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BIOL1115 LECTURE > Chapter 10 > Flashcards

Chapter 10 Flashcards

1
Q

what is an autotroph?

A

organism that produces organic molecules using CO2 as carbon source

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2
Q

why do autotrophs produce their own food?

A

to sustain themselves without eating other organisms

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3
Q

what are photoautotrophs?

A

organisms that use photosynthesis as a process to produce their own food

ex: plants, algae, cyanobacteria

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4
Q

what does CO₂ contribute to photosynthesis?

A

carbon molecules for the glucose

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5
Q

is photosynthesis endergonic or exergonic

A

endergonic

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6
Q

is photosynthesis catabolic or anabolic?

A

anabolic

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7
Q

what is being reduced in photosynthesis?

A

CO₂ is reduced into glucose

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8
Q

what is being oxidized in photosynthesis?

A

H₂O is being oxidized into O₂

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9
Q

what two metabolic stages occurs in photosynthesis?

A
  1. light harvesting rxns
  2. calvin cycle
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10
Q

which plant cells perform photosynthesis?

A

palisade and spongy cells

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11
Q

what occurs in the chloroplast’s thylakoid membrane?

A

the photosynthetic ETC/ light harvesting reactions

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12
Q

what occurs in the chloroplast’s stroma?

A

the Calvin-light-independent cycle

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13
Q

what are photosystems?

A

protein-pigment complexes that absorb light/photons in order to drive the transfer of electrons

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14
Q

describe the flow of electrons in the photosystems

A

H₂O → NADP+ → NADPH

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15
Q

how much of the sugars made by photosynthesis are consumed as fuel for cellular respiration in plant cells?

A

about half of the sugars, rest are used for structure, energy storage, other organic compounds

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16
Q

why do plants need mitochondria for ATP production if ATP is already made in the light-harvesting reactions?

A

plants still need to undergo cellular respiration at night (no light, cannot produce ATP via light-harvesting rxns)

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17
Q

what are the products in the light-harvesting reactions?

A

O₂ , ATP, NADPH

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18
Q

Summarize what occurs in the light-harvesting reactions

A

light/photons are absorbed by electrons from water, transferred through photosystems, reducing NADP+ to NADPH

ATP synthesized by ETC

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19
Q

Summarize what occurs in the Calvin Cycle

A

ATP and NADPH from light-harvesting rxns convert CO₂ into sugars

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20
Q

what happens to excess carbs produced from photosynthesis?

A

converted to starch and stored temporarily in chloroplasts

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21
Q

what is light?

A

type of electromagnetic energy with wave-like properties

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22
Q

what is wavelength?

A

distance between crests of waves?

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23
Q

what is frequency?

A

of waves in a certain distance?

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24
Q

Describe the relationship between amount of energy and wavelength of the light

A

The amount of energy is INVERSELY related to the wavelength of light

(e.g. longer wavelength → lower energy)
(shorter wavelength → higher energy)

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25
Q

what absorbs light that drives the light-harvesting reactions?

A

photosynthetic pigments (pigments that absorb light/take part in photosynthesis)

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26
Q

what are pigments?

A

molecules that absorb wavelengths of visible light

27
Q

why do pigments look coloured?

A

pigments reflect/transmit light they DO NOT absorb

28
Q

why do leaves appear green?

A

leaves have chlorophyll, a pigment that reflects green light because it does not absorb it

29
Q

what is the absorption spectrum?

A

a graph plotting a pigment’s light absorption vs. wavelength

30
Q

what wavelengths of light does chlorophyll best absorb?

A

red and violet-blue

31
Q

what can carotenoids do that chlorophyll can’t?

A
  • absorb wavelengths of light that chlorophyll poorly absorbs
  • protect chlorophyll from damaging high-energy photons
32
Q

how is chlorophyll amphipathic?

A

chlorophyll has a polar head and nonpolar tail

33
Q

what is the purpose of chlorophyll’s porphyrin ring head?

A

absorbs light

34
Q

what is the purpose of chlorophyll’s hydrocarbon tail?

A

allows chlorophyll pigment to be anchored in the lipid membrane

35
Q

what happens when chlorophyll absorbs light?

A

one of its electrons becomes excited, goes from ground state to a higher energy excited state

36
Q

why is heat released when an excited electron returns to its ground state?

A

Because of the 2nd law of thermodynamics - all energy transformations increase entropy of the universe

37
Q

what is fluoresence?

A

the light/visible radiation emitted by a substance after its electrons are excited, which release the light energy it absorbs as heat and fluorescent light

38
Q

why does chlorophyll emit a different coloured light when it is excited?

A

The amount of energy it emits is less than what it initially received because of the 2nd law of thermodynamics, some of the energy dissipates in the form of heat

39
Q

where does electrons in a chlorophyll molecule of a plant cell come from?

A

from H₂O, H₂O is oxidized into O₂, providing electron for chlorophyll

40
Q

what happens to the electrons in a chlorophyll molecule of a plant cell when it absorbs light?

A

the electron becomes excited and transfers its energy to another electron in an adjacent chlorophyll molecule, which transfers energy to another electron in another chlorophyll molecule until it reaches a reaction centre

41
Q

what are antenna chlorophylls?

A

chlorophyll molecules that absorb and transfer energy from light

42
Q

what is a reaction centre?

A

a specially configured pair of chlorophyll molecules that can transfer the high-energy electron to an electron acceptor

43
Q

what happens in the electron transfer phase (reaction centre transfers electron to an electron acceptor) in terms of redox reactions?

A

reaction centre loses electrons, becomes oxidized

electron acceptor gains electrons, becomes reduced

44
Q

what must occur in order for the photosystem II to continue capturing light energy after an electron acceptor moves on the the photosynthetic ETC?

A

another electron must be delivered to the reaction centre to replace the electron that was lost and moved to electron acceptor

45
Q

which molecule is the electron donor in photosynthesis?

A

H₂O, donates electrons and becomes oxidized into O₂, reducing reaction centre

46
Q

why are two photosystems necessary?

A

provides enough energy to pull electrons from water and then use them to reduce NADP+ to form NADPH

47
Q

what is photosystem II?

A

supplies electrons to the beginning of the ETC, when photosystem II loses an electron, photosystem I can pull another electron from water

48
Q

what is photosystem I?

A

energizes electrons with a second input of light energy, so they have enough energy to reduce NADP+ to form NADPH

49
Q

where do protons accumulate in the chloroplast?

A

in the thylakoid lumen (inside thylakoids)

50
Q

what increases the H+ conc. in the thylakoid lumen?

A

the oxidation of H₂O occurs in the thylakoid lumen, which produces O₂ and H+

51
Q

what complex works as a H+ pump to move H+ from stroma to the lumen?

A

cytochrome b6f

52
Q

how do protons flow back into the stroma? what does this do regarding ATP?

A

protons flow back into stroma through ATP synthase, driving ATP synthesis

53
Q

what is photophosphorylation?

A

production of ATP using light/photons in order to provide enough energy to phosphorylate ADP

54
Q

describe the Z scheme

A
  1. electron pulled from water into PS II (LOWEST ENERGY)
  2. electron excited by absorbing light, travels through chlorophyll (HIGHER ENERGY)
  3. electron transfers through ETC (LOWER ENERGY)
  4. PS I energizes electrons using 2nd input of light (HIGHEST ENERGY)
  5. electron energy level used to reduce NADP+ to NADPH (HIGH ENERGY but LOWER than #4)
55
Q

what is the final electron acceptor in the light-harvesting reactions?

A

NADP+

56
Q

how is the energy from electrons used to do work in the light-harvesting reactions?

A

the formation of a proton gradient provides energy for photophosphorylation

57
Q

what are the reactants in the calvin cycle?

A

CO₂, ATP, and NADPH

58
Q

what is the product in the calvin cycle?

A

G3P ( triose phosphate ) which can be used by the cell to make glucose and other carbs

59
Q

can the calvin cycle occur in the dark?

A

yesssss

60
Q

what are the 3 stages of the calvin cycle?

A
  1. Carboxylation
  2. Reduction
  3. Regeneration
61
Q

describe carboxylation in the calvin cycle

A

3x CO₂ is added to 3x 5-carbon RuBP, catalyzed by enzyme rubisco. the 3x 6-carbon molecules are immediately broken down into 6x 3-carbon 3-PGA

62
Q

describe reduction in the calvin cycle

A

the 6x 3-PGA are phosphorylated by ATP

the 3-PGA are reduced when NADPH transfers 2 electrons and 1 H+, forming 6 G3P and releasing Pi

63
Q

describe regeneration in the calvin cycle

A

12-step process, 5 G3P molecules are reorganized and combined to regenerate 3 RuBP, using up ATP

64
Q

for ever 6 G3P, how many can be withdrawn from the calvin cycle?

A

only one, 5 G3P are needed to regenerate RuBP

BIOL1115 LECTURE (11 decks)

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