PHOTOSYNTHESIS

Photosynthesis: Life from Light and Air

CAPTURING THE ENERGY IN LIGHT The process by which organisms obtain energy directly from sunlight is called photosynthesis. CO 2 + H 2 O → C 6 H 12 O 6 + O 2

ENERGY FOR LIFE PROCESSES Autotrophs: most Plants, Algae, and some Bacteria. Autotrophs: most Plants, Algae, and some Bacteria. Autotrophs store energy in various organic compounds, primarily carbohydrates.

Photosynthesis involves a complex series of chemical reactions: Biochemical Pathway Products used in cellular respiration in both plants and animals. Products used in cellular respiration in both plants and animals. The Basic By McGraw Hill

or Oxidation is loss of hydrogen. Reduction is gain of hydrogen. OIL RIG Oxidation is Loss Reduction is Gain (of e-) Redox Reactions:

How are they connected? glucose + oxygen  carbon + water + energy dioxide C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  water + energy  glucose + oxygen carbon dioxide 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  +++ oxidation = exergonic reduction = endergonic Heterotroph and…. Autotroph

N P K … H2OH2O What does it mean to be a plant Need to… collect light energy transform it into chemical energy store light energy in a stable form to be moved around the plant or stored need to get building block atoms from the environment C,H,O,N,P,K,S,Mg produce all organic molecules needed for growth carbohydrates, proteins, lipids, nucleic acids ATP glucose CO 2

LIGHT ABSORPTION IN CHLOROPLASTS Light Reactions or Light Dependent Reactions They begin with the absorption of light in chloroplasts. Review of the Light Reaction With All Details!

CHLOROPLASTS

LIGHT AND PIGMENTS

chlorophylls accessory pigments carotenoids

Photosynthesis gets energy by absorbing wavelengths of light. Accessory pigments with different structures absorb light of different wavelengths: chlorophyll a & b, carotenoids, xanthophylls, antenna pigments

What is Photosynthesis? Light reactions light-dependent reactions convert solar energy to chemical energy ATP & NADPH Calvin cycle light-independent reactions sugar building reactions uses chemical energy (ATP & NADPH) to reduce CO 2 & synthesize C 6 H 12 O 6 It ’ s not the Dark Reactions!

Virtual Cell Photo.

LIGHT REACTIONS 1. ELECTRON TRANSPORT CHAIN: PHOTOSYSTEMS II AND I. 1. chlorophyll a P 680 = absorbs 680nm wavelength red light chlorophyll b P 700 = absorbs 700nm wavelength red light 2. REPLENISHING PHOTOSYSTEM II 3. CHEMIOSMOSIS Photosystem I Go to: D-Drive Youtube Streaming Video Photosystem I file b Virtual Cell:Photosynthesis

ELECTRON TRANSPORT CHAIN The Basic Biochemical Pathway

RESTORING PHOTOSYSTEM II

CHEMIOSMOSIS

What is Photophosphorylation? NONcyclic photophosphorylation cyclic photophosphorylation ATP NADP

Why Cyclic Phosphorolation? Calvin cycle uses more ATP than NADPH 18 ATP + 12 NADPH 1 C 6 H 12 O 6

PUTTING IT ALL TOGETHER Review of the Light Reaction With All Details! Overview Of the Light Reaction

Photosynthesis Animation mat/metabolism/photosynthesis.swf mat/metabolism/photosynthesis.swf mat/metabolism/photosynthesis.swf mat/metabolism/photosynthesis.swf

6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  +++ Experimental evidence Where did the O 2 come from? Where did the O 2 come from? radioactive tracer = O 18 radioactive tracer = O 18 6CO 2 6H 2 O C 6 H 12 O 6 6O26O2 light energy  +++ Experiment 1 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  +++ Experiment 2 Proved O 2 came from H 2 O not CO 2 = plants split H 2 O!

Photosynthesis summary Where did the energy come from? Where did the electrons come from? Where did the H 2 O come from? Where did the O 2 come from? Where did the O 2 go? Where did the H + come from? Where did the ATP come from? What will the ATP be used for? Where did the NADPH come from? What will the NADPH be used for?

So where does CO 2 fit in? How do plants use it? Why do they need it?

LIGHT INDEPENDENT REACTIONS KNOWN AS THE CALVIN CYCLE = C3 Photosynthesis. KNOWN AS THE CALVIN CYCLE = C3 Photosynthesis. CO 2 IS FIXED INTO ORGANIC COMPOUNDS: CARBON FIXATION. CO 2 IS FIXED INTO ORGANIC COMPOUNDS: CARBON FIXATION. THREE MAJOR STEPS, WHICH OCCUR WITHIN THE STROMA. Reduction Reaction= C gains H+ Calvin Cycle How do Plants Capture CO2? Welcome to the Dark Side, Lord Calvin

P.S. The Dark Cycle Does Not Happen in the Dark It is dependent on the products of the light reaction (ATP and NADPH) So when the lights go out…it has no energy to continue. NOVA Capturing C

Think… Why can’t we blow carbon emissions into forests and solve global warming? Why can’t we blow carbon emissions into forests and solve global warming?

ALTERNATIVE PATHWAYS TO FIX CARBON These alternative pathways are generally found in plants that evolved in hot, dry climates. Stomata: passageways FOR CO2 and O2.

C-4: Photosynthesis Intense Sunlight and Hot (e.g. corn and crabgrass) Intense Sunlight and Hot (e.g. corn and crabgrass) Stomata are Partly Closed During Day= CO2 falls and O2 rises Stomata are Partly Closed During Day= CO2 falls and O2 rises We don’t want photorespiration. We don’t want photorespiration. In the Mesophyll PEP carboxylase grabs CO2 not O2. In the Mesophyll PEP carboxylase grabs CO2 not O2. Sends CO2 to the Calvin cycle Sends CO2 to the Calvin cycle

The C4 Pathway FIXES CO 2 INTO A FOUR CARBON COMPOUND OXALOACETATE. HENSE THE NAME: C4 Oxaloacetate in the mesophyll turns into Malate, an acid. Malate is shipped through plasmodesmata into bundle sheath cells and release CO2 Calvin Cycle Starts

The CAM Plants Adaptation to Conditions Adaptation to Dry Conditions Stomata Closed during Day Open at Night Stomata Closed during Day Open at Night Mesophyll stores CO2 at night Mesophyll stores CO2 at night Makes Sugar during Day Makes Sugar during Day All 3 (C3, C-4, and CAM) use the Calvin Cycle All 3 (C3, C-4, and CAM) use the Calvin Cycle Crassulacean Acid Metabolism

The CAM Pathway Plants that use the CAM pathway open their stomata at night and close them during the day—just the opposite of what other plants do.

RATE OF PHOTOSYNTHESIS Review