Glycolysis Overview and Mechanisms
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Questions and Answers

What is the primary cause of fatigue after high-intensity exercise?

  • Depletion of glycogen
  • Insufficient oxygen supply
  • Accumulation of lactate
  • Accumulation of H+ (correct)

What factors influence lactate production during exercise?

  • Exercise duration and age
  • Exercise intensity and fiber type (correct)
  • Oxygen availability and hydration
  • Body temperature and rest periods

Which of the following best describes lactate clearance rates post-exercise?

  • They are increased by light activity. (correct)
  • They are decreased by rest.
  • They are influenced by hydration.
  • They remain constant regardless of activity.

What enzyme is responsible for converting pyruvate to lactate?

<p>Lactate dehydrogenase (A)</p> Signup and view all the answers

Why is glycogen often preferred over glucose for glycolysis during exercise?

<p>Glycogen is stored closer to muscle fibers. (B)</p> Signup and view all the answers

What is the main purpose of glycolysis in biological energy systems?

<p>To break down carbohydrates to resynthesize ATP (C)</p> Signup and view all the answers

Which enzyme is responsible for controlling the rate of glycolysis?

<p>Phosphofructokinase (PFK) (A)</p> Signup and view all the answers

What occurs during fast glycolysis when pyruvate is converted to lactate?

<p>It yields only 2 or 3 ATP but works under high demand (C)</p> Signup and view all the answers

During slow glycolysis, what happens to the pyruvate produced?

<p>It is shuttled into the mitochondria for further processing (D)</p> Signup and view all the answers

Why is making lactate beneficial during high-intensity exercise?

<p>It serves to buffer excess acidity from rapid ATP production (A)</p> Signup and view all the answers

Which statement about slow glycolysis is true?

<p>It yields a higher amount of ATP than fast glycolysis (C)</p> Signup and view all the answers

What distinguishes fast glycolysis from slow glycolysis?

<p>Fast glycolysis is anaerobic and occurs quicker, while slow glycolysis is aerobic and slower (D)</p> Signup and view all the answers

What is the maximum ATP yield from slow glycolysis using glucose?

<p>32 ATP (D)</p> Signup and view all the answers

Flashcards

Glycolysis

A series of 10 enzymatic reactions that break down carbohydrates (glycogen or glucose) to generate ATP or electron carriers for the ETC.

Fast Glycolysis (Anaerobic)

The process where pyruvate from glycolysis is converted to lactate, providing a rapid but limited source of ATP.

Phosphofructokinase (PFK)

The rate-limiting enzyme in glycolysis, controlling the overall speed of the process.

Slow Glycolysis (Aerobic)

The process where pyruvate from glycolysis enters the mitochondria, providing a slower but more sustainable source of ATP.

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Lactate

A metabolic by-product of fast glycolysis, helping to buffer acidity during high-intensity exercise.

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Krebs Cycle and Electron Transport Chain (ETC)

The process in the mitochondria where pyruvate is further broken down to produce ATP, utilizing oxygen.

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Mitochondrial Buffering

The ability of mitochondria to buffer acidity (H+) during exercise. This is slower during high-intensity exercise.

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Speed

The primary reason for producing lactate instead of using the mitochondria in high-intensity exercise.

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Pyruvate to Lactate Conversion

The process where pyruvate is converted to lactate, which is a byproduct of anaerobic glycolysis. This occurs when there is a lack of sufficient oxygen, leading to the accumulation of pyruvate in the cell. Lactate dehydrogenase (LDH) is the enzyme responsible for this conversion.

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Lactate and Metabolic Acidosis

During intense exercise, the buildup of hydrogen ions (H+) in the blood leads to a decrease in pH, which is called metabolic acidosis. This is often attributed to lactate accumulation, but it's actually the H+ ions that cause the acidity, not lactate itself. Lactate is not the cause of muscle fatigue after exercise.

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Lactate Production and Removal

The amount of lactate in your blood is the result of a balance between how quickly it's produced and how fast it's removed. The harder you exercise, the more lactate you produce. Fast-twitch muscle fibers produce more lactate than slow-twitch fibers. After exercise, light activity can help remove lactate from the blood.

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Glycogen vs. Glucose in Exercise

Glycogen, a stored form of glucose in the muscle, is preferred over glucose as the primary energy source for glycolysis during exercise. This is because glycogen is readily available in the muscle and does not require additional energy to be transported into the cell.

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Purposes of Lactate Production

The conversion of pyruvate to lactate serves several important functions:

  1. It regenerates NAD+ which is needed for glycolysis to continue.
  2. It removes excess pyruvate from the cell.
  3. It provides an alternative source of energy production in the absence of oxygen.
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Study Notes

Glycolysis Overview

  • Glycolysis is the breakdown of carbohydrates (either glycogen stored in muscle or glucose from blood) to resynthesize ATP
  • It is a series of 10 enzymatic reactions
  • The process can proceed in two directions (fast or slow).

Fast Glycolysis

  • Hexokinase traps glucose in the cell, and it can either go through glycolysis or be stored as glycogen
  • Controlled by the rate-limiting enzyme phosphofructokinase (PFK)
  • The end product (pyruvate) can be converted to lactate
  • Also called anaerobic glycolysis
  • ATP resynthesis is faster but limited in duration
  • Important for high-intensity exercise
  • Yields 2 ATP (from glucose) or 3 ATP (from glycogen)

Slow Glycolysis

  • The end product of glycolysis (pyruvate) can be shuttled into the mitochondria
  • This process is often referred to as aerobic glycolysis (or slow glycolysis)
  • In the mitochondria, pyruvate goes through the Krebs cycle and electron transport chain
  • Half as fast as fast glycolysis, but provides more ATP
  • Most important for endurance exercise
  • Only yields 32 ATP (from glucose) or 33 ATP (from glycogen)

Lactate Production

  • During fast glycolysis, the reason lactate is produced instead of using the mitochondria to produce more ATP is for speed
  • Lactate helps buffer excess acidity created during high-intensity exercise
  • Mitochondria buffers H+ (acidity) in the ETC, but is too slow in high-intensity exercise

Lactate Myths

  • Metabolic acidosis - exercise-induced decrease in pH may be responsible for fatigue after high-intensity exercise
  • Results from accumulation of H+, not lactic acid
  • Lactate is not the cause of fatigue
  • Lactate concentration is a balance between lactate production and removal
  • Lactate production increases with exercise intensity
  • Light activity during the postexercise period can increase lactate clearance rates

Review Questions

  • Explain the purpose and identify the enzymes of the two steps of glycolysis
  • What are the differences in converting pyruvate to lactate or having it enter the mitochondria?
  • Name the enzyme that converts pyruvate to lactate
  • Why is glycogen preferred over glucose for glycolysis during exercise?
  • Explain the purposes of generating lactate

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Ch. 3.3 - Glycolysis & Lactate PDF

Description

This quiz covers the biochemical process of glycolysis, including both fast and slow glycolysis. You'll learn about the enzymatic reactions, ATP resynthesis, and the roles of key enzymes and pathways in energy metabolism. Test your understanding of how glucose is utilized in different exercise intensities.

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