General Concept: Glycolysis converts glucose into pyruvate, generating ATP and NADH.
Energy Dynamics in Glycolysis
Energy Investment Phase: Consumes two ATP to phosphorylate glucose, transforming it for easier breakdown.
Energy Payoff Phase: Releases energy, producing two NADH and four ATP (net gain of two ATP) from oxidized three-carbon sugars.
Thermodynamic Classifications
Endergonic: Energy is absorbed (investment phase).
Exergonic: Energy is released (payoff phase and overall glycolysis).
Steps of Glycolysis
Ten reactions in two phases.
Energy Investment Phase (first five reactions): Glucose is phosphorylated twice (using ATP) to form fructose-1,6-bisphosphate, which splits into two three-carbon sugars.
Energy Payoff Phase (next five reactions): Three-carbon sugars undergo oxidation, producing NADH and a net gain of two ATP. This phase yields two pyruvate molecules.
Phosphorylation Types
Substrate-Level Phosphorylation: Direct transfer of a phosphate group from a substrate to ADP, forming ATP, catalyzed by enzymes.
Definition of NADH
NADH is formed when NAD++ is reduced by capturing electrons and protons during glycolysis; it acts as an electron carrier.
Further Processing of Pyruvate
Aerobic versus Anaerobic Metabolism: Pyruvate enters aerobic respiration (in mitochondria) with oxygen, or anaerobic respiration/fermentation without oxygen.
Mitochondrial Structure and Functions
Mitochondria Features: Has an outer membrane and a highly folded inner membrane (cristae).
Mitochondrial compartments:
Intermembrane Space: Between inner and outer membranes.
Mitochondrial Matrix: Innermost space with metabolic enzymes.
Pyruvate Processing
Two pyruvate molecules are decarboxylated, each producing one CO2 and converting into a two-carbon acetyl CoA. NAD++ is reduced to NADH.
Role of Acetyl CoA: Links glycolysis to the Krebs cycle by providing two-carbon units; does not directly generate ATP.
Role of Coenzymes
Coenzyme A: Aids in transferring acetyl groups from pyruvate to the Krebs cycle.