons

Amino acids and peptides

Acyl, glycosyl, and phosphoryl groups (correct)

What is a key result of ATP hydrolysis regarding charge?

Relief of electrostatic repulsion Signup and view all the answers

Which feature of a metabolic intermediate is enhanced by attaching a 'good leaving group'?

Activation for subsequent reactions Signup and view all the answers

According to the law of conservation of energy, what is equivalent to the total energy intake of a system?

The summation of internal heat produced, work done, and stored energy. Signup and view all the answers

Which of the following statements accurately describes the relationship between catabolism and anabolism?

Catabolism releases energy through oxidation, while anabolism requires energy through reduction. Signup and view all the answers

Which of the following is NOT one of the five general categories of biochemical reactions?

Hydrolysis of water Signup and view all the answers

What role does stored chemical energy play in endergonic reactions?

It is used to provide the energy needed to drive endergonic reactions. Signup and view all the answers

In the context of metabolism, what is the primary distinction between catabolic and anabolic pathways?

Catabolic pathways produce energy, while anabolic pathways consume energy. Signup and view all the answers

What is a crucial mechanism by which ATP provides energy within biological systems?

Transfer of its chemical groups to other molecules in coupled reactions Signup and view all the answers

How does ATP facilitate thermodynamically unfavorable reactions?

By coupling the unfavorable reaction to the exergonic hydrolysis of ATP Signup and view all the answers

During the complete oxidation of glucose, what is the approximate change in Gibbs free energy?

$-2,840$ kJ/mol Signup and view all the answers

Which part of the ATP molecule is typically targeted first in nucleophilic reactions resulting in adenylylation?

The α-phosphate group Signup and view all the answers

What is the primary function of NAD+ and FAD+ in glucose oxidation?

To carry electrons removed during oxidation steps Signup and view all the answers

What is the primary role of the flow of electrons in oxidation-reduction reactions within living organisms?

To perform work done by living organisms directly or indirectly Signup and view all the answers

Which statement best describes the movement of coenzymes like NAD and NADP in their function?

They move freely from one enzyme to another. Signup and view all the answers

In biological systems, how is energy derived from carbon fuels?

Through oxidation of carbon fuels, which releases stored energy Signup and view all the answers

What is the role of a hydride ion (:H-) in the context of nucleotide cofactors during redox reactions?

It is accepted by the oxidized form of the nucleotide Signup and view all the answers

Why are fats considered a more efficient fuel source than carbohydrates, such as glucose, in terms of energy storage?

Fats are more reduced than carbohydrates, allowing for more oxidation and energy release Signup and view all the answers

What is the primary function of NADPH?

Reductive biosyntheses Signup and view all the answers

In a biological redox “circuit”, what drives the transfer of electrons from glucose oxidation to $O_2$?

The electromotive force proportional to the difference in electron affinity Signup and view all the answers

If a person has a deficiency in niacin, which of the following is a potential consequence?

Pellagra, characterized by dermatitis, diarrhea, and dementia Signup and view all the answers

What is the typical range of ATP consumption for an adult in a resting state?

Approximately 40 kg per day Signup and view all the answers

What happens to the concentration of NAD+ and NADH during metabolic reactions?

They are recycled without a net change in their total concentration Signup and view all the answers

How does FMN differ from FAD in terms of chemical structure?

FMN consists of a portion of the FAD structure, specifically the part above the dashed line. Signup and view all the answers

Study Notes

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

Energy Balance: Energy intake equals internal heat produced plus work plus storage. Heat and work are accounted for in mechanical work and anabolic processes (energy-requiring). Stored chemical energy drives endergonic reactions.

The Nature of Metabolism

Definition: Metabolism is the sum total of all biochemical reactions in an organism.
Catabolism: An oxidative process that releases energy.
Anabolism: A reductive process that requires energy.
Separate Pathways: Catabolism and anabolism are separate pathways, not simply reversed processes.
Unique Thermodynamic Systems: Living things are unique thermodynamic systems.
- Isolated system: No exchange of matter or energy.
- Closed system: Energy exchange may occur.
- Open system: Energy and/or matter exchange may occur.

Biochemical Reactions

Five General Categories:
- C-C bond making or breaking
- Internal rearrangements, isomerizations, and eliminations
- Free-radical reactions
- Group transfers
- Oxidation-reductions

Adenosine Triphosphate (ATP)

Role: ATP plays a crucial role as cellular energy currency, linking catabolism and anabolism.
Energy Donation: Energy donation typically involves the covalent participation of ATP. This process mostly converts ATP to ADP and Pi, in some cases to AMP and two Pi.

ATP Hydrolysis

Charge Separation: Relief of electrostatic repulsion among the four negative charges on ATP.
Hydrolysis Reaction: -ATP + H₂O → ADP + Pi
-ΔG°' = -30.5 kJ/mol ;
(-7.3 kcal/mol)
Coupled Reactions: A thermodynamically unfavorable reaction can become favorable if coupled with hydrolysis of ATP.
Two Step Process: ATP generally contributes to a reaction in a two-step process.

Nucleophilic Reactions of ATP

Nucleophilic Attack: Any of the three P atoms (α, β, or γ) can serve as the electrophilic target for nucleophilic attack.
Adenylylation: Nucleophilic attack at the α-position of the ATP displacing PP₁ and transferring adenylate (5'-AMP) as an adenylyl group.

Firefly Bioluminescence Cycle

Description: The chemical reaction that produces light from fireflies.
Involves a process: The cycle involves ATP, Luciferin, and a luciferase enzyme to produce light.

Flow of Electrons in the Biological System

Role in Metabolism: The flow of electrons in oxidation-reduction reactions is a primary driving force for many biological processes.
ATP Consumption: Shows different ATP consumption rates in resting and strenuous exertion.

Biological Redox Reactions

Glucose Oxidation: Glucose oxidation involves the controlled transfer of electrons to O₂ producing energy in the form of ATP; 6 CO2 + 6 H₂0 + ATP
More Efficient Fuel: Fats are more efficient fuel sources than carbohydrates because the carbon in fats is more reduced.
Electron Carriers/Coenzymes: NAD⁺ and FAD⁺ are specialized coenzymes for carrying electrons in cellular redox reactions.

Coenzymes in Biological Redox Reactions

Channels for Electron Transfer): Electrons released from redox reactions are transferred by nucleotide coenzymes.
Water-Soluble Coenzymes: NAD, NADP, FMN, and FAD are water-soluble coenzymes. NAD and NADP move between enzymes, while FMN and FAD are tightly bound to enzymes.
Recycling of Coenzymes: There is no net production or consumption of NAD⁺ or NADH; they function catalytically, recycling repeatedly.

Coupling of Production and Use of Energy

ATP Synthesis: Cells constantly synthesize ATP in mitochondria.
Energy Provision: ATP releases energy when the terminal phosphate is removed. The resultant ADP and free phosphates are recycled to form ATP.

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Description

Explore the crucial aspects of metabolism and energy changes in this quiz. Learn about the definitions of metabolism, the differences between catabolism and anabolism, and the unique thermodynamic systems of living organisms. Test your understanding of biochemical reactions and their importance in metabolic processes.