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BIOL 331 > second midterm reup > Flashcards

second midterm reup Flashcards

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1
Q

What is facilitated diffusion?

A

involves movement of specific molecules
needs specific channels or carrier proteins
needs no ATP

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2
Q

In a system with charged species, what happens at equilibrium?

A

Influx = efflux, and the electric field will balance out the concentration gradient

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3
Q

What is the primary active transport system?

A

H pumping ATPase - pumps protons out of the cell to generate pH and electric gradietns

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4
Q

How to determine passive or active transport from voltage current plots?

A

Efflux is positive Y axis, influx is negative y axis
- if influx is greater than efflux, and the potential points towards influx, it is passive transport
- if it is different than the one it points to its active transport

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5
Q

Stomatal opening is highly correlated to what?

A

photosynthetically active radiation

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6
Q

Guard cell osmotic adjustment is mediated by what?

A

K+ and malate 2- or Cl-
or sucrose and / or starch

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7
Q

When guard cells are open / closed, what molecules are flowing in/out?

A

Open
- H+ out
- K+ in
- H2O in

Closed
- Cl- out (triggered by ABA)
- K+ out
- H2O out

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8
Q

How does energy transfer occur during photosynthesis?

A

Physical phenomenon
- no chemical changes
- done by resonance energy transfer - energy is transferred from pigment to pigment by resonance until it reaches the reaction center pigment

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9
Q

How does a photosystem harvest light?

A

Light harvesting complex are pigments bonded to proteins
- special pair of chlorophyll a that acts as an electron acceptor

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10
Q

Plants and green algae have what kinds of light harvesting complexes?

A

membrane embedded

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11
Q

Where are both of the photosytems?

A

In thylakoid membranes

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12
Q

What electron carriers move electrons from PSII to cytochromeB6 and to PSI

A

Plastoquinone - PSII - Cyt

Plastocyanin - Cyt - PSI

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13
Q

What does the oxygen evolving complex do?

A
  • Each excitation of P680 is followed by withdrawal of an electron from Mn, when Mn4+ is reached the complex oxidizes 2H2O and releases O2`
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14
Q

Explain electron transfer in PSII

A

Light converts reaction center P680 to excited form
- electron leaves P680* forming P680+
- the electron is transferred to Pheophytin forming Pheo-
- Pheo - passes the elctron to Qa to form Qa-
- Qa_ passes electron to Qb to produce Qb-

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15
Q

What does cytochrome B6f do?

A

transfers electrons and protons
- first PQH2 delivers two protons to lumen, one electron to PC
- next PQ absorbs two electrons and two protons to regenerate and cycle again

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16
Q

How does electron transfer happen in PSI?

A

PSI is surrounded by LCHI complexes
ferrodoxin transfers electrons via ferrodoxinNADPreductase (FNR)
Resultsd in 2NADPH that go to ATP synthase

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17
Q

In the photosystem reactions - what is the electron donor and final electron acceptor

A

Z scheme and linear electron transport taking electrons from water and transferring them to NADP+

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18
Q

The light dependent reactions occur in the

A

thylakoid membranes

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19
Q

What is photophosphorylation?

A

Phosphorylation to make ATP during photosynthesis
- energy from photons
- electrons from H2O
- protons accumulate into the thylakoid of the chloroplasts
- protons move out of the thylakoid space during AATP synthesios

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20
Q

Where is the electron transport cyclic?

A

PSI
- electrons can be moved from ferrodoxin back to PQ onstead of going into NADP+
- used to control ATP levelsd

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21
Q

Overview of three pathways of electron transport

A

Linear
- electrons transferred from H2O to NADPH
- involves PSII, Cyc, PSI
- makes NADPH and ATP

Cyclic
- electrons cycle with no net production of NADPH
- involves Cyc and PSI
- Product only ATP (from proton gradient at CYC)

Water water cycle
- electrons transferred from H2O to H2O
- involves PSII, Cyc, PSI
- product is ATP

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22
Q

the binding change mechanism of ATP synthase accounts for what?

A

ATP synthesis in response to proton flow

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23
Q

What size is ATP synthase?

A

400kD

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24
Q

What can excess excitation energy lead to?

A

photooxidative damage - ROS

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25
How does cyclic electron transport work for photoprotection?
cyclic electron flow back to PQ and Cyc lead to a generation of pH gradient accross thylakoid (protons)- - qE energy dependent quenching is activated
26
How is Rubisco assembly different for large and small subunits?
Large rbcL is encoded by a single gene in the chloroplast genome small subunit rbcS is encoded by a single gene in the nuclear genome Chaperone molecules are required for enezyme assembly
27
How is Rubisco reversibly inhibited?
Inactive when a sugar phosphate inhibitor is bound to enzyme - rubisco activase will remove it and activate enzyme
28
Rubisco mediated carboxylation of RuBP yeilds what?
2 molecules of 3 phosphoglycerate
29
What does Rubisco mediated oxygenation of RuPB yeild?
1 3 phosphoglycerate and 1 2-phosphoglycolate
30
Where is RuBP regenerated in the calcin cycle?
At he final step
31
What does CO2 fixation require ?
3 ATP 2 NADPH
32
How do O2 and CO2 differ in solubility?
SOlubility of CO2 decreases faster than O2 at high temperatures (30C) - the portion of O2 in cytosol and stroma is higher relative to CO2 at high temp
33
How does increases O2 affect photosynthesos
Decreases rate
34
While the carboxylation reaction of Rubisco yeilds two 3PGA that go to calvin cycle for energy, what happens in the oxygenase reaction?
2 PG will be recycled to 3PGA CO2 and NH3
35
Photorespiration is a multi organelle processes across what three organelles?
chloroplast, peroxisome, mitochondrion
36
What is the peroxisome?
- single celled organelle with no inner membrane - no DNA or ribosomes - urate oxidase crystalline core in dense matrix - tehtered to chloroplast
37
What is the main purpose of the photorespiratory cycle?
Takes the 2PG product from the oxygeanse reaction of Rubisco and uses it to reform intermediates - site of ROS
38
What are the two byproducts of photorespiration?
CO2 and NH3 converts glycine to serine
39
What is the glycine decarboxylase complex?
glycine cleavage system in mitochondira during photorespiration - once CO2 and NH3 are released the central C of glycine is transferred to THF - serine hydroxymethyltransferase transfers C to another glycine to form serine
40
When does photorespiration occur?
- C3 plants close stomata to prevent excess water loss in heat - causes low CO2 concentration - increased atm temp and leaf temp decrease Rubiscoaffinity to CO2 - Rubisco combines with O2 instead of CO2 to form 3-PGA and 2PG
41
The oxgenase and carboxylase reactions occur when in rubisco
if O2 or CO2 binds
42
What is the significance of photorespiration (5)
- only found in C3 plants not C4 - prevents total depletion of CO2 in chlorplasts - glycolate detoxification - glycolate oxidase - protects from photoinhibition - ammonium assimilation
43
Why is photorespiration a wasteful process?
- no ATP - 25% carbon is lost as CO2 - reduces efficiency of photosynthetic carbon assimilation (would be 50% more efficient without)
44
What is different about C4 plants compared to C3 plants
they have carbon concentrating mechanisms, and accumulate CO2 in the vicinity of Rubisco producing a high CO2/O2 ratio
45
What were the selection pressures on C4 photosynthesis evolution?
They lived in hot and dry conditions leading to stomatal closure and CO2 limitation causing an increase in photorespiration which is inefficient
46
How do C3 plants differ in terms of structure from C4 plants (4)
C3 - photosynthesis in mesophyll cells - absensce of Kranz anatomy - no chloroplasts in bundle sheath cells - relatively thinner bundle sheath cell layers than C4 C4 - photosynthesis occurs in mesophyll and bundle sheath cells - Kranz anatomy - chloroplasts are in bundle sheath cells - Thicker bundle sheath cell layers
47
What is Kranz anatomy in C4 plants
Bundle sheath cells form a ring around the vascular tissue and mesophyll cells form a ring around bundle sheath cells
48
What are dimorphic chloroplasts in C4 plants?
Mesophyll cells have chloroplasts with grana and bundle sheath cells have chloroplasts without grana
49
Advantages of C4 photosynthesis under hot and dry weather CA / PEPC
- stomata closed preventing water evaporation and CO2 uptake so concentration of CO2 is low - HCO3 (bicarb) is generated from CO2 by carbonic anhydrase (CA) - phosphoenolpyruvate carboxylase (PEPC) fixes HCO3- recycling it
50
Which type of photosynthesis is better under which conditions?
In cool temp C3 is better because C4 requires more ATP for the additional carboxylation steps but in hot and or sunny weather C4 carbon fixation is not carbon limited and does not become fully saturated even in full sunlight
51
What are the two CO2 fixation reactions in C4 photosynthesis?
First CO2 fixation in mesophyll cells using PEPC Second CO2 fixation in bundle sheath cell using RuBP and Rubisco
52
What are the products of the PEPC reaction in C4 photosynthesis?
PEP turns to oxaloacetate via PEPC which goes to malate and aspartate
53
How does PEPC usage differ in CAM plants from C4?
PEPC fixes HCO3- at night - stomata open at night for CO2 uptake - HCO3- is fixed bby PEPC - CO2 is stored as C4 carbon acids in vacuole - Stomata close during the day -CO2 released by decarb process in daytime -rubisco fixes CO2 during the day
54
What is the main difference between C4 and CAM plants to avoid photorespiration?
C4 - carboxylases spatially separated CAM - carboxylases temporally seperated
55
Which type of plant has the highest water use efficiency?
CAM
56
what is a negative effect of increased CO2 levels?
causes a decrease in protein and nutrient content but an increase in carbs
57
What is a test for plant reponses to CO2 fertilization?
Free air CO2 enrichment (FACE)
58
When does starch accumulate and when is it degraded?
accumulates in the day degraded at night
59
What are the two forms of starch?
amylose - linear chains amylopectin - branched chains
60
Which starch branching enzyme has higher affinity for amylose?
starch branching enzyme 1, will act repeatedly to form highly branched amylopectin enzyme 2 will go straight to highly branched
61
3 key enzymes for hydrolytic starch degradation?
A-amylase - targeting endo a1-4 glycosidic bonds Beta amylase - targets exo a1-4 glycosidic bonds limit dextrinase - targets branch points at a 1-6
62
2 Key enzymes for sucrose biosynthesis?
sucrose 6 phosphate synthase and sucrose 6 phosphate phosphatase
63
Where is sucrose and starch synthesized and from what product of the calvin cycle
both from triose phosphate (G3P) sucrose in cytosol starch in chloroplast
64
What is different between sucrose synthase and sucrose invertase?
synthase is reversible for sucrose synthesis and degradation but inveratase is irriversible and only for degradation (UDP glucose v glucose)
65
explain the four steps for generation of UDP glucose for cell wall biosynthesis during sucrose degredation?
- sucrose synthase generates UDP glucose - UDP glucose is the substrate for cellulose synthase - cellulose synthase of an enzyme rosetter synthesizes a long cellulose chain outside t he plasma membrane - microtubules direct movement of cellulose synthase complexes (rosettes) along PM - parallel cellulose chains crystalize to form cellulose microfibril
66
What is the difference between starch and cellulose?
starch is 1 4 linkage of a glucose in the same orientation - storage polysaccharide cellulose is 1 4 linkage of b glucose monomers every glucose is upsidown - structural polysaccharide
67
comparison of photosynthesis and respiration in organelle, reactants, products, energy and role
Organelle - chloroplast v mitochondria Reactants - CO2 and H2O v sugars and H2O Products - Sugars and O2 vs CO2 and H2O Energy - sotred vs released Role - carbon fixation vs oxidation of photoassimilates
68
4 steps of respiration
glycolysis, oxidative pentose phosphate pathway, krebs cycle, oxidative phosphorylation
69
What is glycolysis in plants?
conversion of glucose into 2 pyruvate - forms 4 atp but uses 2 so net 2 - gives 2 NADH
70
What is the oxidative pentose phosphate pathway?
chemical reactions in cytoplasm and plastid - release of CO2 and production of 2 NADPH - makes ribulose 5 phosphate for Rubisco to woek on - major supplier of NADPH in non photosynthetic plastids like roots
71
where does citric acid cycle occur?
mitochondrion matrix
72
2 stages of citric acid cycle?
Stage 1 - carbon condensation (C2 and C4 -- C6) Stage 2 - Oxaloacetate regeneration from succinyl coa
73
What are the total yeilds of the citric acid cycle?
Uses 2 pyruvate to get 6 CO2 2 ATP 8 NADH 2 FADH2
74
What is the goal of oxidative phosphorylation?
the final step in energy production during metabolism - uses the elctron energy from NADH and FADH2 to produce ATP
75
Which complex in oxidative phosphorylation does not contribute to proton pumping?
Complex II - oxidation of succinate synthesized in citric acid cycle instead
76
Which ion plays a central role in electron transport processes?
Fe - heme rings
77
Comparison of chemiosmosis in mitochondria and chloroplast - e- donors and acceptors
Mito - NADH and FADH2 are e- donors - O2 is acceptor Chloro - Light converts H2O to be an e- donor - NADP+ is an e- acceptor
78
List 3 plant micronutrients
B, Cl, Mn, Fe, Ni, Cu, Zn, Mo
79
Are micronutrients usually mobile or immobile?
Immobile
80
What form is iron usually found as in plants?
FeIII - largely oxidized and insoluble
81
What is chelation?
Formation of bonds between two or more binding sites within a ligand with a single central atom
82
To maintain Fe in a way that it can be used (soluble) what happens?
Citrate binds to Fe to make it soluble
83
What are the two different strategies for iron uptake in plants?
Strategy 1 - chelate Fe III with citrate - use FRO2 to turn it into Fe II which is soluble - transport into the cell using iron regulated transporter 1 Strategy 2 - in monocots - Fe III binds to phytosiderophore which is exported out of the cell using TOM1 - Fe(III)-PS moves into the cell using YS/YSL - instead of changing the form of the iron the entire complex is transported into the cell
84
Micronutrients usually have a narrow _____ ______
optimal concentration
85
How do you calculate if a K+ flux system is in dynamic equilibrium?
DeltaE = RT/zIF x ln(a^o/a^c) Will give in mV zI = 1 R = 8.32 K = 273+C (298) F = 96,500
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BIOL 331 (3 decks)

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