Lecture 23 Flashcards

1
Q

standard reduction potential

A
  • a measure of electron affinity (Eº)
  • hydrogen electrode is used as a standard
  • electrons can flow towards or away from reference cell
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2
Q

Postive Eº

A
  • electrons flow from reference cell to wards the test cell
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3
Q

Negative Eº

A
  • electrons flow from test cell towards the reference cell
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4
Q
A
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5
Q

the more negative a redox potential is the …

A
  • lower electron affinity it has (it is more likely to transfer electrons to something else)
  • NADH is a good electron donor and O2 is a good electron acceptor
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6
Q

when electrons are passed down the ETC

A

the reduction potential increases with each transfarr

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7
Q

how to calculate E

A

G = -nFE
- n= number of electrons transferred
- F = faradays constant (96.5)

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8
Q

how do you know if a reaction is spontaneous

A
  • G is negative and E is positive
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9
Q

What role do metals play

A
  • metals are often found bound to a protein and function as an electron carrier
  • Example: NADH dehydrogenase (complex 1) contains iron sulfur centres
    Example: cytochromes have iron containing heme group
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10
Q

photosynthesis

A
  • light driven reaction that creates organic molecules from atmospheric carbon dioxide.
  • requires water and releases O2
  • O2 produced made aerobic respiration widespread
  • carried out in chloroplast
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11
Q

chloroplasts

A
  • specialized intracellular organelles where photosynthesis takes place
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12
Q

thylakoid membrane

A
  • folds to form flattened sacs known as thylakoid which contain internal space known as the thylakoid space
  • thylakoids can be stacked into grand
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13
Q

describe stage 1 and stage 2 of photosynthesis

A

stage 1 (light energy): protons are pumps into the thylakoid space driving the synthesis of atp
- NADP+ is reduced to NADHP
- light energy is required

stage 2 (dark reactions): ATP and NADPH are consumed to drive the manufacture of sugars from CO2

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14
Q

chlorophyll

A
  • light capturing pigments
  • absorbs green light poorly because light is absorbed by electrons by porphyrin ring in blue
  • contains a hydrophobic tail which holds the chlorophyll in the thylakoid membrane
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15
Q

phtosystem

A
  • is a multi protein complex containing chlorophyl that captures light energy and converts it into chemical energy
  • contains a set of antenna complexes and a reaction centre
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16
Q

antenna complexes

A
  • contain chlorophyl that captures light energy and randomly transfer it from one chlorophyll to the next
  • then the energy is eventually accepted by a chlorophyll dimer known as a special pari which is found within a reaction centre
  • the special pair hold its electrons at a lower energy level than other chlorophyll molecule
17
Q

What is charge separated state

A
  • the special pair becomes positively charges while the electron carrier become negatively charges
18
Q

What 2 systems does photosynthesis rely on

A
  • photosystem 1 and 1
  • they work together to produce products that will be used in stage 2 of photosynthesis
19
Q

photosystem II

A
  • photosystem II absorbs light energy and transfers electron to platoquinone
  • plastoquinone transfers its electron to a proton pump, pumping its electrons from the stroma to the thylakoid membrane generating a proton gradient
  • the gradient is used to drive the synthesis of ATP by ATP synthase in the stroma
20
Q

Photosystem I

A
  • photosytem I absorbs light energy and transfers electrons to ferredoxin
  • ferredoxin NADP reductase oxidized ferredoxin and reduces NADP+ to form NADPH in the stroma
21
Q

In both photosystems I and II how do you obtain an electron to replace the special pair electron

A
  • Photosystem II: from water
  • photosystem I: from photosystem II
22
Q

How does photosystem II replace the electron by using water

A
  • its uses a water-splitting molecule
  • four electrons are removed from two water molecules and transferred and replaced electrons lost by four special pairs
  • O2 was released
  • important to make sure no partially oxidized water molecule is released
23
Q

How does photosystem I replace the electron by photosystem II

A
  • the missing electron in photosystem I is re placed by an electron from photosystem II
  • electrons are passed from cytochrome b6-7 complex to plastocyanin which replaces lost electrons from the special pair in photosystem I
24
Q
A