METABOLISM

Question 1

What are anabolic pathways?

Answer 1

biosynthetic, reductive

build complex molecules from simpler ones and typically need an input of energy.

require:
- an energy source
- reducing equivalents - source of H+ (e.g NADPH, NADH)

Question 1

What are catabolic pathways?

Answer 1

degradative, oxidative

involve the breakdown of complex molecules into simpler ones and typically release energy.

provide:
- energy
- reducing equivalents
- precursors

Question 2

STAGE 1 OF GLYCOLYSIS

Answer 2

1) Glucose receives a phosphate group from ATP - irreversible

2) Hexokinase catalyses the change from glucose to Glucose-6-phosphate

3) Phosphoglucose isomerase catalyses the isomerising of Glucose-6-phosphate into Fructose-6-phosphate

4) Phosphofructokinase catalyses the phosphorylation of fructose-6-phophate into fructose-1,6-biphosphate (rate-limiting step)

Question 3

STAGE 2 OF GLYCOLYSIS

Answer 3

1) Fructose-1,6-biphosphate is split into two 3-carbon molecules

• Glyceraldehyde 3-phosphate (GP)
• Dihydroxyacetone phosphate

Question 4

What catalyses Fructose 1,6-biphosphate to Glyceraldehyde

Answer 4

Aldolase

Question 5

What catalyses Fructose-1,6-biphosphate to Dihydroxyacetone phosphate

Answer 5

trios phosphate isomerase

Question 6

STAGE 3 OF GLYCOLYSIS

G-3-p to … catalysed by…

Answer 6

1,3-biphosphoglycerate by G-3-P dehydrogenase

Question 7

1,3-biphosphoglycerate to …. by ….. generating ….

Answer 7

3-phosphoglycerate by phosphoglycerate kinase

• generates ATP

Question 8

phosphoenolypyruvate to …. by… generating….

Answer 8

pyruvate by pyruvate kinase

• generates ATP

Question 9

ATP produced in glycolysis

Answer 9

2

Question 10

First reaction in the citric acid cycle

Answer 10

aldol condensation reaction followed by hydrolysis
oxaloacetate to citrate

Question 11

what catalyses the reaction of oxaloacetate to citrate

Answer 11

citrate synthase

Question 12

Second reaction in the citric acid cycle

Answer 12

citrate to isocitrate

Question 13

what is the intermediate? (citrate to isocitrate)

Answer 13

cis-aconitate

Question 14

Second reaction in the citric acid cycle is catalysed by…

Answer 14

aconitase

Question 15

What is Aconitase? How does it work?

Answer 15

An iron-sulphur protein used in the two-part second reaction of the citric acid cycle.

• one of the iron atoms binds to the citrate
• facilitates the dehydration/hydration reactions

Question 16

Third reaction in the citric acid cycle

Answer 16

isocitrate to oxalosuccinate to alpha-ketogluterate

catalysed to isocitrate dehydrogenase

Question 17

Fourth reaction in the citric acid cycle

Answer 17

alpha-ketoglucerate to succinylcholine coa

catalysed by a-ketoglucerate dehydrogenase complex

production of NADH

Question 18

Fifth reaction in the citric acid cycle

Answer 18

succinyl CoA to Succinate

catalysed by succinyl CoA synthase
production of CoA + GTP

Question 19

Sixth reaction in the citric acid cycle

Answer 19

succinate to fumirate

catalysed by succinate dehydrogenase

key step in production of FADH2

Question 20

7th reaction in the citric acid cycle

Answer 20

fumerate to malate

catalysed by fumerase

Question 21

8th reaction in the citric acid cycle

Answer 21

malate to oxaloacetate

catalysed by malate dehydrogenase

key step in the production of NADH

Question 22

What is type of reaction does PYRUVATE DEHYDROGENASE have

Answer 22

irreversible reaction

Question 23

Isocitrate dehydrogenase is inhibited by …

Answer 23

ATP and NADH

Question 24

A-ketogluterate dehydrogenase is inhibited by ...

Answer 24

ATP, succinyl CoA and NADH

Question 25

Pyruvate dehydrogenase is inhibited by ...

Answer 25

ATP, acetyl CoA and NADH

Question 26

Arsenic and Mercury inhibit Citric Acid Cycle. How?

Answer 26

inhibiting pyruvate dehydrogenase complex by inactivating the dihydrolipomide component of the transacetylase

Question 27

Overall reaction of Citric Acid Cycle

Answer 27

Acetyl CoA + (3NAD+) + FAD + GDP + Pi ------> 2CO2 + 3NADH + FADH2 + GTP + CoA

Question 28

Product yields in citric acid cycle CO2

Answer 28

2

Question 29

Product yields in citric acid cycle GTP

Answer 29

1

Question 30

Product yields in citric acid cycle NADH

Answer 30

3 (six electrons)

Question 31

Product yields in citric acid cycle FADH2

Answer 31

1 (two electrons)

Question 32

Citric acid cycle location in eukaryotic cell

Answer 32

mitochondrial matrix

Question 33

Citric acid cycle location in prokaryotic cell

Answer 33

cytoplasm (mesosomes)

Question 34

ATP YIELD FROM OXIDATION OF PALMITATE

Answer 34

Net yield of 106 ATP 8 acetyl CoA - 8 X 10 ATP = 80 ATP 7 NADH - 7 X 2.5 ATP = 17.5 ATP 7 FADH2 - 7 X 1.5 ATP = 10.5 ATP 108 ATP - 2 ATP (cost of activation to palmitoyl-CoA)

Question 35

Function of the carnitine shuttle

Answer 35

used to transport fatty acyl coA from the cytoplasm to the mitochondrial matrix

Question 36

Does the carnitine shuttle require ATP AND NADPH?

Answer 36

no. Requires no chemical energy supply

Question 37

What inhibits the carnitine shuttle?

Answer 37

Malonyl-CoA