Photosynthesis Flashcards

1
Q

Photosynthesis

A

Conversion process that transforms the energy of sunlight into chemical energy stored in organic molecules

–> Conceptually, “the opposite” of respiration

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2
Q

Photosynthesis General Reaction

A

Sunlight + CO2 + H2O = C6H12O6 + O2

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3
Q

Where does the O2 come from?

A

The splitting of water

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4
Q

Carbon Fixation

A

CO2 –> C6H12O6

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5
Q

Water Splitting

A

H2O –> O2

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6
Q

Types of reactions in photosynthesis:

A

1) Light reactions
2) Calvin cycle reactions

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7
Q

Light reactions

A

The “photo” part

–> Converts solar energy into NADPH and ATP and releases O2

–> REQUIRES LIGHT

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8
Q

Products of Light Reactions

A

1) ATP (for internal consumption)
2) NADPH (to be used in calvin cycle)

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9
Q

Pigments

A

Substances that absorb visible light

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10
Q

Fluorescence

A

Light that is reflected by a substance

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11
Q

Chlorophyll

A

A green pigment found in plants

–> Absorbs red and blue light

–> Reflects green light

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12
Q

2 types of chlorophyll:

A

1) Chlorophyll-a –> Primary light capturing pigment
–> Has a CH3 group on ring

2) Chlorophyll-b –> Accessory light capturing pigment
—> Has a CHO group on ring

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13
Q

Components of Chlorophyll

A

1) Porphyrin Ring (containing Mg center)

2) Hydrophobic tail

3) Side group (distinguishes between types of chlorophyll)

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14
Q

Chlorophyll hydrophobic tail function

A

Anchors chlorophyll to the thylakoid membrane

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15
Q

Porphyrin Ring Function

A

Light absorbing region of chlorophyll

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16
Q

Ground vs Excited Electron States

A

Ground State = Electron in normal orbital

Excited State = Electron in higher orbital

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17
Q

Photosystem

A

A reaction center complex surrounded by several light harvesting complexes

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18
Q

Reaction Center

A

A special pair (2 molecules) of chlorophyll-a

–> Same chlorophyll as other molecules but is special due to location near primary acceptor

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19
Q

Primary Acceptor

A

Molecule that receives the electrons from the reaction center and transfers them to other reactions of ATP/NADPH synthesis

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20
Q

Antenna Pigments

A

Gather light

21
Q

Photoexcitation pathway

A

Sunlight —> The pigments (Chl. a, Chl. b, carotenoids) –> Electrons get transferred to Chl.a molecules –> Electrons are transferred to the reaction center –. electrons are transferred to the primary acceptor

22
Q

Photosystem I

A

P700: Reaction center has chlorophyll-a molecules that absorb light at 700 nm

23
Q

Photosystem II

A

P680: Reaction center has chlorophyll-a molecules that absorb light at 680nm

24
Q

Cyclic Electron Flow

A

ONLY involving Photosystem I
–> Electrons originate from PS1 and go back to PS1
“replenishes itself”
ONLY produces ATP

25
Q

Cyclic Electron Flow Final Electron Acceptor

A

PS1 itself

26
Q

Non-Cyclic Electron Flow

A

The Z scheme

–> Involves transfer of electrons from photosystem II to photosystem I

–> Produces ATP and NADPH

26
Q

Non-Cyclic Electron Flow PROCESS

A

1) Light excites PS2 –> Electrons go to PS2 primary acceptor

2) Electrons from PS2 go to first ETC to produce ATP

3) Water is split to replenish the electrons lost from PS2 –> Releases O2

4) Light Excites PS1 –> Electrons go to PS2 primary acceptor

5) Electrons from PS1 go through second ETC

6) Electrons are accepted by NADP+ through the NADP+ dehydrogenase enzyme to produce NADPH

7) PS1 electrons lost are replenished by ELECTRONS FROM FIRST ETC

27
Q

Chloroplast ETC

A

1) ATP produced in STROMA

2) Protons pumped into thylakoid space

3) Proteins sit in thylakoid membrane

28
Q

Cytochrome Complex

A

Chloroplast ETC

29
Q

2 sources of proton gradient in chloroplasts:

A

1) Pumping H+ into thylakoid space from stroma

2) Splitting of water from light reactions

30
Q

BOTH cyclic and non-cyclic flow are needed because…

A

The calvin cycle requires more ATP than NADPH

–> Therefore the cyclic flow provides that extra ATP needed

31
Q

Calvin cycle

A

Anabolic cycle taking place in the stroma that utilizes ATP, NADPH, and CO2 to create simple sugars

32
Q

3 main steps in the calvin cycle:

A

1) Carbon fixation

2) Reduction

3) RuBP Regeneration

33
Q

Carbon Fixation Step

A

CO2 from the air is attached to the RuBP sugar through the RUBISCO enzyme

34
Q

RuBP

A

Ribulose Bi-phosphate sugar

35
Q

RUBISCO

A

Enzyme that attaches CO2 to RuBP

36
Q

Reduction Step (calvin)

A

A series of reactions which:
1) Utilize NADPH as H+ source
AND
2) Utilize ATP as source for phosphate

to produce:

6 G3P molecules (3 carbon sugars)

37
Q

What occurs to the 6 G3P molecules produced by calvin cycle?

A

1 G3P leaves the cycle to make other biomolecules

5 G3P remain in the cycle to help regenerate RuBP

38
Q

Regeneration of RuBP

A

The remaining 5 G3P molecules are used to recreate RuBP (with the help of phosphorylation from ATP)

39
Q

3 main types of plants:

A

1) C3

2) C4

3) CAM

40
Q

Adapted version of plants (2)

A

1) C4

2) CAM

41
Q

C4 Plants have what kind of separation?

A

Have SPATIAL separation

42
Q

C4 plants are adapted to which envrionment?

A

–> Adapted to SEMI DRY conditions: stomata only half open

43
Q

C4 Plants Calvin Process

A

1) Fix CO2 into oxaloacetate (4C) in MESOPHYLL CELLS

2) Transfer the oxaloacetate to BUNDLE SHEATH CELLS where calvin cycle takes place

44
Q

C4 Examples

A

Corn, Cane sugar

45
Q

CAM plants have what kind of separation?

A

Have TEMPORAL separation

46
Q

CAM Plants are adapted to which environment

A

DRY –> Think desert like

–> Open stomata at NIGHT (when cooler)

–> Close stomata during DAY (when hotter)

47
Q

CAM Plants Calvin Process

A

1) NIGHT: Stomata opens –> takes in CO2 –> produces oxaloacetate

2) DAY: Stomata closed –> light reactions occur –> oxaloacetate undergoes calvin cycle

48
Q

CAM examples

A

Cacti, pineapples