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PHOTOSYNTHESIS. Photosynthesis. Converts sunlight energy into chemical energy. Chemical Equation. 6CO 2 + 6H 2 O + light energy C 6 H 12 O 6 + 6O 2 Carbon dioxide and water are the reactants and glucose and oxygen are the products. - PowerPoint PPT Presentation
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Photosynthesis
• Converts sunlight energy into chemical
energy
Chemical Equation
• 6CO2 + 6H2 O +light energy C6 H 12 O 6 + 6O2
• Carbon dioxide and water are the reactants and glucose and oxygen are the products.
• Chlorophyll is the pigment necessary to run the reaction.
Requirements
• Light Energy (Sun)• Chlorophyll a,b and accessory
pigments (these absorb wavelengths of light)
• Raw materials (CO2 and H2O )
• Enzyme: NADP (taxi cab)
Cross Section of a Leaf
• Leaf has many layers of specialized cells.
• Notice the location of the chloroplasts.
Stomata
• Stomata (leaf mouth) allows gas exchange (O2 and CO2)
• guard cells create the stomata
Inside the Chloroplast
• Saclike membranes called thylakoids contain chlorophyll and accessory pigments.
• Stacks of Thylakoids
are called Grana. • Stroma is the fluid
filled space.
Chloroplast Again
• Chloroplast
Below
Notice the granaare stacks of
thylakoids
The Two Phases of Photosynthesis
• Phase I - Light Dependent Reaction (occurs in thylakoids)– Light energy is absorbed and converted to
chemical energy in the form of ATP and NADPH.
• Phase II - Dark Reaction (Calvin Cycle) (occurs in stroma)– NADPH and ATP that were formed during light
dependent reactions are used to make glucose.
Light ReactionsOverview:
1. Light energy is absorbed in the THYLAKOID.
2. Water is split or pulled apart: 2H and ½ O2
3. CO2 is NOT involved yet.4. ATP is formed.5. Reactants: chlorophyll, light energy, water,
and NADP.
Light Reactions Steps:1. Light energy is absorbed by chlorophyll.2. Electrons in chlorophyll become “excited”
(high energy) and split H2O apart.
H2O: 2H + ½ O2 * 6 molecules of water total are split apart:
12 H+ , 6, ½ O2 (released into air as a byproduct).
3. An electron is released into the electron transport system.
Light Reactions
4. NADP picks up the H + and electrons
and transports them across the thylakoid membrane into the stroma.
NADP + H + NADPH
* 6 H2O are split: 12 NADPH are formed by the Light Reaction.
5. Hydrogen protons (H+) move across the thylakoid into the stroma to create ATPs from ADPs.
Products of Light Reactions
• 6, ½ O2 are released into the air via stomata.
• NADPH and ATP go to the stroma for Phase II (The Calvin Cycle).
Calvin Cycle or Dark Reaction
• Reactants: • ATP and NADPH from Light Reactions• 6 CO2
• 6 RuBP (ribulose bisphosphates)• Products: Glucose (C6H12O6) and 6
RuBP• Takes place in the stroma.
Steps of the Calvin Cycle (Dark Reaction)
• CO2 Fixation:
CO2 combines with RuBP 6CO2 + 6RuBP 12 PGA
PGA is a 3-Carbon molecule and is
UNSTABLE!
Total: 6 CO2 + 6 RuBP 12 PGA
Calvin Cycle
12 PGA + 12 ATP + 12 NADPH
12 G3P + 12 ADP + 12 NADP
* What happens to NADP? ADP?
* PGA and PGAL are 3 Carbon molecules.
Calvin Cycle Con’t.
• Formation of glucose:
2G3P 2Glucose
C3H6O3 + C3H6O3 C6H12O6
* Recall: G3P is a 3- Carbon molecule.
Calvin Cycle
Importance of Photosynthesis
• Forms glucose which is necessary for cellular respiration.
• Forms the source of oxygen we breathe.
Factors that Affect Photosynthesis
• 1. Amount of water• 2. Temperatures• 3. Light Intensity• 4. Amount of CO2
Summary of Photosynthesis