Chapter 15 - Phototrophy

Question 1

Phototrophy

Answer 1

Light eating - process by which energy from sun is captured and converted into chemical energy - ATP

Question 2

Photoautotrophs

Answer 2

Used to describe organism that both convert sunlight into ATP and also use ATP to fix Co2 into organic compounds

Question 3

Photoheterotrophs

Answer 3

organisms that convert sunlight into ATP but utilize pre-made organic compounds in the environment

Question 4

Chlorophylls

Answer 4

Green in color (absorb red and blue, 675 nm and 430 nm). used by cyanobacteria, plants and algae.

Question 5

Bacteriochlolophylls

Answer 5

Absorb higher wavelengths (~870 nm) than chlorophylls, allowing different phototrophs to inhabit same environment

Question 6

carotenoid

Answer 6

absorbs blue light and shows as yellow, orange or red

Question 7

phycobiliproteins - phycoerythrin

Answer 7

red in color

Question 8

phycobiliproteins - phycocyanin

Answer 8

blue in color

Question 9

antennae

Answer 9

light-harvesting pigments which funnel the light to other molecules in reaction centers

Question 10

chlorosome

Answer 10

phototrophic pigments housed here

Question 11

reaction center

Answer 11

perform the conversion of light energy to ATP

Question 12

photophosphorylation 1

Answer 12

Photosystem absorbs light and funnels energy to a reaction center, specifically chlorophyll/bacteriochlorophyll molecules

Question 13

photophosphorylation 2

Answer 13

The chlorophyll/bacteriochlorophyll molecules become excited, changing to more negative reduction potential

Question 14

photophosphorylation 3

Answer 14

The electrons can then be passed through an electron transport chain of carriers, such as ferredoxin and cytochromes allowing for PMF.

Question 15

photophosphorylation 4

Answer 15

Protons are brought back across the plasma membrane through ATPase, generating ATP in the process

Question 16

cyclic photophosphorylation

Answer 16

electrons are returned to the special pair of chlorophyll/bacteriochlorophyll molecules - allows for process to be repeated over and over.

Question 17

non-cyclic photophosphorylation

Answer 17

electrons are diverted elsewhere, and then an external electron source must be used to replenish the system.

Question 18

Anoxygenic phototrophy

Answer 18

no oxygen is generated during process

Question 19

Purple Phototrophic Bacteria

Answer 19

Engage in anoxygeneic phototrophy. Single photosystem with bacteriochlorophyll, allowing them to use cyclic photophosphorylation. In presence of organic compounds, operate as photoheterotrophs.

Question 20

reverse electron flow

Answer 20

used by autotrophic purple bacteria, using the energy from the PMF to drive electrons up the electron tower.

Question 21

Green phototrophic bacteria

Answer 21

engage in anoxygenic phototrophy and utilize a single photosystem. They also use the same system to reduce power, periodically drawing electrons off for NAD+. Require external electron donor. Operate as photoautotrophs.

Question 22

Oxygenic Phototrophy

Answer 22

used by cyanobacteria containing chlorophyll a, with two distinct photosystems, each with a separate reaction center.

Question 23

What does oxygenic phototrophy allow for?

Answer 23

generation of both ATP and reducing power in one process

Question 24

Z Pathway 1

Answer 24

Light energy decreases reduction potential of chlorophyll a in photosystem II

Question 25

Z Pathway 2

Answer 25

Electrons are then passed through an electron transport chain, generating ATP via PMF

Question 26

Z Pathway 3

Answer 26

Electrons then passed to photosystem I (PSI) where they get hit by another photo of light, decreasing their reduction potential even more.

Question 27

Z Pathway 4

Answer 27

The electrons are then passed through a different ETC, eventually being passed off to NADP+ for formation of NADPH

Question 28

Rhodopsin-based Phototrophy

Answer 28

used by archaea - unusual - no use of chlorophyll or bacteriochlorophyll. Instead of bacteriorhodopsin. When this is absorbs light, it undergoes conformational change, pumping proton across cell membranes and development of PMF.

Question 29

bacteriohodoposin/archaeorhodopsin

Answer 29

a retinal molecule related to one found in vertebrate eyes