Photosynthesis
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Transcript of Photosynthesis
Photosynthesis
Objectives:1. Describe the structure of a chloroplast
2. Explain who ATP releases energy3. Explain the steps to photosynthesis
Energy• Energy is stored in chemical bonds and released at a later date. • Cellular energy is stored by ATP• Adenosine Triphosphate• Contains 2 high energy phosphate bonds• Also contains nitrogen base adenine and a ribose sugar
ADP
• Adenosine diphosphate• What is formed when ATP loses 1 phosphate• ATP releases energy and a free phosphate. This forms ADP • When ATP turns to ADP….energy is released• Energy is used to make ATP again
Importance of ATP
• Main compound used to store energy in living things
• Provides all of the energy for cell activities• Adding a phosphate group to ADP stores
energy• Removing a phosphate group from ATP
releases energy and makes ADP
Pigments and Chloroplasts
• Chlorophyll—primary light-absorbing pigment in autotrophs
• Found inside chloroplasts• Chlorophyll a– Found in all plants– Participates directly in light reactions
• Chlorophyll b– Accessory pigment– Indirectly works in photosynthesis– Both a and b absorb red and blue light
Structure of a Chloroplast
Structure of a Chloroplast
• Smooth outer membrane• Inside: stacks of connected sacs called
thylakoids• One thylakoid stack—granum (grana plural)• Gel-like material around the grana--stroma
Function of Stroma
• Light independent reaction• ATP makes glucose• Calvin cycle
Function of Thylakoid Membrane
• Light dependent reaction• Made up of chlorophyll molecules
Photosynthesis Equation
Photosynthesis Overview
Light Dependent Reactions
• Occurs across the thylakoid membranes• Uses light energy• Produces oxygen from water• Converts ADP to ATP• Converts NADP+ to energy carrier NADPH
Steps of the Light Dependent Reaction
• Photosystem II absorbs light energy• Electrons are energized and passed to the
Electron Transport Chain (ETC)• Lost electrons are replaced from the splitting
of water into 2 H+ , free electrons and oxygen• 2 H+ pumped across the thylakoid membrane
More..
• High energy electrons move to photosystem I through the electron transport chain
• Energy is used to transport H+ from stroma to inner thylakoid membrane
• NADP picks up 2 electrons from the ETC and a H+ to form NADPH
• As H+ ions pass through the thylakoid, ATP synthase binds them to ADP to form ATP
Summary
• Reactants:– Water, light
• Products– ATP, NADPH—energy for dark reaction– Oxygen—by product for cellular respiration
Light Independent Reaction
• ATP and NADPH from light reaction are used for energy of this reaction
• CO2 from the atmosphere is used to make sugars (glucose)
• Six carbon sugars made in calvin cycle• Occurs in stroma
The Calvin Cycle
• Two turns of the Calvin Cycle are required to make one molecule of glucose
• 3-carbon dioxide molecules enter the Calvin Cycle to form PGA
• Two molecules of PGA form 1 molecule of glucose
DONE!