Biology Chapter 4: Life Energy

Chapter 4: Life Energy

•  Life energy encompasses bioenergetics, photosynthesis, and causes of extinction, including natural and anthropogenic factors.

Bioenergetics

•  Bioenergetics is the study of energy flow, transformation, and utilization in living cells.
•  It is a field of biochemistry.
•  The goal is to describe how organisms acquire, transform, and utilize energy to perform biological work.
•  Eukaryotic organisms primarily use chloroplasts and mitochondria for energy.
•  Chloroplasts capture sunlight's energy, while mitochondria extract energy from food.
•  ATP is the energy currency of the cell (energy carrier).

Photosynthesis

•  Autotrophs are producers that use light energy, water, and carbon dioxide to make their own food.
•  Heterotrophs rely on other organisms for their energy source.
•  Photosynthesis is a process whereby light energy is captured and used to produce organic molecules (sugar/glucose) and inorganic molecules (oxygen).
•  The process is summarized by the equation: CO2 + H2O + light energy → C6H12O6 + O2.
•  Chloroplasts are the organelles found in plant cells (and some algae) responsible for photosynthesis.

Stages of Photosynthesis

• Photosynthesis occurs in two stages:
  • Light-dependent reactions: Capture light energy, use water, and produce ATP and NADPH. These reactions happen in the thylakoid membrane.  - Light-independent reactions (Calvin Cycle): Use ATP and NADPH to convert carbon dioxide into glucose. These reactions Occur in the stroma.

Causes of Extinction

• Extinction is the complete disappearance of a species.
• The causes of extinction can be:
  • Natural factors (e.g., natural disasters, climate change)
  • Anthropogenic factors (human-caused factors, e.g., habitat loss, pollution, overexploitation, species intrusion)

Cellular Respiration

• A metabolic process that breaks down biochemical energy to produce ATP, the cell's energy currency.
• The inputs, or materials required are glucose and oxygen.
• The outputs are ATP, carbon dioxide, and water.
• Occurs in three stages:
  • Glycolysis: Breakdown of glucose into pyruvic acid.
  • Kreb's/Citric Acid Cycle: Further breakdown of pyruvic acid, producing ATP, NADH, FADH2, and CO2.
  • Electron Transport Chain and Chemiosmosis: Electrons from NADH and FADH2 are transferred to produce a large amount of ATP.

Comparison of Photosynthesis and Cellular Respiration

Chemical Equations

• Photosynthesis: CO2 + H2O + Light Energy → C6H12O6 + O2
• Cellular Respiration: C6H12O6 + O2 → CO2 + H2O + ATP