The Reactions of Photosynthesis Light Dependent Calvin Cycle

The Reactions of Photosynthesis Light Dependent & Calvin Cycle Interactive: 3 videos on web page

Inside a Chloroplast • Thylakoids o Saclike membranes o Arranged in stacks called grana o Organize the chlorophyll into clusters called photosystems • Stroma o Area outside thylakoid membrane

Electron Carriers (used in the electron transport chain) • Sunlight gives energy to electrons in the chlorophyll of a plant • NADP+ o A carrier molecule o Can carry 2 high energy electrons and 1 H+ • NADPH o Results from adding 2 electrons o Traps the energy in chemical form • Can be used by chemical reactions in the cell

Reduction is GAIN Oxidation is LOSS

Light Dependent Reactions • In the thylakoid membrane of the chloroplasts • Use energy from light to split water & make O 2, H+, and e • Converts (dehydration synthesis)ADP to ATP • Converts (reduced) NADP+ to NADPH

5 Steps (Light Dependent Reactions) • 1. Photosystem II- absorbs light and breaks up water • 2. Electron Transport Chain- moves high energy eand transports H+ inside thylakoid • 3. Photosystem I uses the e- & H+ to turn NADP+ into NADPH • 4. Hydrogen Ion movement makes the outside - and inside +. • 5. ATP formation- H+ move outside the membrane and ATP synthase creates ATP.

Light Dependent Reactions Thylakoid compartment (high H+) Light Thylakoid membrane Antenna molecules Stroma (low H+) ELECTRON TRANSPORT CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE

The Calvin Cycle • Uses ATP and NADPH made during the light dependent reactions • Makes High Energy Sugars like Glucose • Does not require light • Occurs in the Stroma

Steps • Fixation: CO 2 molecules+C 5 molecules= C 3 molecules(using enzyme Rubisco) • Reduction: The resulting C 3 molecules are converted to higher energy molecules by using ATP and NADPH o 2 of the C 3 high energy molecules are used to make sugars, lipids, amino acids for metabolism and growth • Regeneration: The remaining C 3 molecules are recycled back into C 5 molecules to start the cycle again.

Factors that Affect the Rate of Photosynthesis • Amount of Water • Temperature o Photosynthetic enzymes function best at 0 -35 degrees C • Light Intensity

Self Quiz 1. What type of organism uses light energy to make its own food 2. Which compound is used to release energy to power the cell: ATP or ADP? 3. What is the name of the process that converts light energy into high energy carbohydrates? 4. Write the equation for the above process. (you may use words or chemical formulas) 5. What is the main light absorbing pigment in plants?