PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general...
-
Upload
victoria-barrett -
Category
Documents
-
view
224 -
download
4
Transcript of PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general...
![Page 1: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/1.jpg)
PHOTOSYNTHESIS
![Page 2: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/2.jpg)
Photosynthesis
-converts sunlight into chemical energy
-very complex
-general reaction:
6CO2 + 6H20 → C6H12O6 + 6O2
![Page 3: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/3.jpg)
• Light from the sun is composed of wavelengths (colors)
• The shorter the wavelength the higher the frequency, thus the higher the energy
• The longer the wavelength the lower the energy, thus the lower the energy
![Page 4: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/4.jpg)
Sunlight (a.k.a. white light)
-sunlight is actually white light made of all wavelength colors
-sunlight is visible light
-different colors=different wavelengths of light
The Visible Spectrum
violet-blue-green-yellow-orange-red
380 nm 750 nm
![Page 5: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/5.jpg)
The Electromagnetic Spectrum-This is what scientists call radiation waves-Radiation=energy that travels and spreads as it
goesExamples: X-rays, gamma rays, visible
light, microwaves, etc.
-The electromagnetic spectrum is organized according to wavelengths
![Page 6: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/6.jpg)
-Wavelengths are measured in nanometers (nm)
-Gamma rays have the shortest wavelengths = 10-5 nm
(highest frequency and energy)
-Radio waves have the longest wavelengths =103 nm
(lowest frequency and energy)
![Page 7: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/7.jpg)
PHOTONS-Photon=quantum=discreet amounts of light
energy-Photons are not objects, but each one has
a distinct amount of energyEx: violet photons contain almost twice as much energy as red photons
*violet wavelengths=380 nm=high frequency=high energy
*red wavelenghts=750 nm=low frequency=low energy
![Page 8: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/8.jpg)
Chlorophyll (the photosynthetic pigment)
-Chlorophyll is a green photosynthetic pigment found in chloroplasts of plants
-There are two main types of chlorophyll(chlorophyll a and chlorophyll b)
-Green is the least effective color for photosynthesis because it is reflected
-What you see is reflected. -Everything else is absorbed
**Thus, red and blue are most effective for photosynthesis.
![Page 9: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/9.jpg)
![Page 10: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/10.jpg)
Absorption SpectrumsAbsorption spectrums are graphs that plot a pigment’s light absorption vs. wavelength
Absorption spectrum of chlorophyll
**Remember:Green wavelengths are between ~475 and 600 nm
![Page 11: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/11.jpg)
Action spectrumsA. Action spectrums tell you how much photosynthesis is occurring at each wavelength
B. Made by illuminating chloroplast with different wavelengths of light and then plotting wavelength against some measure of photosynthetic rate
C. The photosynthetic rates could be measured by finding oxygen production, carbon dioxide absorption or light absorption Action spectrum for chlorophyll
![Page 12: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/12.jpg)
Comparison of absorption and action spectra
Absorption spectrum for chlorophyll
Action spectrum for chlorophyll
*Almost no absorption at green wavelengths
*The photosynthetic rate is very low at green wavelengths
![Page 13: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/13.jpg)
Light energy and water
A. In photosynthesis, light energy is used to split water molecules
B. This process is called photolysis = when a chemical is broken down by photons
C. Water is split into hydrogen ions, oxygen and electrons by photons
D. ATP is also produced
E. ATP and H ions will be used to fix CO2 to make organic molecules
F. Photosynthesis relies on water and sunlight for its initial reaction
![Page 14: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/14.jpg)
General photosynthesis information
A. There are light dependent and light independent reactions
B. Light dependent reactions require lightC. Light independent reactions do not
require light or darkness.-they are independent of light or dark-DO NOT REFER TO LIGHT
INDEPENDENT REACTIONS AS DARK REACTIONS (darkness is not required)
![Page 15: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/15.jpg)
ENRICHMENT ASSIGNMENT
1. READ: The light reactions and the Calvin cycle cooperate in converting light energy to the chemical energy of food: an overview (pp. 117&118 )
2. Briefly outline the section
![Page 16: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/16.jpg)
Light Dependent ReactionsA. Light absorption
1. As chlorophyll absorbs light its electrons are raised to a higher energy level by photons at certain wavelengths
2. The electrons at higher energy levels are said to be excited electrons
3. The excited electrons cause the chlorophyll to become photoactivated
4. Photoactivation is the activation of a particular pigment’s electrons (It is caused by absorbing energy from photons.)
![Page 17: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/17.jpg)
5. After photoactivation the electrons quickly return to their ground state
6. When electrons return to their ground state they give off a photon (discreet amount of energy)
7. The photon (energy) is released in the form of heat
8. This process explains the conversion of light energy into heat energy
![Page 18: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/18.jpg)
B. Chlorophyll organization and light absorption
1. Chlorophyll is found in the thylakoids which are found in chloroplasts
2. Within the thylakoids chlorophyll is arranged into groups called photosystems
3. There are two photosystems:
-Photosystem I – best at 700nm (aka P700)
-Photosystem II – best at 680 nm (aka P680)
![Page 19: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/19.jpg)
**Both photosystems are identical chlorophyll a molecules, except that they interact with different proteins of the thylakoids
6. Excited electrons that have absorbed photons of light pass from molecule to molecule until they reach the chlorophyll at the center of the photosystem
7. The photosystem (the chlorophyll) will then pass the excited electrons to a chain of electron carriers
![Page 20: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/20.jpg)
C. Oxygen production1. Photosystem II absorbs light
2. Its electrons become excited
3. Photosystem II donates its electrons to an electron transport chain and the flow of electrons will generate an ATP molecule
4. Photosystem II has been oxidized (LEO)
5. To get the electrons back (that were donated) an enzyme in the center of photosystem II breaks a water molecule (photolysis)
![Page 21: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/21.jpg)
6. The water is split into hydrogen ions, oxygen and electrons
7. Electrons are donated to PS II (GER)
8. Oxygen and hydrogen ions are byproducts
9. Oxygen is released to the atmosphere
10. The production of oxygen in photosynthesis is done by photolysis and requires sunlight
![Page 22: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/22.jpg)
D. ATP Production
1. an excited electron from the center of PS II is donated and passed along a chain of electron carriers
2. The energy for ATP is generated via a proton gradient that is created as electrons move through an ETC (chemiosmosis)
![Page 23: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/23.jpg)
3. ATP is eventually formed when the H+ ions move through ATP synthase
**their energy is harnessed to bring a phosphate group and ADP
together
4. The electrons from PS II are eventually donated to PS I (after they go through the ETC)
5. When ATP is produced in this manner it is called non-cyclic photophosphorylation(the book calls it non-cyclic electron flow)
![Page 24: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/24.jpg)
E. NADPH Production
1. NADPH = nicotinamide adenine dinucleotide phosphate-oxidase
2. After PS I accepts the electrons that were donated by PS II (the ones that went through the ETC), PS I becomes photoactivated
3. Next PS I donates its excited electrons to NADP+ reductase via another ETC
4. NADP+ reductase is an enzyme that assists in the reduction of NADPH
![Page 25: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/25.jpg)
5. The reduction happens when NADP+ accepts two excited electrons from PS I and a H+ ion from the stroma
6. NADPH is then formed
NADP+ + H+ + 2E-NADP+ reductase
NADPH
***Non-cyclic electron flow is responsible for generation of NADPH and ATP***The purpose of NADPH and ATP production is to provide reducing power and chemical energy to drive the Calvin cycle (to make sugar)
![Page 26: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/26.jpg)
F. Cyclic photophosphorylation(in the book it is cyclic electron flow)1. PS II is not involved2. Produces ATP but not NADPH3. ATP is made via chemiosmosis (the same way as non-cyclic photophosphorylation)4. How it works:
a. PS I absorbs lightb. the excited electrons are given to an
electron acceptorc. the electrons pass through an ETC to
produce ATP via chemiosmosisd. At the end of the ETC the electrons go
back to PS I and the process starts again
![Page 27: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/27.jpg)
**Remember in the chloroplast. . .** 1. Chemiosmosis involves the pumping of H+
ions through the membrane.2. The protons go from the stroma to the
thylakoid space. 3. This creates a proton gradient. 4. The protons later flow through ATP synthase
(back to the stroma) and their energy is captured in order to join a phosphate with ADP
5. This produces ATP.
![Page 28: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/28.jpg)
Go to web animation of light-dependent reactions
![Page 29: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/29.jpg)
Assignment
#1. Draw and annotate a chloroplast.-Include: grana
thylakoids thylakoid membrane stroma ribosomes double membrane circular DNA fat/oil droplets
![Page 30: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/30.jpg)
Light-independent reactions(light not required)
A. Calvin cycle-
1. takes place in the stroma
2. begins with a 5 carbon sugar called ribulose biphosphate
3. Ribulose biphosphate = RuBP
4. ATP and NADPH from the light dependent reactions drive the Calvin cycle
5. ATP provides the energy
6. NADPH provides reducing power
![Page 31: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/31.jpg)
7. RuBP is a carbon dioxide acceptor
8. The reaction is catalyzed by the enzyme ribulose biphosphate carboxylase
9. RuBP carboxylase=rubisco
10. 3RuBP and 3CO2 form:
6 3-Phosphoglycerate
11. ATP is broken down to convert
6 3-Phosphoglycerate to
6 1,3-Biphosphoglycerate
12. NADPH reduces
6 1,3-Biphosphoglycerate to
6 Glyceraldehyde 3-phosphate
![Page 32: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/32.jpg)
13. Only one of the G3P molecules will be converted to glucose, sucrose, starch, fatty acids or amino acids
14. Five G3P molecules will be converted back to RuBP to keep the Calvin cycle continuing
![Page 33: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/33.jpg)
![Page 34: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/34.jpg)
Calvin cycle (more info.)
A. Carbon is:
-absorbed as carbon dioxide
-released as sugar
B. ATP=energy for reactions
NADPH=reducing agent
C. Net sugar production per turn (3 carbon dioxide and 3 RuBP) is 1 G3P.
![Page 35: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/35.jpg)
Phases of the Calvin CycleA. Carbon fixation:
1. Every RuBP is attached to a CO2
3RuBPRubisco
3CO2(a 5 carbon
sugar)
converts to a very unstable6 carbon molecule that isimmediately converted to 6 3-carbon molecules
6 glycerate-3-phosphate
**For every RuBP and CO2 pair, two three carbon molecules are formed
3RuBP + 3CO2 → 6 glycerate-3-phosphate
![Page 36: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/36.jpg)
B. Reduction
1. molecules of glycerate-3-phosphate are phosphorylated to glycerate-1,3-biphosphate
*when ATP is hydrolyzed to ADP
2. glycerate-1,3-biphosphate is reduced when NADPH donates its electrons
*NADPH→NADP+
3. 6 molecules of triose-phosphate are produced
*one is removed from the Calvin cycle and used by the plant to produce sugar
*the other 5 are recycled back into the Calvin cycle and converted back to 3RuBP
![Page 37: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/37.jpg)
C. Regeneration (of RuBP)
1. 5 triose-phosphate (G3P) molecules go through a complex series of reactions to form 3 RuBP
2. The Calvin cycle starts over
3. CO2 will be received by RuBP again
![Page 38: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/38.jpg)
More on the Calvin Cycle
A. Start with 15 total carbons in 3 RuBP
*Remember RuBP is a 5 C molecule
B. 3 CO2 is added for a total of 18 carbons
C. 1 triose-phosphate (G3P) is released (a 3 C molecule is released)
D. The other 5 triose-phosphate molecules are recycled back into 3RuBP(15 C are recycled)
![Page 39: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/39.jpg)
E. Net gain of carbons=3 (the single triose phosphate that was released)
F. Energy consumed during the Calvin cycle =9 ATP and 6 NADPH
G. ATP and NADPH will regenerate in the light-dependent reaction
H. There must always be light dependent reactions for light independent reactions to occur
I. The products of the light reactions are used as fuel for the Calvin cycle
![Page 40: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/40.jpg)
1. Outline photosynthesis (light-dependent and light-independent)
2. Explain how the light-independent reaction depends on the light –dependent reaction
![Page 41: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/41.jpg)
Measuring Photosynthesis*can be done three ways
A. Production of oxygen
1. Aquatic plants release oxygen in bubbles during photosynthesis
2. If the bubbles are collected, their volume can be measured
![Page 42: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/42.jpg)
B. Carbon dioxide absorption
EX: 1. Leaves take in CO2 from the air
2. You could pot a plant in an enclosed
environment and measure the CO2 before and after
EX: 1. Aquatic plants absorb CO2 from the water
2. If plants take up CO2, the pH of the water will rise
3. You could use pH indicators to measure pH before and after
![Page 43: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/43.jpg)
C. Increase in Biomass (measure the increase in sugar molecules)
1. Measure how much mass a plant gains over time2. to do this the plant must be completely dehydrated (dead)3. It is best to measure batches of plants
-select a few from each bunch to be dehydrated at different times)
4. Biomass is an indirect measurement of the photosynthetic rate
![Page 44: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/44.jpg)
Limiting Factors in Photosynthesis
A. For photosynthesis to occur the following criteria must be met:
-suitable temperature
-presence of: chlorophyll
light
carbon dioxide
water
![Page 45: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/45.jpg)
B. Changes to one limiting factor will change the rate of photosynthesis
C. Limiting factors are those that are near their minimum or maximum level
D. Limiting factors determine the rate-limiting stepFor example: If light intensity is the limiting factor, the light dependent reaction will limit the rate of photosynthesis.The limiting-step will be the reduction reaction in the Calvin cycle (when the products of the light dependent stage are needed)
![Page 46: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/46.jpg)
E. Light as a limiting factor1. At low light NADPH and ATP are not produced (b/c they are light-dependent products)
2. If NADPH and ATP are not produced the Calvin cycle will stop at the reduction and phosphorylation reactionsR
ate
of
ph
oto
syn
thes
is
Light intensity
The effect of light intensity on photosynthesis
![Page 47: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/47.jpg)
*At high intensity photosynthesis plateaus
*Light intensity is directly proportional to the rate of photosynthesis
*Light is not usually the limiting factor
![Page 48: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/48.jpg)
F. Carbon dioxide as a limiting factor
1. If there is little or no carbon dioxide the Calvin cycle is limited at carbon fixation
2. RuBP and NADPH will acculmulate
**Carbon dioxide is often a limiting factor because it is never at a high concentration in the atmosphere
![Page 49: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/49.jpg)
Rat
e o
f p
ho
tosy
nth
esis
Carbon dioxide concentration
The effect of carbon dioxide on photosynthesis
*There is no photosynthesis when carbon dioxide is low*Carbon dioxide and photosynthesis are directly proportional*At high carbon dioxide concentrations photosynthesis plateaus
![Page 50: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/50.jpg)
G. Temperature as a limiting factor
1. At low temperature the enzymes that catalyze the reactions work slowly
2. At high temperature rubisco is ineffective (it is denatured)
3. Carbon fixation becomes the rate-limiting step
![Page 51: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/51.jpg)
Rat
e o
f p
ho
tosy
nth
esis
Temperature
The effect of temperature on photosynthesis
*As temperature increases so does the rate of photosynthesis*After the optimum temperature is surpassed the rate quickly falls
![Page 52: PHOTOSYNTHESIS. Photosynthesis -converts sunlight into chemical energy -very complex -general reaction: 6CO 2 + 6H 2 0 → C 6 H 12 O 6 + 6O 2.](https://reader035.fdocuments.net/reader035/viewer/2022062715/56649dac5503460f94a9bb63/html5/thumbnails/52.jpg)
Review Questions 1. Compare action spectra and absorption spectra.
2. What are the functions of ATP and NADPH produced in non-cyclic photophosphorylation
3. What is the purpose of cyclic photophosphorylation?
4. What is the advantage of non-cyclic photophosphorylation over cyclic photophosphorylation?
5. What is the purpose of the Calvin cycle?
6. Explain the relationship between the structure of the chloroplast and its function.