Photosynthesis Mini Unit STEM Biology Photosynthesis Mini Unit

Review: Cellular Respiration ALL living organisms can do a part of cellular respiration Breakdown of glucose into energy (ATP) – where most energy is made if oxygen is present! Cytoplasm and Mitochondria (Matrix and Cristae) After glucose is present in cells To create energy for the cell to do work 4 stages….. (did that already) Who? What? Where? When? Why? How?

Equation for Cellular Respiration ____________ + _____________  __________ + _________ C6H12O6 + 6O2  6CO2 + 6H20. What can I add to the end of the equation? 36-38 ATP Ok so now, what do we know about photosynthesis? Brainstorm on white board. Equation for Cellular Respiration

Who does Photosynthesis? ALL plants Algae Some bacteria These organisms are also called producers, or autotrophs.

What is photosynthesis? A process that captures light energy from the sun and transforms this light energy into high-energy sugar molecules. Has 2 stages (details coming later) What do you think the equation would be for photosynthesis? This Photo by Unknown Author is licensed under CC BY

Equation for Photosynthesis ____________ + ____________  ____________ + ____________ 6CO2 + 6H20  C6H12O6 + 6O2 Opposite of cellular respiration (without the ATP added) What are the reactants? What are the products? The arrow is like an equal sign, so notice that each side equals the other side. Left side of the arrow! Right side of the arrow!

Where does Photosynthesis occur? Chloroplast! 2 membranes – Electron Transport Chain Thylakoid – absorbs the light energy from the sun Stroma – contains the enzymes for the chemical reactions

When does photosynthesis occur? 1st stage of photosynthesis MUST take place in the light! This stage is called the light reactions. 2nd stage of photosynthesis does not require light. This stage is called the dark reactions. This Photo by Unknown Author is licensed under CC BY-SA

Why is photosynthesis important? The glucose made by photosynthesis is used by plant and animal cells It produces oxygen which helps regulate Earth’s environment The oxygen is required for aerobic organisms and gets rid of the CO2 from Earth’s atmosphere Nearly all organisms on Earth depend on photosynthesis Why is photosynthesis important?

How does photosynthesis work? 2 Stages Light dependent reactions Dark Reactions (light independent reactions); also called the calvin cycle ATP is going to be made and used in the process NADPH is going to be made and used in the process Very similar to NADH, but has a phosphate group attached This Photo by Unknown Author is licensed under CC BY

Stage 1: Light Dependent Stage Takes place within and across the membranes of the thylakoids, which are stacked inside the chloroplast. Main function is to capture the light and transfer the energy 6 steps

6 Steps of Stage 1: Light Dependent Energy is absorbed from sunlight into the thylakoid. Water molecules split into oxygen, protons and electrons Oxygen gets released out into the atmosphere Protons stay inside the thylakoid Electrons get the high energy from the sun (transfer of energy) The protons get pumped across the thylakoid membrane, which causes a buildup of them – form of stored energy. The electrons move down the electron transport chain and energy gets transferred to ATP. Now the electron has low energy.

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6 Steps of Stage 1: Light Dependent Energy is absorbed from sunlight again into the thylakoids giving electrons energy again. NADP+ accepts the high energy electrons and makes NADPH, which is an energy-carrying molecule Hydrogen ion diffusion – protons diffuse out of the thylakoid through ATP synthase. ATP is made! (just like cellular respiration)

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Summary of Light dependent phase Required: Water, ADP, NADP+, chlorophyll Products: Oxygen, ATP, NADPH So now we have ATP and NADPH energy……now on to the light independent phase!

Light independent reactions (Dark Reactions) Light is NOT required These reactions can take place anytime the energy of ATP and NADPH are available Energy is needed for the Calvin Cycle, which will make sugars like glucose! 4 steps

Light Independent Reactions (Calvin Cycle) 4 STEPS Carbon Dioxide is added to a 5C molecule already in the cycle – making a 6C molecule The 6C molecule splits into 2 3C molecules. ATP and NADPH provide the energy to rearrange them into these 3C molecules. 1 of the 3C molecules leaves the cycle and the other stays. Once there is 2 3C molecules out of the cycle, a 6C molecule of sugar (glucose) is made. The 3C molecule that stayed in the cycle is transferred back to the original 5C molecule (back in step 1). This transfer requires ATP.

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Summary of Independent Light Reactions (Dark Reactions) Requires: ATP, NADPH, CO2 Products: Glucose Summary of Independent Light Reactions (Dark Reactions)