Cellular Metabolism 1- Carbohydrates And Amino Acids (1)

Question 1

Where does glycolysis take place?

Answer 1

cytosol

Question 2

What are the 6 types of reaction that define metabolism?

Answer 2

1. oxidation- reduction
2. ligation requiring ATP cleavage
3. isomerisation
4. group transfer
5. hydrolytic
6. addition/removal of functional groups

Question 3

What is oxidation-reduction?

Answer 3

electron transfer

Question 4

What is ligation requiring ATP cleavage?

Answer 4

formation of covalent bonds

Question 5

What is isomerisation?

Answer 5

rearrangement of atoms to form isomers

Question 6

What is group transfer?

Answer 6

transfer of a functional group from 1 molecule to another

Question 7

What is hydrolysis?

Answer 7

cleavage of bonds by the addition of water

Question 8

What is the purpose of kinase enzymes?

Answer 8

to transfer phosphate groups

Question 9

What is the 1st reaction in glycolysis?

Answer 9

• group transfer
• enzyme: hexokinase
• glucose–> glucose-6-phosphate (+ H+)

Question 10

What is the 2nd reaction in glycolysis?

Answer 10

• isomerisation
• enzyme: phosphoglucose isomerase
• glucose-6-phosphate–> fructose-6-phosphate

Question 11

What is the 3rd reaction in glycolysis?

Answer 11

• group transfer
• enzyme: phosphofructokinase
• fructose-6-phosphate–> fructose-1,6-bisphosphate

Question 12

What is the 4th reaction in glycolysis?

Answer 12

• hydrolysis…generates 2 high energy compounds
• enzyme: aldolase
• fructose-1,6-bisphosphate–> glyceraldehyde-3-phosphate + dihydroxyacetone phosphate

Question 13

What is the 5th reaction in glycolysis?

Answer 13

• isomerisation
• enzyme: triose phosphate isomerase (TPI)
• dihydroxyacetone–> glyceraldehyde-3-phosphate

Question 14

What is the 6th reaction in glycolysis?

Answer 14

• redox and group transfer…NADH generated
• enzyme: glyceraldehyde-3-phosphate dehydrogenase
• glyceraldehyde-3-phosphate–> 1,3-bisphosphoglycerate

Question 15

What is the 7th reaction in glycolysis?

Answer 15

• group transfer…ATP generated
• enzyme: phosphoglycerate kinase
• 1,3-bisphosphoglycerate–> 3-phosphoglycerate

Question 16

What is the 8th reaction in glycolysis?

Answer 16

• isomerisation
• enzyme: phosphoglycerate mutase
• 3-phosphoglycerate–> 2-phosphoglycerate

Question 17

What is the 9th reaction in glycolysis?

Answer 17

• group removal (dehydration)
• enzyme: enolase
• 2-phosphoglycerate–> phosphoenolpyruvate (+H20)

Question 18

What is the 10th reaction in glycolysis?

Answer 18

• group transfer (ATP produced)
• enzyme: pyruvate kinase
• phosphoenolpyruvate–> pyruvate

Question 19

What is the net result of glycolysis?

Answer 19

• net gain of 2 ATP

- 2 NADH produced

Question 20

What are the 3 fates of pyruvate?

Answer 20

• alcoholic fermentation
• lactate production
• acetyl coA production

Question 21

What 2 reactions occur in alcoholic fermentation of pyruvate?

Answer 21

pyruvate–> acetaldehyde using pyruvate decarboxylase (CO2 produced)

acetaldehyde–> ethanol using alcohol dehydrogenase (NAD+ produced)

Question 22

What is the reaction involved in the generation of lactate using pyruvate?

Answer 22

• reversible rxn
• anaerobic
• pyruvate lactate using lactate dehydrogenase (NAD+ produced)

Question 23

What is the common purpose of alcoholic fermentation and the generation of lactate?

Answer 23

• the regeneration of NAD+
• thus glycolysis can continue in anaerobic conditions
• N.B. NAD+ needed for dehydrogenation of glyceraldehyde-3-phosphate–> essential for the next step which generates ATP

Question 24

What is the purpose of creatine kinase?

Answer 24

• converts creatine phosphate–> creatine + ATP (reversible)

- supply ATP to muscles during exercise

Question 25

How is acetyl coA generated from pyruvate?

Answer 25

- enzyme: pyruvate dehydrogenase complex - NADH produced - decarboxylation - occurs in mitochondria--> acetyl coA committed to entry into TCA cycle

Question 26

What disease is caused by a deficiency of thiamine?

Answer 26

Beri-Beri

Question 27

What is the net result of the TCA cycle (1 turn)?

Answer 27

- 3 NADH - 1 GTP - 1 FADH2 - 2 CO2 (waste)

Question 28

Why does the TCA cycle only operate under aerobic conditions?

Answer 28

the reduced coenzymes are re-oxidised with the help of oxygen in oxidative phosphorylation

Question 29

What are the steps in the TCA cycle?

Answer 29

1. 4C oxaloacetate + 2C acetyl coA --> 6C citrate 2. 6C citrate--> 6C isocitrate 3. oxidative decarboxylation 6C isocitrate--> 5C alpha-ketoglutarate (+ NADH +CO2) 4. oxidative decarboxylation 5C--> 4C succinyl coA (+ NADH +CO2) 5. 4C succinyl coA--> 4C succinate (+GTP) 6. 4C succinate--> 4C fumerate (+FADH2) 7. 4C fumerate--> 4C malate 8. 4C malate--> 4C oxaloacetate (+NADH)

Question 30

What Krebs cycle enzyme is not located in the mitochondrial matrix?

Answer 30

succinate dehydrogenase- in inner mitochondrial membrane

Question 31

What 7 molecules can all 20 amino acids give rise to?

Answer 31

- pyruvate - acetyl coA - acetoacetyl coA - alpha-ketoglutarate - succinyl coA - fumarate - oxaloacetate

Question 32

What is the difference between glucogenic and ketogenic amino acids?

Answer 32

- ketogenic amino acids are converted to either acetyl-CoA or acetoacetyl-CoA - whereas glucogenic amino acids are converted to pyruvate or to citric acid cycle intermediates

Question 33

How does NADH/its high energy electrons cross from the cytosol into the mitochondrial matrix?

Answer 33

- glycerol phosphate shuttle (skeletal muscle, brain) | - malate-aspartate shuttle (liver, kidney and heart)

Question 34

How does the glycerol phosphate shuttle work?

Answer 34

- cytosolic glycerol-3-phosphate dehydrogenase transfers electrons from NADH to DHAP (dihidroxyacetone phosphate)--> to generate glycerol-3-phosphate - mitochondrial glycerol-3-phosphate dehydrogenase transfers the electrons to FAD--> then donates electrons to coenzyme Q (part of ETC)

Question 35

How does the malate-aspartate shuttle work?

Answer 35

- transamination and redox reactions - cytoplasmic and mitochondrial forms of aspartate transaminase and malate dehydrogenase - aspartate (+a-ketoglutarate oxaloacetate (+glutamate) malate