photosynthesis

Question 1

photosynthesis

Answer 1

provides metabolic energy, raw materials and oxygen
calculated to produce a lot of sugar per year.

Question 1

chloroplast

Answer 1

• surrounded by double membrane
• inside is called the stroma, which is the basal material
• complex set of membranes called thylakoid membranes

Question 2

thylaoid

Answer 2

comes in stacks, which are hollow, and have passages. These stacks are called granum….

Question 3

four places for reactions in chloroplast

Answer 3

1. stroma: soluble rxns
2. Inner thylakoid fluids: soluble rxns
3. Grana: membrane bound rxns
4. other membranes: membrane bound rxns

Question 4

chlorophyll a

Answer 4

• most common and abundant type
• in cyanobacteria, algae, plants
• main thing that harvests light
• found in all algae including cyanobacteria

Question 5

structure of chlorophyll a

Answer 5

• long hydrophobic chain (anchor)
• 4 cross linked nitrogen
• magnesium in center
• side groups
• porphyrin ring

Question 6

light absorbance spectrum of chlorphyll a

Answer 6

lots of absorbance at 430 and 662

Question 7

chlorphyll b structure

Answer 7

• only in green algae and plants
• similar in structure to chlorophyll a, with a CHO- group added

Question 8

chlorphyll b absorbance

Answer 8

absorb at 453 and 642

Question 9

chlorophyll c structure

Answer 9

• no tail
• not in green plants, found in diatoms, dinoflagellates, brown algae
• has porphyrin ring, no hydrophobic chain

Question 10

chlorophyll c absorbance

Answer 10

• blue light

Question 11

chlorophyll d

Answer 11

• in cyanobacteria and red algae, no terrestrial plants

Question 12

chlorophyll d absorbance

Answer 12

• infrared light strongly
• infrared can penetrate water

Question 13

carotenoids

Answer 13

• accessory pigments in light harvesting complexes
• antioxidants
• stabilize protein folding
• quench ROS
• thermally dissipate excess energy

Question 14

phycobilins

Answer 14

• water soluble
• cyanobacteria and red algae

Question 15

what happens when pigment absorb light:

Answer 15

electron boosted to high energy level (photoexcitation) can do one of three things:
1. fluorescence, can fall down to lower E level, gives off a light color
2. resonance electron transfer, energy can be transfered from one thing to another until it reaches chlorophyll a
3. high energy e- can be captured, and displaced

Question 16

reactions for photosynthesis

Answer 16

3 CO2 + 6 H2O to give C3H6O4 + 3 O2 + 3 H2O

Very little glucose is produced right away.

Question 17

light dependent rxns

Answer 17

aka energy transduction rxns, as light rxns may be misleading.
- produce ATP and NADPH
- will not occur without light

Question 18

light-independent rxns

Answer 18

aka carbon fixation rxns
- use ATP and NADPH to fix C and produce organic compounds

Question 19

light dependent rxns details

Answer 19

• highly complex, harness light energy
• many pigments, enzymes, proteins
• precise configuration is crucial
• take place on thylakoid membrane
• two photosystems, each with antenna, complex and rxn center

Question 20

photosystem 1 location

Answer 20

• on outer part of thylakoid stacks and the channels between grana
• exposed to stroma

Question 21

PS 1 structure of rxn center

Answer 21

boosts P700 to high energy , associated with Ao e- acceptor molecule, then passed along cytochrome chain from Ao to A1, then iron sulfur proteins, then ferredoxin to cytochrome b (transmembrane complex, spans thylakoid membrane) then finally, sends to plastocyanin

Question 22

PS 1 function: cyclic PP

Answer 22

• cyclic photophosphorylation going from high lvl P700 to low lvl P700… replace themselves.
• Cyt b fills thylakoid with protons to give a + charge. Proton gradient is used to make ATP

Question 23

PS1 function : NonCyclic PP

Answer 23

goes through a different pathway to make NADP into NADPH… which is 3x the E of ATP… no way back from here, so the cant happen unless there are e- to replace it.

Question 24

PS II location

Answer 24

- located within thylakoid membranes

Question 25

structure of PSII

Answer 25

- excited P680, accepted by pheophytin, passed to Qa then Qb then to cytochrome b (proton gradient) - takes in water and releases Hydrogens and electrons to replace the ones we have lost in the NC PP OF PS1.

Question 26

PSII NC PP

Answer 26

light strikes PS II c, boosts P680 e- to high lvl, captured by pheophytin and passed down ETC to Qa and Qb, at the same time water is splitting to replace e- and produce H+ and O2 is the waste product. e- are passed to PSI and boosted again as P700. Then passed through cytochromes to make NADPH. This is NC because it never cycles back.

Question 27

Why do plants have PS I

Answer 27

need both going for photosynthesis to be balanced

Question 28

C3 pathway

Answer 28

carbon fixation. Complex set of rxns; CALVIN CYCLE must cycle 6 times. begin with rubisco, combines with RuBP, makes 3PGA (C3 pathway)

Question 29

rubisco

Answer 29

abundant in plants. massive amounts in leaves. Captured CO2 in the leaf and combines with RuBP to make a 6 C molecule

Question 30

Reduction pathway

Answer 30

reduces PGA to GA3P, produces ADP and NADP from NADPH and ATP, and Pi also released

Question 31

glyceraldehyde production

Answer 31

GA3P is produced after GA3P

Question 32

Regeneration pathway

Answer 32

Ga3P to RuBP, and Pi + ADP produced

Question 33

photorespiration

Answer 33

Rubisco's AS which grabs CO2, can grab C and O which is a problem. Normally would make PGA, but can also go through oxygenase activity to produce phosphoglycolate which is useless.

Question 34

C4 pathway

Answer 34

- PEPCarboxylase in mesophyll cells - forms OA - OA to Malate - Malate moves to bundle sheath cell - Malate decarboxylated to Pyr, CO2 to Calvin (broken in bundle sheath cell) - Pyr transported back to mesophyll cell

Question 35

C4 anatomy

Answer 35

- mesophyll cells: well-developed grana (light-capturing) - bundle-sheath cells: little or mo grana, much starch - Kranz (wreath) anatomy

Question 36

C4 energetics

Answer 36

- C3 pathway: 3 atp c4: 5 atp

Question 37

Advantages of C4 pathway:

Answer 37

- PEP carboxylase binds to bicarbonate, not to O2 so no photorespiration in mesophyll (most important) - anatomy minimizes overall photorespiration and CO2 loss - more efficient at higher temperatures - conserves water (due to not having to open stomata much) - higher net rates - lower N requirements

Question 38

CAM pathway

Answer 38

- uses C3 + C4 , separated temporally - used by many arid plants: succulents, cactus, orchid, stonecrop, welwischia, quillwort, some ferns

Question 39

CAM pathway at night

Answer 39

- cooler, stomata open, CO2 enters mesophyll cells - PEP carboxylase fixes CO2 to produce OA - OA reduced to malate, stored in vacuole

Question 40

CAM pathway during day

Answer 40

- hot, stomata close to conserve water - malate decarboxylated, CO2 enters calvin cycle (rubisco)

Question 41

anatomy of CAM plants

Answer 41

- spongy mesophyll leaves -

Question 42

advantage of CAM

Answer 42

- strongly conserves water - photosynthetic capacity is limited during the day, slow growth