Exam 3

Question 1

what is membrane potential?

Answer 1

the difference in electrical potential between the inside and outside of a cell (mV)

Question 2

what are the main 2 contributing factors to the establishment of membrane potential?

Answer 2

• proton transport (proton pumps)
• different ions have different diffusion rates

Question 3

passive transport occurs along a ____

Answer 3

gradient

Question 4

active transport requires ____

Answer 4

energy

Question 5

short distance transport mechanisms

Answer 5

plasmodesmata (diffusion)

Question 6

long distance transport mechanisms

Answer 6

• xylem and phloem (pressure-driven bulk flow of solutes)
• apoplastic space (diffusion)

Question 7

what are the major solutes?

Answer 7

mineral nutrients, carbs, dissolved gases, phytohormones, amino acids

Question 8

loss of ATP causes a ______ in membrane potential

Answer 8

drop

Question 9

2 forms of active transport

Answer 9

primary and secondary

Question 10

primary active transport

Answer 10

ATP hydrolysis generates energy, and that energy is used directly for ion/solute transport

Question 11

secondary active transport

Answer 11

carrier proteins take advantage of the proton gradient and couple solute movement with the movement of protons into the cell

Question 12

symport proteins

Answer 12

protons moving along their electrochemical gradient are coupled with solutes so the solutes can move into the cell against their gradient

Question 13

antiport proteins

Answer 13

when a proton moves into the cell, the solute moves out of the cell, against its gradient

Question 14

Light reactions

Answer 14

absorption of light, evolution of CO2, electron transfer, ATP and NADPH synthesis

Question 15

where do the light rxns occur?

Answer 15

thylakoids

Question 16

carbon reactions

Answer 16

utilization of NADPH and ATP, CO2 fixation, generate triose phosphates

Question 17

where do carbon rxns occur?

Answer 17

stroma

Question 18

what are the roles of accessory pigments in photosynthesis?

Answer 18

• they help absorb different wavelengths of light and funnel it down towards chlorophyll
• they help deal with excess light by releasing it as heat or reflecting it

Question 19

what are the 3 fates of light incident on a leaf?

Answer 19

absorption, reflection, transmission

Question 20

what are the fates of light absorbed by a pigment?

Answer 20

photochemistry, dissipates as heat, fluorescnce, resonance energy transfer

Question 21

photochemistry

Answer 21

the pigment molecule gets excited, donates an electron to an electron acceptor, starts the electron transport chain

Question 22

resonance energy transfer

Answer 22

energy gets transferred from one pigment molecule to the neighboring pigment, losing some energy each time

Question 23

Where does oxygen evolution occur?

Answer 23

right before photosystem II, it releases O2, H+, and an electron that gets used in the ETC

Question 24

what is the primary electron donor in linear electron transfer?

Answer 24

water

Question 25

what is the primary electron acceptor in linear electron transfer?

Answer 25

NADP+

Question 26

cyclic photo-phosphorylation

Answer 26

in photosystem 1, an electron gets transferred to ferrodoxin, then to the cytochrome complex, and eventually ATP is generated and the electron is cycled back into photosystem 1

Question 27

xanthophyll cycle

Answer 27

xanthophylls (type of carotenoid) can be interconverted depending on light levels (usually on a diurnal cycle) to reduce damage due to excess light

Question 28

violaxanthin

Answer 28

present during low light conditions

Question 29

zeaxanthin

Answer 29

present at high light levels

Question 30

adaptations to excess light

Answer 30

- increase carotenoids (dissipate as heat) - increase anthocyanins (filter light) - reflection - leaf bending (avoidance) - reorientation of plastids

Question 31

carboxylation

Answer 31

rubisco catalyzes a reaction between CO2 and RuBP to form 3PGA

Question 32

reduction

Answer 32

3PGA undergos reactions using ATP and NADPH to make triose phosphates

Question 33

regeneration

Answer 33

triose phophates react with ATP to create RuBP

Question 34

What are the 3 phases of C reactions?

Answer 34

carboxylation, reduction, regeneration

Question 35

Oxygenation

Answer 35

rubisco binds to O2 instead of CO2, resulting in excess 2-PG, which cannot be used in photosynthesis

Question 36

C4 metabolism

Answer 36

spatial separation of carbon fixation, reduces oxygenation and photorespiration

Question 37

CAM metabolism

Answer 37

- temporal separation of C-fixation - stomata only open at night, carbon rxns occur and malic acid accumulates in vacuoles - malic acid is used for light rxns during the day - CO2 gets trapped in the plastid

Question 38

where is starch generated?

Answer 38

chloroplast

Question 39

where is sucrose generated?

Answer 39

cytoplasm