X. PHOTOSYNTHESIS ____________________________________________ – Process of capturing light energy and converting it to chemical energy –Equation: __________________________________ ________________Plants are ________________ – “self-feeders”; also known as producers. –Ultimate source of all organic compounds comes from autotrophs –_______________________ –_______________________ – use sunlight as energy source –Chemoautotrophs –Chemoautotrophs – do not use sunlight as energy source, use other compounds such as ammonia and sulfur

Location of Photosynthesis - Any green part of the plant has chloroplasts (site of photosynthesis) - Leaves contain the most chloroplasts - Green color comes from ___________________ _________________ - Chloroplasts are found mainly in the region of the leaf known as _________________ ________________ - CO 2 enters leaf through openings known as ________________ - H 2 O enters via roots and is transported via veins

Chloroplast Structure o ________________ o ________________ – site of Light Reaction – 1 st step in photosynthesis o __________ o __________ – stacks of thylakoids o _____________ o _____________ – site of Calvin Cycle – 2 nd step in photosynthesis

X. PHOTOSYNTHESIS OVERVIEW, cont

LIGHT REACTION XI. LIGHT REACTION OF PHOTOSYNTHESIS _______________membranesOccurs in _______________ membranes Converts light energy to chemical energy Light energy o Visible light is a small portion of the electromagnetic spectrum. ____________ _____ o Light ____________ by chlorophyll and other photosynthetic pigments to power reactions is _____ seen. Light not utilized by plant is reflected & seen by human eye. o Absorption spectrum o Absorption spectrum – graph illustrating how different pigments absorb different wavelengths of light o Action spectrum o Action spectrum – graph illustrating rate of photosynthesis vs. wavelength _______________ o Light energy measured in _______________.

3 Photosynthetic pigments ***1) Chlorophyll a ***1) Chlorophyll a – absorbs mainly blue-violet and red light 2) Chlorophyll b 2) Chlorophyll b – absorbs mainly blue and orange light 3) Cartenoids 3) Cartenoids – other accessory pigments; expand spectrum of light energy that can be used for photosynthesis LIGHT REACTION XI. LIGHT REACTION OF PHOTOSYNTHESIS

A photon of light energy is absorbed by pigment molecule in Photosystem II. Energy is passes from one molecule to another until it reaches P680 pair of chlorophyll a molecules. Electron is excited to higher energy state – transferred to primary electron acceptor. Water is split to replace electron lost by P680. O 2 is released and H + ions remain. LIGHT REACTION XI. LIGHT REACTION OF PHOTOSYNTHESIS

Excited electron moves from primary electron acceptor to Photosystem I via electron transport chain. As electron “falls”, energy is released. Used to synthesize ATP through chemiosmosis. Light energy is transferred via light-harvesting complexes to P700 in Photosystem I. Excited electron is captured by primary electron acceptor. P700’s electron is replaced by electron transport chain on Photosystem II. Electron from P700 moves through a short electron transport chain, reducing NADP + to NADPH. LIGHT REACTION XI. LIGHT REACTION OF PHOTOSYNTHESIS Noncyclic Phosphorylation

LIGHT REACTION XI. LIGHT REACTION OF PHOTOSYNTHESIS

Cyclic Electron Flow Cyclic Electron Flow Alternative pathway seen in some bacteria, plants May be photoprotective in plants Only utilizes Photosystem I No NADPH production No O 2 release Does generate ATP So…..what’s the point??? –To generate excess ATP without generating NADPH –Calvin Cycle uses more ATP than it does NADPH LIGHT REACTION XI. LIGHT REACTION OF PHOTOSYNTHESIS

CALVIN CYCLE XII. CALVIN CYCLE OF PHOTOSYNTHESIS ______________________Also known as ______________________, Light- Independent Rxn _______________Occurs in _______________ of chloroplasts “Synthesis”“Synthesis” part of photosynthesis ____________________ ___________ –Utilizes __________, __________ generated in Light Reaction, and ___________ to produce organic molecules Anabolic; endergonic _______________Requires enzyme _______________ Three basic steps  Carbon Fixation  Reduction  Regeneration of RuBP

XII. CALVIN CYCLE OF PHOTOSYNTHESISInput 3 CO 2, 9 ATP, 6 NADPH 3 CO 2, 9 ATP, 6 NADPH Output 1 G3P, 6 NADP+, 6 Pi, 9 ADP 1 G3P, 6 NADP+, 6 Pi, 9 ADP

XIII. PLANT ADAPTATIONS ______________Major problems facing terrestrial plants is ______________. At times, solutions to this problem conflict with other metabolic processes, especially photosynthesis. _____________ evaporative loss of waterThe _____________ are not only the major route for gas exchange (CO 2 in and O 2 out), but also for the evaporative loss of water. __________ the stomataOn hot, dry days plants __________ the stomata to conserve water, but this causes problems for photosynthesis.

XIII. PLANT ADAPTATIONS C 4 CAM