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.