Overview
This lecture explains the key stages of glycolysis, highlighting its main steps, products, and important biochemical processes involved in cellular respiration.
Energy Transfer in Respiration
- Energy from glucose can be transferred to other molecules via substrate level phosphorylation or oxidative phosphorylation.
- Substrate level phosphorylation is when energy released from a reaction is used to form ATP directly from ADP and Pi.
- Dehydrogenation/oxidation involves removal of hydrogen and electrons, transferring them to NAD to form reduced NAD.
Introduction to Glycolysis
- Glycolysis is the first stage of respiration.
- It occurs in the cytoplasm and does not require oxygen.
- Glycolysis consists of 10 reactions, but a simplified version is typically studied.
Stages of Glycolysis
- First, glucose (6C) reacts with 2 ATP, each contributing a phosphate group in phosphorylation, forming hexose bisphosphate.
- Hexose bisphosphate splits (lysis) into 2 triose phosphate (3C) molecules.
- Each triose phosphate receives an inorganic phosphate from the cytoplasm, forming triose bisphosphate.
- Each triose bisphosphate is converted to pyruvate (3C); hydrogen is removed (oxidation), forming reduced NAD.
- Phosphate groups are transferred to ADP to form ATP (substrate level phosphorylation).
Products of Glycolysis
- Net gain of 2 ATP (4 produced, 2 used).
- Formation of 2 reduced NAD molecules.
- Production of 2 pyruvate molecules.
Key Terms & Definitions
- Glycolysis — The metabolic pathway that breaks down glucose into pyruvate in the cytoplasm.
- Phosphorylation — Addition of a phosphate group to a molecule.
- Substrate Level Phosphorylation — ATP formation by direct transfer of a phosphate group during a reaction.
- Dehydrogenation/Oxidation — Removal of hydrogen and electrons from a molecule.
- Reduced NAD (NADH) — NAD after it accepts hydrogen and electrons during oxidation.
Action Items / Next Steps
- Review the detailed stages of glycolysis and memorize the sequence of events.
- Prepare for the next video/lesson on the link reaction.