Chapters 19 & 20 Photosynthesis And Calvin Cycle

Front 1

structure of chlorophyll a

Back 1

-substituted tetrapyrrole
-4 nitrogen atoms of pyrroles are coordinated to Mg2+ ion
-has reduced pyrrole ring
-has phytol--hydrophobic 20-C alcohol esterified to acid side chain
-effective photoreceptors because they contain networks of alternating single/dbl bonds (polyenes)

Front 2

wave length at which chlorophyll absorbs best

Back 2

465 and 665nm

Front 3

what does the electron transfer in the 2 photosystems accomplish?

Back 3

reduces NADPH and generates a proton gradient

Front 4

what do photosystem I and II do?

Back 4

-PS I absorbs wavelengths < 700nm and uses light derived high-energy electrons to create NADPH
-electrons needed for this come from PS II (2 water molecules)
-PS II absorbs wavelengths < 680
-molecule of O2 is generated

Front 5

how do electrons travel from PS I to PS II?

Back 5

through cytochrome bf--generates proton gradient across thylakoid membrane that drives formation of ATP

Front 6

similarities and differences of oxidative phosophorylation compared to photosynthesis

Back 6

same: reduction of O2 to H2O/oxidation of H2O to O2, proton gradient to drive ATP synthesis
different: O.P.= oxidation of NADH; Pho=reduction of NADP+

Front 7

calvin cycle

Back 7

"dark reaction"
synthesizes hexoses from CO2 and H2O in stroma

Front 8

3 stages of calvin cycle

Back 8

1) fixation of CO2 by ribulose 1,5-bp to form 2 molecules of 3-phosphoglycerate
2) reduction of 3-phosphoglycerate to form hexose sugars
3) regeneration of ribulose 1,5-bp so that more CO2 can be fixed

Front 9

rubisco

Back 9

ribulose 1,5-bisphosphate carboxylase/oxygenase
catalyzes first step of calvin cycle

Front 10

when/how many ATP/NADPH are used in the calvin cycle?

Back 10

1 ATP from ribulose 5-P to rib 1,5-bp
2 ATP from 3-phosphoglycerate to 1,3-BPG
2 NADPH from 1,3-BPD to glyceraldehyde 3-p

Front 11

list steps of the calvin cycle (each product)

Back 11

ribulose 5-phosphate
ribulose 1,5-bp
3-phosphoglycerate
1,3-BPG
glyceraldehyde 3-phosphate
fructose 6-phosphate

Front 12

purpose of pentose phosphate pathways

Back 12

generates NADPH for synthetic reductive reactions
generates sugars used in other pathways

Front 13

synthesis pathways requiring the PPP

Back 13

fatty acid biosynthesis
cholesterol biosynthesis
neurotransmitter biosynthesis
nucleotide biosynthesis

Front 14

detox pathways requiring PPP

Back 14

reduction of oxidized glutathione
cytochrome p450 monoxygenases

Front 15

tissues with highly active PPP

Back 15

adrenal gland, testes, ovaries--steroid synthesis
liver--fatty acid and cholesterol synthesis
adipose tissue, mammary gland--fatty acid synthesis
red blood cells--maintenance of reduced glutathion

Front 16

PPP reactions take place in...

Back 16

cytoplasm

Front 17

2 parts of PPP

Back 17

1) oxidative generation of NADPH--gluc 6-P is oxidized to ribose 5-P
gluc 6-P + 2NADP+ + H2O--->rib-5-P + 2NADPH + 2H+ +O2
2) interconversion of sugars (nonoxidative)

Front 18

steps of NADPH synthesis in PPP

Back 18

gluc 6-P ---> 6-phosphoglucono-delta-lactone--->6-phosphogluconate---->ribulose 5-P + CO2

Front 19

catalyzes gluc 6-P to 6-phosphoglucono-delta-lactone in PPP

Back 19

glucose 6-phosphate dehydrogenase

Front 20

catalyzes 6-phosphoglucono-delta-lactone to 6-phosphogluconate in PPP

Back 20

lactonase

Front 21

catalyzes 6-phosphogluconate to ribulose 5-P in PPP

Back 21

6-P gluconate dehydrogenase

Front 22

for each glucose 6-phosphate, how many NADPH and ribulose 5-P are made in the PPP?

Back 22

2 NADPH, 1 rib 5-P

Front 23

3 successive reaction in the PPP where sugar interconversion occurs

Back 23

C5 + C5 <---transketolase--->C3+C7
C3 + C7 <---transaldolase--->C6+C4
C4 + C45 <---transketolase--->C6+C3

Front 24

first reaction of sugar interconversion of PPP

Back 24

xylulose 5-P + ribose 5-P <----transketolase----> gluceraldehyde 3-P + sedoheptulose 7-P

Front 25

second reaction of sugar interconversion of PPP

Back 25

GAP + sedoheptulose 7-P <---transaldolase---> fructose 6-P + erythrose 4-P

Front 26

third reaction of sugar interconversion of PPP

Back 26

erythrose 4-P + xylulose 5-P <----transketolase----> fructose 6-P + GAP

Front 27

transketolase mechanism

Back 27

transket: TPP=prosthetic group; a group on enzyme acts like a carbanion in attacking carbonyl group, splitting substrate and forming a new C-C bond; charge on carbanion is stabilized by resonance; N of TPP acts as electron sink

Front 28

transaldolase mechanism

Back 28

transket: no prosthetic group--instead forms schiff base with substrate and N of schiff base acts as an electron sink; a group on enzyme acts like a carbanion in attacking carbonyl group, splitting substrate and forming a new C-C bond; charge on carbanion is stabilized by resonance

Front 29

regulation of PPP

Back 29

regulated by NADP+ at glucose 6-phosphate dehydrogenase step; high NADPH--->glycolysis or glycogen synthesis, high NADP+--->6-phosphoglucono-delta-lactone

Front 30

how does NADPH prevent oxidative damage to cells?

Back 30

reduces antioxidant glutathione so it can function

Front 31

glucose 6-phosphate dehydrogenase deficiency

Back 31

genetic disorder
insufficient NADPH production--fine without oxidative stress
favism--hemolytic anemia after engestion of fava beans (rich oxidants)
malaria requires glutathione and PPP products so may be trade-off

Front 32

what is acceptor of CO2?

Back 32

ribulose 1,5 bisphosphate

Front 33

step of CO2 fixation in C.C. requires what enzyme?

Back 33

rubisco (ribulose 1,5 bisphosphate carboxylase/oxygenase)

Front 34

regulation of PPP

Back 34

first step--regulated by NADP+/NADPH