Cell Metabolism I Flashcards
look over shuttles (42 cards)
3 Main Stages of Cellular Metabolism:
1) glycolysis
2) TCA cycle
3) oxidative phosphorylation
Which stage produces most ATP?
oxidative phosphorilation
What are the waste products from Cellular Metabolism?
CO2
urea
What are the 6 types of reactions?
1) Group transfer (A + BX → AX + B)
2) Ligation requiring atp cleavage (A + B → A-B)
3) Isomerization (A → B)
4) Oxidative reduction (A + :B → :A + B)
5) Hydrolytic (B-C + H2O → B + C)
6) Addition/ removal of functional groups (double bonds)
Kinase is responsible for…?
Catalysing the transfer of phosphate groups from one molecule to another (group transfer)
2 main stages of glycolysis?
- Form a high energy compound (invest ATP)
2. Split a high energy compound (generate ATP)
Glycolysis Stage 1:
Equation
Type of Reaction
Glucose —hexokinase—> glucose-6-phosphate + H+
-Requires 1 ATP, which adds a phosphate to the glucose forming ADP
Group transfer
Glycolysis Stage 2:
Equation
Type of Reaction
Glucose-6-phosphate —-phosphoglucose isomerase—> fructose-6-phosphate
Isomerisation
Stage 3:
Equation
Type of Reaction
fructose-6-phosphate —-phosphofructokinase—-> fructose-1,6-biphosphate
Requires 1 ATP to form ADP
phosphofructokinase is key in the control of sugars entering glycolysis
Group Transfer
Why are stages 2 and 3 important?
To try and make the molecule symmetrical
Stage 4:
Equation
Type of Reaction
fructose-1,6-biphosphate —-aldolase—-> glyceraldehyde-3-phosphate + dihydroxyacetone phosphate
2 high energy compounds produced
Hydrolytic
Stage 5:
Equation
Type of Reaction
dihydroxyacetone phosphate —-triose phosphate isomerase(TPI)—> glyceraldehyde 3-phosphate
End up with 2x glyceraldehyde 3-phosphate (one from stage 4)
Isomerisation
Stage 5:
Equation
Type of Reaction
dihydroxyacetone phosphate —-triose phosphate isomerase(TPI)—> glyceraldehyde 3-phosphate
End up with 2x glyceraldehyde 3-phosphate (one from stage 4)
TPI deficiency is the only enzyme which is fatal if deficiency → death
Isomerisation
Stage 6:
Equation
Type of Reaction
This reaction occurs 2x:
glyceraldehyde 3-phosphate —-glyceraldehyde 3-phosphate dehydrogenase—-> 1,3-biphosphoglycerate
Requires 1 NAD+ and Pi to form NADH (per reaction)
Redox and group transfer
Stage 7:
Equation
Type of Reaction
This reaction occurs 2x:
1,3-biphosphoglycerate —-phosphoglycerate kinase—-> 3-phosphoglycerate
Requires an ADP which accepts a Pi to form ATP (per reaction)
Group transfer
Stage 9:
Equation
Type of Reaction
This reaction occurs 2x:
2-phosphoglycerate —-enolase dehydration—-> phosphoenolpyruvate + H2O
Group removal
Stage 9:
Equation
Type of Reaction
This reaction occurs 2x:
2-phosphoglycerate —-enolase dehydration—-> phosphoenolpyruvate + H2O
Group removal (also known as dehydration)
Stage 10:
Equation
Type of Reaction
phosphoenolpyruvate –pyruvate kinase—-> pyruvate
Requires an ADP which accepts a Pi to form ATP (per reaction)
group transfer
Net result of glycolysis per glucose molecule:
- 2 ATP molecules (use up 2 in part 1 and produce 4 in part 2)
- 2 NADH
What are the 3 fates of pyruvate?
1) alcoholic fermentation
2) lactate production
3) acetyl CoA production
Lactate Production:
Equation
Type of Reaction
pyruvate –LDH—> lactate (reversible)
NADH + H+ → NAD+
anaerobic when O2 is limiting factor
why is it important to regenerate NAD+ in lactate generation and alcoholic fermentation?
-with NAD+ glycolysis is able to continue, in conditions of oxygen deprivation
Why is creatine phosphate useful in muscles?
-the amount of ATP needed during exercise is only enough to sustain contraction for around one second so provides ATP for the second muscle contract
Why can Acetyl CoA readily donate acetate to other molecules?
-the thioester bond is a high-energy linkage, so it is readily hydrolysed, enabling acetyl CoA to donate the acetate (2C) to other molecules
