Lecture 30: Glucose Anabolism (Photosynthesis) Flashcards

1
Q

Photosyntesis overview

What does photosyntesis primarily happen in, general?

A

Plants
and some bacteria and protists

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2
Q

Photosyntesis overview

What are the two stages to photosynthesis?

A

Light Reaction
* light dependant
* converts solar energy to chemical
* produces ATP and NADPH
Dark Reaction - Calvin Cycle
* light independant
* Uses ATP and NADPH from light reaction to make glucose

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3
Q

Photosyntesis overview

What does photosynthesis require to produce glucose?

A

Light energy, H2O, and CO2

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4
Q

Photosyntesis overview

What is the general equation for photosynthesis?

A

6 CO2 + 6 H2O + Energy
–>
C6H12O6 + 6 O2

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5
Q

Photosyntesis overview

What is the light energy used for?

A

powering ATP synthesis (using a proton gradient) and formation of NADPH (biosynthetic reducing power, similar to NADH)

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6
Q

Photosyntesis overview

What are organisms that use CO2 and H2O to form glucose called?

A

autotrophs

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7
Q

Photosyntesis overview

What are organisms that use chemical fuels to form glucose called?

A

heterotrophs

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8
Q

Photosyntesis overview

Where does photosynthesis take place, more specific?

A

Chloroplasts

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9
Q

Photosyntesis overview

What are the parts of a chloroplast?

A
  • Double membrane
  • Inner membrane surrounds the space called the Stroma
  • Within the stroma are membranous sacs called thylakoid
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10
Q

Photosyntesis overview

Where are light reactions located?

A

In the Thylakoid

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11
Q

Photosyntesis overview

Where are dark reactions located?

A

In the Stroma

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12
Q

Chloroplasts Pigments

What are the pigments in chloroplast?

A

Chlorophyll a: pricipal photoreceptor in chloroplasts of green plants
Chlorophyll b: accessory pigment
Carotenoids: accessory pigment

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13
Q

Chloroplasts Pigments

What wavelengths of light do the different pigments absorb?

A

Chlorophyll: Blue (420nm) and red (660nm)
Carotenoids: blue and green (not yellow or red)

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14
Q

Chloroplasts Pigments

What does this light absorption do?

A

Induces electron transfer
(electron in the pigment molecule jumps to a higher energy state and transfers to a nearby molecule that has a lower one)

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15
Q

Photosystems

How many photosystems (PS) are there in green plants?

A

2:
PS I and PS II

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16
Q

Photosystems

What does PS I do?

A

generates NADPH

17
Q

Photosystems

What is the reaction center for PS I called and what does it respond to?

A

P700, wavelegnths less than 700nm

18
Q

Photosystems

What does PS II do?

A

replenishes the elctrons in PS I while generating a proton gradient to synthesize ATP

19
Q

Photosystems

Where are the missing electrons in PS II replaced from?

A

photolysis of water

20
Q

Photosystems

What is the reaction center to PS II called and what does it absorb?

A

P680, wavelengths 680nm and under

21
Q

Light Reactions

What are the two possible routes for electron flow in light reactions?

A

Cyclic Electron Flow (cyclic photophosphorylation)
noncyclic electron flow ( noncyclic photophosphorylation)

22
Q

Light Reactions

What does the cyclic electron flow use and generate?

A

PS I and ETC
ATP

23
Q

Light Reactions

What does the noncyclic electron flow use and generate?

A

PS II and PS I then the ETC

O2 (from splitting H2O), ATP and NADPH

24
Q

Chemiosmosis

What does chemiosmosis do in photosynthesis?

A

The elctron transport chains are arranged with photosystems to bring H through the thylakoid membranes into the middle space. When they try to flow back out, they are forced to move through theATP synthase to make ATP

25
Q

Chemiosmosis

What is photophosphorylation?

A

the use of light energy from photosynthesis to untimately provide the energy to convert ADP to ATP

26
Q

Dark Reactions

What types of carbon fixations do dark reactions have?

A

C3 fixation (Calvin Cycle)
C4 Fixation

27
Q

Dark Reactions

What is C3 fixation?

A

CO2 is fixed to form a 3-carbon unit (rice, wheat, soybeans, trees)

28
Q

Dark Reactions

What is C4 fixation?

A

CO2 is fixed to form a 4-carbon unit (crabgrass, sugarcane, and corn)
common in warmed areas

29
Q

Dark Reactions

What is the Calvin Cycle?

A

A biochemical pathway that allows for carbon fixation

30
Q

Dark Reactions

What does the Calvin Cycle use to synthesize hexose?

A

CO2 and H2O

31
Q

Dark Reactions

How long and how much energy does it take for the Calvin Cycle to produce Glucose?

A

6 turns
18 ATP
12NADPH

32
Q

Dark Reactions

What is the general net equation for the Calvin Cycle?

A

6 CO2 + 18 ATP + 12 NADPH + 12 H2O
–>
C6H12O6 + 18 ADP + 18 Pi + 12 NADP + 6 H

33
Q

Dark Reactions

Q from Lecture: How many molecules of NADPH and how many molecules of ATP are consumed in incorporating a single CO2 molecule into Hexose?

A

3 ATP and 2 NADPH

34
Q

Calvin Cycle

What are the 3 stages of the Calvin Cycle?

A

Stage 1
Stage 2
Stage 3

35
Q

Calvin Cycle

Stage 1:

A

Fixation of CO2 by ribulose 1,5-biphosphate to form 2 molecules of 3-phosphoglycerate

Catalyzed by ribulose 1,5-biphosphate carbxylase/oxygenase (rubisco)

Rate limited step

36
Q

Calvin Cycle

What is rubisco?

general, not specific

A

the most abundant enzyme in the biosphere, key enam

37
Q

Calvin Cycle

Stage 2:

A

reduction of 3-phosphoglycerate to form hexose monophosphates (fructose-6-phosphate to glucose-6-phosphate to glucose-1-phosphate)

uses 2 ATP and 2 NADPH

very similar to gluconeogenic pathway

38
Q

Calvin Cycle

Stage 3:

A

regeneration of ribulose 1,5-biphosphate using transketolase and aldolase

Transketolase converts and 6C and 3C into a 4C and 5C
Alsolase combines the 4C and 3C to form a 7C sugar
The 7C reacts with a 3C to form two additional 5C sugars

C meaning carbon

39
Q

Calvin Cycle

What is the general equation for stage 3?

A

Fructose-6-phosphate + 2 glyceraldehyde-3-phosphate + dihydroxyacetone phosphate + 3 ATP
–>
3 ribulose-1,5-biphosphate + 3 ADP

track the carbons