Welcome to Lesson 8 of the Human Biology Masterclass.
In Lesson 7, we explored the major biological molecules. Now we follow the three macronutrients through the body — from digestion and absorption to energy production, storage, and metabolic regulation.
This lesson is where biochemistry meets nutrition science.
You'll learn:
• How carbohydrates, fats, and proteins are digested and absorbed
• Which digestive enzymes break down each macronutrient
• How glucose enters the bloodstream and is used, stored, or converted
• How glycolysis, aerobic respiration, and lactate production contribute to energy metabolism
• How glycogen is stored and mobilized in the liver and muscles
• How triglycerides are broken down through lipolysis and fatty acids are used for energy
• How beta-oxidation converts fatty acids into acetyl-CoA and ultimately ATP
• How ketone bodies are produced during prolonged fasting or carbohydrate restriction
• How dietary protein contributes to protein synthesis and tissue maintenance
• What nitrogen balance means and how protein metabolism changes during growth, recovery, and energy deficiency
• How insulin and glucagon regulate the fed and fasted states
• How the body switches between storing and mobilizing energy
• What nutrition science tells us about calories, protein, fibre, dietary patterns, and metabolic health
The body does not simply “burn food.” Macronutrients are continuously digested, transported, transformed, stored, and used according to the body's current energy demands and hormonal state.
Understanding these pathways provides an essential foundation for studying metabolism, nutrition, body composition, exercise, and metabolic health.
Next lesson: Lesson 9 – Enzymes: The Catalysts of Life
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