Bioenergetics SBP3411 Quiz

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Questions and Answers

What role do enzymes play in chemical reactions within cells?

They bond with products to deactivate them.

They increase the activation energy required for reactions.

They act as substrates in the reactions.

They lower the activation energy needed for the reactions. (correct)

What is required for an enzyme to effectively facilitate a reaction?

Prolonged interactions with substrates (correct)

Formation of allosteric inhibitors

High temperatures and pressures

Excessive substrate concentration

Which of the following statements about enzymes is true?

Enzymes can only catalyze one type of reaction.

Enzymes are permanently altered after a reaction.

Enzymes are highly selective and produce only required compounds. (correct)

Enzymes eliminate the need for substrates.

What characterizes activated carriers in biological systems?

They store energy temporarily in covalent bonds. Signup and view all the answers

Which activated carrier is considered the most important for energy transfer?

ATP Signup and view all the answers

What does Delta G (ΔG) signify in a chemical reaction?

The amount of disorder caused by the reaction Signup and view all the answers

Which statement best describes the 2nd law of thermodynamics as it relates to chemical reactions?

Chemical reactions must increase the disorder of the universe. Signup and view all the answers

What is the role of activation energy in spontaneous reactions?

It is the energy required to reach a more stable state from a stable state. Signup and view all the answers

Which of the following pathways is correctly associated with biosynthesis?

Anabolic pathway Signup and view all the answers

What are neurotransmission and potential gradients primarily influenced by?

The selective movement of ions and compounds Signup and view all the answers

What is the primary role of enzymes in cellular processes?

To drive intracellular chemical reactions. Signup and view all the answers

Which of the following best describes activated carriers?

Molecules that capture and transfer energy. Signup and view all the answers

What occurs during ATP hydrolysis?

ATP is converted to ADP and inorganic phosphate, releasing energy. Signup and view all the answers

How do cells primarily obtain the energy needed for metabolic processes?

By extracting energy from the oxidation of organic molecules. Signup and view all the answers

What does reaction coupling in metabolic processes involve?

Linking favorable reactions to unfavorable ones to drive processes. Signup and view all the answers

According to the 1st Law of thermodynamics, what can be stated about energy?

Energy can only be transformed from one form to another. Signup and view all the answers

Which types of energy are involved in cellular metabolism?

Mechanical, chemical, and electric energy. Signup and view all the answers

Which of the following energy types is generated during muscle contraction?

Mechanical energy for physical activity. Signup and view all the answers

What role does ATP primarily serve in cellular processes?

It serves as the principal activated carrier of energy. Signup and view all the answers

What drives the hydrolysis of ATP?

The stabilization of released inorganic phosphate by hydrogen bonding with water. Signup and view all the answers

What kind of reaction is phosphorylation considered to be in relation to ATP?

It is a condensation reaction driven by energy release. Signup and view all the answers

What facilitates the synthesis of ATP from ADP?

Phosphorylation reactions coupled with other energetic processes. Signup and view all the answers

Which factor contributes to the high-energy nature of ATP?

The unfavorable repulsion between adjacent negative charges within the structure. Signup and view all the answers

Which cellular processes are regulated through phosphorylation reactions facilitated by ATP?

Protein activity and metabolic pathways. Signup and view all the answers

What is the change in Gibbs free energy (ΔG) for ATP hydrolysis and its significance?

Large negative change, indicating a spontaneous reaction. Signup and view all the answers

Which statement about the release of inorganic phosphate (Pi) during ATP hydrolysis is true?

It is stabilized by hydrogen bonds formed with water. Signup and view all the answers

What is the energy yield from the alternative route for ATP hydrolysis?

-109 kJ/mole Signup and view all the answers

What role does high NADPH concentration serve in metabolic pathways?

Reducing agent for anabolic reactions Signup and view all the answers

Which of the following correctly describes the structural difference between NADPH and NADH?

NADPH contains an additional phosphate group compared to NADH Signup and view all the answers

What is typically necessary for biosynthetic reactions that involve Acetyl Coenzyme A?

Transfer of chemical groups like methyl or carboxyl Signup and view all the answers

Under what conditions is NAD+ considered to be an oxidizing agent?

When it is in high concentration Signup and view all the answers

What type of bond is particularly associated with Acetyl Coenzyme A that aids in recognition by enzymes?

Thioester bond Signup and view all the answers

How does NADPH stabilize the electron arrangement in reactions?

By donating a hydride ion to other compounds Signup and view all the answers

Which reaction would most likely utilize the energy derived from the common route of ATP hydrolysis?

Polynucleotide synthesis Signup and view all the answers

Study Notes

Course Information

Course code: SBP3411
Course name: Bioenergetics
Instructor: Dr. Hanis H. Harith
Department: Biomedical Science, UPM
Email: [email protected]

Learning Outcomes

Describe how cells obtain energy for most cellular processes
Explain the role of enzymes in driving intracellular chemical reactions
Describe the function of activated carriers and identify high-energy bonds in selected activated carriers
Describe ATP synthesis and hydrolysis

Lecture Outline

Source of energy for cellular metabolism
Energetically favorable vs unfavorable reactions
Reaction coupling
Activated carriers

Most Intracellular Reactions Require Energy Input

Catabolic pathways break down food molecules, releasing energy
Anabolic pathways use energy to build complex molecules
Examples of synthesis versus breakdown of macromolecules include condensation and hydrolysis

Sources of Energy for Cellular Metabolism

Kinetic energy (e.g., thermal, radiant, mechanical, electric)
Potential energy (e.g., chemical, concentration gradient)

Cells Convert Energy to Different Forms

First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed
Cells extract energy from the oxidation of organic molecules
Energy is stored in covalent bonds

Energetically Favorable vs Unfavorable Reactions

Second Law of Thermodynamics: Reactions occur only if they increase the disorder of the universe (loss of free energy)
ΔG (Gibbs Free Energy) measures the amount of disorder
Positive ΔG = unfavorable reaction (needs energy input)
Negative ΔG = favorable reaction (releases energy)
Reaction coupling: Coupling an unfavorable reaction to a favorable reaction makes the overall reaction favorable

Activation Energy is Required to Initiate Spontaneous Reactions

Molecules in cells are relatively stable
Spontaneous reaction needs activation energy to overcome stable states
Enzymes lower the activation energy, speeding up reactions
Activation energy lowers the barrier for reactions to occur

Enzymes Lower Activation Energy

Biological catalysts that speed up chemical reactions
Prolonged interaction between enzyme and substrates (multiple non-covalent bonds)
Substrate binding to enzyme rearranges electrons
Highly selective; only specific compounds are required.
Enzymes remain unchanged and can be reused

Enzymes Can Create Biological Order by Reaction Coupling

Coupled reactions: Reactions that share intermediate
Unfavorable reaction coupled to favorable reaction.
Change the overall ΔG to be favorable

Activated Carriers

Small organic molecules that store energy temporarily in covalent bonds
Diffuse rapidly; transport energy where needed
Examples: ATP, NADH, NADPH, acetyl CoA
Energy stored in easily exchangeable forms

ATP: The Principal Activated Carrier in Cells

ATP synthesis involves phosphorylation of ADP and requires reaction coupling
ATP hydrolysis releases energy that drives reactions.
There is unfavorable repulsion between adjacent -ve charges within ATP molecule

ATP Hydrolysis Drives Phosphorylation Reactions

ATP transfers a phosphate group to another molecule (phosphorylation)
Hydrolysis of ATP drives unfavorable reactions

Alternative Route for ATP Hydrolysis

Alternative route produces more energy to drive demanding reactions

NADPH and NADH: Activated Carriers of Electrons

Carry energy in the form of a hydride ion (H-)
Donate H- to achieve a more stable arrangement of electrons
Structural differences determine roles in metabolic pathways

Acetyl Coenzyme A

Contains a large organic portion that facilitates recognition by specific enzymes
Involved in metabolic processes (e.g., citric acid cycle, lipid synthesis)

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Description

Test your understanding of bioenergetics concepts, including how cells obtain energy, the role of enzymes, and ATP synthesis. This quiz will cover key topics such as reaction coupling and activated carriers. Prepare to demonstrate your knowledge on cellular metabolism in relation to both catabolic and anabolic pathways.