ATP-ADP CYCLE AND PHOTOSYNTHESIS

ATP Overview

• Adenosine Triphosphate (ATP)

  • Composed of adenine, ribose sugar, and three phosphate groups (P-P-P).

  • Major energy carrier in cells, providing energy for various cellular processes.

  • Converts to ADP (Adenosine Diphosphate) and an inorganic phosphate (P) when energy is released.

  • ATP-ADP cycle involves energy absorption and release during the conversion process.

ATP Cycle

• Energy Transfer

  • ATP → ADP + P + Energy (when energy is needed, a phosphate is added back to ADP).

  • The formation of ATP from ADP and phosphate requires energy input, approximately equal to that released when ATP is hydrolyzed.

  • The cycle of ATP and ADP is essential for cell metabolism, utilizing energy derived from food.

Photosynthesis Overview

• Definition

  • Process where plants, some bacteria, and protists convert sunlight into chemical energy, creating glucose from CO2 and H2O.

  • Involves the release of oxygen as a by-product.

Autotrophs vs. Heterotrophs

• Autotrophs

  • Organisms that produce their own organic molecules from CO2 and inorganic materials.

  • Include most plants, which are photoautotrophs that require sunlight, water, and minerals.

• Heterotrophs

  • Organisms that consume organic compounds produced by others.

  • Depend on autotrophs for their food and oxygen.

  • Includes animals and decomposers (e.g., fungi, bacteria).

Photosynthesis Process

• Chemical Equation

  • Light energy is converted into chemical energy: 6CO2 + 6H2O -> C6H12O6 + 6O2 (glucose).

• Location

  • Occurs in chloroplasts within leaves, specifically in mesophyll cells.

• Key Structures

  • Stomata: Pores that allow gas exchange (O2, CO2).

  • Chloroplast: Contains thylakoids where light-dependent reactions occur; includes granum for increased surface area.

Thylakoid and Chlorophyll

• Thylakoids

  • Membrane-bound structures in chloroplasts that contain chlorophyll.

  • Sites of the light-dependent reactions which use sunlight to produce ATP and NADPH.

• Chlorophyll

  • Green pigment in thylakoid membranes that absorbs specific light wavelengths (blue and red).

  • Reflects green light, making plants appear green.

Photosynthesis Stages

• 1. Light-Dependent Reactions

  • Occur in thylakoids.

  • Use light energy to produce ATP and NADPH while releasing O2.

• 2. Light-Independent Reactions (Calvin Cycle)

  • Occur in the stroma of chloroplasts.

  • Utilize ATP and NADPH to synthesize glucose from CO2.

Summary of Photosynthesis

• The synthesis of glucose from CO2 and water utilizes ATP and NADPH produced by light reactions, highlighting the integrated nature of energy transfer in living organisms.