Cellular Respiration Quiz
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Questions and Answers

What process generates O2 and organic molecules used in cellular respiration?

  • Fermentation
  • Aerobic respiration
  • Anaerobic respiration
  • Photosynthesis (correct)

Fermentation occurs in the presence of oxygen.

False (B)

What organic molecules are primarily used in cellular respiration to regenerate ATP?

Sugars

Aerobic respiration consumes organic molecules and ________.

<p>O2</p> Signup and view all the answers

Which process provides energy to cells by consuming organic molecules and other compounds aside from oxygen?

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

Match the following processes with their descriptions:

<p>Photosynthesis = Generates O2 and organic molecules Fermentation = Partial degradation of sugars without O2 Aerobic respiration = Uses O2 to consume organic molecules Anaerobic respiration = Similar to aerobic but does not use O2</p> Signup and view all the answers

Cells use ATP to power most cellular work.

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

What flows into an ecosystem as sunlight?

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

What is the primary fuel molecule that is often used to trace cellular respiration?

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

Aerobic respiration does not involve oxygen.

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

What happens to glucose during cellular respiration?

<p>It is oxidized.</p> Signup and view all the answers

During cellular respiration, glucose is oxidized, and __________ is reduced.

<p>O2</p> Signup and view all the answers

Which coenzyme acts as an electron acceptor during cellular respiration?

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

Match the following terms with their definitions:

<p>Oxidation = Loss of electrons Reduction = Gain of electrons NAD+ = Coenzyme that accepts electrons Electron transport chain = Series of steps that pass electrons</p> Signup and view all the answers

The chemical reaction for cellular respiration can be summarized as __________ + __________ → __________ + __________ + Energy.

<p>C6H12O6, O2, CO2, H2O</p> Signup and view all the answers

What is the primary product of glycolysis?

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

What does OIL in the context of oxidation-reduction reactions stand for?

<p>Oxidation Is Loss</p> Signup and view all the answers

What is produced during the oxidation of pyruvate to acetyl CoA?

<p>1 FADH2 (A), 1 CO2 (D)</p> Signup and view all the answers

Glycolysis requires oxygen to proceed.

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

The citric acid cycle produces ATP directly from the breakdown of pyruvate.

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

What is produced during the energy payoff phase of glycolysis?

<p>4 ATP and 2 NADH</p> Signup and view all the answers

The maximum ATP yield from one molecule of glucose through aerobic respiration is about ______ ATP.

<p>30 or 32</p> Signup and view all the answers

What is the primary role of acetyl CoA in cellular respiration?

<p>It links glycolysis to the citric acid cycle.</p> Signup and view all the answers

Match the following processes with their corresponding products:

<p>Glycolysis = 2 Pyruvate, 2 ATP, 2 NADH Pyruvate Oxidation = 2 Acetyl CoA, 2 NADH Citric Acid Cycle = 6 NADH, 2 FADH2 and about 2 ATP Oxidative Phosphorylation = About 26 or 28 ATP</p> Signup and view all the answers

The citric acid cycle is also known as the _____ cycle.

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

Which molecule directly enters the Citric Acid Cycle after pyruvate is oxidized?

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

Match the following products of the citric acid cycle with their quantities per turn:

<p>ATP = 1 NADH = 3 FADH2 = 1 CO2 = 2</p> Signup and view all the answers

The oxidation of glucose is completed in the mitochondrion of eukaryotic cells.

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

Which of the following molecules carries electrons to the electron transport chain?

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

What are the two electron carriers mentioned that transport electrons to the electron transport chain?

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

The citric acid cycle consists of nine steps, each facilitated by a specialized enzyme.

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

How many turns does the citric acid cycle make per glucose molecule?

<p>2 turns</p> Signup and view all the answers

What is the net ATP yield from glycolysis?

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

Obligate anaerobes can perform aerobic respiration.

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

What is the main final electron acceptor in fermentation?

<p>An organic molecule (such as pyruvate or acetaldehyde)</p> Signup and view all the answers

Cellular respiration produces ______ ATP per glucose molecule.

<p>32</p> Signup and view all the answers

Match the type of fermentation with its product:

<p>Lactic Acid Fermentation = Used in cheese and yogurt production Alcoholic Fermentation = Used by yeast</p> Signup and view all the answers

Which of the following statements is true about facultative anaerobes?

<p>They can survive in both aerobic and anaerobic conditions. (A)</p> Signup and view all the answers

Glycolysis is a process that evolved after the advent of significant atmospheric oxygen.

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

What are the two alternative catabolic routes that pyruvate can take in a facultative anaerobe?

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

What is the primary input that initiates the citric acid cycle?

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

NADH is produced during the conversion of isocitrate to alpha-ketoglutarate.

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

What are the two electron carriers mainly involved in ATP synthesis after glycolysis?

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

The compound _____ is regenerated at the end of the citric acid cycle.

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

Match the enzymes with their respective reactions in the citric acid cycle:

<p>Citrate synthase = Condensation of Acetyl CoA and Oxaloacetate Isocitrate dehydrogenase = Conversion of isocitrate to alpha-ketoglutarate Alpha-ketoglutarate dehydrogenase = Conversion of alpha-ketoglutarate to succinyl CoA Succinate dehydrogenase = Conversion of succinate to fumarate</p> Signup and view all the answers

Which molecules donate electrons to the electron transport chain after the citric acid cycle?

<p>NADH and FADH2 (B)</p> Signup and view all the answers

ATP is generated during the conversion of Succinate to Fumarate.

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

Where does oxidative phosphorylation primarily occur?

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

The process of chemiosmosis couples electron transport to _____ synthesis.

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

Match the following compounds with their roles in the citric acid cycle:

<p>NAD+ = Electron carrier FAD = Produces FADH2 GTP = Energy currency similar to ATP CoA = Acoenzyme for acyl groups</p> Signup and view all the answers

What is one of the main outputs of the citric acid cycle?

<p>CO2 (A)</p> Signup and view all the answers

Isocitrate is the first molecule formed in the citric acid cycle.

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

Identify one key difference between NADH and FADH2 in terms of energy production.

<p>NADH produces more ATP than FADH2.</p> Signup and view all the answers

During the citric acid cycle, _____ acid is formed from the hydration of fumarate.

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

What is produced when succinyl CoA is converted to succinate?

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

Flashcards

Energy Acquisition

The process by which living organisms obtain energy from external sources.

Photosynthesis

The process by which sunlight is converted into chemical energy stored in organic molecules.

Cellular Respiration

The process by which cells use organic molecules to generate ATP, the energy currency of the cell.

Fermentation

A partial breakdown of sugars that occurs in the absence of oxygen.

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Aerobic Respiration

The complete breakdown of sugars using oxygen, producing a large amount of ATP.

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Anaerobic Respiration

Similar to aerobic respiration, but uses compounds other than oxygen.

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Energy Flow in Ecosystems

Energy flows into an ecosystem through sunlight and leaves as heat.

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ATP (Adenosine Triphosphate)

The main energy currency of cells, used to power various cellular processes.

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Redox reaction

A chemical reaction where electrons are transferred between molecules. It involves oxidation (loss of electrons) and reduction (gain of electrons).

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Oxidized substance

The substance that loses electrons in a redox reaction. It undergoes oxidation.

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Reduced substance

The substance that gains electrons in a redox reaction. It undergoes reduction.

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NAD+

The molecule that acts as an electron acceptor during cellular respiration. It captures energy released during the breakdown of glucose.

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NADH

The reduced form of NAD+, which carries energy. It passes electrons to the electron transport chain.

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Electron transport chain

A series of protein complexes embedded in the mitochondrial membrane. It uses the energy carried by electrons to generate ATP.

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Oxygen (O2)

The final electron acceptor in aerobic respiration. It is reduced to form water.

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Glycolysis

The breakdown of glucose into two molecules of pyruvate, occurring in the cytoplasm of cells.

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Citric Acid Cycle

This stage requires oxygen and completes the energy-yielding oxidation of glucose.

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Chemiosmosis

The process of synthesizing ATP using the potential energy stored in a proton gradient across a membrane.

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2 ATP

The net gain of ATP produced from one molecule of glucose during glycolysis.

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What is the transition reaction?

The process of converting pyruvate to acetyl CoA, which links glycolysis to the citric acid cycle. This occurs in the mitochondria and is catalyzed by a multienzyme complex.

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What is acetyl CoA?

A molecule with a central sulfur atom holding an acetyl group, crucial for entering the citric acid cycle.

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What is the Citric Acid Cycle?

A series of enzymatic reactions that oxidizes pyruvate to CO2, generating ATP, NADH, and FADH2, key energy carriers. It occurs in the mitochondrial matrix.

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What are the key products of the citric acid cycle?

The citric acid cycle generates 2 ATP, 6 NADH, and 2 FADH2 per 2 turns.

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How many steps are in the citric acid cycle?

The cycle consists of 8 steps, each catalyzed by a specific enzyme, ensuring precise control and efficiency.

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What is the role of NADH and FADH2 in the citric acid cycle?

NADH and FADH2, generated by the citric acid cycle, transfer high-energy electrons to the electron transport chain, driving ATP production.

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What is the role of the electron transport chain?

The electron transport chain uses the energy from electron transfer to pump protons across the mitochondrial membrane, creating a proton gradient that drives ATP production.

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What is oxidative phosphorylation?

ATP synthesis is the process of generating ATP from ADP using the proton gradient created by the electron transport chain.

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Anaerobic Metabolism

A metabolic process that does not require oxygen. It can be either fermentation or anaerobic respiration, depending on the final electron acceptor.

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Aerobic Metabolism

A metabolic process that requires oxygen. It is also called aerobic respiration.

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Facultative Anaerobes

Organisms that can switch between fermentation and cellular respiration depending on the availability of oxygen. Examples include yeast and many bacteria.

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Obligate Anaerobes

Organisms that cannot survive in the presence of oxygen and rely only on fermentation or anaerobic respiration for energy production.

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What is the first step in the citric acid cycle?

The CAC begins with the condensation of acetyl-CoA with oxaloacetate, forming citrate. This is the first step in the cycle.

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What is the isomerization step in the citric acid cycle?

The initial step of the citric acid cycle is the condensation of acetyl-CoA with oxaloacetate to form citrate. Citrate is then isomerized to isocitrate.

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What is the oxidation and decarboxylation step in the citric acid cycle?

Isocitrate is oxidized and decarboxylated to -ketoglutarate, producing NADH and CO2.

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What happens to -ketoglutarate in the citric acid cycle?

-ketoglutarate is oxidized and decarboxylated to succinyl-CoA, producing NADH and CO2.

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How is succinyl-CoA converted to succinate?

Succinyl-CoA is converted to succinate, producing GTP.

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What happens to succinate in the citric acid cycle?

Succinate is oxidized to fumarate, producing FADH2.

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What happens to fumarate in the citric acid cycle?

Fumarate is hydrated to malate.

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What happens to malate in the citric acid cycle?

Malate is oxidized to oxaloacetate, regenerating the starting material for the cycle and producing NADH.

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What is the main energy product of the citric acid cycle?

The citric acid cycle generates energy in the form of ATP.

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What is the main reducing power product of the citric acid cycle?

The citric acid cycle also generates reducing power in the form of NADH and FADH2. These electron carriers will be used in oxidative phosphorylation to generate even more ATP.

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What is the importance of the citric acid cycle in cellular respiration?

The citric acid cycle is a key part of cellular respiration, providing the majority of the energy needed for the cell to function.

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Where does the citric acid cycle take place?

The citric acid cycle occurs in the mitochondria of eukaryotic cells.

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How is the citric acid cycle regulated?

The citric acid cycle is a cyclic pathway that is highly regulated by the cell, ensuring it functions only when needed.

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Why is the citric acid cycle important for life?

The citric acid cycle is essential for life. It provides the energy needed to sustain all of our cells and tissues.

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What is the significance of the citric acid cycle?

The citric acid cycle is a complex and fascinating process that is essential for understanding how living organisms obtain energy from food.

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Study Notes

Cellular Respiration and Fermentation Overview

  • Living cells require energy from external sources.
  • Organisms obtain energy by consuming plants or other organisms that consume plants.
  • Energy flows into ecosystems as sunlight and leaves as heat.
  • Photosynthesis produces oxygen and organic molecules, which are used in cellular respiration.
  • Cells utilize chemical energy stored in organic molecules to regenerate ATP, the energy currency of cells, to power cellular work.

Catabolic Pathways and ATP Production

  • Fermentation is a partial sugar breakdown occurring without oxygen.
  • Aerobic respiration utilizes organic molecules and oxygen to produce ATP.
  • Anaerobic respiration is similar to aerobic respiration, but utilizes compounds other than oxygen.
  • Cellular respiration incorporates both aerobic and anaerobic respiration, but typically refers to aerobic respiration.
  • Glucose is often used to track cellular respiration— a molecule of C6H12O6 + 6 O2 yields 6 CO2 + 6 H2O + Energy (ATP + heat).

The Principle of Redox

  • Redox reactions involve electron transfer between reactants.
  • Oxidation occurs when a substance loses electrons.
  • Reduction occurs when a substance gains electrons; this reduces the amount of positive charge. -OIL RIG: Oxidation Is Loss, Reduction Is Gain helps to remember.

Oxidation of Organic Fuel Molecules During Cellular Respiration

  • During cellular respiration, the fuel (e.g., glucose) gets oxidized, and O2 is reduced.
  • The formula for glucose oxidation by cellular respiration is C6H12O6 + 602 → 6 CO2 + 6 H2O + Energy.

Stepwise Energy Harvest via NAD+ and the Electron Transport Chain

  • Glucose and organic molecules are broken down step-by-step in cellular respiration.
  • Electrons from organic compounds are initially transferred to NAD+ (a coenzyme).
  • NAD+ acts as an oxidizing agent in cellular respiration
  • NADH (reduced form of NAD+) contains stored chemical energy that helps synthesize ATP.
  • NADH transports electrons to the electron transport chain.
  • The electron transport chain releases energy from electrons step-by-step, unlike an uncontrolled reaction, to regenerate ATP.
  • O2 pulls electrons down the electron transport chain in an energy-yielding manner.

The Stages of Cellular Respiration: A Preview

  • Glucose breakdown involves three stages:
    • Glycolysis
    • The Citric Acid Cycle
    • Oxidative phosphorylation

Glycolysis

  • Glycolysis breaks down glucose into two pyruvate molecules.
  • Glycolysis occurs whether or not oxygen is present.
  • Glycolysis occurs in the cytosol and yields a net gain of 2 ATP per glucose molecule.
  • Also produces 2 NADH and 2 Pyruvates.

Transition Reaction Linking Glycolysis to the Citric Acid Cycle

  • Before entering the citric acid cycle, pyruvate gets oxidized to acetyl CoA.
  • This conversion of pyruvate to acetyl CoA links glycolysis to the citric acid cycle.
  • Acetyl CoA has an important role in linking glycolysis and citric acid cycle.

The Citric Acid Cycle

  • The citric acid cycle (Krebs cycle) completes the breakdown of pyruvate.
  • The cycle further oxidizes organic fuel derived from pyruvate, generating ATP, NADH, and FADH2.
  • The cycle has eight steps catalyzed by specific enzymes.
  • The cycle also releases carbon dioxide.
  • The amount of ATP per turn of the cycle is 1, for two turns it becomes 2 ATP
  • There are also two NADH, and two FADH2 per turn, in total it will amount to 6 NADH and 2 FADH2, per glucose.

Oxidative Phosphorylation

  • This stage accounts for most of the ATP production in cellular respiration.
  • It involves electron transport and chemiosmosis.
  • Electron carriers, like NADH and FADH2, contribute electrons to the electron transport chain.
  • The electron transport chain pumps protons across the inner mitochondrial membrane, creating a proton gradient.
  • Chemiosmosis uses this gradient to generate ATP through ATP synthase.
  • The exact amount of ATP produced (typically 30-32 per glucose) varies depending on cellular conditions.

Fermentation

  • Fermentation enables cells to produce ATP without oxygen.
  • It is an anaerobic process that involves glycolysis coupled with reactions regenerating NAD+.
  • Two common types of fermentation are lactic acid fermentation and alcohol fermentation.

Lactic Acid Fermentation

  • Pyruvate is reduced to lactic acid in lactic acid fermentation.
  • This process regenerates NAD+ for glycolysis to continue.
  • Lactic acid fermentation is used by some bacteria and fungi to make cheese and yogurt.
  • It is also used by human muscle cells when oxygen is scarce during intense exercise which causes lactic acid buildup in muscles.

Alcoholic Fermentation

  • Pyruvate is converted into ethanol in two steps, releasing CO2, during alcoholic fermentation.
  • Alcoholic fermentation regenerates NAD+ for glycolysis to continue.
  • Yeast utilizes alcoholic fermentation in brewing, winemaking, and baking due to the production of ethanol and CO2.

Comparing Fermentation and Aerobic Respiration

  • Glycolysis is the initial step in both fermentation and aerobic respiration.
  • NAD+ is the electron acceptor in both cases.
  • Alcoholic and lactic acid fermentations use a different final electron acceptor unlike aerobic respiration, which uses oxygen.
  • Aerobic respiration produces significantly more ATP compared to fermentation.

Other Metabolic Pathways Involved in Glycolysis and the Citric Acid Cycle

  • Glycolysis and the citric acid cycle also incorporate molecules from other macromolecules like proteins, carbohydrates, and fats.

Regulation of Cellular Respiration

  • Feedback mechanisms control cellular respiration's rate.
  • Enzyme concentrations control the flow of metabolic intermediates through cellular respiration.

Calculating ATP

  • The actual number of ATP molecules produced during cellular respiration can range from 30-32 rather than 36.

Cellular Respiration in Prokaryotes vs. Eukaryotes

  • The location of cellular respiration differs between prokaryotes and eukaryotes, which affects ATP yield. In prokaryotes it all happens in the cytosol, whereas it is separated in the mitochondria in eukaryotes making variations in the amount of ATP produced possible.

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Test your knowledge on cellular respiration processes with this quiz. Understand the mechanisms behind ATP regeneration, the role of oxygen, and the involved organic molecules. Perfect for students studying biology or life sciences.

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