Where do we get our energy from?

Photosynthesis: An Overview Some details: Light Reaction Dark Reaction Sunlight Water Oxygen Carbon Dioxide Glucose ATPNADH

Today’s Goal! To explain how energy is transferred from sunlight to glucose via the light and dark reactions of photosynthesis.

The Formula for Photosynthesis

Thylakoids (Light DEPENDENT) Stroma (Light INDEPENDENT) CALVIN Inner and outer membrane of chloroplast THE CHLOROPOPLAST Light dependent and light independent reaction locations

Pigments- Important for the absorption of light energy Three types: 1.Chlorphyll a- absorbs all spectrum of light except for green 2.Chlorophyll b- absorbs most spectrum of light except orange, yellow or red 3.Carotene- absorbs most spectrum of light except for orange

So why are plant leaves green? Another Question: Why are leaves a different color in the fall? See the next slide for the answer from a celebrity presenter.

1.In the Fall the strength of the sun decreases. 2.Plants will decrease their production of chlorophyll a in order to conserve more sugar for the winter months. (remember that when the body builds something it requires energy) 3.The remaining pigments will reflect different spectrum of light depending on the species. Thanks David! Hey! Its David Ortiz…maybe he can explain why the leaves change color in the fall.

Light Reactions-Does this picture look familiar?

Electron Carriers What do they do? Electron carriers take high energy electrons (stored on H) and bring them to electron transport chains (more on these later) The electrons become high energy when exposed to sunlight Examples: 1.With electrons  NADPH or FADH 2 2.Without electrons  NADP+ or FAD+

Light Reactions

e- NADP+ FAD+ e- NADPH FADH Sunlight hits chlorphyll and excites the electrons (woo hoo!) 2. These electrons are transferred to electron carriers Really excited electrons Electron carriers

3. These electrons are used to split water molecules (this is why plants produce oxygen) e- Excited electrons splitting H 2 0 molecule into its base elements H+ O- leaves the plant via stomata H+’s used to help carry electrons (FAD+ becomes FADH 2 when it carries electrons)

This is a close-up shot of the pathway the light energy traveled…from beginning to end.

4. These Hydrogen ions are also shot across an electron transport chain (against the proton gradient…remember the sledding example) H+ The Electron Transport Chain is represented by the dashed line and has one side which is highly positive…shooting the Hydrogen ions against the positive gradient creates energy. H+

5. This produces enough energy to make a small amount of ATP which will be used in the Calvin Cycle ATP SYNTHASE ADP + P Energy from electron transport chain Note the H+ ions returning through ATP Synthase…Oxygen picks up these ions and forms H 2 0…more on this when we get to cellular respiration

This is a close-up shot of the pathway the light energy traveled…from beginning to end.

Light-dependent Reaction-Takes Place in Thykaloid 1. Sunlight hits chlorphyll and excites the electrons (woo hoo!) 2. These electrons are transferred to electron carriers 3. These electrons are used to split water molecules (this is why plants produce oxygen) 4. Hydrogen ions are also shot across an electron transport chain (against the gradient…remember the sledding example) 5. This produces enough energy to make a small amount of ATP which will be used in the Calvin Cycle

Dark Reactions (Calvin Cycle)

1. The plant “breaths in” C02 via stomata Electron micrograph photo of stomata(s) CO2 Plant taking in CO2 Lets zoom in

2. The ATP and NADPH produced in the light reaction is used to break apart the CO2 into its base elements Energy from ATP and NADPH Carbon Dioxide being split into base elements O- C

3. With enough C0 2 and H (remember when the water molecule was split?) a glucose molecule is formed (what was that formula again?) O- C C C C C C ++ H+ C 6 H 12 O 6 Aka: Glucose Oxygen’s from the splitting of H 2 0 Carbon’s from Carbon Dioxide Hydrogen’s from the splitting of H 2 0

The processes we have talked about are how carbon and energy enter the food chain.

Calvin Cycle- takes place in Stroma 2. The ATP and NADPH produced in the light reaction is used to break apart the CO 2 into its base elements 1. The plant “breaths in” C02 3. With enough C0 2 and H (remember when the water molecule was split?) a glucose molecule is formed (what was that formula again?)

Using your notes and the diagram below, explain how energy is transferred from one form (Sunlight) to one that is stored (Glucose). Use the reactions involved in Photosynthesis in your explanation.