L35 - Cell Metabolism 2

Question 1

Where does oxidative phosphorylation take place?

Answer 1

Mitochondria

Question 2

What is oxidative phosphorylation?

Answer 2

• e- transferred from NADH to FADH2 by e- donors to O2
• generates most of ATP (26-30 from complete oxidation of glucose)

Question 3

What does oxidative phosphorylation consist of?

Answer 3

• generation of proton gradient
• production of ATP

Question 4

What are the main steps in oxidative phosphorylation?

Answer 4

• NADH dehydrogenase complex
• cytochrome b-c complex
• cytochrom oxidase complex

Question 5

What are facts about oxidative phosphorylation?

Answer 5

• 1.14 pd between NADH and O2
• 220KJ.mol^-1
• voltage dif = proton gradient (1.4 pH units)

Question 6

What is the chemi-osmotic hypothesis?

Answer 6

Atp synthesis couple to the proton gradient

Question 7

What does ATP synthesis consist of?

Answer 7

• proton transport to mitochondrial intermembrane space
• transport of protons through inner membrane by ATp synthase
• proton gradient drives release of ATP from enzyme

Question 8

What are the stages in chemi-osmotic hypothesis?

Answer 8

• energy of e- transport used to pump protons across membrane
• proton gradient is harnessed by ATP synthase to make ATP

Question 9

What are facts about glycogen metaboism?

Answer 9

• glucose-1-phosphate and UDP glucose - key intermediates
• energy required (UTP)
• UDP - recognition and leaving group

Question 10

What happens in the syntehsis of glycogen a1,4 bonds?

Answer 10

• UDP leaves = oxycation intermediate
• 4hydroxy group on glucose residue adds to oxycation
• occurs with retention of stereochem
• extends glycogen polymer by 1 glucose residue

Question 11

What happens in the synthesis ofa,16 bonds?

Answer 11

• glycogen branching inc solubility
• rapid degradation when glucose needed
• branchin enzyme transfers terminal residues linked by a1,4 to 6 position of internal glucose res
• chains extended and branched further

Question 12

What happens in the degradation of glycogen a1,4 bonds?

Answer 12

• by glycogen phosphorylase (not for 1,6)
• forms oxycation intermediate
• phosphate adds = glucose-1-phosphate
• preserves phosphorylates status of glucose
• = same chem at C1

Question 13

What happens in the degradation of branches glycogen?

Answer 13

• residues removed by glycogen phosphorylase, 1,4 left next to 1,6
• glycosyl transferase moves 3 residues to another chain
• 1,6 linked res removed by 1,6-glycosidase enzyme = glucose
• exported/converted to glucose-6-phosphate

Question 14

What happens in the degradation of triacyl-glycerides?

Answer 14

• fats stored in adipose tissue
• long term high energy store
• hydrolysed to FAs and glycerol

Question 15

What happens in the FA B-oxidation?

Answer 15

• allows ATP synthesis in mitochondria
• acyl-CoA made in cytosol -> to mitochondria (only needed for 1st round)
• B-oxi has 4 intermediates and steps
• last step releases acetyl-CoA (oxid by TCA cycle)
• n-2 fatty acyl-CoA further B-oxidised until broken down

Question 16

What is ATP synthesis like from B-oxidation?

Answer 16

• each cycle yields 14 ATPs
• 2ATP used to activate FA to acyl-CoA ester in 1st round

Question 17

What happens in the FA biosynthesis?

Answer 17

• requires acetyl-CoA and CO2
• carboxybiotin and acetyl-CoA makes malonyl-CoA
• ACetyl-COA carboxylase key regulatory enzyme, in ER
• ATP and CO2 make carboxybiotin
• other biosynthetic enzyme in cytosol
• biosynthesis requires NADPH

Question 18

What is Acyl carrier protein (ACP) like?

Answer 18

• same side chain as CoA (cov link to ACP)
• intermediates moved from active site in FA synthase to next
• biosynthetic pathway has 4 steps (deg but in reverse)
• each cycle adds satureated C2 unit