Bioenergetics and ATP Production Quiz

Bioenergetics

• Bioenergetics is the transfer and utilization of energy in biological systems
• Bioenergetics predicts if a process is possible, kinetics measures the reaction rate.
• Enzymes cannot cause a reaction by themselves.
• They speed up the rate of reaction.
• An enzyme is a catalyst, it lowers the activation energy needed for a reaction.

Free Energy (G) and Energy Changes (ΔG)

• ΔG is a measure of the energy available for useful work.
• ΔG = Final Energy – Initial Energy (-ΔG)
• If ΔG is negative, the reaction is spontaneous (exergonic) and release energy
• If ΔG is positive, the reaction is non-spontaneous (endergonic) and requires energy
• Enzymes do not change the ΔG of a reaction, but they can lower the activation energy needed for a reaction

ATP Production

• ATP is Adenosine triphosphate, the main energy currency of cells
• ATP can be produced by two main ways:
  • Substrate-level phosphorylation
  • Oxidative phosphorylation
• Substrate-level phosphorylation: transferring a phosphate group to ADP from a high-energy molecule in the reaction.
• Oxidative phosphorylation: electrons are transferred through the electron transport chain, which makes a proton electrochemical gradient for ATP synthesis.

ATP Production (Oxidative Phosphorylation)

• NADH , FADH2 are electron carriers in cellular respiration. These molecules donate electrons to the electron transport chain to generate a proton gradient, which drives the synthesis of ATP.

Carbohydrate Metabolism

• The central role of carbohydrates in body metabolism is to store energy.
• Glucose is the primary source of energy in the body.
• Glycogenolysis is the breakdown of glycogen to glucose.
• Glycogenesis is the synthesis of glycogen from glucose.
• Glycolysis is the breakdown of glucose into pyruvate, generating ATP and NADH.
• Gluconeognesis is the synthesis of glucose from non-carbohydrate sources.
• Pentose phosphate pathway: An alternative pathway for glucose metabolism, which produces NADPH and ribose-5-phosphate. The ribose-5-phosphate is used to synthesis nucleotides.
• The pentose phosphate pathway is important for generating NADPH, an electron carrier used in reductive biosynthesis.

TCA Cycle

• Citric acid cycle, tricarboxylic acid cycle, Krebs cycle. All are synonymous.
• The main function of the TCA cycle is to harvest high-energy electrons from carbon fuels by producing ATP, NADH, and FADH2.
• Pyruvate should be transported to mitochondria before entering the TCA cycle.
• The irreversible synthesis of Acetyl-CoA from pyruvate links glycolysis and the TCA cycle.

Oxidative Phosphorylation and ETC

• The electron transport chain (ETC) is a series of protein complexes that transfer electrons from NADH and FADH2 to oxygen. This process generates a proton gradient across the mitochondrial inner membrane.
• ATP synthesis uses the proton gradient to generate ATP.
• NADH and FADH2 donate their electrons during oxidative phosphorylation, and this process generate ATP.

Electron Transport Chain

• Electrons from NADH and FADH2 are captured by the electron transport chain.
• Oxygen is reduced to water.
• ETC complexes pump H+ to outer membrane
• The positive charge out of the membrane generates a flow of H+ into the matrix, driving ATP synthesis.

Glycolysis – NAD+ Regeneration

• The net gain from glycolysis is 2 ATP and 2 NADH.
• Oxygen is required for oxidative phosphorylation to regenerate NAD+ from NADH.
• Without oxygen, fermentation allows glycolysis to continue. Fermentation regenerates NAD+ from NADH, allowing glycolysis to continue operating and producing ATP.

Pentose Phosphate Pathway

• The pentose phosphate pathway's main products are NADPH and ribose-5-phosphate.
• The oxidative reactions of the pentose phosphate convert glucose-6-phosphate to ribulose-5-phosphate, releasing CO2 and producing 2NADPH.
• Non-oxidative reactions help synthesize nucleotides and glycolysis intermediates.

Glycogen

• Glycogen is the storage form of glucose in animals
• Glycogen is a branched polysaccharide made of glucose molecules.
• Skeletal muscles and liver are major storage sites for glycogen, and are involved in maintaining blood glucose homeostasis.
• Glucose-1-phosphate is used for glycogen synthesis
• Glucose-1-phosphate is used in glycogen degradation.

Hormonal Regulation of Glycolysis

• Insulin and glucagon regulate glycolysis.
• Insulin promotes glycogen synthesis and glycolysis
• Glucagon stimulates glycogen breakdown and gluconeogenesis.

Transfer of Cytoplasmic NADH to Mitochondria

• The malate-aspartate shuttle and glycerol-3-phosphate shuttle transport cytoplasmic NADH into the mitochondria.
• These shuttles allow cytoplasmic NADH to contribute to ATP production in the mitochondria.

Glycogen Metabolism

• Glycogen synthesis requires UDP-glucose to incorporate into the glycogen chain
• Glycogen degradation cleaves glucose units from the non-reducing ends of the glycogen branches, generating glucose-1-phosphate.
• One glucose molecule can be removed from a branching point, yielding free glucose.

Energy Gained from 1 Mole Glucose (Oxidative State)

• The total ATP yield from 1 mole of glucose during cellular respiration is 36 or 38 ATP (depending on the shuttle used to transport NADH from the cytoplasm to the mitochondria).

Test your knowledge on bioenergetics, including the principles of free energy and ATP production. This quiz covers key concepts such as enzyme function, energy changes, and the processes of phosphorylation in biological systems. Challenge yourself to see how well you understand these essential topics of cellular energy.