A Road Map for Cellular Respiration Cytosol Mitochondrion High-energy electrons carried by NADH High-energy electrons carried mainly by NADH Glycolysis Glucose 2 Pyruvic acid Krebs Cycle Electron Transport
Phosphoryl transfer reaction. Kinases transfer phosphate from ATP to an acceptor. Hexokinase has a more general specificity in that it can transfer phosphate to other sugars such as mannose. Phosphate group added to #6 carbon from the ATP ENZYME- Hexo – substrate kin – transfer P b/t substate and ATP/ADP ase - enzyme The name of the molecule phosphate on #6 carbon Step 1- add phosphate to #6 C
Isomerization by phosphoglucose isomerase The enzyme opens the ring, catalyzes the isomerization, and promotes the closure of the five member ring. GLUCOSE Aldose sugar An aldehyde with C=O on end C FRUCTOSE ketose sugar A ketone with C=O on a middle C Step 2- glucose fructose
Glucose to fructose - isomerization aldose ketose Step 2- again Changed the structure – moved the carbonyl (C=O) from #1 C to #2 C. An isomer ENZYME- Hexo – phosphohexose isomer – 6 member ring to 5 member ring ase - enzyme
Adding another phosphate The 2 nd investment of an ATP in glycolysis. Step 3- add phosphate to #1 C Name of the molecule Fructose – 5 member ring Phosphate on #1 and # 6 carbons ENZYME- phosphofructo – substate kin – transfer P b/t substate and ATP/ADP ase - enzyme
Cleavage to two triose phosphates Enzyme: aldolase C=O on the end – a aldehydye C=O is on the #1 C C=O in middle – a ketone Dihydroxy – two OH (except phosphate in second OH spot Step 4- break 6C into two 3C sugars
Cleavage of six-carbon sugar: step 4 again shows where the cut is made and why two different sugars result This one will not go down the pathway – that would be a waste of half the original glucose. STOP!!! This one will go down the pathway – the enzymes are shape specific. GO!!!
Salvage of three-carbon fragment ketone aldehyde Step 5- moving the carbonyl - isomerization
Done in two steps – this shows the overall result glyceraldehyde 3-phosphate 1,3 bisphosphoglycerate Step 6- adding another phosphate w/o using ATP!!!! ENZYME- Glyceraldehyde 3-phosphate – substrate dehydrogen – hydrogen removed and replaced by phosphate ase - enzyme Phosphate from cytoplasm
Stage 3: The energy yielding phase. Step 6- adding another phosphate w/o using ATP!!!! An aldehyde is oxidized to carboxylic acid and inorganic phosphate is transferred to form acyl-phosphate. NAD + is reduced to NADH. Note, under anaerobic conditions NAD + must be re-supplied. With oxygen and mitochondria, NADH will go down electron transport chain and generate ATP.
Step 7 Substrate-level phosphorylation Phosphate group moved from the substrate to ADP generating an ATP. Kinase enzyme involved in the change At this point 2ATPs were invested and 2ATPs are produced. Step 7- moving the phosphate group from substrate to ADP
Step 8: Phosphate shift setup Step 8- moving the phosphate group from #3 to #2 C ENZYME- phosphoglycerate – substrate mut – changes the structure (sorry not isomerase) ase - enzyme
Step 8- moving the phosphate group from #3 to #2 C
Generation of second very high energy compound by a dehydration reaction Step 9- forming an enol with a double bond between carbons Dehydration reaction the energy is locked into the high energy unfavorable enol configuration C=C with OH group alkene alcohol
An enol phosphate is formed: step 9 Dehydration elevates the transfer potential of the phosphoryl group, which traps the molecule in an unstable enol form Enol: molecule with hydroxyl group next to double bond
Step 10: Formation of Pyruvate & ATP ENZYME- pyruvate – substrate kin – phosphate transfer between substrate and ATP/ADP ase - enzyme Step 10- forming pyruvate
<ul><li>Substrate level phosphorylation is the synthesis of ATP from ADP that is not linked to the electron transport system. </li></ul>Pyruvate Kinase 2 nd example of substrate level phosphorylation. The net yield from glycolysis is 2 ATP unstable enol form more stable ketone form
Diverse fates of pyruvate To citric acid cycle
In anaerobic yeast, pyruvate->ethanol Pyruvate is decarboxylated. Acetaldehyde is reduced.