[12.3] oxidative phosphorylation

Question 1

what is oxidative phosphorylation?

Answer 1

indirect linking of energy from phosphate to ATP to produce ATP involving energy from the hydrogen atoms that are carried on NAD and FAD

cells produce most of their ATP this way

Question 2

what molecules are taken from the krebs cycle to oxidative phosphorylation?

Answer 2

hydrogen atoms by the coenzymes NAD and FAD

Question 3

where does the electron transfer chain take place?

Answer 3

between the inter-membranal space and the matrix

Question 4

what does the synthesis of ATP in oxidative phosphorylation involve?

Answer 4

transfer of electrons down a series of electron carrier molecules which forms the electron transfer chain

Question 5

describe the electron transfer chain process

Answer 5

1. H atoms produced during glycolysis and the krebs cycle combine with coeznymes NAD and FAD
2. reduced NAD and FAD donate the electrons of the H atoms they are carrying to the first molecule in the ETC
3. the electrons pass along a chain of electron transfer carrier molecules in a series of oxdiation-reduction reactions
4. as the electrons flow along the chain, the energy they release causes the active transport of protons across the IMM into the IMS
5. the protons accumulate in the IMS before they diffuse back into the matrix through ATP synthase channels embedded in the IMM
6. at the end of the chain, the electrons combine with these protons and oxygen to form water

Question 6

what is oxygen called in the ETC?

Answer 6

final electron acceptor

Question 7

describe the equation for forming water at the end of the chain

Answer 7

½O₂ + 2e⁻ + 2H⁺ ➞ H₂O

Question 8

what is the ETC a series of?

Answer 8

redox reactions

Question 9

how is energy released during redox reactions?

Answer 9

• redox reactions release energy when electrons move close to electronegative atoms
• this movement of electrosn through the chain releases the energy needed to produce ATP

Question 10

why is energy released in stages?

Answer 10

• the greater the energy released in a single step, the more of it is released as heat and the less there is available for useful purposes
• when energy is released a little at a time, more of it can be harvested for the benefit of the organism
• this is why the electrons carried by NAD and FAD are not transferred in one step

Question 11

how do electrons move down an energy gradient?

Answer 11

electrons are passed along a series of electron transfer carrier molecules, each of which is at a slightly lower energy level

Question 12

what does chemiosmosis describe?

Answer 12

diffusion of protons across the partially permeable inner mitochondrial membrane, down their electrochemical gradient through ATP synthase channels

Question 13

which substances can also be used as respiratory substrates other than sugars?

Answer 13

• lipids
• protein

Question 14

what happens to lipids before they are respired?

Answer 14

hydrolysed to glycerol and fatty acids

Question 15

what happens to the glycerol after the lipid is hydrolysed?

Answer 15

• phosphorylated
• converted to triose phosphate
• this enters the glycolysis pathway and subsequently the krebs cycle

Question 16

what happens to the fatty acid component after the lipid is hydrolysed?

Answer 16

• broken down into 2-carbon fragments
• these are converted to acetyl coenzyme A
• this then enters the krebs cycle

Question 17

why do lipids release more than double the energy for the same mass of carbohydrate?

Answer 17

• oxidation is lipids produces 2-carbon fragments of carbohydrate and many H atoms
• H atoms are used to produce ATP during OP

Question 18

how can protein be used for respiration?

Answer 18

• hydrolysed to its constituent AA
• have their amino group removed (deamination)
• enters respiratory pathway at different points depending on the number of C atoms they contain

Question 19

what are 3, 4, and 5-carbon AA compounds converted into?

Answer 19

• 3 = pyruvate
• 4 and 5 = intermediates in the krebs cycle