How Plants Convert Solar Energy into Chemical Energy (Glucose) Photosynthesis How Plants Convert Solar Energy into Chemical Energy (Glucose)

Leaves are organs that carry out photosynthesis. Go through the activity: E-Life 8.1 p.2-5

Leaf Cross-section:

Lilac Leaf Cross Section

Plant Cell

The Inside of a Chloroplast Thylakoid space Stroma Outer membrane Inner membrane Grana Thylakoid

Outer membrane Protective covering allows only small molecules to diffuse through (semi-permeable)

Inner membrane Forms border for stroma and regulates passage of materials in and out of the chloroplasts

Stroma Dense fluid within the chloroplast that lies inside the membranes, it is the site of conversion of CO2 to Sugar

Grana Dense layered stacks of thylakoid sacs

Thylakoid membrane Internal membrane system consisting of a flattened sac

Thylakoid Space Serves as site that converts light energy to chemical energy inside the thylakoid membrane

The Chemical Formula of Photosynthesis 6CO2 + 6H2O C6H12O6 + 6O2 Carbon Water Glucose Oxygen dioxide

Photosynthesis consists of Two major Reactions

Light Reactions Overview H2O O2 Occurs on thylakoid membrane Light energy is absorbed by chlorophyll found in Photosystems I & II Water is split releasing O2 NADPH & ATP are formed after series of reactions

Light Dependent Reactions take place on the membrane surface of the Thylakoid Hon LR Aca LR http://dendro.cnre.vt.edu/forestbiology/photosynthesis.swf http://www.science.smith.edu/departments/Biology/Bio231/ltrxn.html

Step 1: Photosystem II (PS II) The pigments in PS II absorb light energy and excites electrons which increases their energy level. The electrons travel to the electron transport chain. The electrons come from broken up water molecules that create 2 electrons, 2 H+ and 1 oxygen. The oxygen is released so we can breathe it and the H+ are released into the thylakoid membrane

Step 2: Electron Transport Chain (ETC) The excited high energy electrons from PS II travel through the electron transport chain to reach PS I The electron’s energy is used by the molecules in the ETC to transport H+ ions from the Stroma to the inner thylakoid space.

Step 3: Photosystem I (PS I) The pigments in PS I use light to reenergize the electrons A molecule NADP+ picks up the high energy electrons and H+ ions to then become NADPH

Step 4: Hydrogen Ion Movement During step 3 when the electrons leave the ETC to go to the NADP+, H+ ions are pumped across the thylakoid membrane. As this continues, the Thylakoid spaces fill up with H+ and becomes Positively charged while the thylakoid membrane is negatively charged. This charge difference provides the energy to make ATP

Step 5: ATP formation A protein called ATP synthase on the thylakoid membrane allows H+ ions to pass through the membrane since they cannot cross on their own. As H+ passes through, the protein rotates like a turbine building up energy, this energy allows the ADP and a Phosphate group join together to produce ATP

Overview of Light reactions Reactants (what goes in): Water, ADP, and NADP+ Products (what comes out): Oxygen, ATP, and NADPH ATP and NADPH move on to the Calvin Cycle

Light Reactions Children’s Story Compose a children’s story about the travels of an electron through the light reactions. Be sure to represent all the elements of the light reactions in your story. Illustrate a scene from your story which will best represent the activity during the light reactions. Attach your story to your illustration.

The Calvin Cycle 1. Occurs in the Stroma 2 The Calvin Cycle 1. Occurs in the Stroma 2. Uses 6CO2 from the atmosphere 3. Energy is provided from ATP and NADPH (from Light Reactions) 4. After 2 cycles, glucose is made.

Step 1: Carbon Fixation 6 carbon dioxide (CO2) molecules enter the cycle from the atmosphere. CO2 combines with 6, 5-carbon molecules and produces 12, 3-carbon molecules

Step 2: Reduction Energy from ATP and high energy electrons NADPH are used to convert the 12 3-carbon molecules into higher energy forms.

Step 3: Release of one G3P Two of the 12 3-Carbon molecules leave the cycle to produce things like sugars, lipids, amino acids, and other compounds needed for the plants metabolism and growth.

Step 4: Regeneration of RuBP The remaining ten 3-carbons are converted back into six 5-carbon molecules. These molecules will combine with 6 new CO2 molecules to begin the next cycle. Remember: the glucose is not made until after the second cycle!

Photosynthesis Essential Questions Name the two most important parts of a chloroplast. Which parts of photosynthesis occurs in each structure? What are the reactants and products of the Light Reactions? The Calvin Cycle? Explain how the Calvin Cycle is indirectly dependent on light. Explain how ATP synthase is a protein channel and an enzyme.

PhotoFinish Alterations Fill 2 beakers with 80 mL sodium bicarbonate solution Once air spaces are vacuumed, pour syringe solution and leaf disks into each beakers (10 disks each). Make sure both sets are ready to start at the same time. May use stop watch feature on phone.

PhotoFinish Cleanup Discard solution down drain—Do NOT let leaf disks down drain!! Discard used spinach and disks in trash Rinse out beakers; return to side Separate syringes, clean out hole punches; return to side Unplug lamp & dry off area