2.1: Cell Metabolism 1 Flashcards
What are the 6 types of reactions that define metabolism?
- Oxidation- Reduction
- Ligation requiring ATP cleavage
- Isomerisation
- Group Transfer
- Hydrolytic
- Addition/ Removal of Functional Groups
What is Oxidation-Reduction?
Electron transfer
What is ‘Ligation requiring ATP cleavage’ ?
Formation of covalent bonds
What is isomerisation?
Rearrangement of atoms to form isomers
What is group transfer?
Transfer of a functional group from one molecule to another
What is a hydrolytic reaction?
Breaking of bonds by the addition of water
What is the addition/removal of functional groups?
Addition of functional groups to double bonds/ removal to form double bonds
What is Glycolysis?
- Anaeorbic process
- Occurs in cell cytoplasm
- 10 reactions
- X1 6-C molecule (glucose) to X2 3-C molecules (pyruvate)
What are the 2 main concepts of glycolysis?
- Formation of a high energy compound - investment of ATP
- Splitting of a high energy compound - produces ATP
What happens in Step 1 of Glycolysis?
- GROUP TRANSFER
- Glucose converted to Glucose-6-Phosphate + H+
- Enzyme: Hexokinase - ATP to ADP
What is a kinase enzyme?
Adds phosphate groups to molecules
What kind of reaction is Step 1 of Glycolysis?
- Irreversible reaction —> commits cell to subsequent reactions
- Traps glucose inside cell by negative charge of phosphate group
What is Step 2 of Glycolysis?
- ISOMERISATION
- Glucose-6-Phosphate converted to Fructose-6-Phosphate
-Enzyme: Phosphoglucose isomerase
What is the purpose of Step 2 of Glycolysis?
-rearranging to make product symmetrical
-fructose-6-phosphate can be split into 2 equal halves
What is Step 3 of Glycolysis?
- GROUP TRANSFER (phosphorylation)
- Fructose-6-Phosphate is converted to Fructose-1,6-Biphosphate
-Enzyme: Phosphofructokinase (ATP to ADP)
What is Step 4 of Glycolysis?
- HYDROLYTIC (splitting) to form 2 high energy compounds
- Fructose-1,6-biphosphate is converted to glyceraldehyde-3-phosphate + dihydroxyacetone phosphate
- ENZYME: Aldolase
Can glyceraldehyde-3-phosphate (Step 4) progress in the glycolysis pathway?
Yes
Can dihydroxyacetone phosphate (Step 4) continue in the glycolysis pathway?
No - so converted into glyceraldehyde-3-phosphate in Step 5
What happens in Step 5 of Glycolysis?
- ISOMERISATION (rearrangement)
- dihydroxyacetone phosphate is converted into glyceraldehyde-3-phosphate
- ENZYME: Triose Phosphate Isomerase (TPI)
Why is deficiency in TPI fatal?
- Dihydroxyacetone phosphate is not converted into glyceraldehyde-3-phosphate THEREFORE cannot continue in glycolysis pathway
- respiration not taking place
- death of cells (neurones/RBC)
What is Step 6 of Glycolysis?
- 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
What is Step 7 of Glycolysis?
- GROUP TRANSFER (phosphorylation of ADP to ATP)
- 1,3-biphosphoglycerate is converted to 3-phosphoglycerate
- ENZYME: phosphoglycerate kinase
What is Step 8 of Glycolysis?
- ISOMERISATION
- 3-phosphoglycerate is converted to 2-phosphoglycerate
- ENZYME: phosphoglycerate mutase
What is Step 9 of Glycolysis?
- GROUP REMOVAL (water)
- 2-phosphoglycerate is converted to phosphoenopyruvate + water
- ENZYME: pyruvate kinase
What is Step 10 of Glycolysis?
- GROUP TRANSFER (phosphorylation of ADP to ATP)
- phosphoenopyruvate is converted to pyruvate
What are the final products of Glycolysis?
- X2 Pyruvate (step 10)
- X2 ATP (step 7 and step 10)
- X2 NADH (step 6)
What are the 3 fates of pyruvate?
- Alcohol fermentation
- Generation of lactate
- Acetyl CoA Generation
Where does alcohol fermentation take place?
Yeast
In what condition does alcohol fermentation?
Anaerobic conditions
What is the 2 step reaction of alcohol fermentation?
- Pyruvate is converted to Acetaldehyde via removal of CO2
- ENZYME: pyruvate decarboxylase - Acetaldehyde is converted to ethanol whilst NADH is converted to NAD+
-ENZYME: alcohol dehydrogenase
Where does generation of lactate take place?
Mammalian muscle
In what conditions do generation of lactate take place?
- Anaerobic
- Intense activity - oxygen in limiting factor
What is the reaction for the generation of lactate?
Pyruvate is converted to lactate whilst NADH is converted to NAD+
- ENZYME: lactate dehydrogenase
Why is regeneration of NAD+ essential?
So glycolysis can continue
Why is creatine phosphate essential in muscles?
- Buffer demands for phosphate for ATP production
- As amt of ATP needed during exercise is only enough to sustain contraction for 1 second
How does Creatine Phosphate act as a buffer for ATP?
Creatine phosphate is converted to Creatine + ATP (ADP + H+ + Pi)
- ENZYME: Creatine Kinase
Where does Acetyl CoA generation take place?
Mitochondria
What is the reaction for Acetyl CoA generation?
Pyruvate + Hs-CoA —> Acetyl CoA + CO2
- NAD+ —> NADH
- ENZYME: pyruvate dehydrogenase complex
What is the bond between the Acetyl group and CoA?
Thioester bond
What is special about the Thioester bond between the Acetyl group and CoA?
High energy therefore readily hydrolysed
Enables Acetyl CoA to donate acetate (2C) to other molecules
Where does Acetyl CoA next enter?
Krebs/TCA Cycle
