The Process of Photosynthesis Things to Learn 1

The Process of Photosynthesis Things to Learn: 1) What happens during Light-Dependent Reactions 2) What happens during Light-independent Reactions 3) The Factors that affect Photosynthesis

Membrane • Chloroplast full of membranes • Essential for photosynthesis • Thylakoid Membrane keep + - charges generated by light absorption on opposite sides of the membrane (KEY FACTOR for light-dependent reactions)

Light-Dependent Reactions • Use energy from Sun to convert ADP & NAPD+ into energy and electron carriers ATP and NADPH • Oxygen is a bi-product

Light-Dependent Reactions • Photosystems: clusters of Thylakoids & proteins essential for lightdependent reactions • Light absorbed by chlorophyll molecules in the photosystems is the beginning of the process

Photosystem II • Light dependent reactions begin here • Discovered after photosystem I • Absorb light • Excite molecules • Water molecules torn apart 2 Hydrogen & 1 Oxygen • Oxygen released to air

Electron Transport Chain • Electrons move along the transport chain • Energy used by proteins to pump more stroma

Photosystem I • Energy has been lost since photo II • Pigments in photo I use light to reenergize • Pass electrons to electron carrier (NADP+) • Stroma pick up these electron & combine w/ H+ ions to become NADPH

Hydrogen Ion movement & ATP Formation • During Photo II: Hydrogen ions split H 2 O • Some Hydrogen ions remain to provide energy for ATP • ATP synthesis: protein that spans the membrane & allows H+ ions to pass through it (combine ADP & phosphate = ATP)

Light-Independent Reactions (CALVINS CYCLE) • Use energy from ATP & NADPH (from light-dep. Reac. ) to synthesize stable high-energy sugars (pg. 295) • Carbon Dioxide enters cycle • During cycle 2 of 12 3 -Carbon molecules are removed & contribute to plant metabolism • Remaining 10 3 -Carbon return for next Calvin Cycle This Photo by Unknown Author is licensed under CC BY-SA-NC

Factors Affecting Photosynthesis • Temperature: best 0 – 35 degrees Celsius • Light intensity: higher intensity = increases rate of photosynthesis • Water: shortage of water can stop photosynthesis

Photosynthesis under extreme conditions • In times of water shortage, plants close small openings in leaves • Reduces water loss, reduces Carbon Dioxide intake • Plants that adapt • C 4: capture low level of CO 2 • CAM: capture CO 2 at night

Key Topics 1) Analyze the information & graph on page 296(Analyze Data), answer questions 1 to 3 2) How do the compounds of ATP & NADPH result from the Sun’s energy during photosynthesis? 3) At what point does “food” for the plant result from photosynthesis? 4) Compare & contrast Light-dependent & Light-independent reactions 5) Explain the series of events that the Electron Transport Chain goes through as it proceeds from Photosystem II to Photosystem I 6) What are the main products of the Carbon Cycle? 7) Where do Light-independent reactions occur?