Organic Chemistry Reactions Overview

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Questions and Answers

What contributes to the stability of ATP compared to its hydrolysis products?

ATP has a higher molecular weight than ADP

High concentration of ATP outside the cell

Presence of Mg2+ which shields negative charges in the molecule (correct)

ATP molecules form strong covalent bonds with water

Which reaction has the largest free energy change?

Glu + P → Glu-6P

Glu + P + ATP → Glu-6P + ADP + P

Glu + ATP → Glu-6P + ADP (correct)

ATP → ADP + P

ATP is considered a high-energy compound primarily because it can:

Donate phosphates to compounds with higher energy levels

Keep ATP levels constant in all conditions

Provide energy through group transfers (correct)

Undergo simple hydrolysis to release energy

What is the role of kinases in biochemical reactions involving ATP?

They are responsible for phosphorylation of lower energy compounds Signup and view all the answers

Which of the following processes requires energy derived from ATP?

The condensation and ordered elongation of DNA, RNA, and proteins Signup and view all the answers

What is the consequence of ATP hydrolysis in cellular processes?

It provides free energy that drives endergonic reactions Signup and view all the answers

What type of group can ATP donate to other molecules?

Phosphoryl, pyrophosphoryl, or adenylyl groups Signup and view all the answers

What is the standard free energy change (∆G) for the hydrolysis of ATP to ADP?

$-30.5$ kJ/mol Signup and view all the answers

What is the Gibbs free energy change ($ riangle G$) associated with breaking phosphoanhydrides of nucleoside triphosphates (NTPs)?

-19 Signup and view all the answers

What is the role of nucleoside diphosphate kinase in energy transfer?

To promote the phosphorylation of NDPs Signup and view all the answers

In biological oxidation-reduction reactions, what does the acronym LEO stand for?

Loss of Electrons is Oxidation Signup and view all the answers

What is the primary effect of reduction in biological systems?

Addition of electrons and often protons Signup and view all the answers

What does dehydrogenation in biochemical substrates signify?

Oxidation of a substrate Signup and view all the answers

Which of the following statements is true regarding redox pairs?

Every oxidation process is paired with a reduction process Signup and view all the answers

Which cofactor is commonly involved in the transfer of protons and electrons during oxidation?

FAD Signup and view all the answers

What is the ΔG' for the reaction catalyzed by creatine kinase?

-12.5 Signup and view all the answers

What is the main characteristic of isomerisation reactions?

They produce different structural forms of the same compound. Signup and view all the answers

What role do inorganic phosphate groups play in biochemical reactions?

They can act as important leaving groups. Signup and view all the answers

How is the equilibrium constant (Keq) defined in terms of the forward and reverse reactions?

It is the ratio of the products to the reactants at equilibrium. Signup and view all the answers

What does the standard free-energy change (ΔG0) indicate about a biochemical pathway?

A negative ΔG0 suggests the pathway can proceed in the forward direction. Signup and view all the answers

What is a key property of ATP hydrolysis in biochemical reactions?

It results in products that are more easily solvated and thus more stable. Signup and view all the answers

What does the relationship ΔG0 = -RT ln Keq represent?

The connection between free energy change and equilibrium constant at a given temperature. Signup and view all the answers

Which factor contributes to ATP's tendency to lose its terminal phosphate group?

Stability of the products formed after hydrolysis. Signup and view all the answers

In group transfer reactions, which of the following is a common nucleophile?

ATP Signup and view all the answers

Which statement about phosphoryl transfer is correct?

They can stabilize reaction intermediates through resonance. Signup and view all the answers

Why is the tetrahedral structure of (orto)phosphate significant?

It contributes to the delocalization of negative charges. Signup and view all the answers

What vitamin deficiency is associated with Pellagra?

Vitamin B3 Signup and view all the answers

Which of the following symptoms is NOT associated with Pellagra?

Anemia Signup and view all the answers

What is the primary role of NAD+/NADH in metabolism?

Acting as a cofactor in redox reactions Signup and view all the answers

Which vitamin is linked to the FAD/FADH2 redox system?

Vitamin B2 Signup and view all the answers

What class of chemical reactions is responsible for breaking C-C bonds?

Elimination reactions Signup and view all the answers

Which of the following diseases is primarily associated with a deficiency in riboflavin?

Ariboflavinosis Signup and view all the answers

In terms of thermodynamics, what does ΔG signify in biochemical reactions?

The maximum amount of work obtainable Signup and view all the answers

What is the consequence of a deficiency in niacin?

Skin condition characterized by roughness Signup and view all the answers

What does a more positive standard reduction potential (E'o) indicate about an oxidizing agent?

It has a stronger tendency to accept electrons. Signup and view all the answers

What occurs when the Gibbs free energy change (ΔG) is less than zero?

The reaction occurs spontaneously. Signup and view all the answers

If the standard reduction potential of a redox pair is -0.42 V, what does this imply about its behavior?

It has a strong tendency to lose electrons. Signup and view all the answers

What is the relationship between ΔE'o and the change in free energy (ΔG) in a spontaneous reaction?

ΔE'o must be positive for ΔG to be negative. Signup and view all the answers

Which of the following redox pairs has the most positive standard reduction potential?

1/2O2 + 2H+/H2O Signup and view all the answers

What effect does a more negative E'o have on a species involved in a redox reaction?

It increases the tendency to lose electrons. Signup and view all the answers

In the redox reaction involving NADH and FMN, what is the consequence of the oxidation of NADH?

FMN is converted to FMNH2. Signup and view all the answers

What is one factor that must be true for ΔG to be negative in a redox reaction?

The difference in reduction potentials must be positive. Signup and view all the answers

Study Notes

Isomerization and Elimination Reactions

Isomerization reactions involve the rearrangement of atoms within a molecule, resulting in the formation of an isomer.
Elimination reactions involve the removal of atoms or groups from a molecule, leading to the formation of a double or triple bond.

Group Transfer Reactions

Group Transfer Reactions involve the transfer of a chemical group from one molecule to another.
Examples of groups transferred include acyl, glycosyl and phosphoryl.
These reactions are classified as nucleophilic substitutions.

Inorganic Phosphate Groups in Biochemical Reactions

These groups act as leaving groups during reactions.
Orthophosphate has a tetrahedral structure similar to that of water.
Pyrophosphate can also act as a leaving group in biochemical reactions.

Bioenergetics and Thermodynamics

The equilibrium constant (Keq) measures the ratio of products to reactants at equilibrium.
The standard free-energy change (ΔG°) is related to the equilibrium constant by the equation: ΔG° = -RTlnKeq.
This equation indicates that a negative ΔG° favors the formation of products.

Consecutive Reactions - Biochemical Pathways

The free energy changes in a biochemical pathway are additive.
If the sum of ΔG values is negative, the pathway is favorable and proceeds in the forward direction.
ATP hydrolysis is a highly exergonic process (ΔG° is significantly negative).
This is why ATP is used in many phosphorylating reactions instead of direct phosphate transfer.

Chemical Versatility of ATP

ATP can donate phosphoryl, pyrophosphoryl, or adenylyl groups.
The position of nucleophilic attack can be determined by 18O labeling.

Redox Pairs

Oxidation-reduction reactions always occur in pairs.
Standard reduction potential (E°') quantifies the tendency of a molecule to gain electrons, with a more positive E°' indicating a stronger oxidizing agent.
The change in free energy (ΔG°) is directly related to the change in standard reduction potential (ΔE°').
The relationship between ΔG° and ΔE°' is: ΔG° = -nFE°', where n is the number of electrons transferred, F is Faraday's constant, and ΔE°' is the change in standard reduction potential.
The ΔE°' must be positive for the reaction to proceed spontaneously.

NAD+/NADH Redox System

NAD+ is an important cofactor for dehydrogenase enzymes.
NADH is the reduced form of NAD+.
Niacin deficiency leads to pellagra, characterized by dermatitis, dementia, and diarrhea.

FAD/FADH2 Redox System

FAD is another important cofactor for dehydrogenase enzymes.
FADH2 is the reduced form of FAD.
Riboflavin (vitamin B2) deficiency causes ariboflavinosis.
Symptoms include angular cheilitis, itchy eyes, light sensitivity, dermatitis, and anemia.

Diseases and Drugs

Pellagra is a disease caused by niacin deficiency.
Ariboflavinosis is a disease caused by riboflavin deficiency.
Niacin and riboflavin are essential vitamins that can be consumed in the diet to prevent these deficiencies.

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Description

This quiz explores various aspects of organic chemistry reactions, including isomerization, elimination, and group transfer reactions. It also delves into the role of inorganic phosphate groups in biochemical reactions and concepts from bioenergetics and thermodynamics. Test your knowledge on these essential topics in organic chemistry.