Ch.9

What is cellular respiration? What is its overall equation for cellular respiration? What is fermentation?

• Glucose is converted to ATP

• Cellular respiration: Glucose + O₂ + ADP + P_i → CO₂ + H₂O + ATP; C₆H₁₂O₆ + 6O₂ →  6CO₂ + 6H₂O

• Fermentation: Glucose + ADP + P_i →  Small organic molecules + ATP

What is the relationship of photosynthesis and cellular respiration? How are the two processes interconnected? Why and how does cellular respiration rely on photosynthesis?

• See above and below

Is cellular respiration used solely for the purpose of glucose breakdown? How else can the pathway be used by the cell? For example, can other sugars, fats, and proteins be broken down via this pathway? Can the pathway be used to generate precursors? What can these precursors be used for?

• Can breakdown components of other macromolecules

• Yes

• Macromolecule synthesis

List the four phases of cellular respiration and briefly describe what is happening at each phase. Also, indicate the cellular location for each of the phases. What important products are generating at each phase? What phase produces the most ATP?

• Glycolysis: one six-carbon glucose is split into two three-carbon pyruvate molecules; cytoplasm of eukaryotes and prokaryotes; ATP, NADH, and pyruvate

• Pyruvate processing: pyruvate is oxidized to form acetyl-CoA; matrix of mitochondria or cytoplasm or prokaryotes; NADH, CO₂, and acetyl-CoA

• Citric acid cycle: acetyl-CoA is oxidized to CO₂ (remaining bonds are broken), and electrons are moved by redox reactions that pass electrons to an electron acceptor (NAD⁺ or FAD⁺ is reduced); matrix of mitochondria or cytoplasm or prokaryotes; NADH, FADH₂, and ATP (or GTP)

• Electron transport and chemiosmosis: NADH and FADH₂ bring the electrons to electron transport chain and are therefore oxidized when they donate electrons to electron transport chain, and electrons flow down the chain, powering the production of ATP; inner membrane of mitochondria or plasma membrane of prokaryotes; O₂ in and H₂O out; ATP; produces the most ATP

Explain the following statement: Energy is harvested in the electron transport chain when electrons “flow” from high energy carriers to low energy carriers and finally to oxygen.

• Electrons from the electron carriers provide energy to drive proton pump, which fuels activity of ATP synthase

• Each electron carrier passes the electrons to the next one in line, and oxygen is the last one

What is substrate level phosphorylation? Do we see this happening in cellular respiration? When or in what phase? What is oxidative phosphorylation? Do we see this happening in cellular respiration? When or in what phase?

• Substrate-level phosphorylation: ATP is produced by enzyme-catalyzed transfer of a phosphate group from a substrate to ADP; glycolysis and citric acid cycle

• Oxidative phosphorylation: proton gradient provides energy for ATP production, and ATP synthase uses this energy to phosphorylate ADP to form ATP; electron transport chain

How is the establishment of H+ gradient tied to ATP production? What is meant by proton motive force and chemiosmosis? What is ATP synthase and how does this channel protein produce ATP from ADP+Pi?

• Proton-motive force: electrical current is used to pump protons from mitochondrial matrix to intermembrane space

• Chemiosmosis: process in which proton-motive force is used to make ATP

• ATP synthase: molecular motor

  • Protons flowing through the F₀ unit spin the rotor

  • Rotor spins F₁ unit

  • As F₁ unit spins, its subunits change shape and catalyze phosphorylation of ADP to ATP

Why is oxygen needed for the continued working of the ETC? What is anaerobic respiration and what types of organisms are capable of this?

• Highly electronegative, and there is large difference between potential energy of NADH and O₂ electrons; allows generation of large proton-motive force for ATP production

• Other electron acceptor; prokaryotes

What types of products will inhibit glycolysis and Citric acid cycle?

• ATP, NADH, and pyruvate

• NADH, FADH₂, and ATP (or GTP)

What is fermentation? Under what circumstances do humans ferment? Is it a benefit under certain conditions/cellular needs? What is the product of human fermentation? What is the product of yeast fermentation?

• Anaerobic respiration

• When oxygen is unavailable or ATP demand is too high

• Yes, when oxygen is unavailable

• Lactic acid and NAD⁺

• Ethanol and NAD⁺

How can other fuels be used in our cells (proteins and fats for example)? How are they used to generate ATP?

• Produce ATP to fuel cellular processes

• Beta-oxidation

What are other ways that cells can use metabolism (ways other than energy production)? What are precursors?

• Synthesizing macromolecules or storage molecules

• Small organic molecules required for synthesis of macromolecules