electron transport and oxidative phosphorylation continued

Question 1

what domains do ATP synthase contain

Answer 1

F0
F1

Question 2

How many subunits does f1 have

Answer 2

5 subunits

Question 3

described F0 unit

Answer 3

• imbedded into the inner mitochondrial membrane
• has proton pore through which protons leak
• the pore consists of a number of sub units
• single unit binds to the outside

Question 4

Describe the F1 subunit

Answer 4

• extends into the mitochondrial matrix
• contains catalytic activity of the synthase in which ATP is stabilised on the surface of this subunit

Question 5

Draw the structure of ATP synthase

Answer 5

Question 6

what does a stator do in ATP synthase

Answer 6

• provides stability

Question 7

what is important about the F1 region

Answer 7

• contains alpha 3 and beta 3 hexene ring
  Functions:
• bind the ADP and Pi
• Catalyse the synthesis of ATP
• Release the ATP

Question 8

Does the alpha 3 and beta 3 hexemar ring rotate?

Answer 8

no
only the gamma structure rotates due to F0

Question 9

what does the alpha units and beta units contain

Answer 9

• alpha unit contains bound ATP but do not participate int he reaction. ATP is not released
• Beta unit= can be found in 3 states
  Open, loose and tense
• ATP only released in open state
• Tense = ADP and Pi close enough to produce ATP

Question 10

what drives the conversion of 3 states of the beta subunit

Answer 10

the rotation of gamma

Question 11

how much does gamma rotate by?

Answer 11

120 degrees anticlockwise

Question 12

what is the evidence found for rotational catalysis

Answer 12

• Genetically engineered F1 allowed for attachment of ATP synthase to a Ni complex
• Biotin was covalently attached to C on F0 - avidin is bound to biotin
• Actin labelled with a fluorescent probe was attached
• When ATP was introduced as a substrate the actin was found to move

Question 13

Describe the mechanisms of the F0

Answer 13

• each unit of c is made up of a pair of a helices
• the top of which extends to the inter membrane space
  -cytoslic half channel = subunit consisting of 2 half channels , a proton can move into the channel but not through it
  Aspartic acid have 2 negative charges
  Hydrogens pushed into subunit due to gradient
  Allows the subunit to freely rotate
  Moves hydrogen into complex where it is occupied and diffuse into mitochondria
  Initial state again

Question 14

How are NAD+/NADH, ADP, ATP transported if they are impermeable to the inner mitochondrial membrane

Answer 14

shuttles

Question 15

How is NADH transported across

Answer 15

• Muscle shuttles
• Glycolysis produces NADH in the cytosol of the cell by oxidation of G3P
• Working aerobically NAD+ must be regenerated and NADH cannot pass through the inner mitochondrial membrane
• the electrons form NADH are transported into the mitochondrial via glyceraol 3 phosphate shuttle

1. A pair of electrons are transferred from NADH to dihydroxyacetone phosphate
2. forming glycerol 3 phosphate via the enzymatic catalysis using cytoplasmic Glycerol 3 phosphate dehydrogenase
3. Glycerol 3 phosphate is re oxidised to DHAP via Glycerol 3 phosphate dehydrogenase
4. electron pair is transferred to FAD forming FADH2
5. The reduced flavin transfers electrons onto Q

Question 16

How are electrons form NADH within the cytosol transported into he mitochondria

Answer 16

• malate aspartate shuttle
  1. electrons are transferred from NADH to oxaloacetare producing malate
  2. Malate then moves through he membrane and is re oxidised. by NAD+ ( malate dehydrogenase)
  3. Glutamine reacts oxaloacetate forming aspartate
  4. Aspartate then moves out via an exit shuttle

Question 17

when does the aspartate shuttle only work

Answer 17

• if NADH/NAD+ ratio is higher in the cytosol than mitochondrial matrix

Question 18

How does ATP/ADP move across inner mitochondrial membrane

Answer 18

• specific transport protein called ATP-ADP trasnlocase
• proteins makes up 14% of membrane

Question 19

how many transporters are encoded in the human genome

Answer 19

40

Question 19

describe other mitochondrial trasnporetes

Answer 19

dicarboxylate carrier
tricarboxylate carrier
pyruvate carrier
phosphate carrier

Question 20

how is the rate of oxidative phosphorylation regulated

Answer 20

• by the amount of ADP in the system
• ADP also regulates TCA cycles as this depends on the NAD+ and FAD

Question 21

What are the consequences if ADP is NOT converted to ATP

Answer 21

• electrons will not flow through the ETC and oxygen will not be the ultimate acceptor of these electrons

Question 22

what else can oxidation produce

Answer 22

heat by adipose tissue ‘ brown fat’

Question 23

what does the brown fat contain

Answer 23

• unique uncoupling protein which passes by F0F1 complex, so energy of oxidation is dissipated as heat

Question 24

what is a phamalocgica uncoupling

Answer 24

• uncouples the Electron transport by directly transporting protons across the mitochondrial membrane
  NADH to O2 is unaffected but ATP is not synthesised

Question 25

describe a pharmoligcal uncoupler

Answer 25

2-4 Dinitrophenol (DNP)
- photographic chemical a fertiliser used int he manufacturing of dyes and explosives

• FDA approved in 1933 for weightless
  1938 banned - extremely dangerous

Question 26

How can oxidative pshophaorylation by inhibited at ETC

Answer 26

• Rotenone
• Antimycin A
• CN- or CO