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 are membranous sacs, the ____________. These have an internal aqueous space, the ___________ lumen. Fig. 10.3

Plants produce organic compounds and O 2 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: CO 2 + H 2 O + light energy -> CH 2 O + O 2 ________ 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 CO 2, _________ 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 _____ 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 CO 2 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

_____________ (light gathering “antenna complex) Located in the ____________________________ contain a few hundred chlorophyll __, chlorophyll __, and ___________________ molecules. Fig 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 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

Fig 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. MitochondriaChloroplast Fig

CO 2 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 CO 2 to ________: a closer look For the net synthesis of one ____ molecule, the cycle must take place _______times, fixing ________ molecules of CO 2. To make one glucose molecules would require ____ cycles and the fixation of ______ CO 2 molecules.

Fig (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 (CO 2 in and O 2 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 CO 2 at _________

Fig 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 C 4 photosynthesis minimizes photorespiration and enhances sugar production. C 4 plants thrive in hot regions with intense sunlight. Fig

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 CO 2 is released from the organic acids.

Fig

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 Plants also store excess sugar by synthesizing _________. Some is stored as starch in chloroplasts or in storage cells in roots, tubers, seeds, and fruits.