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Understanding Photosynthesis: The Life-Sustaining Process of Plants

Photosynthesis is the vital process through which plants, algae, and some bacteria convert sunlight into chemical energy stored in glucose, the primary energy source for most life on Earth. This occurs in chloroplasts, where chlorophyll captures sunlight and water is split, producing oxygen as a byproduct. Photosynthesis involves two stages: light-dependent reactions that occur in the grana and convert solar energy into ATP and NADPH, and the light-independent reactions (Calvin Cycle) that utilize this energy to synthesize glucose from carbon dioxide.

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Understanding Photosynthesis: The Life-Sustaining Process of Plants

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  1. Photosynthesis

  2. Overview of Photosynthesis • All organisms need a constant supply of energy to survive. • For most life on earth, the ultimate source of energy is the sun. • Converting that energy source into something usable is accomplished by photosynthesis.

  3. Overview of Photosynthesis • Photosynthesisis the overall process by which sunlight(solar energy) converts waterand carbon dioxide into chemical energy stored in glucose(sugar/carbohydrate). Oxygenis released as a waste product. • It can be represented by the following chemical reaction: Solar energy + Enzymes 6CO2 + 6H2OC6H12O6 + 6O2 Products = results Reactants = ingredients

  4. Structure of Chloroplast • Photosynthesis takes place in the chloroplast which has 2 main parts: • Grana: pancake-like stacks of thylakoid membrane • Stroma: fluid-like substance that fills the space between the grana

  5. Structure of a Chloroplast • Chloroplast: the organelle where photosynthesis takes place. • Most of the chloroplasts are in leaf cells. • Chloroplasts have 2 main areas: • Grana • Stroma

  6. Parts of the Chloroplast • Grana: stacks of thylakoid membranes • Thylakoid membranes are each individual coin-shaped compartment • Stroma: fluid that surrounds the grana

  7. Two Stages of Photosynthesis Photosynthesis can be divided into two sets of reactions: 1. Light-dependent (“photo”) • Requires sunlight and water (H2O ) • Takes place within & across the membrane of the grana/thylakoids. • 2. Light-independent (“synthesis”)uses energy from the light-dependent reactions to make sugars. • Does not require any sunlight • Occurs in the stroma of chloroplasts. • CO2is needed.

  8. Light-Dependent Reactions • Purpose: • To capture energy from the sun and store that energy in “energy-carrying molecules” (ATP and NADPH) • Location • Occurs in the grana (thylakoid membranes) where the chlorophyll is stored (chlorophyll is the pigment that captures sunlight)

  9. Light-Dependent Reactions • Chlorophyll absorbs energy from sunlight • Water molecules are split into hydrogen and oxygen. • Energy from sun is passed down the Electron Transport Chain (across the thylakoid membrane) and is stored in the bonds of ATP and NADPH • Oxygen is released as a waste product. • ATP, NADPH, and Hydrogen (H+) leave the grana and go into the stroma for the next stage!

  10. Light-Dependent Reactions

  11. Light-Independent Reactions/Calvin Cycle • Purpose: • To use the energy from the “energy-carrying molecules” (ATP and NADPH )from the light-dependent reaction to make sugar (glucose) • Location: • Occurs in the stroma

  12. Summary of the Light-Independent Reactions/Calvin Cycle • CO2is added. • Energy from the light-dependent reactions is used(from ATP and NADPH) • A simple sugar (glucose) is formed by combining hydrogen (from the water) and carbon dioxide.

  13. Light-Independent Reactions ATP/NADPH used to power light-independent reactions CO2 added to a 5-carbon molecule to form a 6-carbon molecule 6-carbon molecule, glucose, kicked out as end-product

  14. Chemosynthesis The process of an organism making its own food using chemicals (“chemo”) instead of sunlight (“photo”) like in photosynthesis. Example: Tubeworm Bush Song: • http://www.youtube.com/watch?v=lDwUVpOEoE4 • http://www.youtube.com/watch?v=g78utcLQrJ4

  15. Think about it… • How does the structure of a chloroplast allow for photosynthesis to occur? • How does energy travel from the sun to your body for you to use it?

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