Cellular Metabolism 1- Carbohydrates And Amino Acids (1) Flashcards
Where does glycolysis take place?
cytosol
What are the 6 types of reaction 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 1 molecule to another
What is hydrolysis?
cleavage of bonds by the addition of water
What is the purpose of kinase enzymes?
to transfer phosphate groups
What is the 1st reaction in glycolysis?
- group transfer
- enzyme: hexokinase
- glucose–> glucose-6-phosphate (+ H+)
What is the 2nd reaction in glycolysis?
- isomerisation
- enzyme: phosphoglucose isomerase
- glucose-6-phosphate–> fructose-6-phosphate
What is the 3rd reaction in glycolysis?
- group transfer
- enzyme: phosphofructokinase
- fructose-6-phosphate–> fructose-1,6-bisphosphate
What is the 4th reaction in glycolysis?
- hydrolysis…generates 2 high energy compounds
- enzyme: aldolase
- fructose-1,6-bisphosphate–> glyceraldehyde-3-phosphate + dihydroxyacetone phosphate
What is the 5th reaction in glycolysis?
- isomerisation
- enzyme: triose phosphate isomerase (TPI)
- dihydroxyacetone–> glyceraldehyde-3-phosphate
What is the 6th reaction in glycolysis?
- redox and group transfer…NADH generated
- enzyme: glyceraldehyde-3-phosphate dehydrogenase
- glyceraldehyde-3-phosphate–> 1,3-bisphosphoglycerate
What is the 7th reaction in glycolysis?
- group transfer…ATP generated
- enzyme: phosphoglycerate kinase
- 1,3-bisphosphoglycerate–> 3-phosphoglycerate
What is the 8th reaction in glycolysis?
- isomerisation
- enzyme: phosphoglycerate mutase
- 3-phosphoglycerate–> 2-phosphoglycerate
What is the 9th reaction in glycolysis?
- group removal (dehydration)
- enzyme: enolase
- 2-phosphoglycerate–> phosphoenolpyruvate (+H20)
What is the 10th reaction in glycolysis?
- group transfer (ATP produced)
- enzyme: pyruvate kinase
- phosphoenolpyruvate–> pyruvate
What is the net result of glycolysis?
- net gain of 2 ATP
- 2 NADH produced
What are the 3 fates of pyruvate?
- alcoholic fermentation
- lactate production
- acetyl coA production
What 2 reactions occur in alcoholic fermentation of pyruvate?
pyruvate–> acetaldehyde using pyruvate decarboxylase (CO2 produced)
acetaldehyde–> ethanol using alcohol dehydrogenase (NAD+ produced)
What is the reaction involved in the generation of lactate using pyruvate?
- reversible rxn
- anaerobic
- pyruvate lactate using lactate dehydrogenase (NAD+ produced)
What is the common purpose of alcoholic fermentation and the generation of lactate?
- 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
What is the purpose of creatine kinase?
- converts creatine phosphate–> creatine + ATP (reversible)
- supply ATP to muscles during exercise
How is acetyl coA generated from pyruvate?
- enzyme: pyruvate dehydrogenase complex
- NADH produced
- decarboxylation
- occurs in mitochondria–> acetyl coA committed to entry into TCA cycle
What disease is caused by a deficiency of thiamine?
Beri-Beri
What is the net result of the TCA cycle (1 turn)?
- 3 NADH
- 1 GTP
- 1 FADH2
- 2 CO2 (waste)
Why does the TCA cycle only operate under aerobic conditions?
the reduced coenzymes are re-oxidised with the help of oxygen in oxidative phosphorylation
What are the steps in the TCA cycle?
- 4C oxaloacetate + 2C acetyl coA –> 6C citrate
- 6C citrate–> 6C isocitrate
- oxidative decarboxylation
6C isocitrate–> 5C alpha-ketoglutarate (+ NADH +CO2) - oxidative decarboxylation
5C–> 4C succinyl coA (+ NADH +CO2) - 4C succinyl coA–> 4C succinate (+GTP)
- 4C succinate–> 4C fumerate (+FADH2)
- 4C fumerate–> 4C malate
- 4C malate–> 4C oxaloacetate (+NADH)
What Krebs cycle enzyme is not located in the mitochondrial matrix?
succinate dehydrogenase- in inner mitochondrial membrane
What 7 molecules can all 20 amino acids give rise to?
- pyruvate
- acetyl coA
- acetoacetyl coA
- alpha-ketoglutarate
- succinyl coA
- fumarate
- oxaloacetate
What is the difference between glucogenic and ketogenic amino acids?
- 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
How does NADH/its high energy electrons cross from the cytosol into the mitochondrial matrix?
- glycerol phosphate shuttle (skeletal muscle, brain)
- malate-aspartate shuttle (liver, kidney and heart)
How does the glycerol phosphate shuttle work?
- 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)
How does the malate-aspartate shuttle work?
- transamination and redox reactions
- cytoplasmic and mitochondrial forms of aspartate transaminase and malate dehydrogenase
- aspartate (+a-ketoglutarate oxaloacetate (+glutamate) malate
