Cellular Respiration Quiz
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Questions and Answers

What is the net gain of ATP from the entire process described?

  • 2 ATP (correct)
  • 4 ATP
  • 6 ATP
  • 0 ATP

    • Which molecule is produced in the energy payoff phase?

  • Pyruvate (correct)
  • NADH (correct)
  • Glucose
  • FADH2

    • What role do the 2 ADP and 2 P play in the energy investment phase?

  • They are converted to ATP. (correct)
  • They create a stable substrate.
  • They are used to regenerate NAD+.
  • They facilitate glucose breakdown.

    • What is formed when glucose is split in the energy investment phase?

    <p>Pyruvate</p> Signup and view all the answers

    What occurs to the substrates during the energy investment phase?

    <p>They are phosphorylated.</p> Signup and view all the answers

    What is the primary energy source generated from cellular respiration?

    <p>ATP</p> Signup and view all the answers

    Which type of respiration is characterized by the complete degradation of carbohydrates in the presence of oxygen?

    <p>Aerobic respiration</p> Signup and view all the answers

    What does anaerobic respiration primarily yield compared to aerobic respiration?

    <p>Less ATP</p> Signup and view all the answers

    In cellular respiration, what happens to the chemical energy in glucose?

    <p>It is converted to ATP</p> Signup and view all the answers

    What is the end product of aerobic cellular respiration along with ATP?

    <p>Water</p> Signup and view all the answers

    Which process is usually referred to when discussing cellular respiration?

    <p>Aerobic respiration</p> Signup and view all the answers

    What is the role of ATP in cellular work?

    <p>It releases energy through hydrolysis</p> Signup and view all the answers

    What is the simplified equation for cellular respiration?

    <p>C6H12O6 + O2 → CO2 + H2O + ATP</p> Signup and view all the answers

    What is the role of NAD+ in cellular respiration?

    <p>To function as an electron carrier during oxidation</p> Signup and view all the answers

    During the reduction of NAD+, what is produced?

    <p>NADH and protons</p> Signup and view all the answers

    Which stage of cellular respiration follows glycolysis?

    <p>Citric acid cycle</p> Signup and view all the answers

    What does the oxidized form of NAD+ allow for in cells?

    <p>The reduction of other molecules</p> Signup and view all the answers

    Which of the following correctly describes the relationship between NAD+ and NADH?

    <p>NAD+ is generated through the oxidation of NADH</p> Signup and view all the answers

    What is the primary function of dehydrogenase enzymes in cellular respiration?

    <p>To catalyze the oxidation of substrates</p> Signup and view all the answers

    Which of the following compounds is formed from the reduction of NAD+?

    <p>NADH</p> Signup and view all the answers

    What is the significance of the electron and proton coupled transfer in NAD+/NADH conversion?

    <p>It contributes to energy equilibrium</p> Signup and view all the answers

    What occurs in the absence of oxygen during the process of glycolysis?

    <p>Fermentation</p> Signup and view all the answers

    Which of the following is NOT a product of fermentation?

    <p>Acetyl CoA</p> Signup and view all the answers

    What is produced during alcoholic fermentation?

    <p>Ethanol and CO2</p> Signup and view all the answers

    Which step of anaerobic respiration can occur in both aerobic and anaerobic conditions?

    <p>Glycolysis</p> Signup and view all the answers

    During lactic acid fermentation, what is primarily produced?

    <p>Lactic acid</p> Signup and view all the answers

    Which statement about NAD+ is correct in the context of fermentation?

    <p>NAD+ can be reused in glycolysis to ensure ATP production continues.</p> Signup and view all the answers

    Which of the following best describes anaerobic respiration?

    <p>It produces energy without the use of oxygen.</p> Signup and view all the answers

    What happens to pyruvate during anaerobic conditions?

    <p>It can be fermented to produce ethanol or lactic acid.</p> Signup and view all the answers

    What is the primary function of the citric acid cycle?

    <p>To produce ATP and electron carriers</p> Signup and view all the answers

    Which molecule combines with acetyl CoA to initiate the citric acid cycle?

    <p>Oxaloacetate</p> Signup and view all the answers

    What is produced as a byproduct of the transformation of isocitrate in the citric acid cycle?

    <p>NADH</p> Signup and view all the answers

    Which molecule is not a product of the citric acid cycle?

    <p>Glucose</p> Signup and view all the answers

    What role does NAD+ play in the citric acid cycle?

    <p>It accepts electrons to form NADH</p> Signup and view all the answers

    What is the net product of glycolysis?

    <p>2 ATP, 2 NADH, 2 pyruvates</p> Signup and view all the answers

    Which compound serves as a substrate for the conversion of succinyl CoA into succinate?

    <p>GDP</p> Signup and view all the answers

    Which of the following steps directly results in the release of carbon dioxide?

    <p>Oxidation of isocitrate to alpha-ketoglutarate</p> Signup and view all the answers

    How many ATP are formed during the energy payoff phase of glycolysis?

    <p>4 ATP</p> Signup and view all the answers

    Which of the following is produced along with pyruvate in glycolysis?

    <p>NADH</p> Signup and view all the answers

    What is produced during the conversion of fumarate to malate?

    <p>FADH2</p> Signup and view all the answers

    How many carbon atoms are found in oxaloacetate?

    <p>4</p> Signup and view all the answers

    What molecule is the starting point for glycolysis?

    <p>Glucose</p> Signup and view all the answers

    What type of reaction occurs when citrate is converted to isocitrate?

    <p>Isomerization</p> Signup and view all the answers

    Which enzyme is responsible for converting Fructose-1,6-bisphosphate to Glyceraldehyde-3-phosphate?

    <p>Aldolase</p> Signup and view all the answers

    Which molecule is directly synthesized from GTP in the citric acid cycle?

    <p>ATP</p> Signup and view all the answers

    What role do NAD+ and NADH play during glycolysis?

    <p>They are electron carriers.</p> Signup and view all the answers

    Which enzyme transforms succinate into fumarate?

    <p>Succinate dehydrogenase</p> Signup and view all the answers

    In glycolysis, how is ATP utilized in the energy investment phase?

    <p>ATP is converted to ADP.</p> Signup and view all the answers

    Which intermediate is formed after Glyceraldehyde-3-phosphate in glycolysis?

    <p>1,3-Bisphosphoglycerate</p> Signup and view all the answers

    Which coenzyme is required for the conversion of pyruvate to acetyl CoA before entering the citric acid cycle?

    <p>CoA</p> Signup and view all the answers

    What is the function of the enzyme aconitase in the citric acid cycle?

    <p>Facilitates the conversion of citrate to isocitrate</p> Signup and view all the answers

    What byproduct is released as a result of converting 2 NAD+ during glycolysis?

    <p>NADH</p> Signup and view all the answers

    Which enzyme facilitates the conversion of glucose to glucose-6-phosphate?

    <p>Hexokinase</p> Signup and view all the answers

    During glycolysis, what is the final product formed from Fructose-1,6-bisphosphate?

    <p>2 Glyceraldehyde-3-phosphate</p> Signup and view all the answers

    Which phase of glycolysis consumes ATP?

    <p>Energy investment phase</p> Signup and view all the answers

    What type of phosphorylation occurs in the energy payoff phase of glycolysis?

    <p>Substrate-level phosphorylation</p> Signup and view all the answers

    Study Notes

    Cellular Respiration Overview

    • Cellular respiration is a process that harvests chemical energy
    • Organisms use it to derive and utilize energy
    • The process consists of 3 stages: glycolysis, Krebs cycle, oxidative phosphorylation

    Learning Objectives

    • Understand the structure and function of mitochondria
    • Locate the different stages of cellular respiration in animal cells
    • Explain the process of how organisms derive and utilize energy through cellular respiration with focus on 3 stages: glycolysis, Krebs cycle, oxidative phosphorylation
    • Describe the process of chemiosmosis in mitochondria including the electron transport chain and ATP production
    • Understand the processes of alcohol fermentation and lactic acid fermentation
    • Compare the processes of aerobic and anaerobic respiration

    Cellular Respiration: Harvesting Chemical Energy

    • Cells require energy from external sources to perform various tasks
    • These include: synthesis of macromolecules, active transport, movement, and reproduction
    • Catabolic pathways breakdown organic compounds to generate energy (e.g., cellular respiration)
    • Anabolic pathways consume energy to build organic compounds (e.g., photosynthesis)
    • Mitochondria and chloroplasts are organelles involved in energy production and conversion

    Sunlight as Ultimate Energy Source

    • Sunlight is the ultimate source of energy for all ecosystems
    • Energy enters an ecosystem as sunlight and exists as heat
    • Photosynthesis takes place in chloroplasts, converting light energy into chemical energy
    • Cellular respiration takes place in mitochondria, releasing energy stored in organic molecules

    Catabolic Pathways: Production of ATP

    • Cells need to produce ATP to remain functional
    • Catabolic pathways break down organic fuels to generate energy
    • The breakdown of organic molecules is exergonic (releases energy as ATP)
    • Reactants are more energy-rich than products
    • Cellular respiration is the most prevalent and efficient catabolic pathway for degrading carbohydrates in the presence of oxygen (aerobic)
    • Anaerobic respiration (fermentation) is a partial degradation of carbohydrates in the absence of oxygen which yields less ATP

    Cellular Respiration: Details

    • Involves transfers of energy in glucose bonds to phosphate bonds in ATP
    • The released energy in ATP hydrolysis is used for cellular work(e.g. endergonic reactions)

    Photosynthesis and Cellular Respiration

    • Photosynthesis: CO2 + H2O + sunlight = C6H12O6 + O2 (produces organic molecules and oxygen)
    • Cellular respiration (aerobic): C6H12O6 + O2 = CO2 + H2O + ATP + energy (releases stored energy as ATP and heat)
    • ATP: A nucleotide that stores energy in phosphate bonds

    Mitochondria and Chloroplasts

    • Energy production and conversion organelles
    • Cellular respiration: energy production from oxidation of organic compounds
    • Chloroplasts: photosynthesis, light and dark reactions
    • Mitochondria: 2 phases of Cellular Respiration (GLYCOLYSIS, Kreb's Cycle, oxidative phosphorylation)

    Mitochondria: Structure

    • Diameter: 1-10 μm
    • Structure: outer & inner membrane, intermembrane space, cristae, matrix containing mtDNA and free ribosomes
    • Inner membrane: cristae formation (contains ETC complexes, ATP synthase)

    Redox Reactions:

    • Redox reactions transfer electrons. Oxidation releases electrons, reduction gains electrons.
    • Catabolic pathways yield energy through electron transfer

    Examples of redox reactions

    • Na + Cl => Na+ + Cl- (Na becomes oxidized, Cl becomes reduced)
    • X + Y => X- + Y+ (X is oxidized, Y is reduced)

    Oxidation of Organic Fuels During Cellular Respiration

    • Glucose is oxidized and O2 is reduced
    • C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (ATP)

    The Stages of Cellular Respiration

    • Respiration consists of three metabolic stages:
      • Glycolysis: the anaerobic stage, in the cytosol
      • The citric acid cycle
      • Oxidative phosphorylation process in the mitochondria.

    Production of ATP during cellular respiration

    • Glycolysis and the citric acid cycle generate a small amount of ATP (10% of total) by substrate-level phosphorylation.
    • Most ATP (90%) is generated by oxidative phosphorylation (by ATP synthase).

    Overview of cellular respiration stages

    • Glycolysis breaks down glucose into pyruvate
    • The citric acid cycle converts pyruvate to acetyl-CoA, producing CO2
    • Oxidative phosphorylation involving electron transport chain (ETC) leading to chemiosmosis and ATP synthesis

    Energy transfer via the redox coenzymes NAD+ and FAD

    • Cells release energy from organic compounds in the form of electrons
    • Redox coenzymes NAD+ and FAD carry electrons
    • Electrons released from oxidizing organic compounds are transferred to NAD+ and FAD, reducing them to NADH and FADH2, which then carry these electrons to ETC
    • These electrons are then transferred to O2, resulting in the production of water.

    Redox Coenzymes NAD and FAD

    • NAD = Nicotinamide adenine dinucleotide
    • FAD = Flavine adenine dinucleotide
    • NADH and FADH2 are carriers of electrons to the electron transport chain

    NAD and FAD: redox coenzymes

    • Each electron is co-transferred with a proton (H+)
    • Dehydrogenases remove these electrons, transferring them to NAD+ or FAD, converting them to NADH and FADH2; this process is used to transport electrons to the ETC.

    Cellular Respiration Stages Summary

    • Glycolysis
    • Citric Acid Cycle
    • Oxidative Phosphorylation

    Cellular Respiration Localization

    • Glycolysis: happens in the cytosol
    • Krebs cycle: occurs in the mitochondrial matrix
    • Oxidative phosphorylation: occurs in the inner mitochondrial membrane

    Glycolysis

    • Glycolysis is the splitting of sugar
    • Breaks down glucose (6C) into 2 molecules of pyruvate (3C)
    • Occurs in the cytosol
    • Anaerobic stage (doesn't require oxygen)
    • Products: 2 ATP, 2 NADH, 2 pyruvate molecules
    • ATP is produced by substrate-level phosphorylation

    Glycolysis: Two Major Phases

    • Energy Investment Phase: requires ATP
    • Energy Payoff Phase: produces ATP and NADH

    Citric Acid Cycle (Krebs Cycle/TCA Cycle)

    • Happens in the mitochondrial matrix
    • Completes oxidation of organic molecules (e.g., CO2 and energy production)
    • Converts pyruvate (a glycolysis product) into acetyl-CoA before beginning the citric acid cycle
    • Acetyl-CoA is produced from glycolysis or beta-oxidation of fatty acids.
    • Acetyl-CoA enters the Krebs cycle.

    Pyruvate Conversion to Acetyl-CoA

    • Pyruvate is converted to Acetyl CoA in the mitochondria, generating NADH and CO2
    • This is a crucial step connecting glycolysis to the Citric Acid Cycle

    Citric Acid Cycle (Krebs Cycle)

    • Pyruvate is broken down into CO2
    • Acetyl-CoA binds to oxaloacetate
    • Citric acid is produced
    • NADH and FADH2 are created and transferred to the ETC

    Krebs cycle (Krebs Cycle/TCA Cycle)

    • Krebs cycle products: Each acetyl-CoA that enters the cycle is converted into 2 CO2, 3 NADH, 1 FADH2, and 1 ATP
    • Krebs cycle energy gain: 1 ATP, 3 NADH, 1 FADH2
    • Net energy profit: 12 molecules of ATP from one Krebs cycle

    Overview of the citric acid cycle

    • 1 glucose molecule generates 2 pyruvates = 2 acetyl-CoA molecules
    • One glucose molecule and 2 citric acid cycles produce:
      • 4 CO2, 2 ATP
      • 6 NADH
      • 2 FADH2

    Oxidative Phosphorylation

    • NADH and FADH2 donate electrons to the ETC
    • ETC powers ATP synthesis
    • Oxidative phosphorylation is coupled with chemiosmosis; this creates an H+ gradient across the inner mitochondrial membrane
    • Chemiosmosis uses energy in the H+ gradient to form ATP

    Electron Transport Chain (ETC)

    • Electrons enter via NADH or FADH2
    • 2 ways electrons enter ETC: NADH oxidation by complex I (NADH dehydrogenase), FADH2 oxidation through complex II (succinate dehydrogenase)
    • Stepwise energy transfer
    • Each electron carrier is more electronegative than the previous one, allowing for energy to be released gradually

    Oxidative Phosphorylation: Electron Transport Chain

    • Oxygen accepts ETC electrons, producing water
    • ETC pumps H+ into the intermembrane space, creating an electrochemical gradient

    Oxidative Phosphorylation: Chemiosmosis

    • ETC causes H+ pumping to the intermembrane space, creating a H+ concentration gradient that generates a membrane potential.
    • Chemiosmosis uses energy for H+ flow through ATP synthase, driving ATP synthesis within the mitochondrial matrix.

    Oxidative Phosphorylation: ATP Production

    • The H+ concentration is greater in the intermembrane space than the matrix.
    • Chemiosmosis involves H+ flow down the gradient through ATP synthase
    • ATP synthase uses energy from the H+ flow to produce ATP

    Proton-motive force (PMF)

    • A gradient of protons is created by the flow of electrons in the ETC.
    • Drives chemiosmosis
    • Stores energy => drives ATP production by ATP synthase, located in the inner mitochondrial membrane

    Chemiosmosis: The Energy-Coupling Mechanism

    • ATP synthase functions reversely as a pump running in reverse
    • Each H+ flowing through ATP synthase causes 120° rotation
    • Every 3 H+ flowing through ATP synthase results in the synthesis of 1 ATP molecule

    ATP synthase (FoF1 ATPase)

    • Enzyme responsible for synthesizing ATP from ADP and Pi
    • Located in the inner mitochondrial membrane
    • Found in mitochondria, chloroplasts, and bacteria
    • A proton pump (H+) that uses proton gradient for ATP synthesis
    • It has 2 parts: Fo(transmembrane), F1(matrix)
    • Proton flow causes changes in binding affinity of ATP/ADP.

    Anaerobic Respiration

    • Cellular (aerobic) respiration produces large amounts of ATP in the presence of oxygen.
    • Anaerobic respiration occurs in the absence of oxygen
    • It utilizes an electron transport chain but with a different electron acceptor from oxygen (e.g., sulfate)

    Fermentation

    • An anaerobic respiration process:
    • Uses phosphorylation instead of an electron transport chain to make ATP
    • Two types are: alcohol fermentation (yeasts produce ethanol and CO2); lactic acid fermentation (animal cells produce lactic acid)

    Anaerobic Cellular Respiration

    • Produces less ATP compared to aerobic respiration (only 2 ATP molecules)
    • Two phases include glycolysis and fermentation

    Aerobic and Anaerobic Respiration

    • Both start with glycolysis, breaking down glucose into pyruvate
    • Different final products (organic compounds vs. water)
    • Aerobic respiration yields significantly more ATP (38 ATP per glucose molecule) while anaerobic respiration (fermentation) produces a much lower yield (2 ATP per glucose molecule)

    Comparison of Aerobic Respiration vs Anaerobic Respiration

    • Obligate anaerobes: microorganisms that carry out fermentation or anaerobic respiration, and can't survive with oxygen.
    • Facultative anaerobes: microorganisms that can survive in both the presence and absence of oxygen.

    Catabolic Pathways Connection

    • Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration.
    • Glycolysis and the citric acid cycle connect to many other metabolic pathways.
    • Excess amino acids from proteins, glycerol from fats, and fatty acids from fats enter different stages of cellular respiration (e.g., glycolysis, acetyl-CoA, citric acid cycle)

    Anabolic Pathways: Biosynthesis

    • The body uses ATP to synthesize other substances
    • Small molecules from food or glycolysis/citric acid cycle are used for biosynthesis.

    Regulation of Cellular Respiration

    • Metabolism is tightly regulated by: supply and demand of intermediates, and energy status
    • Cellular respiration is controlled by allosteric enzymes and feedback inhibition by ATP, among other mechanisms

    Control of Cellular Respiration

    • Phosphofructokinase (PFK) is a crucial control point in glycolysis
    • It's an allosteric enzyme
    • Inhibited by ATP and citrate
    • Stimulated by AMP

    Clinical Correlations

    • Diseases linked to insufficient ATP synthesis are often severe (neuromuscular disorders, encephalopathy)
    • Some diseases may arise from ATP synthase mutations
    • Example include: Leigh syndrome, MELAS syndrome, and Leber's optic neuropathy.

    Summary

    • Mitochondria are crucial for cellular respiration.
    • Cellular respiration has three stages: glycolysis, Krebs cycle, and oxidative phosphorylation
    • Anaerobic respiration includes alcohol and lactic acid fermentation
    • Aerobic vs anaerobic respiration yields different amounts of ATP

    Videos (URLs Provided)

    Glycolysis Animation (URLs Provided)

    Oxidative Phosphorylation Animation (URLs Provided)

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    Cellular Respiration PDF

    Description

    Test your understanding of cellular respiration processes, including the energy investment and payoff phases, as well as the roles of ATP and NAD+. This quiz covers key concepts, from glucose breakdown to the final products of aerobic respiration. Perfect for biology students looking to enhance their knowledge of metabolism.

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