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Cell Biology > Mitochondria + Chloroplasts > Flashcards

Mitochondria + Chloroplasts Flashcards

1
Q

What is the primary function of M + C?

A

ATP synthesis

via ATP synthase

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2
Q

How efficient is ATP synthase?

What does it require?

A

100 ATP/sec

3H+ for 1 ATP

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3
Q

Describe how ATP synthase functions

A

H+ pass through F0
-> stalk rotates
-> conformational change in F1
= facilitates ATP production

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4
Q

What are the 2 subunits of ATP synthase?

A

F0 - embedded in membrane

F1 - peripherally associated with membrane

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5
Q

Where is ATP synthase found?

A

M’s inner membrane
C’s thylakoid membrane
Eubacteria’s inner membrane

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6
Q

What are the 2 components of a proton gradient?

A

Difference in voltage across membrane
= membrane potential

Difference in H+ conc
= pH

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7
Q

How is a proton gradient generated?

A

High energy e- passed along ETC (via series of REDOX reactions)

  • > release large amounts of energy
  • > used to pump H+ across membrane
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8
Q

What is a proton gradient a form of?

A

Stored energy

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9
Q

Describe proton pumping in mitochondria

A
  1. Fats + carbs enter Kreb’s cycle
  2. NADH generated
  3. Passes 2e- onto ETC
    (including cytochrome bc complex)
  4. Passes 2e- onto O2
  5. Forms H2O
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10
Q

What does NADH stand for?

A

Nicotinamide adenine dinucleotide

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11
Q

What are mobile electron carriers?

A

Substances that shuttle e- between proton pumping complexes

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12
Q

Give 2 examples of mobile electron carriers in mitochondria

A

Ubiquinone
- carries e- from NADH dehydrogenase to cytochrome bc complex

Cytochrome c
- carries e- from cytochrome bc complex to cytochrome oxidase complex

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13
Q

What is chemisosmotic coupling?

What is this known as in mitochondria?

A

The linkage of e- transport, H+ pumping and ATP synthesis

Oxidative phosphorylation

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14
Q

What is redox potential?

A

The measure of tendency to acquire or lose e-

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15
Q

What is the redox potential of NADH?

What is the redox potential of H2O?

A

High e- transfer potential
= -ve value

Low e- transfer potential
= +ve value

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16
Q

What happens to the redox potential along the mitochondrial ETC?

A

Increases
(e- affinity increases)

From -ve to +ve
= good e- donor to good e- acceptor

17
Q

How many carbons enter the Kreb’s cycle and how many leave?

What else is produced in each turn of the cycle?

A

2C enter in Acetyl CoA
2C released as CO2

3 NADH
1 GTP
1 FADH2

18
Q

Give 2 examples of agents that interfere with oxidative phosphorylation

What do these do?

A

Cyanide
Carbon monoxide

Block passage of e- to O2
= ATP synthesis grinds to a halt

19
Q

What do uncoupled mitochondria generate?

A

Heat

- H+ flow through mitochondrial membrane but NOT through ATP synthase

20
Q

Why is light required for photophosphorylation?

A

H2O is a poor e- donor

-> requires lots of light energy to extract e-

21
Q

How is the H+ gradient across the thylakoid membrane generated?

A

Proton pumping + protons released when e- are pulled off H2O

22
Q

How are high energy e- produced by light energy?

What then happens to this energy?

A

Sunlight absorbed by chlorophyll
-> e- raised to higher energy level by photons

Channeled into special pair of chlorophyll molecules in reaction centre

23
Q

What do photosystems consist of?

A

Antenna complex + a reaction centre

24
Q

Describe the flow of e- through the 2 photosystems

A 
e- extracted from water 
-> PSII
-> Cytochrome b6-f complex
-> PSI
-> NADP reductase 
= NADPH
25
Q

Give an example of a mobile electron carrier in chloroplasts

A

Plastoquinone

26
Q

How do redox potentials change in photosynthesis?

A

e- moves from high to low energy

with boosts at PSI + PSII

27
Q

In photosynthesis how many NADPH and ATP are produced for every 3C sugar produced?

What is this ATP + NADPH used for?

A

9 ATP
6 NADPH

Carbon fixation in the Calvin cycle

28
Q

What does Rubisco stand for?

A

Ribulose bis phosphate carboxylase

29
Q

What does Rubisco do?

A

Catalyses CO2 + RuBP
= Adds 1C + 5C
= 6C compound
-> cleaved into 2 x 3C compounds

30
Q

What are the similarities between mitochondria + chloroplasts?

A

Use H+ gradients across membranes to produce ATP via ATP synthase

e- transport along ETC drives H+ pump

Cytochrome bc and b6f show sequence similarity

Ubiquinone + plastoquinone resemble one another

31
Q

What are the differences between mitochondria + chloroplasts?

A

M: high energy e- from NADH
C: low energy e- from H2O but excited by light

M: ultimate e- acceptor = O2
C: “ = NADP+

M: chemical bond energy used in cellular processes
C: CB energy + reducing power used in C fixation

Cell Biology (23 decks)

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