Biochemistry: Anabolic vs. Catabolic Pathways

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Questions and Answers

What defines an anabolic pathway?

It breaks down complex molecules into simpler ones.

It requires energy input to build complex molecules. (correct)

It is a spontaneous (exergonic) process.

It releases energy during the reaction.

What does a negative change in free energy (ΔG < 0) indicate about a reaction?

The reaction is spontaneous and releases energy. (correct)

The reaction is non-spontaneous and requires energy.

The reaction occurs without any change in entropy.

The reaction has an equal amount of reactants and products.

Which of the following describes energy coupling?

The process of breaking down energy compounds.

The requirement of constant energy input for all metabolic processes.

The simultaneous occurrence of two unrelated reactions.

Using energy from an exergonic reaction to drive an endergonic reaction. (correct)

What role do enzymes play in metabolic reactions?

They lower the activation energy of reactions. Signup and view all the answers

Which of the following statements about redox reactions is true?

Oxidation occurs when glucose is converted to carbon dioxide. Signup and view all the answers

How do cofactors assist enzymes?

They are non-protein molecules required for enzyme activity. Signup and view all the answers

Which of the following is NOT a property of spontaneous reactions?

They decrease the entropy of the system. Signup and view all the answers

What is the function of competitive inhibitors in enzyme activity?

They bind to the active site and prevent substrate binding. Signup and view all the answers

What is the location of glycolysis in the cellular respiration process?

Cytoplasm Signup and view all the answers

Which of the following is a product of the citric acid cycle?

NADH Signup and view all the answers

What is the role of oxygen in oxidative phosphorylation?

Acts as a final electron acceptor Signup and view all the answers

Which statement accurately reflects the relationship between cellular respiration and photosynthesis?

Products of one process serve as the reactants for the other Signup and view all the answers

What are the outputs of the light reactions of photosynthesis?

Oxygen and ATP Signup and view all the answers

What is the net production of ATP from glycolysis?

2 ATP Signup and view all the answers

During lactic acid fermentation, pyruvate is converted into which of the following?

Lactate Signup and view all the answers

What is the primary purpose of the electron transport chain during oxidative phosphorylation?

Generation of a proton gradient Signup and view all the answers

Study Notes

Anabolic vs. Catabolic Pathways

Anabolic pathways: Build complex molecules from simpler ones; require energy input (endergonic).
Catabolic pathways: Break down complex molecules into simpler ones; release energy (exergonic).
Energy Flow: Anabolic pathways require energy input while catabolic pathways release energy.

Free Energy and Spontaneity

Free energy (G): The amount of available energy to do work.
Change in free energy (ΔG): Determines a reactions spontaneity.
- ΔG < 0: Spontaneous (exergonic)
- ΔG > 0: Non-spontaneous (endergonic)
Entropy (S): A measure of disorder, spontaneous reactions increase entropy.

Enzyme Function

Activation energy (EA): Energy required to start a reaction.
Enzymes lower the EA: This speeds up reactions without changing the overall free energy change (ΔG).
Active site: Binds to substrates, stabilizing the transition state.
Catalysis: Enzymes can orient substrates, stress bonds, or provide a microenvironment to accelerate reactions.

Secondary Molecules in Enzyme Function

Cofactors: Non-protein molecules that help enzymes function (e.g., metal ions).
Coenzymes: Organic molecules that aid in enzyme activity (e.g., vitamins).
Inhibitors: Reduce enzyme activity
- Competitive inhibitors: Bind to the active site.
- Non-competitive inhibitors: Bind elsewhere on the enzyme.

Redox Reactions

Oxidation: The loss of electrons from a molecule (e.g., glucose → CO₂).
Reduction: The gain of electrons by a molecule (e.g., oxygen → H₂O).
Coupled reactions: Oxidation and reduction always occur together.

The Four Stages of Cellular Respiration

Glycolysis:
- Location: Cytoplasm
- Inputs: Glucose, 2 NAD⁺, 2 ATP
- Outputs: 2 Pyruvate, 2 NADH, 4 ATP (net 2 ATP)
- Key point: Breaks down glucose into pyruvate and produces a small amount of ATP.
Oxidation of Pyruvate:
- Location: Mitochondrial matrix
- Inputs: 2 Pyruvate, 2 NAD⁺, 2 Coenzyme A
- Outputs: 2 Acetyl-CoA, 2 NADH, 2 CO₂
- Key point: Converts pyruvate into Acetyl-CoA for the citric acid cycle.
Citric Acid Cycle (Krebs Cycle):
- Location: Mitochondrial matrix
- Inputs: 2 Acetyl-CoA, 6 NAD⁺, 2 FAD
- Outputs: 6 NADH, 2 FADH₂, 2 ATP, 4 CO₂
- Key point: Generates electron carriers (NADH and FADH₂) and ATP while releasing CO₂.
Oxidative Phosphorylation:
- Location: Inner mitochondrial membrane
- Components: Electron Transport Chain (ETC) and Chemiosmosis
- Inputs: NADH, FADH₂, O₂, ADP + Pi
- Outputs: 34 ATP, H₂O
- Key points:
  - Electron Transport Chain (ETC): Electrons from NADH and FADH₂ are passed down the chain to oxygen, creating a proton gradient.
  - Chemiosmosis: Protons flow through ATP synthase to generate ATP.

Fermentation (Anaerobic Respiration)

Purpose: In the absence of oxygen, cells use fermentation to regenerate NAD⁺ for glycolysis.
Lactic Acid Fermentation: In animals, pyruvate is reduced to lactate.
Alcoholic Fermentation: In yeast, pyruvate is converted to ethanol and CO₂.

Key Concepts in Cellular Respiration

Glucose and oxygen are consumed in the mitochondria.
CO₂ and H₂O are produced.
Cellular respiration produces a net of 38 ATP (theoretical maximum in eukaryotes).

Photosynthesis and Cellular Respiration Relationship

Complementary processes: Photosynthesis converts light energy into glucose and oxygen, while cellular respiration converts glucose and oxygen into ATP.
Interdependence: The products of one process serve as the reactants of the other.

The Two Major Parts of Photosynthesis

Light Reactions:
- Location: Thylakoid membranes
- Inputs: Light, H₂O, NADP⁺, ADP + Pi
- Outputs: O₂, ATP, NADPH
- Key point: Light energy is used to split water, generating ATP and NADPH and releasing oxygen.
Calvin Cycle (Dark Reactions):
- Location: Stroma
- Inputs: ATP, NADPH, CO₂
- Outputs: Glucose (C₆H₁₂O₆)
- Key point: CO₂ is converted into glucose using the ATP and NADPH produced in the light reactions.

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Description

This quiz explores the differences between anabolic and catabolic pathways in biochemistry. It covers topics such as energy flow, free energy, spontaneity, and enzyme function. Test your understanding of these fundamental biochemical concepts.