Photosynthesis vs. Cellular Respiration: Energy Production

Fundamental Biological Energy Processes

Photosynthesis and Cellular Respiration: Key Equations

• Photosynthesis: Converts light energy into chemical energy (glucose).

  6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

• Cellular Respiration: Breaks down glucose to release energy (ATP).

  C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Purpose and Scope of Energy Conversion

Photosynthesis allows plants and algae to make their food by converting light energy from the sun into chemical energy stored in glucose.

Cellular Respiration is the process used to generate usable energy, primarily in the form of Adenosine Triphosphate (ATP). ATP is the energy currency of the cell, essential for carrying out all cellular functions.

Organisms Performing These Processes

• Photosynthesis is carried out primarily by plants and algae.
• Respiration is performed by virtually every living species, ranging from single-celled organisms to complex multicellular organisms.

Location of Energy Processes: Organelles

Where does photosynthesis take place? Cellular respiration? Think organelles!

• Photosynthesis occurs in the chloroplasts.
• Cellular respiration primarily occurs in the mitochondria (though glycolysis occurs in the cytoplasm).

Understanding ATP and ADP

What is ATP? Adenosine Triphosphate (ATP) is the source of energy for use and storage at the cellular level.

The ATP/ADP Relationship

ATP has three phosphate groups, and ADP (Adenosine Diphosphate) has two. With the presence of an additional high-energy phosphate bond, ATP contains more energy.

ADP is an energy intermediate used to synthesize ATP, often catalyzed by the enzyme ATP synthase.

When Do Cells Store Energy?

Cells store energy when a phosphate group is added to ADP, forming ATP (ADP + P → ATP).

Aerobic vs. Anaerobic Respiration

What is the difference between aerobic and anaerobic? Think oxygen and energy.

• Aerobic Respiration: Uses oxygen. This process is associated with longer, sustained exercises and yields a high amount of energy (ATP).
• Anaerobic Respiration: Does not use oxygen. This process is associated with short bursts of high-effort activity and yields less energy.

Glycolysis: The Initial Step

Describe What Happens During Glycolysis

Glycolysis is a series of reactions that extract energy from glucose by splitting the six-carbon molecule into two three-carbon molecules called pyruvates.

Inputs and Products of Glycolysis

• Used (Input): Glucose.
• Produced (Output): ATP (net gain) and NADH (an electron carrier).

Anaerobic Fermentation

What are the two types of fermentation in anaerobic respiration? What types of organisms undergo fermentation?

Types of Fermentation and Organisms

Fermentation helps generate energy when oxygen is limited:

1. Alcoholic Fermentation: Occurs in organisms like yeast.
2. Lactic Acid Fermentation: Occurs in muscle cells and certain bacteria.

Products of Fermentation

What are the products of alcoholic fermentation? Lactic acid fermentation?

• The final products of alcoholic fermentation are ethanol and carbon dioxide (CO₂).
• The final product of lactic acid fermentation is lactic acid (lactate).

Ideal Conditions for Yeast Respiration/Fermentation

Note ideal conditions for yeast’s rate of cellular respiration/fermentation:

• Needs glucose (or another fermentable sugar).