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

1. Preparatory Phase (Energy-Investment Phase)
2. 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.