Energy Metabolism Overview

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Questions and Answers

Which biochemical pathway is primarily responsible for the immediate source of ATP during intense exercise?

  • Glycolysis
  • Phosphocreatine breakdown (correct)
  • Krebs cycle
  • Oxidative phosphorylation

What is the net gain of ATP molecules produced by glycolysis?

  • 4 ATP
  • 1 ATP
  • 3 ATP
  • 2 ATP (correct)

Which enzyme is considered rate-limiting in the glycolysis pathway?

  • Pyruvate kinase
  • Hexokinase
  • Phosphofructokinase (correct)
  • Creatine kinase

How does the efficiency of glycolysis compare to other ATP production pathways?

<p>Glycolysis yields a small percentage of ATP from glucose breakdown (A)</p> Signup and view all the answers

What happens during the energy investment phase of glycolysis?

<p>2 ATP molecules are consumed (D)</p> Signup and view all the answers

Which statement correctly describes anaerobic ATP production?

<p>Anaerobic pathways include glycolysis and phosphocreatine breakdown (B)</p> Signup and view all the answers

What is the role of ATPase in energy metabolism?

<p>It catalyzes the breakdown of ATP into ADP and Pi (A)</p> Signup and view all the answers

Which of the following statements accurately describes the relationship between aerobic and anaerobic ATP production?

<p>Both systems interact during various intensities of exercise (A)</p> Signup and view all the answers

What is the primary role of NADH in cellular respiration?

<p>It acts as a hydrogen and electron carrier. (D)</p> Signup and view all the answers

How many molecules of ATP are produced from one molecule of NADH during the electron transport chain?

<p>2.5 ATP (B)</p> Signup and view all the answers

What does the Krebs cycle primarily generate for the electron transport chain?

<p>Hydrogen atoms and electrons (A)</p> Signup and view all the answers

During short-term high-intensity activities, which energy systems contribute more to ATP production?

<p>Anaerobic energy systems (A)</p> Signup and view all the answers

What is the effect of high levels of ATP on ATP production?

<p>Inhibits ATP production (C)</p> Signup and view all the answers

Which molecule must pyruvic acid be converted into for entry into the Krebs cycle?

<p>Acetyl-CoA (D)</p> Signup and view all the answers

What happens to hydrogen ions produced in the Krebs cycle within the mitochondria?

<p>They are accepted by oxygen to form water. (B)</p> Signup and view all the answers

Which molecule does FADH2 generate in the electron transport chain?

<p>1.5 ATP (B)</p> Signup and view all the answers

What is a rate-limiting enzyme?

<p>An enzyme that regulates the rate of a metabolic pathway. (A)</p> Signup and view all the answers

Where does oxidative phosphorylation occur?

<p>On the mitochondrial membrane (C)</p> Signup and view all the answers

Flashcards

What is ATP?

ATP is a molecule that serves as the primary energy currency of cells. It consists of adenine, ribose, and three phosphate groups. Energy is released when one of the phosphate groups is removed, converting ATP to ADP.

What is the phosphocreatine system?

The phosphocreatine system is an anaerobic energy system that provides a quick burst of energy by converting phosphocreatine (PC) to creatine (C) and releasing energy that is used to rephosphorylate ADP to ATP.

What is glycolysis?

Glycolysis is an anaerobic process that breaks down glucose into pyruvate, producing a small amount of ATP (a net gain of 2 ATP molecules). It can occur without oxygen.

What is the Krebs cycle?

The Krebs cycle (also known as the citric acid cycle) is a series of chemical reactions that occur in the mitochondria of cells. It oxidizes pyruvate and generates the electron carriers NADH and FADH2, which are then used in the electron transport chain to produce ATP.

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What is oxidative phosphorylation?

Oxidative phosphorylation is the process by which ATP is produced using energy from the electron transport chain. This process requires oxygen.

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What are rate-limiting enzymes?

Rate-limiting enzymes, such as phosphofructokinase in glycolysis and isocitrate dehydrogenase in the Krebs cycle, control the speed of metabolic pathways by regulating the rate of a specific reaction.

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How do anaerobic and aerobic pathways differ?

Anaerobic pathways, such as the phosphocreatine system and glycolysis, do not require oxygen and provide energy for short, high-intensity activities. Aerobic pathways, including the Krebs cycle and oxidative phosphorylation, require oxygen and are used for sustained, moderate-intensity activities.

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How do anaerobic and aerobic ATP production work together during exercise?

The interaction between anaerobic and aerobic ATP production is crucial for exercise. Anaerobic pathways provide quick bursts of energy at the start of exercise, while aerobic pathways become more dominant as exercise continues and oxygen delivery increases.

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Hydrogen and Electron Carriers

Molecules that transport hydrogen ions (H+) and electrons to mitochondria for ATP generation in aerobic conditions or to convert pyruvic acid to lactic acid in anaerobic conditions.

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NAD (Nicotinamide Adenine Dinucleotide)

A coenzyme that carries electrons and a hydrogen ion (H+) to the electron transport chain for ATP production during aerobic respiration.

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FAD (Flavin Adenine Dinucleotide)

A coenzyme that carries electrons and two hydrogen ions (2H+) to the electron transport chain for ATP production during aerobic respiration.

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Oxidative Phosphorylation

The process of producing ATP using energy from the electron transport chain, which takes place in the mitochondria.

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Electron Transport Chain (ETC)

A series of protein complexes embedded in the inner mitochondrial membrane that use the energy from electrons to pump protons (H+) across the membrane, creating a concentration gradient that drives ATP synthesis.

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Rate-limiting Enzyme

The enzyme that catalyzes the rate-limiting step in a metabolic pathway, controlling the overall pathway's speed.

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Anaerobic ATP Production

The process of producing ATP in the absence of oxygen.

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Aerobic ATP Production

The process of producing ATP in the presence of oxygen; more efficient and generates far more ATP than anaerobic production.

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Anaerobic Energy System

The energy system that primarily contributes to ATP production during short-term, high-intensity activities, like sprinting.

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Aerobic Energy System

The energy system that primarily contributes to ATP production during long-term, low to moderate-intensity activities, like jogging.

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Study Notes

Energy Metabolism Overview

  • Energy metabolism is the process of converting food into usable energy for cells.
  • Food sources are broken down to be used by cells.
  • Energy is transferred from food sources to ATP (adenosine triphosphate) via phosphorylation.
  • ATP is a high-energy compound for storing and conserving energy.
  • Muscle ATP stores are limited, requiring continuous re-synthesis to maintain physical activity.

Objectives

  • Understand anaerobic ATP production pathways.
  • Learn about aerobic ATP production.
  • Analyze the interaction between aerobic and anaerobic ATP production during exercise.
  • Identify rate-limiting enzymes in glycolysis and the Krebs cycle.

High-Energy Phosphates

  • Adenosine triphosphate (ATP) consists of adenine, ribose, and three linked phosphates.
  • ATP synthesis: ADP + P₁ → ATP
  • ATP breakdown: ATP → ADP + P₁ + Energy (catalyzed by ATPase)

Bioenergetics

  • Formation of ATP:
    • Phosphocreatine (PC) breakdown
    • Glycolysis (degradation of glucose/glycogen)
  • Anaerobic pathways: Do not require oxygen; include PC breakdown and glycolysis.
  • Aerobic pathways: Require oxygen; include oxidative phosphorylation.

Anaerobic ATP Production

  • Phosphocreatine system (ATP-PC system): Immediate source of ATP; PC + ADP → ATP + C (catalyzed by creatine kinase)
  • Glycolysis: Glucose breaks down into pyruvic acid or lactic acid.
    • Energy investment phase (requires 2 ATP).
    • Energy generation phase (produces 4 ATP, 2 NADH, and 2 pyruvate or 2 lactate).

Glycolysis Details

  • Glycolysis regulates the whole pathway.
  • Key enzymes like hexokinase and phosphofructokinase are crucial.
  • Substrate-level phosphorylation occurs during glycolysis.
  • The net gain is 2 ATP molecules.
  • Glycolysis efficiency is 30%.
  • Rapid energy transfer is a key function.

Hydrogen and Electron Carrier Molecules

  • Transport H+ and electrons for ATP generation.
  • NAD and FAD transfer H+ to mitochondria (aerobic).
  • NAD + 2H+ → NADH + H+

NADH Shuttled to Mitochondria

  • NADH generated in glycolysis must be converted back to NAD.
  • Conversion to Lactic Acid is one method.
  • 'Shutting' H+ into mitochondria is a mechanism.

The Krebs Cycle

  • Degrades acetyl-CoA to CO₂ and hydrogen atoms.
  • Hydrogens are oxidized in the electron transport chain.
  • ATP is regenerated.
  • Generates electrons (hydrogens) transferred to the electron transport chain via NAD+ and FAD.

Electron Transport Chain

  • Oxidative phosphorylation occurs in mitochondria.
  • Electrons from NADH and FADH₂ are passed to carriers (cytochromes).
  • ATP is produced.
    • Each NADH produces 2.5 ATP. -Each FADH₂ produces 1.5 ATP.
  • H+ from NADH and FADH₂ are accepted by O₂ to form water.

Simplified ETC, and Aerobic ATP Production

  • Electrons pass down a chain of carriers.
  • Oxygen accepts the final electrons.
  • This creates water.

The Krebs Cycle Summary

  • Anaerobic glycolysis releases only 5% of glucose energy potential.
  • Also known as the citric acid cycle, occurring in the mitochondrial matrix.
  • Pyruvate is converted to Acetyl-CoA.

Relationship Between Protein, Carbohydrate, and Fat Metabolism

  • Different macronutrients (proteins, carbohydrates, and fats) can enter the metabolic pathways at various points.

Control of Bioenergetics

  • Rate-limiting enzymes control metabolic pathway speeds.
  • Modulators, such as ATP/ADP levels, affect these enzymes, influencing ATP production.

Factors Affecting Rate-Limiting Enzymes

  • Tables show known stimulators and inhibitors of rate-limiting enzymes in various energy pathways.

Interaction Between Aerobic/Anaerobic ATP Production

  • Exercise energy comes from the interaction of these pathways, with relative contributions varying based on duration and intensity.
    • High-intensity exercises rely more heavily on anaerobic systems.
    • Low to moderate intensity exercises use aerobic systems more.

Contribution of Aerobic/Anaerobic ATP Production (During Specific Events)

  • Graph shows percentages of aerobic or anaerobic contributions to ATP production during different sporting activities, based on duration and intensity.

Example Exam Questions (from Slides)

  • This section covers examples of potential exam questions and associated definitions/principles. These are provided as a helpful summary of probable topic areas.

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