Lesson 6: Understanding the First Two Stages of Cellular Respiration
Stage 1: Glycolysis
💡 What is Glycolysis?
Glycolysis is a word made from two parts:
- Glyco = glucose (a type of sugar)
- Lysis = breaking or splitting
So glycolysis means breaking down glucose.
This process takes one molecule of glucose (which has 6 carbon atoms) and breaks it into two smaller molecules called pyruvic acid (each with 3 carbon atoms).
🔍 Where does Glycolysis happen?
Glycolysis happens in the cytosol (the liquid part of the cell’s cytoplasm) of every living cell.
🔸 It does not require oxygen, so it occurs in both:
- Anaerobic respiration (without oxygen)
- Aerobic respiration (with oxygen)
⚙️ What’s needed for Glycolysis to work?
To carry out glycolysis, the cell uses:
- Enzymes: These are proteins that help speed up chemical reactions. Each step in glycolysis is helped by a specific enzyme.
- ATP: This is the energy currency of the cell. A small amount is invested in the beginning to get more energy out later.
- NAD⁺: This is a coenzyme — like a helper molecule — that carries energy in the form of electrons.
🔄 Glycolysis Has Two Phases
- Preparatory Phase (Energy-Investment Phase)
- Oxidative Phase (Energy-Harvesting Phase)
🔹 1. Preparatory Phase: Using Energy to Break Glucose
This is like putting money into a business before you get any profit. You first invest energy (in the form of ATP) to make glucose more reactive and easier to break.