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Life of Earth 2 > Leaves & photosynthetic pathways > Flashcards

Leaves & photosynthetic pathways Flashcards

(42 cards)

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1
Q

What are the main parts of a leaf?

A 
Blade =
>apex
>margin
>vein
>base

Petiole
Axial bud
Stipule

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2
Q

Which fibres strengthen the leaf?

A

Sclerenchyma

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3
Q

What does the spongy mesophyll contain?

A

Xylem + phloem surrounded by bundle sheath cells

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4
Q

What is phyllotaxy?

A

Leaf arrangement

- efficiently distributing leaves to reduce overlap and maximise light capture

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5
Q

What type of phyllotaxy do most angiosperms have?

A

Alternate phyllotaxy

= leaves arrange din ascending spiral around stem - each leaf emerging 137.5 degrees from the previous one

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6
Q

What are the 3 general types of dicotyledonous leaves?

A

Simple
Compound
Doubly compound

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7
Q

How do veins differ in monocots & dicots?

A

Monocots: parallel veins

Dicots: branched network of major veins

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8
Q

During the redox reaction of photosynthesis, which compound is reduced and which is oxidised?

A

CO2 reduced into glucose

H2O oxidised into O2

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9
Q

Chlorophyll absorbing light results in what?

A

Water splitting into protons + electrons

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10
Q

How many protons + electrons are transferred to NADP+?

What is produced?

A

1 proton + 2 electrons

NADPH
reduced NADP

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11
Q

Light energy is initially converted into chemical in the form of which 2 compounds?

A

NADPH
= source of electrons as ‘reducing power’ that can be passed on to another electron acceptor

ATP
by photophosphorylation of ADP

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12
Q

Photosynthesis is made of which 2 reactions?

A

Light reaction

Calvin cycle

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13
Q

What is the main objective of the Calvin cycle?

A

Forms sugar (G3P) from CO2 using ATP + NADPH

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14
Q

What do photosynthetic pigments do?

A

Absorb light

- diff pigments absorb diff wavelengths

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15
Q

What happens to wavelengths that aren’t absorbed?

Give an example.

A

Reflected

Green (500-600nm) = why plants are green

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16
Q

What is the main photosynthetic pigment?

What are the 2 accessory pigments?

A

Chlorophyll a

> Chlorophyll b - broadens spectrum for photosynthesis

> Carotenoids - absorb excessive light that would damage chlorophyll

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17
Q

Describe the excitation of chlorophyll by light

Study These Flashcards
A
  1. chlorophyll absorbs light
  2. energy from absorbed photons excites electrons
  3. electrons move from ground state = unstable
  4. electrons drop back to ground state releasing heat/light
18
Q

What are light-harvesting systems made up of?

What function do they carry out?

Study These Flashcards
A

chlorophyll a, chlorophyll b + carotenoids bound to proteins

transfer photon energy to reaction centre

19
Q

What is the reaction centre?

Study These Flashcards
A

An organised association of proteins holding a special pair of chlorophyll a molecules

20
Q

Describe how a photosystem harvests light

Study These Flashcards
A
  1. photon excites electron in pigment
  2. energy transferred through other pigments
  3. excited electron transferred to special pair of chlorophyll a molecules in reaction centre
  4. pass excited electron to primary electron acceptor - becomes reduced
21
Q

What are the 2 photosystems and the wavelengths they absorb?

Study These Flashcards
A

PS II = 680nm

PS I = 700nm

22
Q

What happens in PS II once an electron is passed from the P680 chlorophyll a to the primary electron acceptor?

Study These Flashcards
A

P680 with a missing electron
= P680+
(has an electron hole)

23
Q

An enzyme then catalyses the photolysis of what…?

Study These Flashcards
A

H2O
–>
2 e + 2 H+ + 1/2 O2

24
Q

What are the products of the photolysis of water used for?

Study These Flashcards
A

Electrons supplied to the P680+ –> replacing those passed to primary electron acceptor

H+ released into thylakoid lumen

O atom immediately combines w/ another O atom

25
What is the 1st ETC made up of?
> Plastoquinone > a cytochrome complex > Plastocyanin
26
What happens as electrons pass through the cytochrome complex?
H+ (protons) are pumped into thylakoid lumen | --> contributes to proton gradient used in chemiosmosis
27
What happens in PS I when P700 transfers an excited electron to the primary electron acceptor?
P700 converted to electron deficient form = P700+ electrons replaced via ETC
28
What is the 2nd ETC made of?
Ferredoxin
29
What does NADP+ reductase do?
Catalyses the transfer of e from ferredoxin to NADP+
30
What happens in the conversion of NADP+ to NADPH?
2 electrons required for the reduction | Removes 1 H+ from stroma
31
What are the 3 main phases of the Calvin cycle?
1. Carbon fixation (using Rubisco) 2. Reduction 3. Regeneration of RuBP
32
What is the sugar produced in the Calvin cycle?
G3P = glyceraldehyde 3-phosphate
33
What happens in hot, arid environments? These conditions favour what process?
Stomata close --> O2 builds up photorespiration
34
What happens in photorespiration?
Rubisco adds O2 instead of CO2 in the Calvin cycle | --> produces 2-C compound
35
Why isn't photorespiration good?
Consumes O2 + organic fuel Releases CO2 Doesn't produce ATP or sugar
36
Why might photorespiration be an evolutionary relic?
Rubsico 1st evolved at a time when atmosphere had much less O2 + more CO2 It limits damaging products of light reactions that build up in absence of Calvin cycle
37
Why are C4 plants special?
Minimise cost of photorespiration by incorporating CO2 into 4C compounds in mesophyll cells. - -> 4C compounds exported to bundle-sheath cells - -> release CO2 for Calvin cycle
38
Which enzyme do C4 plants need?
PEP carboxylase | - higher affinity for CO2 than Rubisco
39
What do CAM plants do?
Use crassulacean acid metabolism to fix carbon 1. Open stomata at night - -> incorporate CO2 into organic acids 2. Close stomata in day - -> CO2 released & used in Calvin cycle
40
What are the pros of C4 plants?
Beneficial in high light, low nutrient envrios as require less Rubisco
41
What are the cons of C4 plants?
Regeneration of PEP in C4 pathway requires more ATP than in C3 photosynthesis --> bad for low light enviros
42
What are CAM plants usually associated with and why?
Succulence & low photosynthetic capacity As photosynthesis is proportional to vacuolar storage

Life of Earth 2 (20 decks)

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