Photosynthesis

Overview of Photosynthesis What is photosynthesis? 6 CO2 + 6 H2O C6H12O6 + 6 O2 light energy Photosynthesis is the process of converting light energy into food energy (glucose and chemical energy stored in chemical bonds). Photosynthesis is carried out by plants and algae.

Structures of Photosynthesis Cross-section of a leaf: Cuticle Epidermis Palisade mesophyll Spongy mesophyll Vein Stomata Guard cell

Which layer of the leaf does the majority of photosynthesis? How much area is needed for the most efficient photosynthesis? What is the path of sunlight as it hits a leaf? How important is photosynthesis to a plant??? Turn and talk with your table

Structures of Photosynthesis Cross-section of a leaf: Cuticle Epidermis Palisade mesophyll Spongy mesophyll Vein Stomata Guard cell

What is Solar Energy and Visible Light? Visible light is made of photons that travel at various wavelengths and frequencies. The longer the wavelength, the lower the energy. The shorter the wavelength, the higher the energy. Photons (packets of energy) are formed when an electron is energized and moves to a higher energy level, which is unstable. When the electron falls back to its original energy level, then a photon is released that travels at a particular wavelength.

What is Solar Energy and Visible Light? Visible light is one form of energy in the electromagnetic spectrum. Different colors of light have different wavelengths. Which color of light contains the most energy? Least energy?

What is Solar Energy and Visible Light? Visible light is one form of energy in the electromagnetic spectrum. Different colors of light have different wavelengths. Which color of light contains the most energy? Least energy? MOST! LEAST!

How do Plants Capture Solar Energy for use in Photosynthesis? Each plant cell contains 40-50 chloroplasts. Chloroplasts contain pigments that either absorb or reflect different wavelengths of visible light. Absorbed wavelengths are used for photosynthesis. Each thylakoid membrane contains 250-400 chlorophyll pigments

Parts of a Chloroplast

Photosynthesis has two reactions: What are the two main reactions of photosynthesis? Reactants? Products? Where are they located? Light-Dependent Reactions = Energy-capturing reactions. Captures solar energy and traps it as ATP and NADPH. Occurs in thylakoid membranes. Light-Independent Reactions = Synthesis reactions. Uses the ATP and NADPH and captured CO2 to make glucose. Occurs in the Stroma.

What factors affect the rate of photosynthesis? Amount of visible light and CO2: Amount of H2O, minerals, temperature:

Discuss with your table: Why does the temperature graph have such a sudden drop-off in the rate of photosynthesis?

Light-Dependent Reactions: 1. Photosystem II absorbs light energy and transfers an excited electron to the primary electron acceptor.

Light-Dependent Reactions: 2. The Primary Electron Acceptor molecule transfers high-energy electrons to the Electron Transport System, which establishes a H+ ion gradient across the thylakoid membrane.

Light-Dependent Reactions: 3. Energy from the Electron Transport Chain establishing a H+ ion gradient is used for the production of ATP (“Photophosphorylation”)

Light-Dependent Reactions: 4. The electron from the Electron Transport System is accepted by the reaction center chlorophyll of Photosystem I. 5. The Electron Acceptor molecule of Photosystem I sends its electron to ultimately form NADPH.

Light-Dependent Reactions Reviewed Where does the light reaction take place? At the thylakoid membrane What are the inputs to the light reactions? Light energy and water What are the products of the light reaction? ATP, NADPH, and O2

Light-Independent Reactions (Calvin Cycle) Synthesis reactions that occur in the stroma CO2 + ATP + NADPH → Glucose Carbon dioxide – enters the leaf via stomata ATP and NADPH – from the Light reactions No light required, but typically occurs during the day

Three stages of the Calvin Cycle:

Three stages of the Calvin Cycle: 1. Carbon Dioxide Fixation – CO2 is bound to RuBP (a 5-carbon molecule), which makes Rubisco (START) 2. Carbon Dioxide Reduction- ATP and NADPH are used to convert the Rubisco into 2 G3Ps, which will make glucose (PROCESS) 3. Regeneration of RuBP - Remaining molecules using ATP are converted back to RuPB – (RESET)ing the cycle.

Photosynthesis Review What are the two reactions of photosynthesis?

Photosynthesis Review What are the two reactions of photosynthesis? How are the light reactions connected to the Calvin cycle?