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Bio Lect 7 Flashcards

1
Q

How were dark reactions identified?

A

By injecting carbon-14 into algae in suspension after shining light, then stopping the reaction with a strong acid

This process halts all chemical reactions and allows for the extraction of compounds for analysis.

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2
Q

What role does CO2 play in the identification of dark reactions?

A

Fast CO2 injection initiates the process for dark reaction analysis

This step is crucial for tracing carbon compounds formed during the reaction.

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3
Q

What is the significance of using perchloric acid in the identification of dark reactions?

A

It rapidly ‘quenches’ the reactions by killing cells and denaturing enzymes

This halts all ongoing chemical processes, allowing for accurate analysis.

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4
Q

What is C3 photosynthesis?

A

A type of photosynthesis where the main product of RuBisCO is a three-carbon compound

This is the most common form of photosynthesis in plants.

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5
Q

What is the purpose of thin-layer chromatography in the study of dark reactions?

A

To improve separation of intermediates after reaction quenching

This technique allows for the identification and analysis of various compounds produced.

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6
Q

What are the steps involved in analyzing dark reactions after injection of carbon-14?

A
  1. Shine light on algae
  2. Inject carbon-14
  3. Quench with strong acid
  4. Extract compounds
  5. Run thin-layer chromatography

The process involves running the chromatography plate with two solvents for better separation.

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7
Q

True or False: The main product of RuBisCO in C3 photosynthesis is a four-carbon compound.

A

False

RuBisCO primarily produces a three-carbon compound in C3 photosynthesis.

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8
Q

What is chlorella suspension?

A

Algae

Chlorella is a type of green algae known for its high nutritional value.

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9
Q

What is the purpose of using two light sources in the dark reaction experiment?

A

To ensure proper illumination while avoiding excessive heat on the sample

High heat shields are employed to protect the sample from heating.

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10
Q

What is a key component used to shield the sample from heat in the dark reaction experiment?

A

High heat shields

These shields prevent the sample from being heated by the light sources.

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11
Q

True or False: The dark reaction experiment involves heating the sample directly.

A

False

The use of heat shields indicates an intention to avoid directly heating the sample.

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12
Q

Fill in the blank: In the dark reaction experiment, _______ are used to prevent heating of the sample.

A

high heat shields

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13
Q

What does the time sequence of product 14C labeling indicate?

A

It indicates the sequence of transitions.

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14
Q

What is the initial compound in the Calvin cycle?

A

Ribulose-1,5-bisphosphate (RuBP)

RuBP is a 5-carbon compound with 2 phosphate groups.

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15
Q

What enzyme catalyzes the reaction between RuBP and CO₂ in the Calvin cycle?

A

Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase)

Rubisco facilitates the carboxylation step.

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16
Q

What is formed when RuBP reacts with CO₂?

A

A 6-carbon intermediate

This intermediate immediately breaks down into two molecules of 3-phosphoglycerate (3-PGA).

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17
Q

What type of molecules are produced from the breakdown of the 6-carbon intermediate?

A

3-phosphoglycerate (3-PGA)

Each 3-PGA molecule contains 3 carbon atoms.

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18
Q

What are the two essential molecules used to reduce 3-PGA into G3P?

A

ATP and NADPH

These are produced in the light reactions of photosynthesis.

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19
Q

What is the product of the reduction of 3-PGA?

A

Glyceraldehyde-3-phosphate (G3P)

G3P is a 3-carbon sugar.

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20
Q

What can G3P be used to synthesize?

A

Glucose and other carbohydrates

G3P is a key intermediate in carbohydrate synthesis.

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21
Q

What must be regenerated in the Calvin cycle to keep the cycle going?

A

Ribulose-1,5-bisphosphate (RuBP)

This regeneration process requires additional ATP.

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22
Q

How many times must the Calvin cycle turn to produce one molecule of glucose?

A

6 times

This is because only one carbon is fixed per cycle.

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23
Q

What is produced for every 6 molecules of CO₂ that enter the Calvin cycle?

A

One molecule of glucose

Glucose is a 6-carbon compound.

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24
Q

Fill in the blank: The Calvin cycle runs _______.

A

Clockwise

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25
What two molecules are formed when gaseous CO2 and ribulose 1,5-bisphosphate react?
Two molecules of 3-phosphoglycerate (PGA) ## Footnote This reaction is a part of the Calvin cycle in photosynthesis.
26
Is the reaction between CO2 and ribulose 1,5-bisphosphate metabolically reversible?
No, the reaction is metabolically irreversible. ## Footnote This irreversibility is crucial for the regulation of the Calvin cycle.
27
What percentage of the soluble protein in plant leaves does RuBisCO make up?
About 50% ## Footnote RuBisCO is essential for the process of carbon fixation.
28
What is RuBisCO known as in terms of its abundance?
The most abundant enzyme in nature. ## Footnote Its widespread presence highlights its importance in photosynthesis.
29
What are the components of RuBisCO in terms of subunits?
8 large subunits + 8 small subunits. ## Footnote The structure of RuBisCO is critical for its function in catalyzing the fixation of carbon dioxide.
30
Which subunits of RuBisCO are nuclear-encoded?
Large subunits. ## Footnote This indicates the complexity of the enzyme's synthesis and assembly.
31
Which subunits of RuBisCO are chloroplast-encoded?
Small subunits. ## Footnote This reflects the dual genetic origin of this important enzyme.
32
What is RuBisCO?
An enzyme involved in the process of carbon fixation in photosynthesis ## Footnote RuBisCO stands for Ribulose-1,5-bisphosphate carboxylase/oxygenase.
33
In which organisms can RuBisCO be found?
Cyanobacteria, plants, and algae ## Footnote RuBisCO is a crucial enzyme for photosynthesis across different life forms.
34
How many subunits can RuBisCO be made up of?
Eight, Six or four subunits ## Footnote This indicates variability in the structure of RuBisCO across different species.
35
True or False: RuBisCO must always be made up of exactly 8 subunits.
False ## Footnote RuBisCO can consist of different numbers of subunits.
36
What is the primary function of chlorophyll?
Capture light ## Footnote Chlorophyll is essential for photosynthesis as it absorbs light energy.
37
What enzyme catalyzes a competing oxygenation reaction alongside carboxylation?
RuBisCO ## Footnote RuBisCO can use O2 instead of CO2, leading to photorespiration.
38
How much greater is carboxylation compared to oxygenation in normal conditions?
3 times greater ## Footnote Under typical circumstances, carboxylation occurs more frequently than oxygenation.
39
What process recycles the toxic products of the oxygenation reaction?
Photorespiration ## Footnote Photorespiration is a wasteful pathway that helps mitigate the effects of oxygenation.
40
What are the products of photorespiration?
Glyoxylate, serine, glycine, and CO2 ## Footnote These products result from the recycling process during photorespiration.
41
What does photorespiration consume to produce its products?
NADH and ATP ## Footnote Photorespiration requires energy and reducing equivalents, which are derived from NADH and ATP.
42
What reaction does Rubisco catalyze as a carboxylase?
Rubisco adds CO₂ to ribulose-1,5-bisphosphate (RuBP) in the Calvin cycle. ## Footnote This reaction is crucial for carbon fixation in photosynthesis.
43
What reaction does Rubisco catalyze as an oxygenase?
Rubisco adds O₂ to ribulose-1,5-bisphosphate (RuBP), leading to photorespiration. ## Footnote Photorespiration can reduce the efficiency of photosynthesis.
44
Fill in the blank: Rubisco is both a _______ and an oxygenase.
carboxylase
45
True or False: Rubisco only functions as a carboxylase.
False
46
What primary reaction does Rubisco carry out?
Carboxylation reaction (adding CO₂ to RuBP) ## Footnote This is the primary function of Rubisco in the photosynthetic process.
47
What secondary reaction does Rubisco perform?
Oxygenation reaction (reacting with O₂ instead of CO₂) ## Footnote This occurs when Rubisco binds with O₂, leading to photorespiration.
48
In the natural environment, how often does Rubisco bind with O₂ compared to CO₂?
For every four turnovers, one involves O₂ binding ## Footnote This indicates the inefficiency of Rubisco in natural conditions.
49
What is the consequence of Rubisco's reaction with O₂?
Leads to photorespiration ## Footnote Photorespiration is less efficient than photosynthesis and can reduce the overall productivity of plants.
50
How efficient is Rubisco under controlled conditions when comparing CO₂ and O₂?
Has about a 250-fold greater affinity for CO₂ than for O₂ ## Footnote This indicates that under optimal conditions, Rubisco can function more effectively.
51
Fill in the blank: Rubisco is relatively _______ due to its tendency to react with O₂.
inefficient ## Footnote This inefficiency arises from the occurrence of photorespiration.
52
What types of organisms have evolved methods to overcome the limitations of RuBisCO?
Plants, algae, and photosynthetic bacteria (cyanobacteria) ## Footnote These adaptations have emerged to enhance photosynthesis efficiency.
53
What structure do cyanobacteria form to concentrate CO2 around RuBisCO?
Carboxysomes ## Footnote Carboxysomes are specialized microcompartments that increase the efficiency of carbon fixation.
54
What structure do some algae form to concentrate CO2 around RuBisCO?
Pyrenoids ## Footnote Pyrenoids are organelles within chloroplasts that facilitate carbon fixation.
55
What is the purpose of C4 photosynthesis in some Angiosperms?
To 'feed' RuBisCO ## Footnote C4 photosynthesis enhances CO2 concentration to improve the efficiency of carbon fixation under certain conditions.
56
What is the purpose of CAM photosynthesis in some Angiosperms?
To 'feed' RuBisCO ## Footnote CAM photosynthesis allows plants to fix CO2 at night, reducing water loss during the day.
57
What is the structure of carboxysomes?
Semi-crystalline protein structures incorporating RuBisCO ## Footnote Carboxysomes play a crucial role in carbon fixation in bacteria.
58
What proteins do cyanobacteria express to accumulate carbon dioxide?
Transport proteins to accumulate CO2 and HCO3- inside ## Footnote This mechanism enhances their ability to perform photosynthesis.
59
What are pyrenoids?
Membrane-bound structures found in the chloroplasts of some algae ## Footnote Pyrenoids are important for carbon concentration mechanisms in algae.
60
What do pyrenoids concentrate?
CO2 ## Footnote Pyrenoids, like carboxysomes, include RuBisCO which aids in carbon fixation.
61
True or False: Pyrenoids include RuBisCO.
True ## Footnote This is similar to carboxysomes which also incorporate RuBisCO.
62
What are carboxysomes and pyrenoids known to contain?
Carbonic anhydrase (CA) ## Footnote Carbonic anhydrases are enzymes that play a crucial role in carbon fixation processes.
63
What is the function of carbonic anhydrases?
Catalyze the reversible reaction between CO₂ and water to form carbonic acid ## Footnote Carbonic acid dissociates into bicarbonate and a proton.
64
What does the structure of carboxysome facilitate ?
It Facilitates transport of bicarbonate from inside the cyanobacterium into the carboxysome ## Footnote This transport is crucial for carbon fixation.
65
What type of transporters do cyanobacteria have in their envelope membrane?
Transporters that move CO₂ or bicarbonate ## Footnote These transporters help in the efficient uptake of carbon sources.
66
What happens to bicarbonate once it is inside the carboxysome?
Converted back into CO₂ ## Footnote This CO₂ is then fixed by RuBisCO.
67
What does RuBisCO produce from fixed CO₂?
PGA (3-phosphoglycerate) ## Footnote PGA is a key intermediate in the Calvin cycle.
68
How many times did C4 photosynthesis evolve in angiosperms?
C4 photosynthesis evolved over 68 times in angiosperms ## Footnote Angiosperms are flowering plants.
69
What is another name for C4 photosynthesis?
Hatch-Slack pathway ## Footnote Named after the scientists Hatch and Slack who described the pathway.
70
What does C4 photosynthesis fix HCO3- into?
Malate ## Footnote This occurs with the help of pyruvate.
71
In C4 photosynthesis, what happens to malate after it is formed?
Malate is transported to a second cell type for decarboxylation and refixation by RuBisCO ## Footnote RuBisCO is an enzyme involved in the first major step of carbon fixation.
72
Why is C4 photosynthesis considered more efficient?
It avoids O2 by fixing HCO3- first ## Footnote This adaptation helps in environments with high temperatures and light intensity.
73
What does C4 photosynthesis depend on?
Spatial separation of the C4 and C3 (RuBisCO) fixation reactions
74
What is the only major C4 crop?
Maize
75
What process does C4 photosynthesis enhance?
CO₂ fixation ## Footnote C4 photosynthesis enhances CO₂ fixation by separating processes between mesophyll and bundle sheath cells.
76
What enzyme converts CO₂ to bicarbonate in the mesophyll during C4 photosynthesis?
Carbonic anhydrase ## Footnote Carbonic anhydrase converts CO₂ to bicarbonate in the mesophyll.
77
What is the role of PEP carboxylase in C4 photosynthesis?
Fixes bicarbonate to phosphoenolpyruvate (PEP) ## Footnote PEP carboxylase fixes bicarbonate to PEP, forming oxaloacetate.
78
What compound is formed from phosphoenolpyruvate (PEP) in the mesophyll?
Oxaloacetate ## Footnote Oxaloacetate is formed from PEP in the mesophyll.
79
What does oxaloacetate quickly convert to in the mesophyll?
Malate ## Footnote Oxaloacetate quickly converts to malate.
80
Where does malate move to after being formed in the mesophyll?
Bundle sheath cells ## Footnote Malate moves to the bundle sheath cells after being formed.
81
What happens to CO₂ when malate reaches the bundle sheath cells?
It is released for Rubisco to use in the Calvin cycle ## Footnote Malate releases CO₂ for Rubisco to use in the Calvin cycle.
82
What happens to the remaining pyruvate after CO₂ is released from malate?
It returns to the mesophyll to be recycled into PEP ## Footnote The remaining pyruvate returns to the mesophyll for recycling into PEP.
83
What is the benefit of the spatial separation in C4 photosynthesis?
Concentrates CO₂ around Rubisco ## Footnote The spatial separation concentrates CO₂ around Rubisco, reducing photorespiration.
84
In which environments does C4 photosynthesis improve photosynthetic efficiency?
Hot, dry environments ## Footnote C4 photosynthesis improves photosynthetic efficiency especially in hot, dry environments.
85
What does CAM stand for?
Crassulacean Acid Metabolism
86
What is the key feature of CAM photosynthesis?
Temporal separation of the C4 and C3 (RuBisCO) fixation reactions
87
In CAM plants, where are C4 acids stored?
In the vacuole
88
What happens to C4 acids in CAM plants during the day?
Decarboxylation and refixation by RuBisCO
89
True or False: CAM photosynthesis occurs only at night.
False
90
Fill in the blank: CAM plants store _______ in the vacuole.
C4 acids (malate)
91
What does CAM stand for in photosynthesis?
Crassulacean Acid Metabolism
92
What is a key requirement for CAM photosynthesis?
Fine control of gene expression over the day-night cycle
93
How does CAM photosynthesis manage stomatal activity?
Uses an 'inverted' cycle of stomatal opening/closing
94
What is the primary benefit of CAM's stomatal cycle?
Saves water and concentrates CO2 in the leaf
95
What is the only major CAM crop?
Pineapple
96
What percentage of RuBisCO turnover does photorespiration account for in C3 plants?
30-50%
97
In which type of plants does photorespiration occur that accounts for 30-50% of RuBisCO turnover?
C3 plants
98
What does CAM stand for in the context of water use?
Crassulacean Acid Metabolism ## Footnote CAM is a photosynthetic process that allows certain plants to conserve water.
99
What is a significant benefit of CAM in plants?
Much more savings in water use ## Footnote CAM plants open their stomata at night to minimize water loss.

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