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Metabolism Overview

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28 Questions

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

Ribulose-1,5-bisphosphate (RuBP)

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

Glyceraldehyde-3-phosphate (G3P)

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

Oxidative phosphorylation

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

Reducing carbon dioxide to organic molecules

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

Fermentation

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

Cellulose

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

Regenerating the CO2 acceptor molecule RuBP

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

The conversion of glucose to fructose-1,6-bisphosphate

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

Pyruvate

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

Oxygen

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

Anabolic reactions synthesize molecules with more bonds, while catabolic reactions degrade molecules with fewer bonds.

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

Entropy increases.

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

Free energy is the difference between enthalpy and entropy.

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

Enzymes catalyze reactions by reducing the activation energy required for the reaction to occur.

How do substrates interact with enzymes during a catalyzed reaction?

Substrates bind to the active site of the enzyme, forming an enzyme-substrate complex.

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

The structure (shape) of the protein that forms the enzyme.

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

Positive G indicates a non-spontaneous reaction, while negative G indicates a spontaneous reaction.

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

Anabolic reactions synthesize higher free energy products, while catabolic reactions degrade lower free energy products.

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

Spontaneous reactions always increase the entropy of the system.

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

Anabolic reactions are endergonic and require energy, while catabolic reactions are exergonic and release energy.

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

Enzymes decrease the activation energy required for a reaction to occur, thereby increasing the reaction rate.

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

If a reaction has a negative enthalpy change and a positive entropy change, the free energy change is always negative.

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

Anabolic reactions have a positive free energy change and are non-spontaneous, while catabolic reactions have a negative free energy change and are spontaneous.

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

Reaction coupling is the process of combining an exergonic reaction with an endergonic reaction to make the overall process spontaneous.

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

ATP is a high-energy molecule that is continuously used and regenerated in cellular processes to drive endergonic reactions.

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

NADH and NADPH are high-energy electron carriers that capture and release electrons in redox reactions to generate energy.

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

The light reactions use two photosystems to capture light energy and generate high-energy electrons, which are used to produce ATP and NADPH.

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

The ETC in the light reactions generates a proton gradient across the thylakoid membrane, which is used to produce ATP through chemiosmosis.

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

Explore the concept of metabolism, which encompasses all anabolic and catabolic reactions in a cell. Learn about the network of reaction pathways, anabolic reactions that synthesize molecules with more bonds, and catabolic reactions that degrade molecules to release energy.

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