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

– ChemoautotrophsChemoautotrophs – 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 __________________________________- CO2 enters leaf through openings known as

________________________________- H2O enters via roots and is transported via veins

Chloroplast Structureo ________________________________ – site

of Light Reaction – 1st step in photosynthesis

o __________ __________ – stacks of thylakoids

o __________________________ – site of Calvin Cycle – 2nd step in photosynthesis

X. PHOTOSYNTHESIS OVERVIEW, cont

XI. LIGHT REACTIONLIGHT REACTION OF PHOTOSYNTHESIS• Occurs in ______________________________ membranesmembranes

• 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 spectrumAbsorption spectrum – graph illustrating how different pigments absorb different wavelengths of light

o Action spectrumAction spectrum – graph illustrating rate of

photosynthesis vs. wavelengtho Light energy measured in ______________________________.

3 Photosynthetic pigments ***1) Chlorophyll a***1) Chlorophyll a – absorbs mainly blue-violet and red light

2) Chlorophyll b2) Chlorophyll b – absorbs mainly blue and orange light3) Cartenoids3) Cartenoids – other accessory pigments; expand spectrum of

light energy that can be used for photosynthesis

XI. LIGHT REACTIONLIGHT 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. O2 is released and H+ ions remain.

XI. LIGHT REACTIONLIGHT 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.

XI. LIGHT REACTIONLIGHT REACTION OF PHOTOSYNTHESIS

Noncyclic PhosphorylationNoncyclic Phosphorylation

XI. LIGHT REACTIONLIGHT REACTION OF PHOTOSYNTHESIS

Cyclic Electron FlowCyclic Electron Flow• Alternative pathway seen in

some bacteria, plants

• May be photoprotective in plants

• Only utilizes Photosystem I

• No NADPH production

• No O2 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

XI. LIGHT REACTIONLIGHT REACTION OF PHOTOSYNTHESIS

XII. CALVIN CYCLECALVIN 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 FixationReductionRegeneration of RuBP

XII. CALVIN CYCLE OF PHOTOSYNTHESISInputInput

3 CO3 CO22 , 9 ATP, 6 NADPH , 9 ATP, 6 NADPH

OutputOutput

1 G3P, 6 NADP+, 6 Pi, 9 ADP1 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.

• The __________________________ are not only the major route for gas exchange (CO2 in and O2 out), but also for the evaporative evaporative loss of waterloss of water.

• On hot, dry days plants __________ the stomata__________ the stomata to conserve water, but this causes problems for photosynthesis.

XIII. PLANT ADAPTATIONSC 4 CAM