Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MCB 3010 > FINAL EXAM: CARBS > Flashcards

FINAL EXAM: CARBS Flashcards

1
Q

plants are versatile

A

they can:

use energy of sunlight to support biosynthesis

build organic compounds from CO2

move intermediates between cellular compartments

adapt to changing environments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

assimilation of CO2 by plants

A

animal cells: use 3C intermediates (pyruvate, lactate) for synthesis — must eat it

plant cells: make 3C intermediates for further synthesis

using Co2 to make intermediates = carbon assimilation aka carbon fixation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

3C intermediates for plants

A

make glyceraldehyde-3P (GA3P)

made from CO2, H2O, ATP, and NADPH from photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

plastids

A

organelles in plants and algae

enclosed by a double membrane

own small genome

can specialize

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

chloroplasts

A

photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

amyloplasts

A

starch storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

chromoplasts

A

pigment storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

elaioplats

A

lipid storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

carbon assimilation

A

occurs in the stroma of chloroplasts via Calvin cycle

once called dark reaction but runs under light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what does carbon assimilation require

A

ribulose 1,5-bisphosphate which is constantly regenerated using ATP energy and NADPH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

carbon assimilation produces

A

3-phosphoglycerate, then glyceraldehyde-3P (GA3P) in quillibrium with DHAP

triose phosphates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

CO2 is reduced in carbon assimilation

A

with oxidation of NADPH that was generated in the light reactions of photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

three stages of calvin cycle

A
  1. carbon assimilation
  2. 3-phosphoglycerate reduction
  3. regeneration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

carbon assimilation stage

A

3 ribulose 1,5-bisophosphate + 3CO2

6 3-phosphoglycerate

rubisco catalyzes

(6c divided in half)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

3-phosphoglycerate reduction stage

A

6 3-phosphoglycerates converted to 6 triose phosphates (reduction to DHAP and GA3P) using NADPH and ATP from photophosphorylation

5 triose phosphates go to regenerate ribulose 1,5-bisphosphate; 1 utilized for other pathways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

3-phosphoglycerate reduction is catalyzed by

A

phosphoglycerate kinase and glyceraldehyde 3P dehydrogenase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

regeneration stage

A

5 triose phosphates made to 3 ribulose 1,5-bisphosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

overall calvin cycle reaction

A

3CO2 + 6NADPH + 5H2O + 9ATP

glyceraldehyde-3P + 6NADP+ + 2H+ + 9ADP + 8Pi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

where can the glyceraldehyde 3P go from calvin cycle?

A

energy production via glycolysis, starch, or sugar synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

rubisco

A

catalyzes carbon assimilation

large Mg2+ containing enzyme

carboxylase and oxygenase functionality

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

carboxylase functionality in rubisco

A

adds Co2 to ribulose 1,5-bisphosphate

makes new CC bond

cleaves 6C intermediate into 2 3phosphoglycerates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

oxygenase functionality in rubisco

A

less useful in plants

reacts with O2 instead of CO2 in an inefficient side reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

rubisco reaction

A

ribulose 1,5-bisphosphate + H2O + CO2

2 molecules of 3phosphoglycerate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

rubisco exits in two major forms: form 1

A

plants, algae, cyanobacteria

8 large catalytic subunits (encoded by plastid genome) + 8 small subunits (encoded by nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

rubisco exists in two major forms: form II

A

photosynthetic bacteria only

2 catalytic subunits, resemble large plant subunits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

rubisco quality

A

inefficient

low turnover of 3/sec

50% of plant enzymes are rubisco

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

catalytic role of Mg2+ in rubisco’s carboxylase activity

A

Mg2+ is held by negatively charged side chains of Glu, Asp, and carbamoylated Lys

brings together the reactants in a correct orientation, stabilizes the negative charge that forms upon the nucleophilic attach of enediolate to CO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

carbamoylated Lys

A

negative CO2 binds to N on side chain of lysine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

rubisco is activated via covalent modification

A

highly regulated

inactive until Lys-201 is carbamoylated by CO2 (CO2 binds to R group nitrogen; allows binding of Mg2+ to the enzyme which is critical for catalytic activity)

rubisco activase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

rubisco activase

A

ribulose 1,5-bisP bound in active site blocks Lys-201 from being carbamoylated

rubisco activase changes rubisco conformation - causes ribulose-1,5-bisP to leave and exposes Lys-201

reaction requires ATP

triggered by light in some species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

rubisco can be inhibited by a nocturnal inhibitor

A

2-carboxyarabinitol 1-phosphate inhibits carbamoylated rubisco

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

2-carboxyarabinitol 1P

A

inhibits carbamoylated rubisco;

transition state analog of beta-keto acid intermediate

synthesized in the dark in some plants

  • binds to rubisco, doesn’t work in inappropriate times**
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

stage 2: 3-phosphoglycerate reduced to glyceraldehyde 3P reaction

A

6 3PG + 6ATP + 6NADPH + 6H+

6 GA3P + 6ADP + 6NADP+ + 6Pi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

3PG reduced to GA3P

A

requires NADPH and ATP from photosynthesis

similar to gluconeogensis but uses NADPH

enzymes: 3phosphoglycerate kinase; glyceraldehyde 3phosphate dehydrogenase

driven forward by high conc. of NADPH and ATP in chloroplast stroma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

enzymes for stage 2 calvin cycle

A

3PG kinase

GA3P dehydrogenase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

phosphoglycerate kinase

A

3PG + ATP

= 1,3bisphosphoglycerate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

glyceraldehyde-3P dehydrogenase

A

1,3-bisphosphoglycerate + NADPH

glyceraldehyde-3P

redox

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

fates of glyceraldehyde-3P

A

5 of 6 recycled to make ribulose 1,5-bisphosphate

remaining:
converted to starch in chloroplast for storage
converted to sucrose in cytosol for export
broken down in glycolysis in cytosol for energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

stage 3: regeneration of ribulose 1,5-bisphosphate reaction

A

3 GA3P + 2DHAP + 3ATP

3 ribulose 1,5,bisphosphate + 2Pi + 3ADP

5 three carbon sugars converted to 3 five carbon sugars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

stoichiometry and energy cost of CO2 assimilation

A

fixation of 3 CO2 molecules yields one GA3P

9 ATP and 6 NADPH are consumed

light reactions of photosynthesis produce ATP and NADPH at about this same ratio (3/2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

fates of Pi from ATP hydrolysis in stages 2 and 3

A

8 of 9 Pi: available to combine with ADP to regenerate ATP

9th Pi: incorporated into GA3P and could be moved to cytosol

  • requires that Pi be transferred from cytosol back into chloroplast
  • uses special Pi-triosephosphate antiporter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Pi-triose phosphate antiporter

A

needed for sucrose synthesis

sucrose made in cytosol (unlike starch in chloroplast stroma)
- used for transport to distant plant tisuses

inner membrane is impermeable to phosphorylated compounds

antiporter exchanges GA3P or DHAP for one Pi

  • sends triose phosphates into cytosol for sucrose synthesis
  • sends Pi back into the chloroplast
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

carbon assimilation is more effective when its light

A

photosynthesis of one molecule of GA3P (plus recycled ones) requires 24 photons of light

  • H+ go from stroma to thylakoid lumen
  • creates alkaline conditions in stroma

Mg2+ transport from thylakoid lumen to stroma

enzymes of assimilation more active in alkaline, high Mg2+ conditions of stroma during photophosphorylation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

plants oxidize water to ____ and reduce ____ to make _________

A

oxidize water to O2 and reduce CO2 to make carbohydrates

45
Q

plants carry out cellular respiration

A

O2 reduced to water

Substrates oxidized to CO2

46
Q

wasteful side reaction

A

catalyzed by rubisco
in chloroplasts

consumes O2 and yields CO2

photorespiration reaction is enhanced by light and is costly; does not yield energy

47
Q

oxygenase activity of rubisco

A

O2 competes with CO2 for active site

1/3 or 4 turnovers = O2 binds
worse in hot, dry climates where plants close their stomata to limit water loss

ribulose 1,5-bisphosphate bound by O2 and split to form 3PG and 2PG

48
Q

oxygenase activity: ribulose 1,5-bisphosphate bound by O2 and split

A

into 2PG and 3PG

2PG is metabolically useless
salvaging its carbons requires energy and reactions in several organelles
2 2PG are converted to serine + CO2

serine eventually salvaged to 3PG

49
Q

glycolate pathway

A 
2PG to glycolate, goes out of chloroplast to peroxisome
converted to glyoxylate
then glycine
goes to mitochondria
2 Glycine releases CO2 and NH3
becomes serine
serine goes to peroxisome
becomes hydroxypyruvate
then glycerate
goes to chloroplast
then 3PG
50
Q

most plants cannot avoid oxygen binding to rubisco

A

atmosphere is mostly O2
pure water has more O2
Km for oxygen is much higher

some plants, C4 and CAM have a bypass mechanism to avoid this side reaction

51
Q

C4 vs C3 plants

A

most crops: C3 — first step in calvin cycle is CO2 fixation to make 3C product, 3PG

C4: earlier step before rubisco — bypass assimilation step by fixing CO2 to make a 4C compound (oxaloacetate from PEP)
- hotter climates

52
Q

C4 plants

A

physically separate CO2 capture from rubisco reaction

53
Q

C4 plants physically separate CO2 capcture from the rubisco reaction

A

CO2 and PEP are used to make oxaloacetate (4C) using PEP carboxylase in mesopyll cells of leaf

oxaloacetate is converted to malate or aspartate

malate or aspartate pass into bundle-sheath cells and release CO2 during conversion to another molecule (malate to pyruvate or aspartate ot PEP)

54
Q

in bundle sheath cells

A

[CO2]»»[O2] and here is where rubisco is located

O2 can not replace CO2 in this system

C4

55
Q

why do C4 plants often outperform C3 plants in heat and drought?

A

C4 pathway has higher energy cost (2ATP) but as temperature increases (and affinity of rubisco for CO2 decreases), gain in efficiency outweighs energy cost

C4 plants sometimes do better in heat and drought than C3 plants do

56
Q

CAM plants separate CO2 trapping and carbon assimilation in TIME

A

another pathway to avoid rubisco reaction with oxygen

found in plants that grow at high temps, dry conditions; minimize loss of water vapor

57
Q

how do CAM plants separate CO2 trapping and carbon assimilation?

A

time

58
Q

how do Cr plants separate CO2 capture from rubisco reaction?

A

physically

59
Q

CAM plants open stomata only at night to allow entry of gases

A

at night: air is cooler, more moist; stomata open

  • CO2 absorbed at night is fixed to PEP to make oxaloacetate(4C) via PEP carboxylase
  • oxaloacetate is reduced to malate and stored in vacuoles

daytime: stomata close
- malate converted to pyruvate by NADP-linked malic enzyme
- CO2 released from malate and used by rubisco
- since stomata are closed, [O2] is low; rubisco only binds CO2

60
Q

excess triose phosphates are converted to

A

starch and sucrose

61
Q

starch in plants

A

made in chloroplasts for short-term storage

or made in amyloplasts of nonphotosynthetic tubers, seeds, roots for long term storage
- sucrose goes from cells capable of photosynthesis to these other parts of plant to provide monomers

starch provides bulk of energy storage for most plants

62
Q

sucrose in plants

A

made in cytosol for transport

63
Q

first thing made from triose phosphates to convert to starch/sucrose

A

glucose-1P

64
Q

glucose-1P made from triose phosphates to make starch/ sucrose

A

ALDOLASE: combines DHAP and GA3P to make fructose-1,6-bisP

FRUCTOSE-1,6-BISPHOSPHATASE: removes phosphate to make fructose-6P

PHOSPHOHEXOSE ISOMERASE: converts fructose-6P to glucose-6P

PHOSPHOGLUCOMUTASE: converts glucose-6P to glucose-1P

65
Q

aldolase

A

combines DHAP and GA3P to make fructose-1,6bisP

66
Q

fructose-1,6-bisophosphatase

A

removes phosphate to make fructose-6P

67
Q

phosphohexose isomerase

A

converts fructose-6P to glucose-6P

68
Q

phosphoglucomutase

A

converts glucose-6P to glucose-1P

69
Q

starch synthesis

A

ADP glucose = monomers

similar to glycogen synthesis

70
Q

ADP-glucose

A

reaction of glucose-1P with ATP

requires further breakdown of PPi

ADP-glucose pyrophosphoyrlase

71
Q

ADP-glucose pyrophosphorylase

A

makes ADP-glucose from glucose-1P with ATP

72
Q

amylose

A

straight chain polysaccharide

alpha1-4 bonds

catalyzed by starch synthase

73
Q

amylopectin

A

branched chain polysacc

alpha1-4 bonds by starch synthase

alpha1-6 branches by branching enzyme

74
Q

UDP-glucose

A

sucrose or cellulose synthesis

UDP-glucose pyrophosphorylase

75
Q

ADP-glucose

A

starch synthesis

ADP-glucose pyrophosphorylase

76
Q

starch synthesis is regulated at

A

ADP-glucose pyrophosphorylase

77
Q

activator of ADP-glucose pyrophosphorylase

A

3PG

produced during photosynthesis — precursor

78
Q

inhibitor of ADP-glucose pyrophosphorylase

A

Pi

Pi accumulates when condensation of ADP and Pi slows

so low ATP

(wants to use sugars in glycolysis to make ATP instead of storing them as starch)

79
Q

sucrose synthesis substrates

A

fructose-6P and UDP-glucose

80
Q

synthesis of fructose-6P and UDP-glucose

A

ALDOLASE: combines DHAP + GA3P to make fructose-1,6-bisP

FRUCTOSE-1,6-BISPHOSPHATASE: dephosphorylates fructose-1,6-bisP to form fructose-6P

PHOSPHOHEXOSE ISOMERASE/PHOSPHOGLUCOMUTASE: some fructose6P converted to glucose 6P and then to glucose 1P

UDP-GLUCOSE PYROPHOSPHORYLASE: glucose-1P and UTP to make UDP-glucose

81
Q

sucrose synthesis reaction 1

A

substrates: UDP glucose + fructose-6P

sucrose-6P made with alpha1-beta2 bond between glucose and fructose-6P

sucrose-6P synthase

82
Q

sucrose 6P synthase

A

makes sucrose-6P with alpha1-beta2 bonds between glucose and fructose-6P

83
Q

sucrose synthesis reaction 2

A

sucrose-6P dephosphorylated to make sucrose by sucrose-6Phosphatase

84
Q

sucrose-6phosphatase

A

dephosphorylates sucrose-6P

85
Q

sucrose synthesis needs to be synthesized in cytosol

A

triose phosphate precursors must be exported from chloroplasts using Pi-triose phosphate antiporter

86
Q

Regulation of sucrose synthesis

A

occurs at interconverstion of F1,6BisP to F6P

FBPase1
PP-PFK1

87
Q

forward enzyme of sucrose synthesis

A

fructose-1,6-bisphosphatase (FBPase-1)

88
Q

reverse enzyme of sucrose synthesis

A

PPi-dependent phosphofructokinase-1 (PP-PFK-1)

similar to glycolytic enzyme except using pyrophosphate instead of ATP as phosphate donor

89
Q

regulation of sucrose synthesis: dark

A

no photosynthesis, no triose phosphoates, no sucrose synthesis — but breakdown needed

FBPase1 inhibited (don’t make it)
PP-PFK-1 active (break down hexoes for energy)
90
Q

regulation of sucrose synthesis: in light

A

triose phosphates made, so sucrose synthesized

FBPase1 active (make sucrose_
PP-PFK1 inhibited (don’t break down hexoses)
91
Q

regulation of sucrose synthesis: sucrose-6P synthase regulation

A

activated by: glucose 6P (precursor to substrate)

inhibited by: Pi (not being transported into chloroplasts)

92
Q

plants in the light

A

triose phosphates made in chloroplasts; made into starch or sent to cytosol with Pi transported back in

cytosol: hexoses and then sucrose are synthesized; sucrose transported to non-photosynthetic cells

nonphotosynthetic cells: sucrose broken down to hexoses to make starch or to be oxidized using glycolysis/CAC (ATP from oxpho in mito)

mostly no need for long term storage because sun comes back

93
Q

plants in the dark

A

no triose phosphates made

starch broken down into glucose which can be used for energy by glycolysis/CAC

ATP by oxpho in mito

94
Q

synthesis of cellulose for cell walls

A

glucose monomers with beta1-4 linkages

allows H bonds within chain and between chains to make strong microfibrils

synthesized from intracellular precursors but fiber grows outside of plasma membrane

95
Q

monomer for cellulose synthesis

A

UDP-glucose

96
Q

UDP-glucose generated by

A

sucrose synthase

UDP-glucose pyrophosphorylase

97
Q

generating UDP-glucose: sucrose synthase

A

breaks down sucrose

sucrose + UDP = UDP-glucose + fructose

may be in complex with cellulose synthase
different enzyme than sucrose-6P synthase

98
Q

generating UDP-glucose: UDP-glucose pyrophosphorylase

A

synthesize UDP-glucose

glucose-1P + UTP = UDP-glucose + PPi

99
Q

cellulose synthase

A

makes chains of cellulose

involves primer

  • synthase complexes and forms rosettes within the plasma membrane
  • multiple chains of cellulose synthesized at each rosette; forms microfibrils that extend outside the membrane
  • 18 chains/microfibril
  • cellulose can have different lengths up to 15k glucose monomers
100
Q

plants convert lipids to carbs

A

plants store lipids and proteins in seeds for germination, growth

LIPASES: remove fatty acids from glycerol

  • glycerol modified to enter gluconeogenesis
  • FA broken down by beta-oxidation to acetyl-CoA

glyoxylate cycle, CAC, and gluconeogenesis: convert acetyl-CoA from fatty acids into hexoses
- fructose and glucose can be used to synthesize sucrose to move energy to other cells in the germinating plant

101
Q

glycerol from stored triacylglycerols in seeds to glucose

A

glycerol goes to DHAP and then to GA3P to enter gluconeogensis

must have both to make fructose-1,6-bisP bc pathways for both starch and sucrose

102
Q

glyoxylate cycle

A

plants, some invertebrates, some microorganisms
- in glyoxysomes of plants

uses: 2 acetyl-CoA in a cycle similar to CAC

103
Q

glyoxylate cycle: 2acetyl-COA

A

utilizes acetyl-CoA from FA catabolism

produces succinate which goes into CAC

uses some of CAC reactions but different isozymes

bypasses the decarboxylation steps with 2 enzymes

104
Q

2 enzymes that bypass the decarboxylation steps in glyoxylate cycle

A

isocitrate lyase

malate synthase

105
Q

isocitrate lyase

A

cleaves isocitrate to succinate and glyoxylate

106
Q

malate synthase

A

makes malate from glyoxylate and acetyl-CoA (2nd)

107
Q

glycoxylate cycle

A 
1st acetyl-CoA + oxaloacetate|| citrate synthase
=
aconitase
=
isocitrate || isocitrate lyase
=
succinate (goes to CAC) and glyoxylate
=
glycoxylate + 2nd acetyl-CoA || malate synthase
=
malate + NAD+ || malate dehydrogenase
=
oxaloacetate + NADH
108
Q

process in glyoxysome

A

FA beta oxidation
makes acetyl-CoA

acetyl coA + oxaloacetate
citrate
isocitrate = succinate and glyoxylate
glyoxylate + acetyl-CoA
malate
oxaloacetate
succinate into CAC
fumarate
malate
goes to cytosol
converted to oxaloacetate
PEP —> gluconeogenesis
hexose —> sucrose

MCB 3010 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions