*part of the reaction where 6 carbon molecule becomes two 3 carbon molecules
Which of the two products of the aldolase reaction is a direct glycolytic intermediate?
Glyceraldehyde-3-phosphate is the substrate for the next steps of glycolysis
the other product, Dihydroxyacetone-phosphate, must be isomerized into glyceraldehyde-3-phosphate to continue through glycolysis
reversibly isomerizes dihydroxyacetone-phosphate into glyceraldehyde-3-phosphate
takes the 2nd 3-carbon produced by PFK 1 and converts it so as to continue the process of glycolysis
glyceraldehyde 3-phosphate dehydrogenase
catalyzes the reversible two step conversion of glyceraldehyde 3-phosphate --> 1,3-bisPhosphoglycerate first glyceraldehyde 3-phosphate is oxidized at carbon 1 (aldehyde converted into COOH) & NAD+ --> NADH (reduced)
the energy released drives the endergonic second reaction where Pi is transferred to the GAP intermediate to form 1,3-bisphosphoglycerate
The reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase is an example of what two things coupled?
it's an example of phosphorylation coupled to oxidation (oxidation is the thing that provides the energy for the subsequent phosphorylation)
Which glycolytic enzyme catalyzes a reaction that yields NADH?
oxidation of Carbon1 results in reduction of NAD+ --> NADH
What's another name for glyceraldehyde-3-phosphate?
as ligands bind to an enzyme, the enzyme's affinity for the ligand will decrease
Which glycolytic enzyme exhibits negative cooperativity?
it can bind up to 4 NAD+ molecules that become harder to add after successive molecule binding
means the enzyme activity is buffered from changes in substrate concentration
enzyme resists losing NAD+ when glycolysis is at a high rate (eg. in anaerobic muscle)
enzyme keeps NAD+ when glycolysis is at a normal or low rate so the rate can be maintained
How many NAD+ molecules can glyceraldehyde-3-phosphate dehydrogenase bind?
Which glycolytic enzyme uses inorganic phosphate NOT ATP to phosphorylate its substrates?
1,3-bisphosphoglycerate --> 3-phosphoglycerate
reversibly transfers high energy phosphate group to ADP forming ATP
one ATP generated from each 1,3-bisphosphoglycerate (triose-phosphate) ==> the reaction generates 2 moles of ATP per original mole of glucose
SUBSTRATE LEVEL PHOSPHORYLATION
the formation of ATP (or GTP) by the direct transfer of a phosphate group from a reactive metabolic intermediate to ADP (or GDP)
3-phosphoglycerate --> 2-phosphoglycerate
reversibly transfers its own phosphate to form the intermediate 2,3-bisPhosphoglycerate
the intermediate donates its 3-phosphate back to the enzyme releasing 2-phosphoglycerate
2-phosphoglycerate --> phosphoenolpyruvate
reversible reaction that involves the removal of water to make a HIGH energy phosphate bond
What molecule strongly inhibits enolase?
What type of a reaction does enolase catalyze?
Which enzyme catalyzes the conversion of 2-phosphoglycerate to phosphoenolpyruvate (PEP)?
phosphoenolpyruvate (PEP) --> pyruvate [+ ATP]
reaction is irreversible
another key site of glycolysis regulation
Pyruvate kinase is stimulated by what and inhibited by what?
glucose-6-phosphate b/c G-6-P is it's product so it doesn't want to overproduce it's product
Phosphofructokinase is activated by ____________ (2)and inhibited by ___________ (3)
activated: F-2,6-bisP, ADP, AMP
inhibited: ATP, Citrate, fatty acids (products down the line)
Pyruvate kinase is activated by ____________ (2) and inhibited by ___________ (4) is
activated: F-1,6-bisP, F-2,6-bisP
inhibited: ATP, NADH, Alanine, fatty acids, SuccinylCoA(products down the line)
Which glycolytic enzyme is regulated by phosphorylation?
pyruvate kinase is inactivated by phosphorylation
What induces glucokinase AND pyruvate kinase transcription?
a high carbohydrate diet and insulin
transcription of both is decreased in low carbohydrate diet, starvation
The hormone insulin induces the synthesis of which glycolytic enzymes?
Glucokinase and pyruvate kinase
What is the net yield of ATP in the conversion of one glucose molecule to two pyruvates during glycolysis?
TWO moles of net ATP are net produced per ONE mole of glucose
Which glycolytic enzymes catalyze reactions that yield ATP?
phosphoglycerate kinase & pyruvate kinase
What can glucose-6-phosphate be used for besides its role as a glycolytic intermediate?
can be used to synthesize:
pentoses (for nucleotide and nucleic acid biosynthesis)
The pentose phosphate shunt produces NADPH and pentose sugars. Pentose sugars from this shunt may enter the glycolytic pathway as which glycolytic intermediate(s)?
Fructose-6-phosphate and glyceraldehyde-3-phosphate
What can dihydroxyacetone-phosphate be reduced to and later used for?
it can be reduced to glycerol phosphate, which is a precursor for neutral fat & phospholipid biosynthesis
Which glycolytic enzymes use ATP to phosphorylate their substrate, thereby producing ADP?
hexokinase and phosphofructokinase-1 (PFK-1)
What molecule inhibits hexokinase?
2-deoxyglucose - competitively inhibits production of glucose-6-phosphate from glucose
______ can be synthesized from 3-phosphoglycerate
an example of not always going back the way you came because serine is degraded by a dehydratease
NAD+ is derived from which vitamin?
Vitamin B3 (niacin)
Pyruvate can be inter-converted with which amino acid?
Alanine by by reversible transamination
What can be made from 1,3 bisphosphoglycerate and what process does this product regulate!?
2,3 bisphosphoglycerate can be made, and it regulates hemoglobin
this is 2,3-BPG! It's an allosteric effector that interacts with deoxygenated hemoglobin beta subunits & decreasing their affinity for oxygen, promoting oxygen to be released near tissues that need it most
Which glycolytic intermediate(s) can be oxidized to acetyl-CoA, which is used for synthesis of fatty acids, cholesterol, steroid hormones and oxidative metabolism?
Which toxic substance is able to inhibit hexokinase?
hexokinase converts it to 2-deoxyglucose-6-phosphate
because this product's not a substrate for the hexose phosphate isomerase it accumulates and exerts feedback inhibition on hexokinase
prevents the production of ATP by glyceraldehyde-3-phosphate dehydrogenase
it does not stop the process of glycolysis, it only prevents the net gain of ATP
Which toxic substances can react with the sulfhydryl group of glyceraldehyde-3-phosphate dehydrogenase to block the glycolytic process altogether?
mercury compounds and trivalent arsenicals
recessive metabolic disorder (phosphofructokinase deficiency/Glycogen storage disease type VII)
deficiency of the M subunit of the phosphofructokinase 1 enzyme impairs the ability of cells (eg. RBCs/skeletal muscle cells) to phosphorylate fructose-6-phosphate prior to its cleavage into glyceraldehyde-3-phosphate
this limits energy production & directly affects glycolysis
How does the regulation of lactate dehydrogenase in skeletal muscle differ from that in cardiac muscle?
In skeletal muscle, if more pyruvate is produced than can enter the TCA cycle, pyruvate will be converted to lactate by lactate dehydrogenase
In the heart, rising pyruvate concentrations inhibit lactate dehydrogenase; this is because lactate is an acid that can cause muscle cramps in excess
pyruvate inhibition of lactate dehydrogenase in the heart has a protective effect on cardiac function