ch 8

Question 1

during photosynthesis, the ultimate electron donor is __.

Answer 1

water

Question 2

The oxidation of water is linked with the reduction of carbon dioxide through a series of redox reactions making up the __.

Answer 2

photosynthetic electron transport chain

Question 3

Photosynthesis is a __ reaction. During photosynthesis, CO2 molecules are reduced to form higher-energy __ molecules

Answer 3

redox; carbohydrate

Question 4

Photosynthesis begins with the absorption of light by protein-pigment complexes known as __

Answer 4

photosystems

Question 5

photosystems:

Answer 5

use absorbed light energy to drive redox reactions and thereby set the photosynthetic electron transport chain in motion. movement synthesizes ATP and NADPH

Question 6

__ are the energy sources needed to synthesize carbohydrates from CO2 in the __.

Answer 6

ATP and NADPH; Calvin cycle

Question 7

In the ocean, photosynthesis occurs in the surface layer about 100 m deep, called the __

Answer 7

photic zone

Question 8

The __ proposes that the ancestor of the chloroplast was a free-living cyanobacterium that was engulfed by a eukaryotic cell.

Answer 8

endosymbiotic hypothesis

Question 9

filling much of the center of the chloroplast is a third, highly folded membrane known as the __.

Answer 9

thylakoid membrane

Question 10

Thylakoid membranes form structures that resemble flattened sacs, which are grouped into stacks called __.

Answer 10

grana

Question 11

Within the grana is the __, and the area outside is the __.

Answer 11

lumen; stroma

Question 12

Calvin Cycle step 1: carboxylation:

Answer 12

CO2 absorbed from the air is added to a 5-carbon molecule, ribulose-1, 5-bisphosphate (RuBP). reaction is catalyzed by rubisco (very slow enzyme). The 6-carbon molecule formed is broken down into two 3-carbon molecules of 3-phosphoglycerate (3-PGA)

Question 13

__ is the reducing agent in the Calvin Cycle.

Answer 13

NADPH

> transfers the energy and electrons that allow carbohydrates to be synthesized from CO2

Question 14

In the Calvin Cycle, the reduction of 3-PGA involves 2 steps:

Answer 14

1) ATP is used to phosphorylate 3-PGA

2) NADPH transfers two high-energy electrons to the phosphorylated compound

Question 15

Calvin Cycle step 2: reduction:

Answer 15

For every six triose phosphate molecules that are produced, only one can be withdrawn from the Calvin cycle because ribulose-1,5-bisphosphate needs to be regenerated using the other triose phosphates

Question 16

Calvin Cycle step 3: regeneration:

Answer 16

The 5-carbon molecule needed for carboxylation is regenerated. lots of reshuffling is required to produce three 5-carbon RuBP molecules from the five remaining 3-carbon triose phosphate molecules.

Question 17

Calvin cycle regeneration: __ and __ are needed for each molecule of CO2 incorporated by rubisco.

Answer 17

Three NADPH; three ATP

Question 18

Excess carbohydrates are converted to __ and stored

Answer 18

starch

Question 19

Light is a type of __

Answer 19

electromagnetic radiation

Question 20

The wavelengths of visible light are from __

Answer 20

400−700 nm

Question 21

__ are molecules that absorb some wavelengths of visible light. __ look colored because they reflect light enriched in the wavelengths that they do not absorb.

Answer 21

pigments

Question 22

Chlorophyll:

Answer 22

photosynthetic pigment, appears green. it has a large, light-absorbing head containing magnesium at its center and a long hydrocarbon tail that allows the pigment to be anchored in the lipid membrane

Question 23

carotenoids:

Answer 23

orange/yellow
found in the thylakoid membrane, are able to absorb light from regions of the visible spectrum that are poorly absorbed by chlorophyll.

Question 24

Absorption of __ by a chlorophyll molecule results in one of its electrons being elevated to a higher energy state

Answer 24

visible light

Question 25

For isolated chlorophyll in the lab, most of the light energy absorbed by the electron is rapidly released as __ and some is reemitted as __.

Answer 25

heat; fluorescent light

Question 26

chlorophyll in a photosystem absorbs light and __ the energy to another chlorophyll molecule, which then transfers the energy to another. The energy is passed from chlorophyll to chlorophyll until it reaches a specially configured pair of chlorophyll molecules known as the __

Answer 26

transfers; reaction center

Question 27

The chlorophylls in the __ act as __, transferring absorbed energy from one to the other until it reaches a reaction center

Answer 27

thylakoid membrane; antenna

Question 28

__ systems are necessary to provide enough energy to pull electrons from water and then use them to reduce NADP+.

Answer 28

2

Question 29

Photosystem II:

Answer 29

supplies electrons to the beginning of the electron transport chain. When photosystem II loses an electron, it is able to pull another electron from water.

Question 30

Photosystem I:

Answer 30

energizes the electrons with a second input of light energy, so they have enough energy to reduce NADP+.

Question 31

Electrons pass between photosystem II and I through the

Answer 31

cytochrome b6f complex

Question 32

Plastoquinone Pq vs plastocyanin Pc

Answer 32

Plastoquinone Pq carries electrons from photosystem II to the cytochrome b6f complex, while plastocyanin Pc carries electrons from the cytochrome b6f complex to photosystem I by diffusing through the thylakoid lumen

Question 33

How do protons accumulate in the thylakoid lumen?

Answer 33

1) The oxidation of water releases protons and O2 into the lumen
2) the cytochrome b6f complex functions as a proton pump. As electrons transit through the complex, some of the energy that is released by each redox reaction is used to drive protons from the stroma side of the thylakoid membrane to the lumen

Question 34

cyclic electron transport:

Answer 34

protects the cell from high energy electrons- electrons are shunted into an alternate pathway that increases the production of ATP while decreasing the production of NADPH. Electrons from photosystem I are redirected from ferredoxin back into the electron transport chain

Question 35

antioxidant detoxification:

Answer 35

Antioxidants such as ascorbate, beta-carotene, and other antioxidants are able to neutralize reactive oxygen species.

Question 36

Xanthophyll:

Answer 36

yellow-orange pigments that slow the formation of reactive oxygen by reducing excess light energy; these pigments accept absorbed light energy directly from chlorophyll and then convert this energy to heat

Question 37

__ occurs when __ adds O2 instead of CO2 to RuBP, resulting in one molecule with three carbon atoms (3-PGA) and one molecule with only two carbon atoms
(2-phophoglycolate)

Answer 37

Photorespiration; rubisco

Question 38

__ is theoretically around 4% of incoming solar energy, but actual yields are closer to 1% to 2%

Answer 38

Maximum photosynthetic efficiency