photosynthesis

Question 1

who found that mass increase during plant growth doesn’t come from the soil?

Answer 1

Jan Baptista van Helmont

Question 2

who found that plants make oxygen?

Answer 2

joseph priestley

Question 3

what is photosynthesis?

Answer 3

process by which some cell can harvest energy from sunlight to produce energy rich organic compounds

Question 4

in which bacterial groups can anoxygenic photosynthesis be found?

Answer 4

purple sulphur bacteria
green sulphur bacteria
green non-sulfur bacteria
heliobacteria

Question 5

what becomes reduced in photosynthesis?

Answer 5

carbon dioxide becomes reduced into glucose

Question 6

what becomes oxidizes in photosynthesis?

Answer 6

water becomes oxidized into oxygen

Question 7

what am I:
-uses the energy from sunlight to create ATP and organic molecules
-contains their own circular DNA and ribosomes
-double plasma membrane

Answer 7

chloroplast

Question 8

where does the light dependent step occur?

Answer 8

in the thylakoid

Question 9

where does the light independent step occur?

Answer 9

in the stroma

Question 10

what are pigments?

Answer 10

-molecules that absorb light energy in the visible range
-required from the successful completion of photosynthesis in the chloroplast

Question 11

which pigment is the only one to directly convert light to chemical energy and contains a prophyrin ring?

Answer 11

chlorophyll a

Question 12

what is the main role of carotenoids and flavonoids?

Answer 12

-assist photosynthesis by capturing energy from wavelengths that are not efficiently absorbed by chlorophyl
-act as antioxidants to counter the production of free radicals generated during photosynthesis

Question 13

where are photosystems located?

Answer 13

-in the thylakoid membrane

Question 14

what is a photosystem made up of?

Answer 14

-antenna complex: pigments capture light energy and channel it to the reaction center
-reaction center: chlorophyll molecule loses an electron

Question 15

what are the roles of the antenna complex?

Answer 15

-capture and transfer the energy from the light to the reaction center
-proteins in the complex orient the pigments in an optimal direction for the absorption of light energy
-when light energy is captured, pigments transfer the energy directly to other pigments until only the energy is transferred to the reaction center
-after transfer, the excited electron in each molecule return to the low energy level it had before the photon was absorbed
-it is thus the energy, not the excited electrons, that pass from one pigment to the next

Question 16

what are the roles of the reaction center?

Answer 16

-special pair of chlorophyll-a acts as trap for photon energy passing an excited electron to acceptor precisely positioned as its neighbour
-excited electron itself is transferred, not just the energy

Question 17

what is the primary electron acceptor in the reaction center?

Answer 17

plastiquinone

Question 18

what happens after the chlorophyll donates its electron to the primary electron acceptor in the reaction center?

Answer 18

water passes a low-energy electron to the chlorophyll

Question 19

the energy of how many photons is required to complete the oxidation of two water molecules?

Answer 19

4

Question 20

what is the peak absorption of photosystem II?

Answer 20

680 nm

Question 21

what is the peak absorption of photosystem I?

Answer 21

700 nm

Question 22

how are PS II and PS I linked?

Answer 22

by the cytochrome complex

Question 23

what carries the electron in the first part of the electron transport chain to the cytochrome b6-f complex?

Answer 23

plastiquinone

Question 24

what has a proton pump that will use the energy from electrons to pump protons into the thylakoid lumen?

Answer 24

cytochrome b6-f complex

Question 25

which protein will transport the electrons to PS I?

Answer 25

plastocyanin

Question 26

In the reaction center of PS I, to which protein are the excited electrons donated to?

Answer 26

ferredoxin

Question 27

After having received the excited electrons, to what does ferredoxin donate it?

Answer 27

NADP+ creating NADPH

Question 28

where is the enzyme NADP reductase located?

Answer 28

stroma side of the thylakoid membrane

Question 29

what am I: -coenzyme -carries the energy captured from the light to the stroma where it will be used to generate high energy organic molecules (sugars)

Answer 29

NADPH

Question 30

How is ATP created from the H+ gradient?

Answer 30

-electron transport chain allows the pumping of H+ into the thylakoid lumen -ATP is generated with ATP synthase

Question 31

what is produced during the light dependent step of photosynthesis?

Answer 31

-NADPH -ATP

Question 32

where does the light-independent step occur?

Answer 32

stroma

Question 33

what are the 3 phases of the Calvin cycle?

Answer 33

1) carbon fixation 2) reduction 3) regeneration of RuBP

Question 34

describe what happens during carbon fixation

Answer 34

- a carbon atom from CO2 is added to RuBP by Rubisco (multienzyme complex) -resulting 6C molecule splits into 2 PGA

Question 35

describe what happens during reduction

Answer 35

-energy from ATP adds a phosphate to #C molecule -phosphate is replaced by H from NADPH -2 G3P molecules will combine to make glucose (not part of calvin cycle)

Question 36

what happens during the regeneration of RuBP

Answer 36

-10 molecules of G3P will be used to regenerate 6 RuBP -multistep process that requires 6 ATP

Question 37

What do the cells use to build a carbohydrate like glucose?

Answer 37

-carbon form CO2 -energy from ATP produced by the light dependent step -reduction potential of NADPH by light dependent step which provides a source of H+ and electrons needed to bind them to the carbon atoms

Question 38

how does the chloroplast make extra ATP?

Answer 38

cyclic phosphorylation

Question 39

describe how cyclic phosphorylation works

Answer 39

-light energy absorbed at PS I is used for ATP synthesis rather than NADPH synthesis -high-energy electrons generated are transferred by ferredoxin and plastoquinone to cyt-bf complex rather than NADP+ -cyt-bf complex uses the electrons to pump H+ from stroma to thylakoid lumen -electrons are returned to PS I by plastocyanin -H+ gradient is used to create ATp by ATP synthase

Question 40

what am I: -carboxylation and oxidation of RuBP are catalyzed at the same site on Rubisco, thus CO2 and O2 compete with each other -oxidation of RuBP occurs when O2 levels are high -amount of fixed carbon is lost

Answer 40

photorespiration

Question 41

via what component do plants regulate water and gases?

Answer 41

stomata

Question 42

why do plants close their stomata at high temperature, which limits the entrance of CO2 and the exit of O2?

Answer 42

to prevent water loss

Question 43

true or false: photorespiration is a problem at low temperatures

Answer 43

false

Question 44

what is the solution to photorespiration?

Answer 44

to separate the calvin cycle from the light dependent step

Question 45

what am I: -temperate plants that do not possess any mechanism to regulate photorespiration

Answer 45

C3

Question 46

what am I: -tropical plant -fixation of CO2 and the Calvin cycle occur in 2 different cells -e.g. corn, sugar cane, and grasses

Answer 46

C4

Question 47

in C4 plants, where is the carbon fixed by PEP carboxylase?

Answer 47

in the mesophyll cell

Question 48

does the C4 process require ATP to function?

Answer 48

yes

Question 49

in C4 plants, where does the Calvin cycle occur?

Answer 49

Bundle-sheath cell

Question 50

In C4 plants, each CO2 transported in the bundle-sheath cell costs the equivalent of...

Answer 50

2 ATP

Question 51

what am I: -type of tropical plant -fixation of CO2 and the Calvin cycle occur in the same cells, but at different times

Answer 51

CAM

Question 52

why does the fixation of CO2 into oxaloacetate by PEP carboxylase occur at night in CAM plants?

Answer 52

since the stomata are open due to the cooler temperature

Question 53

does CAM photosynthesis need ATP to occur?

Answer 53

yes