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2 Parts of Photosynthesis
Light Dependent Reaction
Calvin Cycle or Light Independent Rxn(aka Dark Reaction)
Structure of a Chloroplast
The light reactions take place in the thylakoid membrane
The dark reactions take place in the stroma
Light energy is packaged into photons.
Light is a form of Electromagnetic energy move in waves.
Each level of wavelength emits various amounts of energy.
Molecules of plants that absorb light are called Pigments.
Chlorophyll is the major absorbing pigment in green plants and photosynthesis.
Pigments
Pigments are light-absorbing compounds.
Pigments appear colored because they absorb light of certain wavelengths and reflect that of others.
Chlorophyll a is the primary pigment in green plants that absorbs red and blue/violet light and reflects green light.
GAS EXCHANGE
Stomata Anatomy
1.Stomata are microscopic openings found on the bottom sides of the leaves.
2.The stomata is bounded by two half moon shaped guard cells.
3.Found on the bottom surface of the leaf because the guard cells are partially light activated, plants under direct light would constantly have their stomata open and would thus lose much water and the plant would die.
4.Guard cells
Each guard cell contains water and ions.
Stomata Physiology
1. LIGHT : Guard cells Swell; stomata open.
A. Carbon Dioxide diffuses into the cell to be used for photosynthesis.
B. Water and Oxygen diffuse out of the leaf.
2. DARK: Guard cells Shrink; stomata close
No photosynthesis takes place.
Light Reaction
Also called Light Dependent ReactionPigments that are in the chloroplasts intercept light and begin the light reactions of photosynthesis.The light reactions occur in two photosystems (located in the thylakoid membrane):
Photosystem: a unit of several hundred chlorophyll a molecules and associated acceptor molecules
-photosystem I (PSI) -photosystem II (PSII)
1. Light Energy is absorbed by the grana.
2. Water is split into H+ , and O2 The oxygen is then released.3. The Electrons from water are excited and passed down from PhotosystemII to PhotosystemI. The free Hydrogen ions are transported across the thylakoid membrane and are used to produce ATP and NADPH.
Steps of LIGHT Reaction
STEPS of LIGHT REACTION4. The electrons arrive at Photosystem I and are excited again by the sunlight .5. They are then passed to NADP and form NADPH.6. The build up of H+ inside the Thylakoid causes the H+ to move through ATP Synthetase.7. This energy forces a phosphate onto ADP to generate ATP. This movement is due to a difference in concentration.
AP Biology
From Light reactions to Calvin cycle Calvin cycle
chloroplast stroma
Need products of light reactions to drive synthesis reactions ATP NADPH
stroma
thylakoid
ATP
Dark ReactionThe dark reaction is also known as the Calvin Cycle, after an American scientist (Melvin Calvin) who figured out the pathway.The dark reaction is also known as the C3 Cycle because the first stable products of this pathway are molecules that contain three carbon atoms.The Calvin Cycle occurs in the stroma.
12 NADPH + H+
~
e12 ADP + P
12 ATP
12 NADP+
e-
10 PGAL
~
e6 ADP + P
6 ATP
6 CO2C
6 RuBPC C C C C
12 PGAC C C
12 PGALC C C
2 PGALC C C
GlucoseC C C C C C
C C C C C C
unstablecompound
Calvin Cycle1. Takes place in the stroma
2. Carbon dioxide is fixed to RuBP by the enzyme Rubisco.3. One - 3 Carbon molecule known as G3P is formed for each Carbon dioxide(3) that gets fixed. It takes two turns of the cycle to produce ONE 6 carbon molecule of sugar.4. ATP and NADPH are necessary to run this reaction and generate ADP, and NADP+ for the light reactions.
1.Compounds that store energy are ATP, NADPH, FADH, & NADH2. The most important energy storing compound is ATP (Adenosine triphosphate.)3. ATP releases energy when a bond holding a phosphate group is broken. This creates a new molecule called ADP (adenosine di-phosphate)4. What is the difference between ATP and ADP? # of Phosphates5. Cells generate 10 million new ATP molecules per second.