Metabolism Overview

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Questions and Answers

In the Calvin Cycle, which molecule is used to initially fix carbon from CO2?

  • Ribulose-1,5-bisphosphate (RuBP) (correct)
  • 3-Phosphoglycerate
  • Fructose-1,6-bisphosphate
  • Glyceraldehyde-3-phosphate (G3P)

Which of the following is NOT a product of the light reactions in photosynthesis?

  • Oxygen
  • Glyceraldehyde-3-phosphate (G3P) (correct)
  • NADPH
  • ATP

In cellular respiration, which process generates the most ATP per glucose molecule?

  • Citric acid cycle
  • Oxidative phosphorylation (correct)
  • Pyruvate oxidation
  • Glycolysis

Which of the following is NOT a function of the electron transport chain in cellular respiration?

<p>Reducing carbon dioxide to organic molecules (C)</p> Signup and view all the answers

In the absence of oxygen, what process allows glycolysis to continue by recycling NADH back to NAD+?

<p>Fermentation (B)</p> Signup and view all the answers

Which of the following is NOT a potential substrate for cellular respiration when glucose is unavailable?

<p>Cellulose (D)</p> Signup and view all the answers

In the Calvin Cycle, what is the primary function of the regeneration phase?

<p>Regenerating the CO2 acceptor molecule RuBP (D)</p> Signup and view all the answers

In glycolysis, which of the following is considered the 'investment phase'?

<p>The conversion of glucose to fructose-1,6-bisphosphate (B)</p> Signup and view all the answers

In the citric acid cycle, which of the following is NOT a product?

<p>Pyruvate (B)</p> Signup and view all the answers

Which of the following is the final electron acceptor in the electron transport chain during aerobic respiration?

<p>Oxygen (B)</p> Signup and view all the answers

Which of the following best describes the relationship between anabolic and catabolic reactions in metabolism?

<p>Anabolic reactions synthesize molecules with more bonds, while catabolic reactions degrade molecules with fewer bonds. (B)</p> Signup and view all the answers

According to the Second Law of Thermodynamics, what happens to the entropy of a system during a spontaneous reaction?

<p>Entropy increases. (D)</p> Signup and view all the answers

What is the relationship between free energy (G) and the other thermodynamic quantities, enthalpy (H) and entropy (S)?

<p>Free energy is the difference between enthalpy and entropy. (B)</p> Signup and view all the answers

Which of the following statements best describes the role of enzymes in biochemical reactions?

<p>Enzymes catalyze reactions by reducing the activation energy required for the reaction to occur. (A)</p> Signup and view all the answers

How do substrates interact with enzymes during a catalyzed reaction?

<p>Substrates bind to the active site of the enzyme, forming an enzyme-substrate complex. (D)</p> Signup and view all the answers

Which of the following is the primary factor that determines the specificity and function of an enzyme?

<p>The structure (shape) of the protein that forms the enzyme. (C)</p> Signup and view all the answers

What is the relationship between the direction of change in free energy (G) and the spontaneity of a reaction?

<p>Positive G indicates a non-spontaneous reaction, while negative G indicates a spontaneous reaction. (B)</p> Signup and view all the answers

How do anabolic and catabolic reactions differ in terms of their effect on the energy level of the products?

<p>Anabolic reactions synthesize higher free energy products, while catabolic reactions degrade lower free energy products. (C)</p> Signup and view all the answers

What is the relationship between the spontaneity of a reaction and the change in entropy of the system?

<p>Spontaneous reactions always increase the entropy of the system. (A)</p> Signup and view all the answers

How do anabolic and catabolic reactions differ in terms of their energy requirements?

<p>Anabolic reactions are endergonic and require energy, while catabolic reactions are exergonic and release energy. (A)</p> Signup and view all the answers

Which of the following accurately describes the role of enzymes in cellular processes?

<p>Enzymes decrease the activation energy required for a reaction to occur, thereby increasing the reaction rate. (B)</p> Signup and view all the answers

Which of the following statements accurately describes the relationship between enthalpy, entropy, and free energy in chemical reactions?

<p>If a reaction has a negative enthalpy change and a positive entropy change, the free energy change is always negative. (D)</p> Signup and view all the answers

Which of the following statements accurately describes the difference between anabolic and catabolic reactions?

<p>Anabolic reactions have a positive free energy change and are non-spontaneous, while catabolic reactions have a negative free energy change and are spontaneous. (A)</p> Signup and view all the answers

Which of the following statements accurately describes the role of reaction coupling in cellular processes?

<p>Reaction coupling is the process of combining an exergonic reaction with an endergonic reaction to make the overall process spontaneous. (C)</p> Signup and view all the answers

Which of the following statements accurately describes the role of ATP in cellular processes?

<p>ATP is a high-energy molecule that is continuously used and regenerated in cellular processes to drive endergonic reactions. (D)</p> Signup and view all the answers

Which of the following statements accurately describes the role of NADH and NADPH in cellular processes?

<p>NADH and NADPH are high-energy electron carriers that capture and release electrons in redox reactions to generate energy. (D)</p> Signup and view all the answers

Which of the following statements accurately describes the role of the light reactions in photosynthesis?

<p>The light reactions use two photosystems to capture light energy and generate high-energy electrons, which are used to produce ATP and NADPH. (C)</p> Signup and view all the answers

Which of the following statements accurately describes the role of the electron transport chain (ETC) in the light reactions of photosynthesis?

<p>The ETC in the light reactions generates a proton gradient across the thylakoid membrane, which is used to produce ATP through chemiosmosis. (D)</p> Signup and view all the answers

Flashcards

Allosteric Effectors

Binding at a site other than the active site, altering enzyme shape to inhibit or activate function.

Reaction Coupling

Combining a positive ΔG reaction with a negative ΔG reaction resulting in a net negative ΔG.

Oxidation

Losing electrons during a chemical reaction.

Reduction

Gaining electrons during a chemical reaction.

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NADH (or NADPH)

Captures high-energy electrons for later use in electron transport chains.

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Laws of Thermodynamics

Energy is transformed, with some lost as entropy.

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Free Energy (G)

Chemical energy available to do work (G = Enthalpy - Entropy).

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Photosynthesis

Transforms light energy into chemical energy.

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Cellular Respiration

Breaks down glucose to make ATP.

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Glycolysis

Uses glucose to make 2 ATP, 2 NADH, and 2 pyruvate.

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Citric Acid Cycle

Oxidizes acetyl-CoA to CO2, making 2 ATP, 6 NADH, and 2 FADH2.

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Electron Transport Chain

Donates high-energy electrons, generating proton motive force and producing ATP through chemiosmosis.

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Metabolism

Sum of all anabolic and catabolic reactions.

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Anabolic Reactions

Synthesize molecules, using/storing energy (endergonic).

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Catabolic Reactions

Degrade molecules, releasing energy (exergonic).

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Study Notes

Enzyme Regulation

  • Allosteric effectors bind to enzymes at sites other than the active site, altering the protein's shape to inhibit or activate enzyme function
  • Metabolic pathways can be regulated at different steps depending on cellular demands
  • Negative feedback loops use pathway products to inhibit enzymes at the beginning of the pathway

Energy Transformations

  • Positive ΔG reactions are accomplished through reaction coupling, combining a positive ΔG reaction with a negative ΔG reaction to yield a net negative ΔG
  • The most common means of reaction coupling uses ATP hydrolysis to generate phosphorylated intermediate molecules of higher energy
  • ATP is continuously used and regenerated from ADP + Pi

Redox Reactions

  • Oxidation is the loss of electrons, while reduction is the gain of electrons by molecules
  • NADH (or NADPH) is a high-energy electron carrier in metabolism, capturing high-energy electrons and holding them for later use in electron transport chains

Thermodynamics

  • The First and Second Laws of Thermodynamics state that energy is transformed, but always at the cost of energy lost through entropy
  • Free energy (G) is chemical energy available to do work, expressed as the difference between enthalpy (total energy) and entropy
  • Any reaction involves a change in free energy, ΔG, between reactants and products
  • The direction of change in free energy indicates if it is positive or negative ΔG (anabolic or catabolic)

Photosynthesis

  • Photosynthesis transforms light energy into chemical energy, synthesizing new carbon backbones from CO2
  • In eukaryotes, photosynthesis occurs in chloroplasts, using components in the stroma, thylakoid membranes, and thylakoid lumen
  • The light reactions use two photosystems to capture light and generate high-energy electrons
  • The Calvin Cycle fixes inorganic carbon from CO2 into organic carbon chains, storing energy in chemical bonds

Cellular Respiration

  • Cellular respiration breaks down glucose to make ATP using substrate-level and oxidative phosphorylation
  • The process begins with glycolysis, which uses glucose to make 2 ATP, 2 NADH, and 2 pyruvate
  • The citric acid cycle oxidizes acetyl-CoA to CO2, making 2 ATP, 6 NADH, and 2 FADH2
  • The electron transport chain donates high-energy electrons, generating proton motive force and producing ATP through chemiosmosis

Metabolism

  • Metabolism is the sum of all anabolic and catabolic reactions in a cell, connected in a network of reaction pathways
  • Anabolic reactions synthesize or "build" molecules with more bonds, using or storing energy (endergonic), reducing entropy, and being non-spontaneous
  • Catabolic reactions degrade or "break" molecules, increasing entropy and releasing energy (exergonic), and being spontaneous

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