Cellular Respiration Quiz

Aerobic and Anaerobic Respiration

• Aerobic respiration uses oxygen as the final electron acceptor in the electron transport chain. This process converts nutrient energy into ATP.
• Anaerobic respiration uses a molecule other than oxygen (e.g., sulfate or nitrate) as the final electron acceptor.

Glycolysis

• The complete aerobic oxidation of glucose yields 30-32 ATP molecules.
• Glucose oxidation in eukaryotes occurs in four stages: glycolysis, citric acid cycle, electron transport chain, and ATP synthesis.
• Glycolysis is the first stage of glucose metabolism.
• The overall reaction of glycolysis converts glucose, 2NAD+, 2ADP, and 2P¡ into 2 pyruvate, 2NADH, 2ATP, and 2H+.
• Substrate-level phosphorylation is used to create ATP.

Mitochondrial Structure

• Mitochondria have an outer membrane and an inner membrane with cristae.
• The matrix is the innermost compartment of the mitochondria.
• Cristae junctions are folds in the inner mitochondrial membrane.
• Ribosomes are present in the matrix of mitochondria.

Production of Acetyl CoA from Pyruvate

• Glucose, transported to the mitochondrial matrix, is converted to acetyl-CoA .
• The overall reaction produces one molecule of NADH and releases one molecule of CO₂.
• The enzyme involved is pyruvate dehydrogenase.

TCA Cycle

• This cycle is a series of enzyme-catalyzed reactions that produce NADH + H+, FADH₂, and one GTP from each acetyl-CoA molecule.
• This cycle converts pyruvate to CO₂ and releases energy in a usable form.

Net Results of Glycolysis and the Citric Acid Cycle

• Summarizes the production of ATP, CO2, NADH, and FADH2 produced during these processes.
• Lists net results (e.g., 2 ATP, 6 NADH, total ATP= 30-32).

Malate-Aspartate Shuttle

• This shuttle transports reducing equivalents from the cytosol into the mitochondrial matrix, facilitating ATP generation.

Glycerol-3-phosphate Shuttle

• Electrons from cytosolic NADH are transferred to dihydroxyacetone phosphate, producing glycerol-3-phosphate.
• These electrons are subsequently passed on to coenzyme Q, contributing to ATP production.

Activation of Free Fatty Acid

• Free fatty acids are activated to fatty acyl-CoA before oxidation in the mitochondria.
• This process involves the joining of a fatty acid with CoA via ATP, producing fatty acyl-CoA.

B-Oxidation of Fatty Acids

• Free fatty acids are oxidized to Acetyl-CoA.
• The free fatty acid is degraded into Acetyl-CoA molecules sequentially via four steps (dehydrogenation, hydration, dehydrogenase, thiolysis).

Electron Transport Chain

• This series of proteins in the inner mitochondrial membrane carries electrons to oxygen.
• The protein components and their prosthetic groups (e.g. FMN, Fe-S, heme) are described.
• The role of coenzyme Q, including its ability to carry electrons and protons, is detailed.

Q Cycle

• This cycle is a mechanism in the Electron Transport Chain for transferring electrons between protein complexes. Details of electron flow through cyt b protein complexes are explained.
• Explaining its role in the transfer of electrons and protons.

Structure of Cytochrome Oxidase (Complex IV)

• This complex in the electron transport chain catalyzes the reduction of oxygen to water, using electrons from cytochrome c.
• It describes the structure including subunits (I, II, III, IV), heme a and a3, and copper ions, CuA and CuB.

Transfer of Electrons

• The transfer of two electrons from NADH to oxygen in the electron transport chain is accompanied by the pumping of protons across the inner mitochondrial membrane. This proton gradient ultimately drives ATP synthesis.

Changes in Redox Potential and Energy

• Details on how electrons flow through the electron transport chain with associated changes in redox potential.
• The energy released during the electron transport chain is used for ATP synthesis.
• Redox potential is described as a measure of the tendency to gain electrons, important in the sequential transfer within each complex and the overall chain.

Generation and Inactivation of Toxic Reactive Oxygen Species (ROS)

• ROS are reactive species derived from oxygen.
• The different forms of ROS (e.g., superoxide, H₂O₂, hydroxyl radical) and the enzymes (e.g., superoxide dismutase, catalase) that reduce ROS formation are described.
• Potential damage caused by ROS and how they are inactivated is shown.

Chemiosmotic Hypothesis

• Proposes that the proton gradient generated across the inner mitochondrial membrane (or thylakoid membrane) during electron transport drives ATP synthesis.
• This gradient provides the energy to power ATP synthesis by ATP synthase.

ATP Synthesis

• Describes the mechanism of ATP synthesis by ATP synthase dependent on pH gradient. Explains components: F₀ and F₁.

Rotational Catalysis Model

• The rotation of the y subunit of ATP synthase is driven by the flow of protons across the membrane, triggering conformational changes in the αβ subunits and driving ATP synthesis.

Direct Evidence for Rotation of the γ Subunit

• Describes the experiments indicating the rotation of γ subunit within the ATP synthesis complex confirming Boyer's theory.
• Details of the experimental design and data collected.

Products of Photosynthesis

• The principal products of photosynthesis are starch and sucrose.

Light Harvesting Complexes and Photosystems

• The components of light harvesting complexes (LHC) are highlighted.
• Chlorophyll is described.
• The roles of photosystems I & II (PSI & PSII), including the special pair of chlorophylls P700 & P680 are clarified.
• Details of photoelectron transport are included.

Cyclic Electron Flow

• Describes the two pathways involved in cyclic electron flow (NADH dehydrogenase-like complex-dependent pathway and PGR5-PGRL1-dependent pathway).
• Highlights that cyclic electron flow generates ATP without producing NADPH or releasing O2. This process is crucial under special environmental conditions, such as low CO2 levels or high light intensity.

Photoelectron Transport

• Photoelectrons are transported from photosystem II (PSII) to photosystem I (PSI).
• An overview of the flow of electrons, highlighting components like water, plastoquinone, cytochrome b6f complex, and plastocyanin.
• Details of the roles of photosystems I and II in the process are shown.

Three-Dimensional Structure of Photosynthetic Reaction Center

• The overall structure of the reaction center is described.
• Different components are labeled and explained, including the subunits, special pair of bacteriochlorophyll a, accessory chlorophylls, pheophytins, and quinones.
• The involvement of bacteriochlorophyll molecules and their role in light absorption are included.

Cyclic/Linear Electron Flow

• Non-cyclic flow- the linear electron flow from water to NADPH is described.
• Cyclic electron flow - and how it is used to produce ATP is clarified.

Redox Control of the Calvin Cycle

• How thioredoxin helps regulate the Calvin Cycle enzymes, maintaining their activity in a reduced state.

CO2 Fixation and Photorespiration

• How CO2 is fixed, and the process of photorespiration.
• The role of rubisco in CO2 fixation and conditions for occurrence of photorespiration are further clarified.

Leaf Anatomy, C3 and C4 Plants

• Describes the leaf anatomy in C3 and C4 plants, highlighting differences in CO2 uptake pathways.
• Locations of carbon fixation and the Calvin cycle are detailed. C4 metabolic pathway is included, explaining the role of mesophyll and bundle sheath cells in C4 plants.

Overview of Various Stages of Photosynthesis

• Summary of photosynthetic pathways: light-dependent (initial steps of photosynthesis) and light-independent (dark reactions - Calvin Cycle) aspects are more elaborately detailed.

Pi-Triose Phosphate Antiport System

• Describes the mechanism of Pi and triose phosphate transport across the thylakoid membrane for CO2 fixation, including the details on the Pi-triose phosphate antiport.