Photosynthesis – Capturing the Energy in Light Chapter 8-1

1. Energy and Life A. Photosynthesis: the process in which energy from the sun is converted into organic compounds. Autotrophs: organisms that make their own food from inorganic substances and energy (usually carbohydrates) C. Heterotrophs: must obtain energy from eating autotrophs or other heterotrophs.

2. Chemical Energy and ATP A. ATP- Principal chemical compound that cells use to store and release energy. (Adenosine triphosphate) 1. Adenine, a 5 carbon sugar called Ribose and 3 phosphate groups. B. Storing Energy – ADP is a compound that looks like ATP but only has 2 phosphate groups. 1. When a cell has energy available, it can store small amounts of it by adding a phosphate group to ADP producing ATP. 2. ATP is like a fully charged battery.

3. Using Biochemical Energy A. Uses of ATP 1). In Active Transport 2). Produces Movement 3). Powers important events like protein synthesis. ATP can be generated easily from ADP, as needed by the cell.

8:2 Photosynthesis Overview 1. Plants use the energy of sunlight to convert water and carbon dioxide into high energy carbohydrates, oxygen and a waste product. 2. Where does the mass of a fully grown tree come from? (seedling to tall tree???) A. Van Helmont’s Experiment – 1600’s Jan van Helmont experimented whether plants use the soil to help them grow. This experiment lasted 5 years. The seedling grew to 75 Kg but the soils mass had not changed. He concluded that the plants mass had come from the water he had added. (water is one of the 3 important components to the production of glucose.)

B. Priestley’s experiment – Discovered the a candle needs oxygen to continue burning. When he added a plant in with the covered burning candle it remained light for a lot longer. The plant must release oxygen. C. Jan Ingenhousz – Jan later proved that the plant could only release oxygen when exposed to light. Both scientist proved that light is necessary for photosynthesis to occur.

4. Properties of Light A. Visible spectrum is the mixture of colors that make up white light. B. Light travels through space as waves of energy. C. Different colors have different wave length. 1. Red: longest wavelength, lowest energy 2. Violet: shortest wavelength, highest energy

5. Pigments A. Pigments absorb and reflect colors. B. The color you see is the color that is reflected, all the rest are absorbed.

6. Chloroplast Pigments A. Chlorophyll A and B absorb reds and oranges and reflect green. B. Chlorophyll A, is directly involved in the light reaction. C. Accessory pigments aid in the absorption of light and are not directly involved with photosynthesis.

7. Parts of the chloroplast A. Each chloroplast is surrounded by a pair of membranes. B. Inside the membrane are flattened sacs called Thylakoids, That are filled with chlorophyll pigment. C. Thylakoids are layered on top of one another to form stacks called Grana. D. Surrounding the Thylakoids is a solution called the Stroma

Begin the light reactions and it’s steps

I The Light Reaction 8:3 in photosynthesis Involves the A. The 1st reaction in photosynthesis Involves the absorbing of light by the chloroplast.

Structure of Leaf to Chloroplast

II. Photosynthesis A. Basic chemical formula 6 CO2 + 6 H2O → C6H12O6 + 6 O2 B. Reactants: carbon dioxide (gas), water and light. C. Products: sugar and oxygen (gas) D. The reaction must occur in the presence of LIGHT, without it the photosynthetic reaction will not occur.

Photosynthesis – chemical formula

III. Electron Transport- A. The transport of electrons in a chain from one place to the other. A. Photosystem: a group of pigments, chlorophylls and carotenoids, that are imbedded in the thylakoid membrane. B. Photosystems I and II play different roles in photosynthesis.

Second day Steps in the light reaction

IV. Step 1 of the Light Reaction 1. Light energy forces electrons to reach a high energy level in Chlorophyll A of photosystems II. P-II is the first to pass electrons in the first of 2 electron transport chains.

V. Step 2 of the Light Reaction 2. The excited electrons leave chlorophyll A and enter the primary electron acceptor. The primary electron acceptor donates electrons to the electron transport chain, losing energy as they go, transferring electrons between light collecting molecules.

VI. Step 3-6 of the Light Reaction 3. At the same time, light is also being absorbed by photosystem I, pushing more electrons from chlorophyll A down the 2nd ETC. 4.The electrons are accepted by a new electron acceptor. 5. The new acceptors is NADP which is the final electron acceptor. 6. When NADP accepts electrons it becomes NADPH.

VII. Restoring Photosystem II 4. When electrons are lost in photosystem II they need to be replaced. 5. Water provides the electrons, by splitting water. 2H2O  4H+ + 4e- +O2 6. By splitting water, electrons are replaced in Photosystems II, and oxygen is produced which is the by-product of photosynthesis.

VIII. Chemiosmosis A. Chemiosmosis: the formation of ATP B. ATP synthase, a protein, binds ADP with a phosphate group producing ATP.

IX. Chemiosmosis A. The energy lost during the transport of electrons down the E.T.C. is harnessed and used by ATP Synthase to attach a phosphate group on to ADP producing ATP, which will be used in the next reaction of photosynthesis

X. Conclusion A. NADPH and ATP produced in the light reaction is necessary and will be used in the Dark Reaction. B. ATP is a product catalyzed by ATP synthase. C. Always remember in photosynthesis, P-II always passes electrons to P-I. D. Splitting water produces oxygen.

Chart – Light Reaction Location – Thylakoid Membrane (Chloroplast) Function –Produces 02, ATP, NADPH all for the next reaction, (Calvin Cycle, Dark Reaction) Reactants – Water, ADP, NADP, Light, CO2 and chlorophyll. Products – ATP, Oxygen and NADPH