UNIT 7 PHOTOSYNTHESIS

Question 1

Primary producers on earth

Answer 1

photo autotroph

Question 2

photosynthesis

Answer 2

converts the energy from sunlight into chemical energy and use it to assemble simple inorganic raw material into complex organic molecules.

Question 3

2 parts of photosynthesis

Answer 3

the light-dependant reaction and the Calvin cycle

Question 4

light dependant reaction

Answer 4

capture light energy by pigment molecules and utilize this energy to synthesize NADPH and ATP.

Question 5

Calvin cycle

Answer 5

CO2 fixation. The electrons carried by NADPH and ATP are used to convert co2 from inorganic to organic form.

Question 6

product of the Calvin cycle

Answer 6

it takes 3 turns of the cycle to produce one extra G3P that the cell can use.

Question 7

Where does photosynthesis take place?

Answer 7

chloroplast

Question 8

3 fates for the electron possessed by a pigment molecule

Answer 8

• electron returns to it’s ground state. releasing heat to bioluminescence
• the electron returns to it’s ground state and the energy released is transferred to a neighbour molecule.
• the excited electron is accepted by an electron receptor

Question 9

Inductive resonance

Answer 9

when the electron returns to is ground state and the energy released is transferred to a molecule close by.

Question 10

fluorescence

Answer 10

emission of light of a longer wavelength than the absorbed light.

Question 11

chlorophyll

Answer 11

major photosynthetic pigment. Types A and B are most common.

Question 12

What are accessory pigments?

Answer 12

carotenoids and chlorophyll b

Question 13

What does accessory pigments do?

Answer 13

After light absorption they donate excitation e energy by inductive resonance of chlorophyll a.

Question 14

Action spectrum

Answer 14

Plot of the effectiveness of light of particular wavelength in driving photosynthesis. Show the spectrum of light that is most effective for photosynthesis.

Question 15

Each photosystems is composed of what?

Answer 15

Large antenna complex of pigment proteins that surrounds a central reaction centre.

Question 16

What is in the reaction centre in photosystems?

Answer 16

Small number of proteins that binds a pair of chlorophyll a as well as the primary electron receptor.

Question 17

PSI

Answer 17

P700

Question 18

PSII

Answer 18

P680

Question 19

Photosystem works?

Answer 19

Once excite p680* can be oxidized to P680+ by the primary electron receptor pheophytin.

Question 20

Water-splitting complex

Answer 20

The reformation of p680 into p680+ is facilitated by this enzyme subunit.

Question 21

Linear electron transport

Answer 21

P680 oxidize to P680+, the electron is transferred from the primary acceptor to plastoquinone which migrates through the lipid bilayer and links PSII and the cytochrome complex. From there, the electron pass to plastocyanin which links cytochrome complex and PS1. P700 is oxidized and reduced by the electron donation from plastocyanin, the electrons from P700 is then passed to ferrédoxine which transfer electrons to NADP+ which is reduced to NADPH.

Question 22

What is used to synthesize ATP by chemiosmosis?

Answer 22

Proton-motive force

Question 23

How many photons of light needs to be absorbed to make 4 electrons?

Answer 23

8, 4 per photosystem

Question 24

Cyclic electron transport

Answer 24

When PSI functions independently from PSII

Question 25

Difference between linear electron transport and cyclic electron transport?

Answer 25

Reduce ferrédoxine donates electrons back to the plastoquinone pool instead of giving it to the NADP+ reductase complex. This allows plastoqunone to move protons across the membrane without the need for PSII so ATP is produced but not NADPH.

Question 26

Why is the cyclic electron transport so important?

Answer 26

Because the Calvin cycle needs more ATP then NADPH and once we’ve got enough NADPH from the light dependant reaction, ATP can be produced in the cyclic electron transport without energy loss.

Question 27

Calvin cycle

Answer 27

11 reactions that use NADPH to reduce CO2into sugar, requires energy from ATP

Question 28

3 phases of the Calvin cycle

Answer 28

• Fixation
• reduction
• regeneration

Question 29

Fixation phase of the Calvin cycle

Answer 29

incorporation of a carbon atom from CO2 into RUBP to produce 2 3-phosphoglycerate.

Question 30

Reduction phase of the Calvin cycle

Answer 30

Each two 3-phosphoglycerate gets a phosphate from the hydrolysis of ATP which produces 3-biphosphoglycerate which is reduced, producing G3P

Question 31

Regeneration phase of the Calvin cycle

Answer 31

Each Calvin cycle turn makes 2 G3P (6atoms) 5 of these atoms makes RuBP which is needed to start the cycle again. So it takes 3 turns to produce one extra G3P.

Question 32

What is needed to synthesize the G3P from the Calvin cycle?

Answer 32

9 ATP and 6 NADH.

Question 33

G3P

Answer 33

3-carbon sugar, base of more complex carbs (glucose)

Question 34

Rubisco

Answer 34

Enzyme that catalyses the first reaction of the Calvin cycle. most abundant enzyme on earth.

Question 35

Photorespiration

Answer 35

Because rubisco is inefficient at fixing CO2 because it catalyzes O2 into RuBP, making a toxic molecule while loosing a carbon and using ATP.

Question 36

C4

Answer 36

CO2 combines with PEP producing oxaloacetate, then reduced to malate. It gets to the Calvin cycle site and get oxidized to pyruvate, releasing co2. That pyruvate is then converted back to PEP in a ATP consuming reaction. it prevents photorespiration by a high rate of CO2 at rubisco site and low 02.

Question 37

CAM plants

Answer 37

Run Calvin cycle and C4 at different times. At night they allow O2 in and is fixed to oxaloacetate, then converted to malate which is store till day. Daytime, malate is transported and release CO2 by breaking it down, it enters the Calvin cycle. It maintains a high co2 at rubisco site and avoir photorespiration.

Question 38

Where will the light dependant reaction and the Calvin cycle take place in eukaryotes?

Answer 38

Chloroplast

Question 39

Thylakoid

Answer 39

Closed flat sac

Question 40

PSI produces

Answer 40

NADPH

Question 41

Absorption spectrum

Answer 41

The light that is absorbed (blue, red, green)