chapter 10 photosynthesis photosynthesis nourishes almost all of the living world directly or...
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CHAPTER 10 PHOTOSYNTHESIS
• Photosynthesis nourishes almost all of the living world directly or indirectly.
• _____________
• produce their organic molecules from _____ and other ____________ raw materials
• are the ultimate source of __________ compounds for all ___________________organisms
1. Plants and other ______________ are the producers of the biosphere
• ______________
• are the _______________ of the biosphere.
• Some feed on plants and other animals.
• _____________ feed on dead organisms
• Most are completely dependent on _______________ for food and for __________, a byproduct of photosynthesis.
• ___exits and _____ enters the leaf through microscopic pores, ___________, in the leaf.
Fig. 10.3
• A typical __________ cell has ________chloroplasts
• Each chloroplast has _____ membranes around a central aqueous space, the ________.
• In the stroma aremembranous sacs, the ____________.
• These have an internal aqueous space, the ___________ lumen.
Fig. 10.3
• Plants produce organic compounds and O2 from ___ and _____.
• Using glucose as our target product, the equation describing the net process of photosynthesis is:
• __________________________________________
• In reality, photosynthesis adds one _____ at a time:
• CO2 + H2O + light energy -> CH2O + O2
• ________ is the general formula for a sugar.
2. Photosynthesis is a ________ reaction.
• It reverses the direction of _______ flow in respiration.
• Water is split and electrons transferred with H+ from water to CO2, _________ it to sugar.
• ______ covalent bonds (unequal sharing) are converted to ____________ covalent bonds (equal sharing).
• Light boosts the ________________ of electrons as they move from water to sugar.
Fig. 10.4
Fig. 10.5
4. _____ is generated by _____________________ for the Calvin cycle.
1. ___________(in thylakoids)
absorbs light energy
2. Electrons and hydrogen are transferred to _______
______________ drive Calvin cycle
6. _____ is fixed into organic
molecules by the Calvin Cycle
The ____________ incorporates CO2 from the atmosphere into an organic molecule
3. _________ is generated
6 steps
• A _____________________ measures the ability of a pigment to absorb various wavelengths of light.
• An ___________ __________ plots a pigment’s light absorption versus wavelength.
Fig. 10.8
In the thylakoid are several pigments that differ in their absorption spectrum.
• _______________, the dominant pigment, absorbs best in the red and blue wavelengths, and least in the green.
Fig. 10.9a
•_______________ and _________________ funnel the energy from other wavelengths to chlorophyll a.
•_______________ also give photoprotection
against excessive light.
The structure of chlorophyll a and b
_________________
___________________
Fig. 10.10
• _____________ (light gathering “antenna complex)
• Located in the ____________________________
• contain a few hundred chlorophyll __, chlorophyll __,and ___________________ molecules.
Fig. 10.12
•All photon energy is are transferred to a chlorophyll a molecule (the __________ ___________).
•There are two types of photosystems- _____________ and __________________
•These two photosystems work together to use light energy to generate ___________________.
Reaction center
• _____________ (light gathering “antenna complex)
• Located in the ________________________
• contain a few hundred chlorophyll __, chlorophyll ___,and ______________ molecules.
Fig. 10.12
•All photon energy is are transferred to a chlorophyll a molecule (the ________ _________).
•There are two types of photosystems- ___________ and ________________
•These two photosystems work together to use light energy to generate ________________.
Fig. 10.13
Fig. 10.14
• The light reactions use the solar power of _______ absorbed by both photosystem I and photosystem II to provide ________________ in the form of ATP and ________ _________ in the form of the electrons carried by ________.
An analogy
2. ___________________ –Convert ___________ energy from food molecules into ATP. _____________- Convert ________energy into ATP to drive ______________ to make glucose.
Compare mitochondria and chloroplasts
1. Both generate ATP via ______________
•ATP __________ molecules harness the proton-motive force to generate ATP as H+ diffuses back across the membrane.
Mitochondria Chloroplast
Fig. 10.16
• CO2 enters the cycle and leaves as _________.
• Each turn of the Calvin cycle fixes _____ carbon.
• The actual sugar product of the Calvin cycle is glyceraldehyde-3-phosphate (G3P).
3. The Calvin cycle uses ____ and ________ to convert CO2 to ________: a closer look
• For the net synthesis of one ____ molecule, the cycle must take place _______times, fixing ________ molecules of CO2.
• To make one glucose molecules would require ____ cycles and the fixation of ______ CO2 molecules.
Fig. 10.18
3 (P-C-C-C-C-C-P)3 (P-C-C-C + C-C-C-P)
3 CO2
Carbon Fixation
3 (P-C-C-C-P + P-C-C-C-P)
Each cycle fixes one carbon
The Calvin Cycle
6 ATP used
6 NADPH used
1 (P-C-C-C)
5 (P-C-C-C)
3 ATP used
Total energy used for 3 carbon sugar = __ ATP + ___ NADPH
“Rubisco”
• The ____________ are not only the major route for gas exchange (CO2 in and O2 out), but also for the evaporative loss of _________.
• On hot, dry days plants close the stomata to conserve water, but this causes problems for photosynthesis.
4. Alternative mechanisms of ___________ ________ have evolved in hot, arid climates
•_________________-__________
•But photorespiration can drain away as much as _____ of the carbon fixed by the Calvin cycle
• Some plants (_____________) have a mechanism to minimize photorespiration
One solution
• The ________ fix ____ in a four-carbon compound via _______________________(PEP) to form _________________.
• Several thousand plants, including ____________ and corn, use this pathway.
• The mesophyll cells pump these ________-carbon compounds into ________________ cells.
• The bundle sheath cells strip a carbon, _________, from the four-carbon compound and return the three-carbon remainder to the mesophyll cells.
• The bundle sheath cells then uses rubisco to start the __________ with an abundant supply of _____.
A better solution- to fix CO2 at _________
Fig. 10.18
C4 plant response to hot, dry weather:CO2 is shuttled into oxaloacetate (a 4-carbon compound)
CO2 can later be shutted back into the Calvin Cycle
• C4 photosynthesis minimizes photorespiration and enhances sugar production.
• C4 plants thrive in hot regions with intense sunlight.
Fig. 10.19
• A __________ strategy to minimize photorespiration is found in succulent plants, cacti, pineapples, and several other plant families.
• These plants, known as _____________ for _____________________________ (CAM), open stomata during the night and close them during the day.
• During the night, these plants fix _________ into a variety of organic acids in mesophyll cells.
• During the day, the light reactions supply ATP and NADPH to the Calvin cycle and CO2 is released from the organic acids.
Fig. 10.20
• In photosynthesis, the energy that enters the __________________ as sunlight becomes stored as _______________ in organic compounds.
5. Photosynthesis is the biosphere’s ______________ foundation: a review
Fig. 10.21
• Plants also store excess sugar by synthesizing _________.
• Some is stored as starch in chloroplasts or in storage cells in roots, tubers, seeds, and fruits.