Factors Affecting Enzyme-Controlled Reactions in Photosynthesis and Respiration

Photosynthesis

• The primary function of photosynthesis is to produce glucose and oxygen from carbon dioxide and water.
• The site of photosynthesis in a plant cell is the chloroplast.

Factors Affecting Photosynthesis

• CO2 concentration is not the factor that does NOT determine the rate of photosynthesis.

Chloroplast Structure

• Grana in chloroplasts are responsible for increasing the surface area for light-dependent reactions.

Light-Dependent Stage

• During the light-dependent stage, ATP and NADPH are produced.
• Photophosphorylation plays a crucial role in generating ATP from light energy.

Light-Independent Stage

• If CO2 concentration is in short supply, the light-independent reaction will slow down.
• Low temperature affects Rubisco and other molecules, making them less efficient.

Cellular Compartmentation

• Glycolysis occurs in the cytoplasm.
• The end product of glycolysis is pyruvate.
• The Krebs cycle takes place in the mitochondrial matrix.
• The Krebs cycle produces 2 ATP, 6 NADH, and 2 FADH2 per glucose molecule.

Calvin Cycle

• The final stage of photosynthesis uses ATP and reduced NADP to produce glucose.
• The enzyme RuBisCo catalyzes the reaction of combining RuBP with carbon dioxide in the Calvin cycle.
• The main function of reduced NADP and ATP in the light-independent reaction is to produce glucose.

Limiting Factors

• A limiting factor in photosynthesis is light intensity.

Light-Independent Reaction

• If light intensity is low, the levels of GP, TP, and RuBP will decrease.
• Glucose is not produced during the light-independent reaction.

Oxidative Phosphorylation

• Oxidative phosphorylation occurs in the mitochondrial intermembrane space.
• The main source of ATP production in aerobic respiration is oxidative phosphorylation.
• During oxidative phosphorylation, the concentration of hydrogen ions in the intermembrane space increases.
• ATP synthase generates ATP from the energy released by the proton gradient.
• Hydrogen ions are moved across the inner mitochondrial membrane during oxidative phosphorylation through proton pumps.
• Reduced coenzymes (NADH and FADH) play a crucial role in generating ATP during oxidative phosphorylation.
• Oxygen acts as the final electron acceptor in the process of producing water.

Energy Yield

• The theoretical yield of 38 ATP molecules per glucose is rarely achieved in real life due to energy losses during oxidative phosphorylation.

Glycolysis

• Pyruvate produced during glycolysis in the cytoplasm needs to be transported into the mitochondrial matrix by active transport.

Respiratory Substrates

• The amount of energy released from respiratory substrates is determined by their energetic potential.
• The Respiratory Quotient (RQ) can be used to determine which respiratory substrate is being used.

Anaerobic Respiration

• Anaerobic respiration occurs in the absence of oxygen.