Biochemistry Chapter on Metabolic Reactions

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Questions and Answers

Which of the following is NOT a characteristic of endergonic reactions?

Activation energy is typically high.

They require energy inputs to proceed.

They release energy into the environment. (correct)

Reactants have less energy than products.

Which type of metabolic reaction is involved in the breakdown of a complex carbohydrate into simpler sugars?

Photosynthetic

Anabolic

Catabolic (correct)

Endergonic

What is the role of NAD+ in metabolic reactions?

It helps regulate gene expression.

It acts as an energy-carrying, hydrogen-accepting coenzyme. (correct)

It acts as a catalyst, accelerating the reaction rate.

It provides structural support for enzymes.

What happens to NAD+ when it gains electrons during a metabolic reaction?

It becomes reduced. Signup and view all the answers

Which metabolic pathway is responsible for converting light energy into chemical energy stored in glucose?

Photosynthesis Signup and view all the answers

Which of the following statements accurately describes the relationship between oxidation and reduction?

Oxidation is the loss of electrons, while reduction is the gain of electrons. Signup and view all the answers

Which statement BEST describes the relationship between anabolic and exergonic reactions?

Anabolic reactions are endergonic, requiring energy inputs to occur. Signup and view all the answers

In a chemical reaction, what is the activation energy?

The energy required to start the reaction. Signup and view all the answers

What is the role of oxygen produced during the photolysis of water?

Released as a byproduct for aerobic respiration Signup and view all the answers

What happens to protons generated during the photolysis of water?

They contribute to a proton gradient for ATP production Signup and view all the answers

What is the significance of the electrons produced during the photolysis of water?

They reduce NADP⁺ to NADPH Signup and view all the answers

During which reactions does photolysis of water occur?

Light-dependent reactions Signup and view all the answers

What is produced by the photolysis of water in terms of molecular composition?

2H₂O → 4H⁺ + 4e⁻ + O₂ Signup and view all the answers

How do C₄ and CAM photosynthesis types differ from C₃ photosynthesis?

They are more efficient in water usage Signup and view all the answers

Why is ATP important in the process of photosynthesis?

It transfers energy for key steps in photosynthesis Signup and view all the answers

What process is primarily responsible for generating ATP during the light-dependent reactions?

Chemiosmosis Signup and view all the answers

What is the main role of NADH in cellular respiration?

Donates electrons to the electron transport chain Signup and view all the answers

What product is formed when ATP is hydrolyzed?

Adenosine Diphosphate (ADP) Signup and view all the answers

Which of the following statements about ATP is false?

ATP stores energy in stable low-energy bonds. Signup and view all the answers

How much ATP does each NADH generate in the electron transport chain?

2.5 ATP Signup and view all the answers

What is the significance of coenzyme A (CoA) in metabolism?

Transfers acetyl groups to the citric acid cycle Signup and view all the answers

Which molecule serves as a final electron acceptor in aerobic respiration?

Oxygen (O₂) Signup and view all the answers

What is the main waste product of cellular respiration?

Carbon Dioxide (CO₂) Signup and view all the answers

Which coenzyme is derived from vitamin B2?

FAD Signup and view all the answers

What determines the energy yield from FADH₂ compared to NADH?

The point at which they donate electrons to the ETC Signup and view all the answers

In what process is lactic acid produced?

Anaerobic respiration Signup and view all the answers

What is the primary function of coenzymes?

To facilitate biochemical reactions alongside enzymes Signup and view all the answers

During which reaction is ATP produced?

Electron transport chain Signup and view all the answers

Which process does NOT require oxygen?

Anaerobic respiration Signup and view all the answers

Which of the following is NOT a product of the Light-Dependent reactions of photosynthesis?

Pyruvate Signup and view all the answers

Which of the following processes occurs in the cytoplasm?

Glycolysis Signup and view all the answers

Which process is commonly used by yeast in brewing and winemaking?

Alcoholic Fermentation Signup and view all the answers

How many ATP molecules are produced per glucose molecule through glycolysis?

2 Signup and view all the answers

What type of phosphorylation occurs in the Light-Dependent reactions of photosynthesis?

Photophosphorylation Signup and view all the answers

Which of the following processes is most efficient in hot, dry environments?

C₄ Photosynthesis Signup and view all the answers

What is the primary role of NADPH in photosynthesis?

Electron carrier Signup and view all the answers

Which of the following statements is CORRECT about the Calvin cycle?

It converts CO₂ into glucose. Signup and view all the answers

What is the role of RuBisCO in photosynthesis?

Fixing carbon dioxide Signup and view all the answers

What is the function of ATP synthase in both respiration and photosynthesis?

Generating ATP from ADP and Pi Signup and view all the answers

Which of the following is NOT a characteristic of anaerobic respiration?

It requires oxygen. Signup and view all the answers

Which statement BEST describes the purpose of fermentation?

To regenerate NAD⁺ for glycolysis. Signup and view all the answers

Which of the following statements correctly describes the relationship between glycolysis and oxidative phosphorylation?

Glycolysis produces pyruvate, which is then used as the starting molecule for oxidative phosphorylation. Signup and view all the answers

In what way is C₄ photosynthesis similar to CAM photosynthesis?

Both involve the initial fixation of CO₂ into a 4-carbon compound. Signup and view all the answers

How does the production of ATP in photosynthesis differ from ATP production in cellular respiration?

Photosynthesis uses light energy to drive ATP production, while respiration uses chemical energy from food. Signup and view all the answers

Study Notes

Metabolic Processes Overview

Metabolism encompasses all chemical reactions within a living organism or cell.
Anabolic reactions build complex molecules from simpler ones, requiring energy (endergonic).
Catabolic reactions break down complex molecules into simpler ones, releasing energy (exergonic).
Cellular respiration (in mitochondria) converts glucose's chemical energy to metabolic energy.
Photosynthesis (in chloroplasts) converts solar energy to chemical energy stored in glucose.

Energy in Reactions

Chemical energy changes during reactions, altering energy stored in reactants and products.
Endergonic reactions absorb energy; reactants have less energy than products, and activation energy is often high.
Exergonic reactions release energy; reactants have more energy than products, do not require external energy.
Anabolic reactions are endergonic; catabolic reactions are exergonic.

Oxidation and Reduction

Oxidation involves a loss of electrons (or a gain of oxygen); reducing agents cause oxidation in other substances.
Redox reactions involve simultaneous oxidation and reduction with electron transfer.
NAD⁺ is a crucial coenzyme in energy transfer, accepting high-energy electrons and being reduced to NADH.

ATP (Adenosine Triphosphate)

ATP is the cell's primary energy currency, storing energy in phosphate bonds.
ATP hydrolysis releases energy by breaking a high-energy phosphate bond, forming ADP and inorganic phosphate (Pi).
Hydrolysis yields approximately 30 kJ/mol of energy.

Key Metabolic Molecules

ATP: Stores energy in high-energy phosphate bonds; crucial energy source for cellular processes; produced during cellular respiration.
NADH: Carries high-energy electrons in cellular respiration; produced in glycolysis, citric acid cycle and beta-oxidation; donates electrons to the electron transport chain generating ATP (~2.5 per NADH).
FADH₂: Carries electrons in cellular respiration; produced in citric acid cycle and beta-oxidation; donates electrons to the electron transport chain generating ATP (~1.5 per FADH₂).
CO₂: Waste product released in cellular respiration from decarboxylation reactions; substrate in photosynthesis.

Coenzymes

Coenzymes are organic molecules aiding enzymes in biochemical reactions and often carry electrons or atoms.
Key coenzymes: Oxygen (terminal electron acceptor in aerobic respiration); Coenzyme A (transfers acetyl groups); FAD, NAD⁺, Coenzyme Q (electron carriers in cellular respiration).

Biochemical Processes

Lactic Acid Fermentation: Anaerobic; glucose broken down to lactic acid.
Anaerobic Respiration: Anaerobic using alternative electron acceptors.
Oxidative Phosphorylation: Aerobic; ATP production via electron transport chain and chemiosmosis.
Glycolysis: Breakdown of glucose into pyruvate; essential early step in glucose metabolism.
Alcoholic Fermentation: Anaerobic; glucose broken down to ethanol and CO₂.

Photosynthesis

Photosynthesis converts light energy, CO₂, and H₂O into glucose and O₂.
Two main stages: Light-dependent reactions (generate ATP and NADPH) and Light-independent reactions (Calvin Cycle).

Light-Dependent Reactions

Occur in thylakoid membranes of chloroplasts; require light energy.
Photosystem II splits water, releasing O₂, protons, and electrons; a proton gradient drives ATP synthesis.
Electron transport chain transfers electrons, producing ATP and NADPH.

Light-Independent Reactions (Calvin Cycle)

Occur in the stroma of chloroplasts.
Carbon fixation attaches CO₂ to RuBP, leading to glucose synthesis through various steps.

ATP and Photosynthesis

ATP is essential for both light-dependent and light-independent reactions, driving glucose synthesis.

Branches of Photosynthesis

C₃ plants: Common, less efficient in hot, dry conditions due to photorespiration.
C₄ plants: More efficient in hot, dry environments, concentrating CO₂.
CAM plants: Adapt to very dry conditions by fixing CO₂ at night.

Photolysis of Water (in Photosynthesis)

Water splitting releases oxygen, protons, and electrons.
Oxygen is a byproduct and essential for aerobic respiration.
Protons help build a gradient for ATP production.
Electrons fuel the electron transport chain, forming NADPH.

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Description

Test your knowledge on metabolic reactions with this quiz focused on key concepts from biochemistry. Explore topics such as endergonic and exergonic reactions, the role of NAD+, and the conversion of light energy into chemical energy. Challenge yourself to understand the intricacies of metabolic pathways and chemical reactions.