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Plant Phys > Respiration and Lipid Metabolism - 11 > Flashcards

Respiration and Lipid Metabolism - 11 Flashcards

1
Q

Define aerobic respiration

A

a biological process which organic compounds are oxidized in a slow and controlled manner to make energy from carbohydrates. The released energy is stored in ATP to be used later.

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2
Q

Sucrose respiration is the reversal of what process

A

photosynthetic process
(instead uses sugar and water to make carbon dioxide and H+ and oxygen)

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3
Q

what are the 4 main processes of respiration

A
  1. glycolysis
  2. oxidative pentose phosphate pathway
  3. TCA cycle
  4. oxidative phosphorylation (ETC and ATP synthesis)
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4
Q

Glycolysis starts with _____ and splits it by what two pathways and explain each with their products

A

sucrose
1. Invertases = hydrolyzes sucrose in cell wall, vacuole and cytosol to split and produce 1 glucose and 1fructose. Which then creates 2 ATP by enzyme hexokinase turning into fructose-6-phosphate or glucose-6-phosphate.
2. sucrose synthase = combines sucrose with UDP to produce 1 fructose and 1 UDP-glucose in cytosol. UDP-glucose then converted to UTP and glucose-6-phosphate.

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5
Q

Explain metabolic redundancy

A

that invertases and sucrose synthatase pathways both exist with similar function and can replace each other without clear loss of function

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6
Q

After creates fructose-6-P and 2 glucose-6-P turns into ____ through what 3 catalytic reactions
then turns into triose phosphates

A

turns into fructose 1,6-bisphosphate
reactions:
1. ATP-dependent phosphofructokinase
2. fructose 1,6-bisphosphate phosphotase
both irreversible
3. PPi-dependent phosphofructokinase
reversible

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7
Q

Once the triose phosphate (glyceraldehyde 3-phosphate) is created, it is then converted to produce ____ by what enzyme
then what enzyme makes ATP

A

1,3-bisphosphoglycerate
3-phosphate dehydrogenase allows phosphorylation of G-3-P into 1,3-bi
phospoglycerate kinase

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8
Q

For every sucrose entering glycolysis pathway, how many ATP are generated

A

4

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9
Q

What happens in next 2 steps after it becomes 1,3-bisphosphoglycerate and what is produced

A

phosphate group is transferred, water molecule is removed to yield phosphoenolpyruvate (PEP)

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10
Q

What are the 2 alternative pathways for metabolizing PEP

A
  1. PEP carboxylase forms oxaloacetate, then reduced to form malate (and NADPH)
  2. pyruvate kinase produces pyruvate and yields ATP
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11
Q

What process occurs when molecular oxygen is unavailable

A

glycolysis can be main source of energy through fermentation to reduce pyruvate to regenerate NAD+ for glycolytic ATP production

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12
Q

glycolysis occurs in

A

cytosol!

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13
Q

Define gluconeogenesis

A

synthesis of sugars through the reversal of glycolysis, using the breakdown of lipids or proteins instead of carbohydrates. important for seed germination

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14
Q

What additional enzyme is in gluconeogenesis

A

fructose 1,6-bisphosphate phosphatase

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15
Q

Why is gluconeogenesis either reversible or irreversible

A

irreversible because it is catalyzed by ATP-dependent phosphofructokinase

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16
Q

Function of the oxidative pentose phosphate pathway (OPPP)

A

it oxidizes sugars just like glycolytic pathway, an alternative route

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17
Q

where does OPPP occur

A

cytosol and plastids

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18
Q

Explain first 2 reactions in OPPP

A

glucose-6-phosphate into ribulose 5-phosphate with the loss of 1 CO2 and generation of 2 NADPH

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19
Q

Explain remaining reactions of OPPP after it is in ribulose 5-phosphate form

A

converts into glycolytic intermediates of glyceraldehyde 3-phosphate and fructose-6-phosphate
can be further metabolized into pyruvate by glycolysis

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20
Q

For every 6 glucose 6-phosphate molecules entering OPPP, how many NADPH are formed and regenerated

A

12 formed
5 regenerated

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21
Q

What percentage of glucose breakdown does OPPP contribute

A

10-25%, rest from glycolysis

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22
Q

What are the 3 roles that OPPP plays in plant metabolism

A
  1. generates NADPH in cytosol
  2. generates NADPH in plastids (lipid biosynthesis and N assimilation)
  3. generates supply of substrates for biosynthetic processes (aromatic AAs, lignin, flavonoids)
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23
Q

Where does TCA cycle take place

A

mitochondrial matrix

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24
Q

Where does pyruvate need to move through in order to reach the TCA cycle

A

after glycolysis transported through inner mitochondrial membrane barrier by specific transport proteins to mitochondrial matrix

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25
First step of TCA and what are the products
start is pyruvate decarboxylated in oxidation reaction by pyruvate hydrogenase to give acetyl-CoA (cofactor coenzyme A and pyruvate), NADH, and CO2
26
Second and third steps in TCA
citrate synthase combine acetyl-CoA with oxaloacetate to give citrate citrate to isocitrate by enzyme aconitase
27
Where does the energy conserved in synthesis of ATP come from in TCA
large amount of free energy comes from thioester bond of succinyl-CoA is conserved in synthesis of ATP
28
after succinyl-CoA into succinate, what is the next step
succinate to fumarate by succinate dehydrogenase and also makes 1 FAD
29
What are the final 2 steps of TCA cycle
fumarate forms malate, malate is then oxidized by malate dehydrogenase to regenerate oxaloacetate and produces another NADH.
30
What product is generated in order to continue the TCA cycle
oxaloacetate
31
As 1 molecule of pyruvate enters TCA cycle, what is produced as biproducts
3 molecules of CO2, and free energy released is conserved to form 4 NADH, 1 FADH2, and 1 ATP
32
How does plant tissues use malate
they store malate in their vacuoles and the degradation of malate is important in regulating levels of organic acids in cells
33
Instead of malate being degraded, what else is malate used for
malate can be produced via the PEP carboxylase which can replace TCA cycle intermediates that were used in biosynthesis, known as anapleurotic
34
ATP is important because? and where do we generate more of it from
it is the energy carrier used by cells to drive life processes, and the energy conserved in the TCA in the form of NADH and FADH2 must be converted to ATP for useful work
35
Define oxidative phosphorylation
occurs in the inner mitochondrial membrane and is the process of reducing oxygen to generate ATP
36
How are the individual electron transport proteins organized
organized into 4 transmembrane multiprotein complexes (I through IV) all localized in the inner mitochondrial membrane
37
What is complex I called
NADH dehydrogenase
38
What occurs in complex I
electrons from NADH that were generated in TCA, are oxidized here, then transferred to ubiquinone. for every pair of electrons passing through the complex, 4 protons are pumped through into the intermembrane space
39
Define ubiquinone
a small, lipid-soluble electron carrier that can diffuse within the membrane bilayer after complex I and also after complex II
40
What is complex II called
succinate dehydrogenase
41
What occurs in complex II
this complex has 2 roles: 1. catalyzes the oxidation of succinate in the TCA cycle where 2. the reducing equivalents/ electrons from succinate are transferred by FADH2 and a group of iron-sulfur centers to ubiquinone does NOT pump proteins
42
What is complex III called
cytochrome bc1 complex
43
What occurs in complex III
it oxidizes reduced ubiquinone and transfers electrons by an iron-sulfur center across the intermembrane space to cytochrome c. this is done by iron-sulfur centers = two b-type cytochromes and a membrane bound cytochrome c1.
44
what proton pumping occurs in complex III
four protons per pair of electrons are pumped out of the matrix using Q cycle mechanism
45
Define cytochrome c
small protein attached to outer surface of inner membrane and serves as a mobile carrier to transfer electrons between complex III and IV
46
What is complex IV called
cytochrome c oxidase
47
What occurs in complex IV
it contains 2 copper centers and cytochromes a and a3. it is the terminal complex of the electron transport chain. it reduces 4 electrons of O2 to give 2 molecules of H20.
48
What proton pumping occurs in complex IV
two protons are pumped out of the matrix per electron pair
49
What are the 3 supplementary branches of the electron transport chain not found in mammalian mitochondria and function
1. NADPH dehydrogenases on matrix surface of inner membrane (bypass) 2. NADPH dehydrogenases on the outer surface of inner membrane (enter ETC at level of upiquinone pool) 3. alternative oxidase (additional respiratory pathway for oxidation of ubiquinol)
50
The number of ATP synthesized depends on what
nature of the electron donors, because coupled with electron transport
51
Explain chemiosmotic hypothesis
explains that ATP generated during respiration is mostly produced by electrochemical coupling
52
where does the electrochemical proton gradient build up
in the inner mitochondrial membrane because it is highly impermeable to protons
53
What is complex V
It is called the F0-F1-ATP synthase and is an integral membrane protein complex
54
What occurs in complex V
protons pass through and is coupled to ongoing synthesis of ATP
55
In the F0-F1-ATP synthase, what is produced for each ATP synthesized
3 H+ pass through the complex from intermembrane to matrix, down electrochemical proton gradient
56
Define uncouplers
chemical compounds that increase proton permeability of membranes and uncouples the formation of proton gradient with ATP synthesis, reduces amount of ATP synthesized
57
most ATP is synthesized in _____ but used in _____
mitochondrial matrix but used in the outside of the mitochrondrion
58
Define adenine nucleotide transporter
facilitates the exchange of ADP and ATP across the mitochondrial inner membrane so ATP can be used outside
59
Phosphate transporter function
active uptake of inorganic phosphate using chemical potential of proton motive force to drive exchange of inorganic phosphate in for OH- out
60
Explain exchange of pyruvate
pyruvate in for OH- out leading to continued uptake of pyruvate from cytosol using proton motive force
61
aerobic respiration yields how many molecules of ATP per molecule of sucrose
60 (coming from formation of ATP, NADH and FADH2 into ATP)
62
The complete oxidation of sucrose leads to the formation of how many ATP, NADH, and FADH2
8 ATP (4 from glycolysis and 4 from TCA) 4 NADH in cytosol + 16 NADH and 4 FADH2 in mitochondrial matrix
63
what are examples that lower ATP yield in plants and create flexibility
alternative oxidase, uncoupling protein, NADPH dehydrogenases
64
What are the two main products of respiratory processes
1. ATP 2. metabolic intermediates used for biosynthesis
65
The respiratory pathways are controlled by _____
gene expression
66
What are key short-term regulators of the rates of glycolysis, TCA, and oxidative phosphorylation
substrates of ATP synthesis, ADP and Pi
67
What does the post-translational regulation of the pyruvate dehydrogenase complex (entry point into TCA cycle) involve
involves phosphorylation and dephosphorylation by a protein phosphatase
68
what results from the build up of TCA cycle intermediates
buildups reduces the rate of conversion of fructose 6-phosphate into fructose 1,6-bisphosphate, inhibiting glycolysis
69
Why is the bottom-up control of glycolysis beneficial
allows regulation of net glycolytic flux to pyruvate, can adjust demand for removal of precursors from TCA, and makes plant adjust growth and development to its carbohydrate status
70
Lots of the reduced carbon that is metabolized by glycolysis and TCA are diverted to what purpose if not oxidized to CO2
diverted to biosynthetic purposes, and produce building blocks for plant metabolites
71
What factors affect the respiration rate of an intact plant
species, growth habit, age, environmental variables (light, external O2, CO2 concentrations, temperature, nutrients, and water supply)
72
green tissues photosynthesize, what tissues respire
all tissues, 24 hours a day
73
in unfavourable growth conditions what happens to respiration and photosynthetic rates
respiration increases, photosynthesis decreases meaning lower overall carbon yield of the plant
74
respiratory losses increase with ___ as the ratio of what changes
age ratio of P/S tissue to non P/S tissue decreases
75
Explain each of the 2 considered components in respiration
1. maintenance respiration = needed to support function and turnover of tissues already present 2. growth respiration = provides energy needed for converting sugars into building blocks that make up new tissues
76
how does respiration rates vary with developing vs. mature plant tissues
high rate with developing than mature
77
What is respiratory quotient
that compounds are built with different ratios of CO2 release to O2 consumption
78
how does oxygen affect respiration rates
rates decrease if atmospheric O2 concentration is below 5%.
79
how does temperature affect respiration rates
increase between 0-30 and plateaus at 40-50 degrees temperature coefficient Q10, is the increase in respiration rates for every 10 degree increase.
80
animals use fats for energy storage, plants use fats for ____ and ___
energy and carbon storage
81
triacylglycerols vs. polar glycerolipids
triac = oils stored in fats and seeds polar glyc = form lipid bilayers of cellular membranes requires plastid and endoplasmic reticulum cooperation so synthesize these
82
lipids have a more reduced form of carbon than carbohydrates therefore oxidation of fat or oil produces more...
ATP than oxidation of starch but requires larger investment of metabolic energy
83
fats and oils exist mainly in what form
triacylglycerols, linked by ester bonds to 3 hydroxyl groups of glycerol
84
where are triacylglycerols synthesized
plastids and ER
85
Where are triacylglycerols stored
in cytoplasm of either cotyledon or endosperm cells in oil body organelles
86
Define oil bodies
single-layer phospholipids with hydrophobic hydrocarbon chains facing triacylglycerol interior
87
polar glycerolipids are the main ____ lipid in membranes
structural
88
plants, animals, and microbes all use membrane lipids as precursors for compounds that are used in _____ and ____
intracellular and long-range signalling
89
Jasmonate hormone
activates plant defences against insects and many fungal pathogens
90
Define glyoxylate cycle
occurs in glyoxosomes and mitochondria. function is to convert two molecules of acetyl-CoA into succinate to be exported to the mitochondria for further processing. the stored lipids come from germination in oil-storing seeds. lipid breakdown is converted into carbohydrates by gluconeogenesis

Plant Phys (15 decks)

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