Grade 12 Biology Unit 3: Energy Transformation

This unit 3 explores the fundamental processes of energy transformation within living cells, the very core of what it means to be alive. You’ll investigate how organisms capture, store, and use energy by diving deep into the two most important metabolic pathways on Earth: photosynthesis and cellular respiration.

Chapter 3.1 – Cellular Metabolism

This chapter introduces the concept of all the chemical reactions occurring within a cell.

• Define metabolism as the sum of all life-sustaining chemical reactions in an organism.
• Distinguish between the two main types of metabolic pathways:
  • Anabolism: Building complex molecules from simpler ones, which requires energy.
  • Catabolism: Breaking down complex molecules into simpler ones, which releases energy.

Chapter 3.2 – Photosynthesis

Discover how plants, algae, and some bacteria convert light energy into chemical energy.

• Summarize the overall process of photosynthesis, where carbon dioxide and water are used in the presence of light to produce glucose and oxygen.
• Identify the key photosynthetic pigments, like chlorophyll a and chlorophyll b, that absorb light energy.
• Analyze the two major stages of photosynthesis:
  • Light-Dependent Reactions: Where light energy is captured to produce ATP and NADPH.
  • Light-Independent Reactions (Calvin Cycle): Where the captured energy is used to convert CO₂ into sugar (glucose).

Chapter 3.3 – Contributions of Photosynthesis

Understand the critical role photosynthesis plays in sustaining life on Earth.

• Justify how photosynthesis is essential for the continuity of life by forming the base of most food chains.
• Explain its role in maintaining the O₂ and CO₂ balance in the atmosphere.
• Discuss how photosynthesis helps mitigate global warming by consuming atmospheric carbon dioxide.

Chapter 3.4 – Cellular Respiration

Learn how cells break down glucose to release stored chemical energy in the form of ATP.

• Identify the mitochondrion as the primary site of cellular respiration in eukaryotes.
• Outline the main stages of aerobic respiration (which requires oxygen), including glycolysis, the Krebs cycle, and the electron transport chain.
• Differentiate between substrate-level phosphorylation and oxidative phosphorylation as methods of ATP production.
• Discuss the process of fermentation (anaerobic respiration) and its significance in daily life (e.g., in making bread and yogurt).

Learning Outcomes

By the end of this unit 3, you’ll be able to:

• Summarize the process of photosynthesis using a chemical equation.
• Analyze the absorption spectra of chlorophyll pigments.
• Discuss how energy is harvested during aerobic respiration.
• Differentiate between substrate-level phosphorylation and oxidative phosphorylation.
• Explain the electron transport system in mitochondria.
• Calculate the amount of energy yielded from a given molecule of glucose.