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PF&F > Lecture 6 Photosynthesis > Flashcards

Lecture 6 Photosynthesis Flashcards

1
Q

Photosynthesis # of CO2 vs Cellular Respiration

A

Photosynthesis = 3CO2
Cellular Respiration = 1CO2

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2
Q

___ is always the mobile e- carrier to transfer e- carrier between the CC & P700

A

Plastocyanin

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3
Q

Sunlight + ATP + CO2 + H2O –(in chloroplasts)–> Glucose + O2

A

Photosynthesis

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4
Q

Glucose + O2 –(Cytoplast & Mitochondria)–> ATP + CO2 + H2O + heat

A

Cellular Respiration

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5
Q

Where does photosynthesis take place in ?

A

Chloroplasts

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6
Q

Where does cellular respiration take place in?

A

Cytoplasm + Mitochondria

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7
Q

Light E from sun by fixation of atmospheric carbo is converted into ____ energy

A

Chemical Energy

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8
Q

Energy transduction reaction (light reaction) produces ___ & ___

A

ATP & NADPH
Occurs in thylakoid membranes

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9
Q

e- carrier of photosynthesis

A

NADPH

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10
Q

___ & ___ fuel Calvin Cycle

A

ATP & NADPH
Produces sugars

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11
Q

Transpiration

A

Plant’s loss of water, mainly through the stomata of leaves

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12
Q

Pigments

A

Substances that absorb light
Used as E for organisms

Black = complete absorption
White = Complete reflection

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13
Q

Chlorophyll

A

Pigment that absorbs light in violet, blue & red spectrum
BUT reflects green

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14
Q

What are the 3 main chlorophyll pigments

A
  • Essential
  • Accessory
  • Carotenoids: visible in autumn when chlorophyll breaks down (red/ fall colours)
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15
Q

All photosynthetic reactions occur in the __

A

Chloroplast

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16
Q

Chloroplast contains ___

A

Chlorophyll

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17
Q

Thylakoid membranes contain ___

A

Pigments

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18
Q

2 major reactions in photosynthesis

A
  1. Light Reaction
    (E transduction reaction; Photolysis)
  2. Light independent reaction
    (Carbon Fixation Reaction)
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19
Q

Light E is absorbed by pigments via ___ ___ in the ____ ____

A

Antenna complexes / Thylakoid membranes

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20
Q

The light shines down and ___ an e- causing it to bounce around antenna complex

A

Excites

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21
Q

Excited e- are funneled by the antenna complexes to 2 transmembrane proteins known as: Photosystems __ & __

A

2 & 1 (in this order)

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22
Q

Why is PS2 before PS1?

A

PS2 was discovered first hence the order.

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23
Q

PS1 Light absorption peak

A

P700

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24
Q

PS2 Light Absorption Peak

A

P680

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25
Q

Photolysis

A

Separation of water molecules by the action of light E

Photo-sun
Lysis-cut

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26
Q

In photolysis, after pulling e- in pigment, excited e- is replaced by stealing e- from water molecules inside ___ ____

A

Thylakoid membranes

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27
Q

Photolysis creates concentration gradient of __ & __ within thylakoid

A

H+ & O2

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28
Q

Non-cyclic (Linear) e- Flow: PS2 & PS1

A

Starts at PS2, Ends at PS1
Excited e- from PS2 gets transferred to NADPH from PS1
Linear e- flow driven from 2 photochemical reactions

29
Q

Light Reaction

A

Light + H2O = O2 + ATP + NADPH
Free energy charge = 51 kcal/mole
Total E from non-cyclic e- flow = 6 ATP & 6 NADPH

30
Q

Calvin Cycle cost

A

E cost = 9 ATP & 6 NADPH

31
Q

Why is the Calvin cycle E Cost a problem?

A

Because of unequal amounts of ATP/ NADPH means we will run out of ATP first

32
Q

Cyclic (non-linear) e- flow

A

PS1 can work independently of PS2
Uses same machinery but reconfigure direction towards CC
Passes thru P700 in order to create just ATP without PS2

33
Q

Light Independent Reaction

A

Uses ATP & NADPH generated from PS1 & PS2 + CO2
2nd major photosynthetic reaction AKA Carbon-Fixation Reaction
2nd in series of photosynthetic reactions

34
Q

Stomata

A

Special openings in stems and leaves of terrestrial plants
- allows CO2 to enter plant cells
- knows when to open and close these openings

35
Q

3 Different Carbon Fixation Pathways

A
  1. C3 - Calvin Cycle
  2. C4 - Hatch Slack
  3. CAM - Crassulacean Acid Metabolism
36
Q

Carbon fixation pathway involving temperate plants with no special mods

A

C3 Plant

37
Q

Carbon fixation pathway involving hot weather plants with separate fixation & Calvin cycle

A

C4 Plant

38
Q

Carbon fixation pathway involving desert plants with temporal separation including night gas exchange and day photosynthesis

A

CAM Plant

39
Q

3 Steps of C3 - Calvin Cycle

A
  1. Carbon Fixation
  2. PGA Reduction to PGAL
  3. RuBP Regeneration
40
Q

Step 1 C3: Carbon Fixation

A

CO2 bind with RuBP, gets split and broken by enzyme Rubisco to create PGA
RuBP: ribulose 1,5-biphosphate (5-C molecule)

41
Q

Step 2 C3: PGA Reduction (5 total)

A
  • Uses most of ATP & NADPH produced by light reaction of photosynthesis
  • Turning PGA to PGAL
  • ATP & NADPH reduce 3PGA to G3P
  • Taking ATP, moves phosphate around & turns into ADP
  • From there we pull out, remove to create PGAL
  • We oxidize to create PGAL
42
Q

Step 3 C3: RuBP Regeneration

A

-Most PGAL generated in step 2 is used to regenerate RuBP
- 5/6 molecules creates a cyle
- Regeneration requires 3 ATP
- Remaining PGAL moved to cytosol, converted to sucrose
- PGAL stored in chloroplast, converted to starch
- Starch is stored in chloroplast in daylight, but exported to the rest of the plant as sucrose at night

43
Q

Problems with C3 Calvin Cycle

A

Hot & dry condition plants cut stomata to prevent evaporative loss, CO2 stops moving altogether

44
Q

Salvage Pathway C3

A

In absence of CO2, RuBP binds to O2 and initiates photorespiration

45
Q

Photorespiration

A

Costly process that consumes O2 & starch, doesn’t produce ATP or NADPH and instead produces useless metabolite: Phosphoglycolate

46
Q

What is formed during photorespiration and is metabolically useless?

A

Phosphoglycolate

47
Q

Solution to photorespiration is known as which pathway?

A

C4 or Hatch-Slack Pathway

48
Q

Hatch-Slack Pathway C4

A

Uses spatial separation, C4 plants employ both the C3 and C4 pathways of Carbon Fixation

49
Q

Problem with Photorespiration

A

Very costly in E to restart Calvin cycle

50
Q

2 types of chloroplast in C4 Plants

A
  1. Normal chloroplasts in mesophyll cells
  2. Grana-less chloroplasts in bundle sheath cells
51
Q

Spatial Separation

A

Where carbon fixation and Calvin cycle occur in different types of cells

52
Q

Main Advantages of C4 Pathway (3 total)

A
  • PEP greater affinity for CO2 than RuBP
  • PEP allows plant to function in conditions where CO2 is limited
  • Can bind to ANY CO2 present, will not bind O2
53
Q

In the C4 Pathway, CO2 binds to ___ instead of RuBP which creates Oxaloacetate

A

PEP

54
Q

PEP stands for

A

Phosphoenolpyruvate

55
Q

In C4 Pathway, oxaloacetate changes (reduced) to ___

A

Malate

56
Q

In C4 Pathways, Malate is converted to __ & __

A

CO2 & Pyruvate

57
Q

In C4 Pathways, CO2 enters ___ ___ and Pyruvate regenerates ___

A

Calvin Cycle & PEP

58
Q

What restarts the entire C4 Pathway cycle?

A

PEP Regeneration

59
Q

CAM stands for

A

Crassulasean Acid Metabolism

60
Q

CAM Pathway

A

Uses temporal separation of carbon fixation

61
Q

What plants primarily use CAM pathways?

A

Primarily in succulents (pineapple & cacti) in tropical locations

62
Q

Stomata in CAM plants

A

In extreme heat the stomata in CAM plants are closed during the day but open at night

63
Q

In CAM Pathway, CO2 is converted to ___

A

Malate

64
Q

In CAM pathways, Malate is stored in ___ during ___

A

Vacuoles & Dark

65
Q

When can Carbon fixation of CO2 occur in CAM Pathways?

A

Carbon fixation of CO2 occurs at night when CO2 can move into the plant through open stomata

66
Q

In CAM pathway, Calvin cycle occurs during the day through conversion of ___ back into __ & __

A

Malate, CO2, Pyruvate

67
Q

Calvin cycle during day conversion turns malate back into __ & __

A

CO2 & Pyruvate

68
Q

Night (stomata open)

A

CAM Plants open their stomata during the night to minimize rate of transpiration.
- Start from chloroplast broken down into PEP
- Reacts with CO2, creates oxaloacetate
- Oxaloacetate is reduced to malate + stored as malic acid in vacuole

69
Q

Day (stomata closed)

A

CAM plants keep stomata closed during daytime to reduce loss of water.
They can do this because they fix CO2 into organic acids during the night.
- Malic acid taken from vacuole, decarboxylated, produces CO2 to pyruvate
- CO2 goes to Calvin Cycle
- Pyruvate degraded further in Citric Acid Cycle (respiration) - creates more usable CO2

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