Cellular Respiration: Aerobic & Anaerobic Processes
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Questions and Answers

During the Q cycle, what is the immediate destination of the first electron released from QH₂ when it binds to Complex III?

  • Ubiquinone (Q) at the Qi site
  • Iron-sulfur (Fe-S) center (correct)
  • Cytochrome c
  • Cytochrome b

In the Q cycle, the reduction of ubiquinone (Q) to semiquinone (Q⁻) occurs where?

  • At the Q₀ site of Complex III (correct)
  • At the Qi site of Complex III
  • In the intermembrane space
  • In the mitochondrial matrix

What is the role of the semiquinone (Q⁻) formed during the first half of the Q cycle?

  • It is further reduced to QH₂ in the second half of the cycle. (correct)
  • It transfers electrons to the Fe-S center.
  • It directly reduces cytochrome c.
  • It is immediately oxidized to regenerate Q.

How many protons (H⁺) are effectively translocated into the intermembrane space as a result of one full Q cycle?

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

Which of the following is a primary function of the Q cycle in the electron transport chain?

<p>To recycle ubiquinone/ubiquinol and contribute to the proton gradient (C)</p> Signup and view all the answers

In aerobic respiration, what molecule serves as the final electron acceptor?

<p>Oxygen ($O_2$) (D)</p> Signup and view all the answers

What are the net products of glycolysis from one molecule of glucose?

<p>2 ATP, 2 NADH, 2 Pyruvate (C)</p> Signup and view all the answers

During the conversion of pyruvate to acetyl-CoA, what products are generated per molecule of pyruvate?

<p>1 NADH and 1 CO2 (A)</p> Signup and view all the answers

What is the rate-limiting enzyme of the TCA cycle?

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

In the electron transport chain (ETC), approximately how many ATP molecules can be generated from one NADH molecule?

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

During beta-oxidation of fatty acids, what molecule facilitates the transport of acyl groups into the mitochondrial matrix?

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

Which of the following is NOT a direct product of each cycle of beta-oxidation?

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

What is the fully reduced form of Coenzyme Q?

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

Which complex in the electron transport chain does NOT directly contribute to proton pumping across the inner mitochondrial membrane?

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

In Complex I of the electron transport chain, what is the initial electron acceptor from NADH?

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

Why does actual chloroplast function require more than the theoretical minimum of 1.14 V for electron transfer in oxygenic photosynthesis?

<p>The actual cellular environment deviates from standard conditions. (D)</p> Signup and view all the answers

What is the role of pheophytin in the photosystem II reaction center?

<p>It acts as an intermediate electron carrier. (A)</p> Signup and view all the answers

How does the Mn/Ca cluster facilitate oxygen evolution in Photosystem II?

<p>By accumulating positive charges and oxidizing water. (A)</p> Signup and view all the answers

Which component of the photosynthetic electron transport chain is analogous to cytochrome c reductase in mitochondria?

<p>Cytochrome b6f (B)</p> Signup and view all the answers

What is the primary function of Rubisco in the Calvin cycle?

<p>Catalyzing the carboxylation of ribulose 1,5-bisphosphate. (C)</p> Signup and view all the answers

How many photons are theoretically required to facilitate the transfer of four electrons from water to NADP+?

<p>4 (A)</p> Signup and view all the answers

Which of the following represents the correct sequence of electron transfer between Photosystem II and NADPH?

<p>PSII → cytochrome b6f → plastocyanin → ferredoxin → NADPH (C)</p> Signup and view all the answers

A researcher is studying a mutant plant cell that can perform the light-dependent reactions of photosynthesis but cannot fix carbon dioxide into sugars. Which of the following is the most likely cause of this?

<p>A mutation that inactivates Rubisco. (A)</p> Signup and view all the answers

During the electron transport chain, the transfer of two electrons from NADH to molecular oxygen is coupled with the outward pumping of protons. Which of the following is the correct distribution of protons pumped by Complexes I, III, and IV, respectively?

<p>4 H+, 4 H+, 2 H+ (B)</p> Signup and view all the answers

Which of the following statements accurately describes a step in the path of electron transfer through Complex IV of the electron transport chain?

<p>Electrons are passed through two heme groups near a copper ion in Subunit 1. (B)</p> Signup and view all the answers

Superoxide dismutase (SOD) plays a crucial role in managing reactive oxygen species. What is the primary function of SOD?

<p>Converting superoxide radicals (O2-) into hydrogen peroxide (H2O2). (C)</p> Signup and view all the answers

If the bacterial F0 component of ATP synthase has 10 'c' subunits, how many degrees of rotation does one H+ cause, and how many H+ are needed for one full rotation?

<p>36 degrees, 10 H+ (C)</p> Signup and view all the answers

In the thylakoid experiment, vesicles at pH 4 were rapidly mixed with a solution at pH 8. What key observation confirmed ATP synthesis?

<p>H+ movement accompanied the ATP synthesis (D)</p> Signup and view all the answers

What is the role of the phytol tail in the structure of chlorophyll?

<p>To anchor the chlorophyll molecule within the photosynthetic membrane. (D)</p> Signup and view all the answers

The F1 component of ATP synthase has a specific structure. Which statement accurately describes its composition?

<p>It includes (3α+3β) resting on a γ subunit, along with δ and ε subunits. (D)</p> Signup and view all the answers

What energetic challenge was introduced by the evolution of using H₂O as an electron donor in oxygenic photosynthesis?

<p>Water requires more energy to oxidize compared to previous electron donors. (A)</p> Signup and view all the answers

Flashcards

Q Cycle

A series of electron transfer steps in the electron transport chain involving ubiquinol (QH₂) and ubiquinone (Q).

Complex III

A protein complex in the electron transport chain where the Q cycle occurs, facilitating electron transfer from QH₂ to cytochrome c and ubiquinone.

Oxidation of Ubiquinol (QH₂)

The process where QH₂ donates electrons, leading to the release of protons and reduction of ubiquinone to semiquinone.

Semiquinone (Q ⁻)

A partially oxidized form of ubiquinone resulting from the first electron donation in the Q cycle.

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Proton Motive Force

The energy generated by the pumping of protons into the intermembrane space during the Q cycle, used for ATP synthesis.

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Aerobic Respiration

A type of respiration that uses oxygen as the final electron acceptor.

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Anaerobic Respiration

A type of respiration that uses sulfates or nitrates as the final electron acceptor.

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Glycolysis

The process taking place in the cytoplasm that breaks down glucose into 2 pyruvate, yielding 2 ATP.

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TCA Cycle

A cycle that produces NADH, FADH2, and GTP from acetyl CoA, with 2 CO2 as waste.

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Beta Oxidation

The process of fatty acids breaking down into acetyl CoA, occurring in the mitochondria.

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NADH Yield

Each NADH molecule can produce approximately 2.5 ATP during cellular respiration.

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FADH2 Yield

Each FADH2 molecule yields about 1.5 ATP in the electron transport chain.

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Coenzyme Q (Ubiquinone)

A key electron carrier in the electron transport chain that exists in three forms: oxidized, semi-reduced, and fully reduced.

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Isocitrate Dehydrogenase

The rate-limiting enzyme in the TCA Cycle that converts isocitrate to alpha-ketoglutarate.

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Redox Potential

The measure of the tendency of a chemical species to acquire electrons and be reduced.

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Photosystem II

A protein complex in plants that captures photons and uses the energy for water oxidation and electron transfer.

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P680

The reaction center chlorophyll in photosystem II that absorbs light primarily at 680 nm.

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Mn/Ca Cluster

A group of metal ions associated with photosystem II, critical for water oxidation and oxygen production.

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Cytochrome b6f

A protein complex that transfers electrons from quinones to plastocyanin in the photosynthetic electron transport chain.

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Plastocyanin (pC)

A copper-containing protein that transfers electrons from cytochrome b6f to photosystem I.

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Rubisco

An enzyme that catalyzes the first step of the Calvin cycle, fixing CO2 into organic molecules.

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G3P

Glyceraldehyde-3-phosphate, a product of the Calvin cycle that can be used to form glucose and other carbohydrates.

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Complex IV structure

Complex IV has 13 subunits, vital for electron transfer.

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Heme and copper in Complex IV

Subunit 1 contains two hemes and a copper ion for electron transfer.

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Proton pumping in Complex IV

Transfer of two electrons from NADH to O2 pumps out 10 H+ ions.

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Toxic reactive oxygen species

H2O2 and hydroxyl radicals are generated and can be converted by metal ions.

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ATP synthesis gradient

ATP synthase relies on pH gradient for ATP generation.

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ATP synthase structure

F0 and F1 subunits, produce ATP with H+ movement, 4 H+ per ATP.

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Photosynthesis stages

Photosynthesis involves light absorption, electron transport, ATP generation, and carbon fixation.

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Chlorophyll structure

Chlorophyll consists of a porphyrin ring with Mg2+ and a phytol tail.

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Study Notes

Aerobic vs. Anaerobic Respiration

  • Aerobic respiration uses oxygen as the final electron acceptor
  • Anaerobic respiration uses sulfate or nitrate as the final electron acceptor
  • Complete aerobic oxidation of one glucose molecule yields 30-32 ATP
  • Overall reaction: 1 glucose + 6 O2 + 30 Pi + 30 ADP + 30 H+ → 6 CO2 + 30-32 ATP + 36 H2O

Glycolysis

  • Takes place in the cytoplasm
  • Yields 2 NADH, 2 pyruvate, and 4 ATP (net gain of 2 ATP)

Pyruvate to Acetyl CoA

  • Occurs in the mitochondrial matrix
  • Pyruvate dehydrogenase converts pyruvate to Acetyl CoA
  • Yields 1 NADH and 1 CO2

TCA Cycle

  • Rate-limiting step is isocitrate dehydrogenase
  • Produces 3 NADH, 1 FADH2, 1 GTP, and 2 CO2
  • 1 NADH yields 2.5 ATP
  • 1 FADH2 yields 1.5 ATP

Beta Oxidation of Fatty Acids

  • Acyl groups are transported via carnitine transporter
  • Acyl-CoA is broken down into acetyl-CoA
  • Important steps include cytosolic acyltransferase, carnitine transporter, and mitochondrial carnitine acyltransferase
  • Acyl-CoA undergoes oxidation, hydration, oxidation, and thiolysis
  • Final product is 1 Acyl CoA with n-2

Other Details

  • Odd-number fatty acids yield 1 mol propionyl-CoA per mole of fatty acid
  • Coenzyme Q, Ubiquinone, Dihydroquinone/Ubiquinol
  • Electron transport chain (ETC) components: Complex I, II, III, IV
  • Complex I: NADH dehydrogenase
  • Complex II: Succinate dehydrogenase
  • Complex III: Cytochrome c reductase
  • Complex IV: Cytochrome c oxidase
  • Q cycle occurs between Complex II and III
  • QH2 binds to Qo of cyt b
  • Oxidized QH2 (Q) binds to Qi site of cyt b
  • One e- of QH2 moves to Fe-S center while the second e- moves to cyt b
  • Complex I, III, and IV pump protons (H+) into the intermembrane space

Photosynthesis

  • Products of photosynthesis are starch, and sucrose.
  • Photosynthesis involves four stages: Light absorption, electron transport, ATP generation, and Carbon fixation.
  • Chlorophyll is the primary pigment for photosynthesis.
  • Oxygenic photosynthesis requires modifications to the photosynthetic machinery, utilizing H₂O as an electron donor.
  • Redox potential differences (O₂/H₂O = +0.82 V, NADP⁺/NADPH = -0.32 V) lead to a total difference of 1.14 V.
  • Light energy (e.g., photons) is converted into chemical energy.
  • Photosystem 2 (PSII) and photosystem 1 (PSI) are crucial components of the photosynthetic electron transport chain
  • The Mn/Ca cluster is essential for the oxygen-evolving complex.
  • The Calvin cycle (stage IV) involves CO₂ fixation, using Ribulose-1,5-bisphosphate carboxylase/oxygenase (RUBISCO).
  • The Calvin cycle generates 3-phosphoglycerate and ultimately produces glucose, fructose, and sucrose.

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BIOL 408 Ch. 12 PDF

Description

Overview of aerobic and anaerobic respiration, glycolysis, pyruvate conversion, and the TCA cycle. Key steps and yields of ATP, NADH, and other molecules are discussed. Also, beta oxidation of fatty acids is explained.

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