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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
Photolysis
Separation of water molecules by the action of light E Photo-sun Lysis-cut
26
In photolysis, after pulling e- in pigment, excited e- is replaced by stealing e- from water molecules inside ___ ____
Thylakoid membranes
27
Photolysis creates concentration gradient of __ & __ within thylakoid
H+ & O2
28
Non-cyclic (Linear) e- Flow: PS2 & PS1
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
Light Reaction
Light + H2O = O2 + ATP + NADPH Free energy charge = 51 kcal/mole Total E from non-cyclic e- flow = 6 ATP & 6 NADPH
30
Calvin Cycle cost
E cost = 9 ATP & 6 NADPH
31
Why is the Calvin cycle E Cost a problem?
Because of unequal amounts of ATP/ NADPH means we will run out of ATP first
32
Cyclic (non-linear) e- flow
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
Light Independent Reaction
Uses ATP & NADPH generated from PS1 & PS2 + CO2 2nd major photosynthetic reaction AKA Carbon-Fixation Reaction 2nd in series of photosynthetic reactions
34
Stomata
Special openings in stems and leaves of terrestrial plants - allows CO2 to enter plant cells - knows when to open and close these openings
35
3 Different Carbon Fixation Pathways
1. C3 - Calvin Cycle 2. C4 - Hatch Slack 3. CAM - Crassulacean Acid Metabolism
36
Carbon fixation pathway involving temperate plants with no special mods
C3 Plant
37
Carbon fixation pathway involving hot weather plants with separate fixation & Calvin cycle
C4 Plant
38
Carbon fixation pathway involving desert plants with temporal separation including night gas exchange and day photosynthesis
CAM Plant
39
3 Steps of C3 - Calvin Cycle
1. Carbon Fixation 2. PGA Reduction to PGAL 3. RuBP Regeneration
40
Step 1 C3: Carbon Fixation
CO2 bind with RuBP, gets split and broken by enzyme Rubisco to create PGA RuBP: ribulose 1,5-biphosphate (5-C molecule)
41
Step 2 C3: PGA Reduction (5 total)
- 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
Step 3 C3: RuBP Regeneration
-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
Problems with C3 Calvin Cycle
Hot & dry condition plants cut stomata to prevent evaporative loss, CO2 stops moving altogether
44
Salvage Pathway C3
In absence of CO2, RuBP binds to O2 and initiates photorespiration
45
Photorespiration
Costly process that consumes O2 & starch, doesn't produce ATP or NADPH and instead produces useless metabolite: Phosphoglycolate
46
What is formed during photorespiration and is metabolically useless?
Phosphoglycolate
47
Solution to photorespiration is known as which pathway?
C4 or Hatch-Slack Pathway
48
Hatch-Slack Pathway C4
Uses spatial separation, C4 plants employ both the C3 and C4 pathways of Carbon Fixation
49
Problem with Photorespiration
Very costly in E to restart Calvin cycle
50
2 types of chloroplast in C4 Plants
1. Normal chloroplasts in mesophyll cells 2. Grana-less chloroplasts in bundle sheath cells
51
Spatial Separation
Where carbon fixation and Calvin cycle occur in different types of cells
52
Main Advantages of C4 Pathway (3 total)
- 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
In the C4 Pathway, CO2 binds to ___ instead of RuBP which creates Oxaloacetate
PEP
54
PEP stands for
Phosphoenolpyruvate
55
In C4 Pathway, oxaloacetate changes (reduced) to ___
Malate
56
In C4 Pathways, Malate is converted to __ & __
CO2 & Pyruvate
57
In C4 Pathways, CO2 enters ___ ___ and Pyruvate regenerates ___
Calvin Cycle & PEP
58
What restarts the entire C4 Pathway cycle?
PEP Regeneration
59
CAM stands for
Crassulasean Acid Metabolism
60
CAM Pathway
Uses temporal separation of carbon fixation
61
What plants primarily use CAM pathways?
Primarily in succulents (pineapple & cacti) in tropical locations
62
Stomata in CAM plants
In extreme heat the stomata in CAM plants are closed during the day but open at night
63
In CAM Pathway, CO2 is converted to ___
Malate
64
In CAM pathways, Malate is stored in ___ during ___
Vacuoles & Dark
65
When can Carbon fixation of CO2 occur in CAM Pathways?
Carbon fixation of CO2 occurs at night when CO2 can move into the plant through open stomata
66
In CAM pathway, Calvin cycle occurs during the day through conversion of ___ back into __ & __
Malate, CO2, Pyruvate
67
Calvin cycle during day conversion turns malate back into __ & __
CO2 & Pyruvate
68
Night (stomata open)
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
Day (stomata closed)
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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