Cellular Respiration and Glycolysis
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Questions and Answers

What is the primary function of the proton-motive force in prokaryotes?

  • To synthesize glucose from carbon dioxide
  • To regulate the pH of the cellular environment
  • To decompose waste products into harmless substances
  • To generate ATP and transport molecules across the membrane (correct)

How many ATP molecules are produced by substrate-level phosphorylation during cellular respiration?

  • Eight ATP molecules
  • Two ATP molecules
  • Four ATP molecules (correct)
  • Six ATP molecules

What is the efficiency of respiration based on the conversion of glucose to ATP?

  • 50%
  • 25%
  • 15%
  • 34% (correct)

Which molecule primarily carries electrons to the electron transport chain during cellular respiration?

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

What process is described as driving cellular work such as ATP synthesis through the flow of H+ across a membrane?

<p>Chemiosmosis (C)</p> Signup and view all the answers

What adaptation is observed in hibernating mammals regarding their metabolism?

<p>Lowered metabolism and energy conservation during inactivity (A)</p> Signup and view all the answers

What happens to electron carriers during electron transport?

<p>They alternate between reduced and oxidized states. (C)</p> Signup and view all the answers

What does the process of oxidative phosphorylation primarily involve?

<p>Conversion of NADH and FADH2 into ATP through electron transport (D)</p> Signup and view all the answers

Which molecule receives electrons from NADH first in the electron transport chain?

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

What is the approximate maximum number of ATP molecules generated from each NADH during oxidative phosphorylation?

<p>3 ATP (A)</p> Signup and view all the answers

What is the primary function of ATP synthase?

<p>To catalyze ATP production (B)</p> Signup and view all the answers

What percentage of energy in gasoline is converted to useful work by the most efficient automobile?

<p>25% (A)</p> Signup and view all the answers

How does the rotor of ATP synthase contribute to ATP production?

<p>By enabling the flow of H+ through the enzyme (D)</p> Signup and view all the answers

Which component is NOT a protein in the electron transport chain?

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

What maintains the H+ gradient that drives ATP synthesis in ATP synthase?

<p>The pumping of electrons (B)</p> Signup and view all the answers

Which statement about ATP synthase is true?

<p>It consists of multiple subunits made up of polypeptides. (A)</p> Signup and view all the answers

What two-carbon compound is formed from pyruvate during fermentation?

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

Which type of organism can only survive through fermentation or anaerobic respiration?

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

What is the main purpose of the Calvin cycle in photosynthesis?

<p>To incorporate CO2 into organic molecules (D)</p> Signup and view all the answers

How much ATP is produced by aerobic respiration compared to fermentation per glucose molecule?

<p>32 ATP for respiration and 2 ATP for fermentation (B)</p> Signup and view all the answers

Which equation represents the process proposed for photosynthesis in sulfur bacteria?

<p>CO2 + 2H2S → [CH2O] + H2O + 2S (D)</p> Signup and view all the answers

What is the byproduct of alcoholic fermentation by yeast?

<p>Carbon dioxide and ethanol (B)</p> Signup and view all the answers

What role does NADPH play in the Calvin cycle?

<p>It provides electrons for carbon reduction (D)</p> Signup and view all the answers

What process occurs in human muscle cells under anaerobic conditions?

<p>Lactic acid fermentation (D)</p> Signup and view all the answers

What is the significance of light reactions in the context of the Calvin cycle?

<p>They produce NADPH and ATP needed for the Calvin cycle (B)</p> Signup and view all the answers

Which metabolic pathway can facultative anaerobes utilize depending on oxygen availability?

<p>Both fermentation and respiration (C)</p> Signup and view all the answers

How are the metabolic steps of the Calvin cycle classified?

<p>Light-independent reactions (D)</p> Signup and view all the answers

What happens to pyruvate under aerobic conditions?

<p>Converted to acetyl CoA (B)</p> Signup and view all the answers

What is the role of NADH in fermentation?

<p>To regenerate NAD+ (C)</p> Signup and view all the answers

What is the outcome of water splitting in photosynthesis according to van Niel's hypothesis?

<p>It provides hydrogen atoms and releases oxygen (B)</p> Signup and view all the answers

What does an absorption spectrum measure?

<p>The wavelengths of light transmitted through a pigment solution (D)</p> Signup and view all the answers

Who is the Calvin cycle named after?

<p>Melvin Calvin (C)</p> Signup and view all the answers

What primary function do glycolysis and the citric acid cycle serve in metabolic pathways?

<p>They enable cells to convert one kind of molecule to another as needed. (D)</p> Signup and view all the answers

Which statement about glycolysis is true?

<p>Glycolysis takes place in the cytosol without membrane-enclosed organelles. (B)</p> Signup and view all the answers

What is the role of anabolic pathways in metabolism?

<p>They consume ATP to synthesize complex molecules. (C)</p> Signup and view all the answers

How can excess carbohydrates and proteins be processed by the body?

<p>They can be converted to fats through glycolysis and the citric acid cycle intermediates. (A)</p> Signup and view all the answers

What regulates the metabolic economy related to cellular respiration?

<p>Feedback mechanisms based on supply and demand. (C)</p> Signup and view all the answers

What do feedback mechanisms prevent during cellular respiration?

<p>The diversion of intermediary molecules from necessary pathways. (B)</p> Signup and view all the answers

Which of the following statements about metabolism is true?

<p>Metabolism can utilize various organic molecules to produce ATP. (B)</p> Signup and view all the answers

What happens to an excess amino acid in a cell?

<p>It may be diverted to synthesize pathways related to that amino acid. (D)</p> Signup and view all the answers

What recent understanding has emerged regarding lactate's role in muscle performance?

<p>Lactate may enhance muscle performance rather than hinder it. (D)</p> Signup and view all the answers

Which cellular process does not occur in fermentation?

<p>Utilization of an electron transport chain (C)</p> Signup and view all the answers

What is the fate of excess lactate produced during glycolysis?

<p>It is transported to the liver for conversion to pyruvate. (B)</p> Signup and view all the answers

What differentiates anaerobic respiration from fermentation?

<p>Anaerobic respiration has an electron transport chain while fermentation does not. (C)</p> Signup and view all the answers

What type of organisms can perform fermentation?

<p>Any organism capable of glycolysis. (A)</p> Signup and view all the answers

What is produced as a by-product of sulfate-reducing bacteria during anaerobic respiration?

<p>Hydrogen sulfide (H2S) (B)</p> Signup and view all the answers

What is the net ATP production from glycolysis during fermentation, anaerobic respiration, and aerobic respiration?

<p>2 ATP (B)</p> Signup and view all the answers

Which of the following accurately describes the role of NAD+ in cellular respiration?

<p>It acts as an oxidizing agent that accepts electrons. (C)</p> Signup and view all the answers

Flashcards

Chemiosmosis

The process of moving protons (H+) across a membrane to generate ATP, using energy from electron transport.

Electron Transport Chain

A series of protein complexes that transfer electrons from NADH and FADH2 to oxygen, releasing energy to pump protons (H+) across the membrane.

Redox Reactions (Electron Transport)

Electron carriers in the transport chain switch between reduced (accepting electrons) and oxidized (donating electrons) states.

ATP Synthase

An enzyme that uses the proton gradient to produce ATP from ADP and inorganic phosphate.

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Proton Gradient

A difference in proton concentration across a membrane, storing potential energy.

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NADH

A coenzyme that carries high-energy electrons produced during glycolysis and the Krebs cycle, transferring them to the electron transport chain.

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Ubiquinone

A small, hydrophobic molecule that acts as an electron carrier in the electron transport chain.

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Inner Mitochondrial Membrane/Prokaryotic Plasma Membrane

The location where the proton gradient is generated to drive ATP synthesis in ATP synthase.

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Photosynthesis in sulfur bacteria

CO2 + 2H2S → [CH2O] + H2O + 2S. This reaction is a simplified representation of how sulfur bacteria convert carbon dioxide and hydrogen sulfide into sugars, water, and sulfur.

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Photosynthesis in plants

CO2 + 2H2O → [CH2O] + H2O + O2. Plants use carbon dioxide and water to make sugars, releasing oxygen as a byproduct.

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Calvin cycle

The second stage of photosynthesis, where carbon fixation, reduction, and regeneration occur to produce sugar.

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Carbon fixation

The process of incorporating carbon dioxide into organic molecules in the Calvin cycle.

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Light reactions

First stage of photosynthesis, which produces ATP and NADPH. Crucial for the Calvin cycle.

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Absorption spectrum

A graph that plots a pigment's light absorption versus wavelength.

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Spectrophotometer

A device that measures the fraction of light transmitted through a solution containing a pigment.

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Light-independent reactions

Metabolic steps of the Calvin cycle; do not directly require light

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Proton-motive force

The potential energy stored across a membrane due to a difference in proton concentration, used by prokaryotes for ATP generation, nutrient/waste transport, and flagella rotation.

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Substrate-level phosphorylation

Direct ATP synthesis coupled with the transfer of a phosphate group from a high-energy substrate to ADP.

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Oxidative phosphorylation

ATP production through the electron transport chain, using the proton-motive force.

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ATP production (efficiency)

Cellular respiration converts glucose energy to ATP with ~34% efficiency.

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NADH contribution

Each NADH from the citric acid cycle/pyruvate conversion produces enough energy for 3 ATP via the proton-motive force.

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Cellular Respiration's Efficiency

Cellular respiration is highly efficient, converting glucose energy into ATP.

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Respiration's Energy Flow

Energy flows from glucose to NADH to electron transport chain to proton-motive force to ATP, with energy loss as heat.

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Hibernating Mammals' Metabolism

Hibernating mammals reduce their metabolism to conserve energy during inactivity.

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Lactate and Muscle Fatigue

Recent research suggests that increased potassium ions (K+), not lactate, are the primary cause of muscle fatigue and pain. Lactate may enhance muscle performance.

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Fermentation

A metabolic process that oxidizes organic fuel and produces ATP without oxygen or electron transport chains.

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Anaerobic Respiration

A type of respiration that occurs in organisms possessing an electron transport chain, but without using oxygen as the final electron acceptor.

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Aerobic Respiration

Cellular respiration using oxygen as the final electron acceptor in the electron transport chain.

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Electron Transport Chain (ETC)

A series of protein complexes that pass electrons from one to another, generating a proton-motive force to produce ATP.

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Glycolysis

The process that oxidizes glucose into two pyruvate molecules with NAD+ as the oxidizing agent, producing a net of 2 ATP.

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Pyruvate

An end product of glycolysis, and a key intermediate in cellular respiration and fermentation.

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Proton-motive Force

The energy stored in the form of a proton gradient across a membrane, used by the cell to produce ATP during respiration.

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Glycolysis Ubiquity

Glycolysis is a widespread metabolic process in the cytosol, not needing organelles, suggesting early evolution.

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Anabolic Pathways

These pathways build molecules and consume ATP, not produce it.

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Metabolic Interchanges

Glycolysis and the citric acid cycle connect different metabolic pathways, allowing molecule conversions.

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Fuel Diversity

Carbohydrates, proteins, and fats can all be used to produce ATP via cellular respiration.

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Macromolecule to Fuel

Polysaccharides, disaccharides and other macromolecules can be broken down into usable fuel for cellular respiration. Fats can also be converted.

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Excess Food Storage

Even with a fat-free diet, excess food is stored as fat via glycolysis and the citric acid cycle intermediaries.

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Feedback Regulation

Cellular respiration is controlled by feedback mechanisms that adjust reactions to meet needs.

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Amino Acid Regulation

Cells use feedback to prevent excess amino acid synthesis from interfering with other metabolic processes.

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Aerobic Respiration Efficiency

Aerobic respiration produces significantly more ATP (up to 32 molecules) per glucose molecule compared to fermentation (2 molecules).

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Lactic Acid Fermentation

Pyruvate is directly reduced to lactate by NADH, without CO2 release. This regenerates NAD+ for glycolysis.

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Alcohol Fermentation

Pyruvate is converted to acetaldehyde then ethanol, releasing CO2. NADH reduces acetaldehyde, regenerating NAD+ for glycolysis.

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Facultative Anaerobes

Organisms that can survive with or without oxygen, using fermentation or respiration.

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Obligate Anaerobes

Organisms that can only survive without oxygen, using only fermentation or anaerobic respiration.

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Pyruvate as a Fork in the Road

Pyruvate is a critical juncture for metabolism, leading to either fermentation or aerobic respiration (acetyl CoA formation).

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Acetyl CoA Formation

Under aerobic conditions, pyruvate is converted to acetyl CoA, preparing it for entry into the citric acid cycle.

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Glycerol Metabolism

Digested fats are converted to glycerol, which can be metabolized into an intermediate of glycolysis, ultimately contributing to cellular energy production.

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Study Notes

Cellular Respiration

  • Cellular respiration is the process by which cells harvest chemical energy from organic molecules.
  • It involves three key pathways: glycolysis, the citric acid cycle, and oxidative phosphorylation.
  • Fermentation is a simpler pathway that does not require oxygen.
  • Redox reactions are crucial to catabolic pathways, where electrons are transferred, releasing stored energy to synthesize ATP.
  • Oxidation is the loss of electrons, while reduction is the gain of electrons.
  • Organic molecules store potential energy in the arrangement of their electrons.
  • Enzymes catalyze the breakdown of organic molecules into simpler products, releasing energy.

Glycolysis

  • Glycolysis is the first stage of cellular respiration, taking place in the cytosol.
  • This stage breaks down glucose, a six-carbon sugar, into two three-carbon pyruvate molecules.
  • It involves both energy investment and energy payoff phases.
  • Net yield: 2 ATP and 2 NADH per glucose molecule.
  • Glycolysis does not require oxygen.

Pyruvate Oxidation/Citric Acid Cycle

  • Pyruvate is oxidized to acetyl CoA, entering the citric acid cycle.
  • The citric acid cycle completes the oxidation of the organic fuel derived from pyruvate, releasing CO2.
  • Net yield: 1 ATP, 3 NADH, and 1 FADH2 per acetyl CoA molecule.
  • This stage requires the presence of oxygen.

Oxidative Phosphorylation

  • Oxidative phosphorylation is the third stage of cellular respiration and is the major source of ATP.
  • It consists of the electron transport chain and chemiosmosis.
  • Electrons from NADH and FADH2 are passed along a series of proteins in the electron transport chain, releasing energy that is used to pump protons (H+) across the inner mitochondrial membrane, creating a proton gradient.
  • Chemiosmosis uses the energy of this gradient to drive ATP synthesis via ATP synthase.
  • Oxygen acts as the final electron acceptor, forming water.
  • High yield of ATP: about 28-34 ATP per glucose molecule.

Fermentation

  • Fermentation is a metabolic pathway that regenerates NAD+ from NADH in the absence of oxygen.
  • Two common types are alcohol fermentation and lactic acid fermentation.
  • Alcohol fermentation produces ethanol and CO2.
  • Lactic acid fermentation produces lactate.
  • Fermentation yields a much lower amount of ATP (2 ATP per glucose) compared to cellular respiration.

Photosynthesis

  • Photosynthesis is the process by which plants capture light energy and convert it into chemical energy in the form of sugars.
  • The overall equation for photosynthesis is: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
  • Photosynthesis occurs in chloroplasts, specifically in the thylakoid membranes and stroma.
  • Light reactions occur in thylakoid membranes, capturing light energy, splitting water, and producing ATP and NADPH.
  • The Calvin cycle occurs in the stroma, using ATP and NADPH to reduce CO2 and synthesize sugars.

Cell Division

  • Cell division is essential for growth, repair, and reproduction in both prokaryotes and eukaryotes.
  • The eukaryotic cell cycle includes interphase (G1, S, G2) and the mitotic (M) phase (mitosis and cytokinesis).
  • Mitosis ensures that daughter cells receive identical genetic material.
  • Cytokinesis is the division of the cytoplasm.
  • Several checkpoints regulate the cell cycle.

Cancer

  • Cancer results from uncontrolled cell division, due to genetic changes that negatively affect cell cycle control.
  • Cancer cells typically do not exhibit density-dependent inhibition or anchorage dependence, dividing excessively and invading other tissues.

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Cellular Respiration & Fermentation (BSc1010) PDF

Description

Explore the essential processes of cellular respiration, including glycolysis and its stages. This quiz covers key pathways, energy yield, and the role of enzymes in breaking down glucose molecules. Test your knowledge and understanding of how cells harvest energy!

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