Chapter 13

Question 1

________ moves protons from Photosystem II to photosystem I. Note Photosystem I is at a high energy state than photosystem II

Answer 1

proton motive force

Question 2

moelcular structures and complexes that are receptive to light? These are the things that absorb light and they go to a excited state and they emit a color and go back to a ground state? ( this is the color you see

Answer 2

chromophore

Question 3

what has pigment molecules that absorbs light?

Answer 3

photoreceptor molecules

Question 4

resonance energy transfer

Answer 4

excitation energy is transferred to a neighboring molecule via resonance

Question 5

Electron transfer result in ____________–

Answer 5

photoinduced charge separation

Question 6

_______________ is the primary light acceptor in most photosynthetic systems

Answer 6

chlorophyll

chlorophyll is part of the special pair in the reaction center that undergoes charge separation

Question 7

chlorophyll is a heterocyclic ring derived from ______________ with a ________ in the middle

Answer 7

pyrrole

Mg

Question 8

Which has a higher oxidation state? chlorophylls alpha or beta

Answer 8

chlorophyll beta has a higher excitation state

Question 9

Antenae pigments are:

Answer 9

light-harvesting complexes that enhance the efficiency of photons.

Forex. chlorophyll alpha, chlorophyll beta, lutein, beta carotene

Question 10

antenna chlorophylls, carotenoids and other accessory pigments aborb light as energy and transfer it between molecules to the _______________

Answer 10

reaction center

The reaction center is where photochemical reaction occurs to convert the energy of a photon into a separation of charge, initiating electrong flow

Question 11

what are the two photosystems that generate a proton gradient and NADPH? give brief description of roles

Answer 11

PS II- replenishes electrongs, proton gradient for ATP synthesis

PSI- generates reducing power

Question 12

Photosystem II (680) is composed of what dimers

Answer 12

This special pair is called D1 and D2

Question 13

Photosystem II and oxygen generation?

Answer 13

When energy is transferred to P680 in PSII, the newly energized electron is ejected and donated to pheophytin

The oxygen-evolving complex is responsible for transfer of electrons from water to oxidized P680

P680* is a strong oxidant that extracts electrons from water to maintain redox balance while generating O2.

This reaction, the photolysis of water, occurs at the manganese complex of photosystem II.

The photolysis of water is the source of O2 for all of life.

Question 14

the __________________ is the source of all O2 for all life

Answer 14

photolysis of water

Question 15

photosystem I uses light energy to generate reduced ferredoxin, a power reductant

Answer 15

1. Reaction center
2. electron transport chain
3. biosynthetic reducing power

Question 16

Photosystem I and NADPH Synthesis

Answer 16

Absorption of a photon by P700 leads to the release of an electron that is passed through a series of electron carriers

The first electron carrier is chlorophyll a and the last is ferredoxin

Question 17

____________ transports electrons from PS1 to reductase

Answer 17

ferredoxin

Question 18

• Ferredoxin donates its electron to ferredoxin-NADP oxidoreductase
• to produce NADPH, two electrons are needed; this is the ____________ pathway

Answer 18

noncyclic electron transport pathway

-The abosorptions of eight photons yields an ATP/ NADPH ratio 3:2

Question 19

2 Hydrogens enter from the __________ and 4 hydrogens are emitted into the ____________ to make a proton gradient

Answer 19

stroma

thylakoid lumen

Question 20

Photosystem I produces a powerful
reductant, whereas photosystem II produces a powerful
oxidant. Identify the reductant and oxidant and describe
their roles.

Answer 20

Photosystem I generates ferredoxin, which reduces NADP1 to NADPH, a biosynthetic reducing power.

Photosystem II activates
the manganese complex, an oxidant capable of oxidizing water, generating electrons for photosynthesis, and generating protons to form a proton gradient and to reduce NADP1 and O2.

Question 21

____________ drives ATP synthesis

Answer 21

proton gradient

Question 22

cyclic electron flow, what does it make? and what it not make?

Answer 22

no NADPH or O2 is generated, it make ATP instead

Question 23

More NADH is made if there are multiple folds (there is more photosystem II and cytochrome bf), while equal amounts of ATP can be made just outside the membrane

Answer 23

General (went with a photo)

Question 24

in non cyclic _______ photons are required to yield two molecules of NADPH and ___________ molecules of ATP

Answer 24

eight photons

three ATP

Question 25

in cyclic photophosphorylation, _____ photons yield ____ ATP but no NADPH

Answer 25

two photons one ATP

Question 26

the calvin cycle traps CO2 gas as ______________, a precursor to hexose sugars

Answer 26

phosphorglycerate

Question 27

What are the three stages of the Calvin Cycle?

Answer 27

1. Fixation of CO2 by ribulose 1,5-bisphosphate to form two molecules of 3-phosphoglycerate 2. The reduction of 3-phosphoglycerate to hexose sugars 3. The regeneration of ribulose 1,5-bisphosphate

Question 28

The fixation of CO2, the rate LIMITING STEP in hexose synthesis, is catalyzed by ____________

Answer 28

rubisco

Question 29

Ribulose Can work with what enzymes?

Answer 29

phosphopentose isomerase phosphopentose epimerase phosphoribulose kinase

Question 30

___________ molecules of ATP and ___________ molecules of NADPH are required for the incorporation of each molecule of CO2 into hexosse

Answer 30

three molecules of ATP two molecules of NADPH

Question 31

what are the two fates of the fix carbons from photsynthesis?

Answer 31

Starch, which is synthesized and stored in the chloroplast. 2. Sucrose, which is synthesized in the cytoplasm from 3-phosphoglycerate. Sucrose is the transport form of carbohydrates in many plants.

Question 32

the synthesis of sucrose uses what enzyme

Answer 32

sucrose 6 phosphate synthase

Question 33

why is the calvin cycle crucial to the functioning of all life forms?

Answer 33

The Calvin cycle is the primary means by which gaseous CO₂ is converted into organic matter (biomolecules) All carbon atoms in your body have passed thru rubisco and the Calvin cycle at some point

Question 34

Rubisco increases with?

Answer 34

light exposure alkaline pH/Mg+2

Question 35

_______________ plays a key role in regulating the calvin cycle

Answer 35

thioredoxin

Question 36

Photosystem I generates reduced ferredoxin and NADPH, both of which regulate enzymes of the Calvin cycle. Ferredoxin-thioredoxin reductase activates key enzymes by reducing _____________.

Answer 36

disulfide bonds

Question 37

Enzyme activation/deactivation by thioredoxin reduced ______ alters activity of several Calvin cycle enzymes-both positively and negatively

Answer 37

thioredoxin

Question 38

what affects photosynthesis?

Answer 38

PH, MG+2, ferredoxin-thioredoxin system, phytochrome

Question 39

plants that produce glycerate-3-phosphate as the first stable product of photsynthesis are called ____________--

Answer 39

C3 plants

Question 40

Photorespiration – instead of fixing carbon, fixes oxygen In hot _______, Rubisco’s affinity for O2 increases Plants need to conserve water, so plants close stomata, so CO2 cannot diffuse in...and O2 can’t diffuse out...O2:CO2 increases

Answer 40

conditions

Question 41

C4 metabolism—

Answer 41

Sugar cane and maize (corn) can thrive under drought and high-temperature conditions

Question 42

Crassulacean Acid Metabolism (CAM)

Answer 42

Mechanism to conserve water (dessert plants) | Open stomata only at night

Question 43

photorespiration

Answer 43

Light-dependent process where oxygen is consumed and CO2 is produced Multistep process initiated by RIBULOSE BISPHOSPHATE CARBOXYLASE

Question 44

rubico can react with O2 instead of CO2 to generate ____________ and __________-

Answer 44

phophoglycerate and phosphoglycolate

Question 45

Because O2 is consumed and CO2 is generated, the process is called ______________

Answer 45

photorespiration

Question 46

why does photorespiration occur?

Answer 46

occurs when the CO2 levels inside a leaf become low. This happens on hot dry days when a plant is forced to close its stomata to prevent excess water loss.

Question 47

what enzyme is used in C4 metabolism?

Answer 47

phosphoenolpyruvate (it has a higher affinty for Co2) Oxaloacetate is reduced to malate, which then diffuses into the bundle sheath cells

Question 48

What are athe best regulators of photsynthesis?

Answer 48

1. Ph-During light reaction, protons are pumped out of the stroma, increasing pH 2. Mg2+—Light increases the stromal concentration of Mg2+, which is required for activity of some enzymes 3. The ferrodoxin-thioredoxin system—Thioredoxin (small protein) transfers electrons from ferredoxin to several enzymes Alters the activity of these enzymes (e.g., NADP+-glyceraldehyde-3-phosphate dehydrogenase among others) 4. Phytochrome—120-kD protein that possesses a red-light sensitive chromophore Activation triggers several transduction pathways, activating hundreds of plant responses to light (e.g. seed germination)

Question 49

water serves as a source of ____________ when electrons are transferred from photosystem II to photosytem I to NADP+. When H2O gives up its electrons, the oxygen in H2O is oxidized to O2

Answer 49

source of electrons

Question 50

the __________ shows where electrons go during photosynthesis

Answer 50

z scheme

Question 51

what is the path of electrons through the photosytem in the presence of light?

Answer 51

H20 --> PSII -->plastoquinone -->cytochrome bf complex --> plastocyanin --> photosystem I -->ferredoxin --> ferredoxin-NADP oxidoreductase -->NADP

Question 52

what is the function of photosystem II?

Answer 52

is to oxidize water molecules and donate energized electrons to electron carriers which eventually reduce photosystem I

Question 53

Give locations of the following: PQ cyt bf PC FNR

Answer 53

PQ in membrane cyt bf in membrane PC in lumen FNR in stroma

Question 54

______electron transport pathway involves Ferredoxin-->FNR.

Answer 54

noncyclic FNR uses two electrons to reduce NADP to NADPH

Question 55

in _________ electron transport pathwayFerredoxin-->PQ

Answer 55

cyclic an extra H is made to make an additional ATP

Question 56

_________________ is the light-driven synthesis of ATP from ADP + P

Answer 56

photophosphorylation

Question 57

what are the phases of the calvin cycle?

Answer 57

1. carbon fixation- uses rubisco, requires ATP 2. reduction of glycerate 3- phosphate- by NADPH to form glyceraldehyde-3-phosphate 3. regeneration of ribulose-1-5- bisphosphate= of every six glyceraldehyde-2-phosphates formed, five are regenerated to form three molecules of ribulose-1,5,-bisphosphate

Question 58

Photosynthesis depends on _________,____________, and _________-

Answer 58

temperature, cellular CO2 concentration, and light

Question 59

light affects enzymes (rubisco) by indirect mechanism? which and desribe

Answer 59

1. PH 2. MG+2 3. Ferredoxin-thioredoxin system 4. phytochrome

Question 60

compare mesophyll cells and bundle sheath cells

Answer 60

mesophyll cells - in direct contact with air - lack rubisco - light reactions make ATP, NADPH bundle sheath cells - in contact with vascular tissue - have rubisco - calvin cycle reactions use CO2 released