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Muscle Cell Respiration and Lactic Acid

• Lactic acid production in muscle cells indicates fermentation due to an inability to use the electron transport chain.

Genetically Modified Plants

• Modifying plants to increase pigment production enhances light energy capture and boosts photosynthesis.
• Absorbing a larger range of light wavelengths will subsequently increase the overall rate of photosynthesis.

Chlorophyll's Role

• Chlorophyll absorbs sunlight energy and gives it to electrons for the electron transport chain.

Plant Adaptations for Low-Water Environments

• C4 or CAM pathways reduce water loss by minimizing stomatal opening.

Factors Affecting Enzyme Reaction Rates

• Decreasing the activation energy of the reaction can NOT increase the reaction rate.

Enzymes and Equilibrium

• Adding an enzyme to a solution at equilibrium will not change the equilibrium state.

Cellulase Enzyme Activity and pH

• Low pH can denature cellulase enzymes, altering their active site structure and reducing activity.

CO2 Release During Catabolism

• Most CO2 from catabolism is released during the citric acid cycle.

Light Reaction Products

• The light reaction of photosynthesis generates high-energy electrons that end up in NADPH through linear electron flow.
• The light reactions also produce ATP and Oxygen.

Partial ETC Function in Low Oxygen

• Cells maintain partial electron transport chain (ETC) function under low oxygen conditions to regenerate NAD+, reducing reliance on lactic acid fermentation.

Dinitrophenol (DNP) and Cellular Respiration

• DNP causes protons to freely pass through the inner mitochondrial membrane, bypassing ATP synthase.
• This results in oxygen consumption remaining the same, but ATP production decreases due to the loss of the proton gradient.

Rubisco and Photorespiration

• Rubisco's oxygenase activity wastes ATP and NADPH, reducing overall photosynthetic efficiency.
• This occurs when oxygen levels are high.

Proton Accumulation in Organelles

• In mitochondria protons accumulate in the intermembrane space, while in chloroplasts, protons accumulate in the thylakoid lumen.

Light-Independent Reaction Failure

• A defect in RuBisCO prevents the fixation of carbon dioxide into organic molecules.
• This would explain why light-independent reactions fail, despite normal light-dependent reactions.

ATP Yield from NADH and FADH2

• FADH2 contributes less ATP per molecule than NADH, because FADH2 donates electrons later in the ETC than NADH.
• This leads to fewer protons being pumped across the inner mitochondrial membrane.

C4 Plants and Photorespiration

• C4 plants minimize photorespiration by spatially separating carbon fixation from the Calvin cycle.
• They use PEP carboxylase to concentrate CO2 in bundle sheath cells.

C4 Plant CO2 Concentration

• C4 plants minimize photorespiration by increasing the CO2 concentration around RuBisCo.
• They incorporate CO2 into a four-carbon compound in the mesophyll cell.

Isolated Pigment Electrons

• When a pigment's electrons become isolated, they fall back into their ground state.
• This gives off heat or light

Linear vs. Cyclic Electron Flow

• Linear electron flow uses two photosystems, producing ATP, NADPH, and O2.
• Cyclic electron flow uses one photosystem, producing ATP.

Photosynthesis as a Redox Process

• Photosynthesis involves the transfer of electrons where H2O is oxidized to produce O2
• CO2 is reduced to form sugar molecules.

Increased Matrix pH

• When the pH of the matrix increases electrons flow along the electron transport chains of the mitochondria.

Mitochondrial Membrane and ATP Synthesis

• The inner mitochondrial membrane generates and maintains the H+ gradient that drives ATP synthesis by using the EC chain.
• Electrons pass a series of protein complexes embedded in the membrane, actively pumping protons from the matrix to the intermembrane space.

Inactive Allosteric Site

• When an allosteric active site becomes inactive, the original substrates cannot react.
• The allosteric inhibitors stabilize the enzyme.

Preventing Spontaneous Breakdown

• Activation energy barriers prevent molecules from spontaneously breaking down into less ordered, more stable molecules.

Impact of Low Oxygen and High Glucose

• In a medium lacking oxygen but supplemented with high glucose, ATP production would rely on glycolysis only.
• Leading to a buildup of NADH and no proton gradient formation.

ATP Generation During Fermentation

• During fermentation in the absence of oxygen, substrate-level phosphorylation in glycolysis generates ATP.
• This converts ADP to ATP.

Rubsico's Persistence

• Rubisco evolved when atmospheric oxygen levels were low.
• Selective pressure has not been strong enough to favor a complete replacement

Water's Role in Photosynthesis

• Water donates electrons to replace those lost by chlorophyll in Photosystem II.

Oxidizing Agent

• Pyruvate acts as the oxidizing agent in the reaction Pyruvate + NADH + H+ →Lactate + NAD+

ATP Synthase Inhibition

• Inhibiting ATP synthase will cause the proton gradient across the inner mitochondrial membrane to dissipate.
• Reducing the efficiency of oxidative phosphorylation.