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Bio 131 > Exam 3: Calvin Cycle > Flashcards

Exam 3: Calvin Cycle Flashcards

1
Q

What products from the light-dependent reactions are used in the Calvin Cycle?

A

NADPH and ATP

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2
Q

Where does the Calvin Cycle take place?

A

Outside of the thylakoid, in the stroma

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3
Q

What are the three steps of the Calvin Cycle?

A
  1. CO2 fixation
  2. Reduction
  3. Regeneration
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4
Q

Step 1: What happens?

A

CO2 reacts with RuBP, forms 2 molecules of 3PG

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5
Q

Step 2: What happens?

A

3PGA is phosphorylated by ATP and reduced by NADPH to form G3P

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6
Q

Step 3: What happens?

A

G3P from step 2 forms RuBP to keep the cycle going, needs ATP

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7
Q

How many times does the calvin cycle turn in order to make 1 G3P?

A

3 times

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8
Q

Step 1: What is the ratio of molecules for the 3 turns of the cycle?

A

3 RuBP + 3 CO2 –> 6 3PGA

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9
Q

Step 2: What is the ratio of molecules for the 3 turns of the cycle?

A

6 3PGA + 6 ATP + 6 NADPH –> 6 G3P (1 of them is used to make glucose/fructose, the remaining 5 move on to step 3)

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10
Q

Step 3: What is the ratio of molecules for the 3 turns of the cycle?

A

5 G3P + 3 ATP –> 3 RuBP

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11
Q

Which enzyme fixes CO2?

A

Rubisco

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12
Q

Which enzyme is the most abundant on Earth?

A

Rubisco

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13
Q

How many polypeptides does rubisco have?

A

16

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14
Q

How many active sites does rubisco have?

A

8

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15
Q

Which two molecules can bind to rubisco?

A

CO2 and O2

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16
Q

Why is rubisco inefficient?

A

When oxygen binds, only 1 3PG is produced and 2PG is produced which produces CO2 when broken down.

17
Q

How many reactions can rubisco facilitate per second?

A

3

18
Q

What is the process when O2 binds to rubisco?

A

Photorespiration

19
Q

Carbon fixation is favored over photorespiration when CO2 concentration is ___ and O2 concentration is ___

A

High, low

20
Q

What prevents the rapid evaporation of water when it is hit by sunlight?

A

The leaf surface is coated in cuticle, which is a waxy substance that prevents gas exchange

21
Q

Stomata are normally ___ during the day and ___ during the night

A

Open, closed

22
Q

In dry conditions, is photorespiration or carbon fixation more likely?

A

Photorespiration because of the build-up of O2

23
Q

What are C3 plants?

A

90% of plants, these are 3 carbon plants

24
Q

What are the 2 mechanisms that plants in dry environments use to adapt to conditions?

A
  1. C4 pathway
  2. CAM plants
25
Q

How does the C4 pathway work?

A

Spatially separates carbon fixation from the calvin cycle, fixes CO2 into 4-carbon orgnanic acids

26
Q

Which enzyme facilitates the C4 pathway?

A

PEP carboxylase

27
Q

Where does PEP carboxylase fix CO2?

A

Mesophyll cells

28
Q

Where do the 4-carbon organic acids travel to?

A

Bundle sheath cells

29
Q

What do the 4-carbon organic acid release that initiates the calvin cycle?

A

a CO2 molecule

30
Q

How do CAM plants work?

A

Temporally (time) separates carbon fixation and the Calvin cycle. The stomata is only open during the night. This allows the calvin cycle to occur during the night.

31
Q

When is CO2 stored in CAM plants?

A

during the night

32
Q

During the day, what is released from the organic acids that have CO2 fixed into them?

A

CO2

33
Q

In which environments is C4 favored?

A

Warm and dry, where evaporation is favored

34
Q

In which environments is C3 favored?

A

Normal and cooler

35
Q

What is G3P made into? What is this process called?

A

Glucose and fructose; gluceogenesis

36
Q

What are glucose and fructose combined into?

A

Sucrose (disaccharide)

37
Q

When photosynthesis is slow, what is glucose stored as?

A

Sucrose

38
Q

When photosynthesis is fast/sucrose is high, what is glucose stored as?

A

Starch

39
Q

When is starch broken down and what for?

A

at night, to make more sucrose for transport

Bio 131 (25 decks)

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