2.1: Cell Metabolism 1

Question 1

What are the 6 types of reactions that define metabolism?

Answer 1

1. Oxidation- Reduction
2. Ligation requiring ATP cleavage
3. Isomerisation
4. Group Transfer
5. Hydrolytic
6. Addition/ Removal of Functional Groups

Question 2

What is Oxidation-Reduction?

Answer 2

Electron transfer

Question 3

What is ‘Ligation requiring ATP cleavage’ ?

Answer 3

Formation of covalent bonds

Question 4

What is isomerisation?

Answer 4

Rearrangement of atoms to form isomers

Question 5

What is group transfer?

Answer 5

Transfer of a functional group from one molecule to another

Question 6

What is a hydrolytic reaction?

Answer 6

Breaking of bonds by the addition of water

Question 7

What is the addition/removal of functional groups?

Answer 7

Addition of functional groups to double bonds/ removal to form double bonds

Question 8

What is Glycolysis?

Answer 8

• Anaeorbic process
• Occurs in cell cytoplasm
• 10 reactions
• X1 6-C molecule (glucose) to X2 3-C molecules (pyruvate)

Question 9

What are the 2 main concepts of glycolysis?

Answer 9

1. Formation of a high energy compound - investment of ATP
2. Splitting of a high energy compound - produces ATP

Question 10

What happens in Step 1 of Glycolysis?

Answer 10

• GROUP TRANSFER
• Glucose converted to Glucose-6-Phosphate + H+
• Enzyme: Hexokinase - ATP to ADP

Question 11

What is a kinase enzyme?

Answer 11

Adds phosphate groups to molecules

Question 12

What kind of reaction is Step 1 of Glycolysis?

Answer 12

• Irreversible reaction —> commits cell to subsequent reactions
• Traps glucose inside cell by negative charge of phosphate group

Question 13

What is Step 2 of Glycolysis?

Answer 13

• ISOMERISATION
• Glucose-6-Phosphate converted to Fructose-6-Phosphate
  -Enzyme: Phosphoglucose isomerase

Question 14

What is the purpose of Step 2 of Glycolysis?

Answer 14

-rearranging to make product symmetrical
-fructose-6-phosphate can be split into 2 equal halves

Question 15

What is Step 3 of Glycolysis?

Answer 15

• GROUP TRANSFER (phosphorylation)
• Fructose-6-Phosphate is converted to Fructose-1,6-Biphosphate
  -Enzyme: Phosphofructokinase (ATP to ADP)

Question 16

What is Step 4 of Glycolysis?

Answer 16

• HYDROLYTIC (splitting) to form 2 high energy compounds
• Fructose-1,6-biphosphate is converted to glyceraldehyde-3-phosphate + dihydroxyacetone phosphate
• ENZYME: Aldolase

Question 17

Can glyceraldehyde-3-phosphate (Step 4) progress in the glycolysis pathway?

Answer 17

Yes

Question 18

Can dihydroxyacetone phosphate (Step 4) continue in the glycolysis pathway?

Answer 18

No - so converted into glyceraldehyde-3-phosphate in Step 5

Question 19

What happens in Step 5 of Glycolysis?

Answer 19

• ISOMERISATION (rearrangement)
• dihydroxyacetone phosphate is converted into glyceraldehyde-3-phosphate
• ENZYME: Triose Phosphate Isomerase (TPI)

Question 20

Why is deficiency in TPI fatal?

Answer 20

• Dihydroxyacetone phosphate is not converted into glyceraldehyde-3-phosphate THEREFORE cannot continue in glycolysis pathway
• respiration not taking place
• death of cells (neurones/RBC)

Question 21

What is Step 6 of Glycolysis?

Answer 21

• REDOX and GROUP TRANSFER (phosphorylation)
• X2 glyceraldehyde-3-phosphate is converted to 1,3-biphosphoglyerate
• X2 NAD converted to X2 NADH
• ENZYME: glyceraldehyde-3-phosphate dehydrogenase

Question 22

What is Step 7 of Glycolysis?

Answer 22

• GROUP TRANSFER (phosphorylation of ADP to ATP)
• 1,3-biphosphoglycerate is converted to 3-phosphoglycerate
• ENZYME: phosphoglycerate kinase

Question 23

What is Step 8 of Glycolysis?

Answer 23

• ISOMERISATION
• 3-phosphoglycerate is converted to 2-phosphoglycerate
• ENZYME: phosphoglycerate mutase

Question 24

What is Step 9 of Glycolysis?

Answer 24

• GROUP REMOVAL (water)
• 2-phosphoglycerate is converted to phosphoenopyruvate + water
• ENZYME: pyruvate kinase

Question 25

What is Step 10 of Glycolysis?

Answer 25

- GROUP TRANSFER (phosphorylation of ADP to ATP) - phosphoenopyruvate is converted to pyruvate

Question 26

What are the final products of Glycolysis?

Answer 26

1. X2 Pyruvate (step 10) 2. X2 ATP (step 7 and step 10) 3. X2 NADH (step 6)

Question 27

What are the 3 fates of pyruvate?

Answer 27

1. Alcohol fermentation 2. Generation of lactate 3. Acetyl CoA Generation

Question 28

Where does alcohol fermentation take place?

Answer 28

Yeast

Question 29

In what condition does alcohol fermentation?

Answer 29

Anaerobic conditions

Question 30

What is the 2 step reaction of alcohol fermentation?

Answer 30

1. Pyruvate is converted to Acetaldehyde via removal of CO2 - ENZYME: pyruvate decarboxylase 2. Acetaldehyde is converted to ethanol whilst NADH is converted to NAD+ -ENZYME: alcohol dehydrogenase

Question 31

Where does generation of lactate take place?

Answer 31

Mammalian muscle

Question 32

In what conditions do generation of lactate take place?

Answer 32

1. Anaerobic 2. Intense activity - oxygen in limiting factor

Question 33

What is the reaction for the generation of lactate?

Answer 33

Pyruvate is converted to lactate whilst NADH is converted to NAD+ - ENZYME: lactate dehydrogenase

Question 34

Why is regeneration of NAD+ essential?

Answer 34

So glycolysis can continue

Question 35

Why is creatine phosphate essential in muscles?

Answer 35

- Buffer demands for phosphate for ATP production - As amt of ATP needed during exercise is only enough to sustain contraction for 1 second

Question 36

How does Creatine Phosphate act as a buffer for ATP?

Answer 36

Creatine phosphate is converted to Creatine + ATP (ADP + H+ + Pi) - ENZYME: Creatine Kinase

Question 37

Where does Acetyl CoA generation take place?

Answer 37

Mitochondria

Question 38

What is the reaction for Acetyl CoA generation?

Answer 38

Pyruvate + Hs-CoA —> Acetyl CoA + CO2 - NAD+ —> NADH - ENZYME: pyruvate dehydrogenase complex

Question 39

What is the bond between the Acetyl group and CoA?

Answer 39

Thioester bond

Question 40

What is special about the Thioester bond between the Acetyl group and CoA?

Answer 40

High energy therefore readily hydrolysed Enables Acetyl CoA to donate acetate (2C) to other molecules

Question 41

Where does Acetyl CoA next enter?

Answer 41

Krebs/TCA Cycle