18-Glycolysis
phosphoglucose isomerase aldose ketose
2nd step of glucolysis is done by enzyme ____________________ ______________. This reaction is readily reversible (not a controlling step) and functions in both glycolysis and gluconeogenesis. Conversion of an _______ to a __________
increased right
pyruvate kinase mutations lead to __________ levels of 2,3 BPG, causing a _______ shift in oxygen dissociation curve.
2 4 2 2 mitochondria oxygen
-Glycolysis consumes ____ ATP and generates ____ATP. Thus, the process results in the generation of ___ net ATP. - The process also generates ___ NADH. -What happens to pyruvate depends upon the presence or absence of ________________ in the cell or upon the availability of _____________ in mitochondria - containing cells.
positive negative positive negative
-Pi and AMP are __________ effectors of PFK-1. -AMP is a __________ effector of F1,6BPase, which catalyzes the reverse reaction, converting F1, 6BP into F6P and Pi. -Fructose 2,6-bisphosphate. This is a _________ effector of PFK-1 and a __________ effector of F1,6BPase.
AMP Positive F6P Negative allosteric
1. Fructose 2,6- bisphosphate behaves like _____. a. __________ effector of 6-phosphofructo-1-kinase (PFK-1). This involves an increase in the affinity of PFK-1 for ____ and also a decrease in the inhibitory effect of ATP. b. _______________ _______________ effector of fructose 1,6-bisphosphatase.
1,3BPG 3PG
2,3-BPG can be formed from either ___________ or __________
Aldolase trioses
4th reaction uses _____________ to convert F-1,6 BP to DHAP and G3P. We now have two phosphorylated ________. Only glyceraldehyde- 3- phosphate is used in glycolysis.
Glycerol-3-phosphate dehydrogenase
A patient who is suffering from Pellagra has a deficiency in what enzyme? -this enzyme will be deficient because need NAD+--> NADH
inhibitor inhibitor pyruvate Oxygen ATP
ATP: ATP is an allosteric _________ of PFK-1. Citrate: Glycolysis and citric acid cycle are coupled via PFK-1 because citrate, an intermediate in citric acid cycle, is an allosteric __________ of PFK-1. When the citric acid cycle is saturated with high levels of citrate, citrate leaves mitochondria via a transporter (tricarboxylate transporter) and takes action on PFK-1. This prevents generation of ________, which feeds into citric acid cycle. Pasteur effect: _________ inhibits glycolysis. The consumption of glucose in the presence of oxygen generates much more _______. This effect is probably due to the inhibition of PFK-1 by ATP.
lactate dehydrogenase NAD+
Anerobic Glycolysis -When pyruvate cannot be oxidized within mitochondria for some reason (e.g., hypoxia, genetic defects in pyruvate dehydrogenase or citric acid cycle enzymes, genetic defects in electron transport chain), pyruvate is reduced to lactate by ____________ ___________ and this regenerates _________.
right left
Citrate or ATP shift the sigmoidal curve of PFK-1 to the ________ AMP and F-2,6BPG shift the curve to the _______ because they are activating the enzyme
exercise lactate glycogen
Deficiencies in the activities of phosphofructokinase, phopshoglycerate kinase, phosphoglycerate mutase, and lactate dehydrogenase represent important genetic defects in glycolysis. All of these have certain common clinical features : __________ intolerance, myoglobinuria, hemolytic anemia, absence of ___________ increase in forearm exercise test, and increased ____________ deposition in the liver and skeletal muscle.
gluconeogenesis alanine protein aminoacid lipolysis
Diabetes contd... This also results in an increase in ______________, producing more glucose from gluconeogenic precursors _________ and glycerol. These precursers come from muscle and adipocytes as a result of increased _______ and ___________ breakdown and ___________ to provide energy because of the decreased utility of glucose as the energy source.
inactivates activates reduces activates no increases skeletal muscle
Different tissues express different isoforms of the bifunctional enzyme PFK-2K/F-2,6BPase, encoded by different genes. 1) The liver isoform possesses sites for protein kinase A-dependent phosphorylation. cAMP _________PFK-2 and __________ F-2, 6-BPase and thus ____________ F-2, 6-BP levels. 2) The heart isoform has phosphorylation sites for protein kinase A, but at different part of the molecule. Increase in Norepinephrine (adrenaline)-->cAMP ___________ PFK-2 and has _____ effect on F-2, 6-BPase and hence ____________ F-2,6-BP levels. 3) The ___________ _____________ isoform does not possess phosphorylation sites for protein kinase A and hence has no effect on F-2, 6-BP levels.
regulator all
F-2,6BP is not a product of glycolysis. -- In fact, its only known function is as a ____________. -- It is found in _____ cells.
fructose 6-phosphate PFK-2 (6-phosphofructo 2-kinase) fructose 2,6-bisphosphatase bifunctional
Fructose 2,6-bisphosphate is synthesized from __________ (an intermediate in glycolysis) via the enzyme _____________________. Fructose 2,6-bisphosphate is destroyed in cells by the enzyme _______________________. Both of the above enzyme activities are located on the same protein. It is a ____________ enzyme and is referred to as 6-phosphofructo-2- kinase/fructose 2,6-bisphosphatase.
α adenylate cyclase cAMP decrease inhibit stimulates blood glucose
Glucagon (a 29-aa hormonal peptide) is released by the ___-cells of the pancreas and interacts with a glucagon receptor on the surface of the liver plasma membrane. The binding of glucagon to the receptor is "sensed' by ____________ __________ (enzyme located on the inner surface of the plasma membrane). --> This enzyme catalyzes the conversion of cytosolic ATP to _______ and PPi. cAMP ultimately causes a _________ in the levels of fructose 2,6-bisphosphate. --> cAMP acts as a second messenger. Note, cAMP acts to ________ glycolysis in liver, but in most other cells cAMP ____________ glycolysis. The difference is that liver is the primary organ, which controls _________ _________ levels. Liver can make glucose (gluconeogenesis) as well as degrade glucose (glycolysis) as needed.
insulin hypoglycemic
Glucokinase is inducible by ____________ It is known as a ______________ hormone
insulin decreases
Glucokinase is inducible in liver by _______. cAMP ____________ glucokinase levels in liver.
fructose-6-phosphate (F6P) fructose-1-phosphate binding dissociation
Glucokinase is inhibited by ______________[which is generated by reaction # 2] and stimulated by _____________. Regulation occurs via an inhibitory protein. 1).F6P stimulates the __________ of the inhibitory protein. 2).F1P stimulates the __________ of the inhibitory protein.
glyceraldehyde-3-phosphate pyruvate 2 4
Glycolysis consists of two phases. In the first phase, glucose is broken down to two molecules of _________________-___-_____________ in a series of five reactions. -In the second phase, another series of five reactions convert these two molecules of glyceraldehyde-3-phosphate into two molecules of ___________. -Phase I consumes ___ ATP and Phase II generates ___ ATP. The net ATP production in the entire process is 2.
pyruvate or lactate oxygen
Glycolysis is a set of reactions that converts glucose to ______________ or ____________. This is the first metabolic pathway to be elucidated and hence is considered as a paradigm of metabolic pathways. -Glycolysis is also called Embden-Meyerhoff pathway. -The complete set of reactions occurs in the cytoplasm of virtually every animal cell. The entire process occurs without molecular ____________.
isoenzymes same
Hexokinase and glucokinase are ___________. Therefore, irrespective of the isoenzyme catalyzing the reaction, the Keq, ∆G, and ∆Go for the 1st glycolysis reaction remain the _______.
most .1 high G6P liver and pancreas 10 low G6P F6P
Hexokinase: found in _____ cells Km is ____ mM- low -->affinity is _______ negative feedback from _________ Glucokinase: found in _________ and ________ Km is ___mM-high -->affinity for glucose is _____ not inhibited by _______ but is inhibited by _______
low
Hexokinase: Allows for the phosphorylation of glucose when blood levels of glucose are _____. -->This permits tissues that rely on glycolysis extensively to carry out the phosphorylation.
Persistent Hyperinsulinemia up normal more insulin
If there is a mutation in the K+ channel, this causes a disease called ________ _______________. It is opposite than diabetes because blood glucose goes _____, glukokinase is __________, ATP is produced ________ but channel is already dead which means the membrane is depolarized in cell b/c potassium channgel not functioning-independent of BG. When the K+ channel is blocked/dead, the Ca2+ channel is always activated and is always secreting ___________, more than you need.
pyruvate glucokinase CO2 ATP depolarization calcium insulin
In Beta cells of pancreas: after large meal, glucose increases and is taken up into b cells, then converted to _____________- which requires ___________ -and then converted to _______ - and this makes ________- which blocks K+ channel- neutralizing the inside negative membrane potential, causing ________________- which stimulates a voltage system _____________ channel and the intracellular levels of this rise. -this channel is the signal that causes the exocytosis of the little vesicles of _______________ which will revv up glycolysis and lower blood glucose levels
lactate ETC
In RBCs & in anaerobic conditions, pyruvate is converted to __________ to regenerate NAD+ -In mitochondria-possessing cells w/O2, regeneration of NAD+ occurs via ________
no resistance increase liver GLUT4 decreases liver
In diabetes, insulin activity is low type 1 - ___ insulin; type 2 - insulin ___________. -Consequently, glucagon levels __________. Thus, glucagon/insulin ratio is higher in diabetes. -There is no change in glucose uptake in ________ because this tissue does not express __________, the insulin-responsive facilitative glucose transporter. -In skeletal muscle and adipocytes, glucose uptake _________ because of the absence of insulin-dependent recruitment of GLUT4 into the plasma membrane. In _______, glucose is not metabolized effectively because of the cAMP pathway
mitochondria glycolysis lactate
In erythrocytes (RBC), there is no _____________. But these cells entirely depend on ___________ for energy. Therefore, these cells produce _________ in glycolysis all the time.
malate - aspartate α-glycerophosphate
In mitochondria - possessing cells under aerobic conditions, NAD+ is regenerated by either ____________-____________ shuttle or ___ - ________________shuttle, which transfer the reducing equivalents from NADH into mitochondria for electron transport chain, thus regenerating NAD+ in the cytoplasm.
insulin
In pancreas, ATP from glycolysis is responsible for ________ secretion, so it must change proportionally with blood glucose
increase activates phosphorylates inhibited degradation less more Glycolysis
Increased levels of glucagon cause __________ in cAMP levels. a. This second messenger _______ cAMP dependent protein kinase (PKA). b. This _______________ 6-phosphofructo-2- kinase (PFK-2)/fructose 2,6 bisphosphatase. c. The synthesis of fructose 2,6- bisphosphate is ________ and its __________ is promoted. d. A decrease in fructose 2,6 -bisphosphate makes 6-phosphofructo-1-kinase(PFK-1) _______ effective and fructose 1,6 -bisphosphatase _________ effective. e. _______________ is inhibited.
fructose 2,6-bisphosphate
Insulin opposes the action of glucagon. Glucagon and insulin clearly act in opposition to one another, and the insulin/glucagon ratio of blood determines the intracellular levels of ________________________ and therefore the rate of glycolysis.
Allosteric Covalent Transcription
It is obvious that glycolysis must be controlled. Enzymatic control can be exercised by three different common methods. a. __________ effectors. The transient binding of molecules to the enzyme to change the conformation. Effect is observed in milliseconds. b. ___________ modification. Generally phosphorylation. Effect in seconds. c.____________ of enzyme. Effect observed in hours.
anerobic
LA cntd... Strenuous exercise leads to __________ glycolysis. This causes overproduction of lactate.
Bicarbonate Dichloroacetate dehydrogenase
LA cntd... ______________ is usually administered to control acidosis associated with lactate overproduction. ___________________ is used as a drug to treat lactic acidosis because it activates pyruvate _______________ in mitochondria, which facilitates the conversion of pyruvate to acetyl CoA so that lactate production is decreased.
hypoxia anemia mitochondrial oxygen liver ethanol
Lactic Acidosis: Accumulation of plasma lactate may be secondary to tissue ______________(circulatory insufficiency due to shock, heart failure), severe ________, _____________ enzyme defects and inhibitors of _________ transport (carbon monoxide, cyanide), _______ disease, and _________.
lactate 7.1 CO2 and H2O glycolysis PFK-1
Lactic acidosis 1. Characterized by high blood levels of __________ (generally greater than 5 mM, while normal levels are usually less than 1.2 mM). Blood pH can be less than _____ in severe cases. 2. Most tissues can convert lactate to _______ and _______ through the TCA cycle. a. If the oxygen supply is inadequate, cells must rely on ____________ for ATP production. b. A decrease in ATP enhances glycolysis at the level of ________ and produces more pyruvate and hence lactate.
glucokinase Maturity Onset absence hyperglycemia hypoglycemia
Mutations in _____________ gene leading to inactivation of the enzyme are associated with a form of non- insulin-dependent diabetes mellitus (type 2) called ___________ __________ diabetes of the Young (MODY). Complete ______________ of the enzyme activity will lead to type 1 diabetes because of the lack of insulin secretion in response to blood glucose. This condition is associated with severe ________________. Mutations in the gene leading to increased activity of the enzyme will cause hyperinsulinemic _________________.
electron transport chain oxidized NAD+ lactate cytoplasm
NAD+ regeneration occurs via two mechanisms depending on the cell type and the availability of oxygen: 1. In mitochondria-containing cells and in the presence of oxygen, the regeneration occurs via __________ _________ ______. Then pyruvate is the end product of glycolysis, and the pyruvate gets ___________ in mitochondria. When oxygen is not available, even in mitochondria-containing cells, ________ cannot be regenerated in mitochondria. Then the only way to regenerate NAD+ and keep glycolysis going is to convert pyruvate into __________ using NADH. This process occurs in _____________ and also regenerates NAD+
allosteric Pi, AMP, Fructose-2,6 biphosphate ATP and Citrate Insulin Glucagon
PFK-1 is an _______________ enzyme that is highly regulated It's Allosteric activators are: -____, ________, and __________-_____ ___________ Allosteric inhibitors are: -_______ and _________ Hormonal regulators are: ______________= activator _____________= inhibitor
glycogen glycolysis insulin
Pancreatic B-cells are different than liver because they don't store __________, they don't go through __________, they only regulate blood glucose by secreting ______________ to work on liver cells to decrease blood glucose.
F,1-6BP
Pyruvate Kinase is allosterically activated by AMP and ____________
red ATP lyse Reticulocytes Heinz bodies hemolytic anemia
Pyruvate kinase deficiency and hemolytic anemia 1. Genetic defect causing a 5 -20% reduction in ______ cell pyruvate kinase levels. a. It's rare but the most common genetic disease associated with the glycolytic pathway. 2. Results in markedly lower ________ concentrations in erythrocytes. 3. Cells swell and ________. 4. _______________ are unaffected because these "immature" red cells contain mitochondria and are able to generate ATP through oxidative phosphorylation. 5. The levels of 2, 3 bisphosphoglycerate are high in erythrocytes. 6. No ________ _________ seen in this deficiency 7. The 2nd most common genetic cause of ______________ __________, only next to glucose 6-phosphate dehydrogenase deficiency.
ATP fructose 1,6-bisphosphate phosphorylation Active Inactive cAMP carbohydrate insulin
Pyruvate kinase: reaction # 10 1. Inhibited by high concentrations of _______. 2. Isoenzyme found in liver is activated by _________________ 3. Liver enzyme is subject to _______________. --> __________ in the dephosphorylated state. --> _________ in the phosphorylated state. -Inactivation by phosphorylation is a function of_______-dependent protein kinase in liver. Enzyme is inducible by high __________ concentration and also high __________levels.
Triose phosphate isomerase
Reaction #5: done by enzyme ____________ ____________ _________. a. Catalyzes the interconversion of dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. b. Because of the interconversion, one glucose molecule can be converted to two glyceraldehyde- 3- phosphate molecules.
pyruvate kinase ATP substrate-level phosphorylation anaerobic aerobic citric acid cycle malate/aspartate α-glycerophosphate
Reaction 10 is catalyzed by __________ _________ and converts PEP to pyruvate and generates _______ Again, this is ____________-____________ _____________ -This reaction completes that part of glycolysis that is common to both ___________and ___________ metabolism. -Under aerobic conditions and the presence of mitochondria, pyruvate can enter the ________ __________ __________. -NAD+ is regenerated by ____________/____________ shuttle or by ___-__________________ shuttle
PFK-1 irreversible allosteric ATP
Reaction 3 uses ___________ to convert F6P to F-1,6BP Reaction is the rate-limiting step of glycolysis. -It is ___________, and the committed step. It is an ____________ enzyme and also a major regulatory enzyme. -We have invested our second ______molecule.
Arsenate (AsO4 3-) inorganic phosphate (Pi) unstable 3-phosphoglycerate ATP thiol Iodoacetic acid (ICH2COOH)
Reaction 6- G3PDH This reaction is a target for _________- which resembles ____________ _____________. When this occurs, the product of the reaction is 1-arseno-3-phosphoglycerate. This product is ________ and decomposes into arsenate and ________________ with no _______ formation. After this step, glycolysis continues. e. The enzyme G6P3DH contains an essential ______ (cysteine- SH) group at the active site. ____________ _________ is also an inhibitor of this reaction. It reacts with the active site SH group and inhibits the enzyme.
glyceraldehyde-3-phosphate dehydrogenase one phosphate acid anhydride 3 NAD+
Reaction 6: uses enzyme ____________ ___-______________ ______________. The enzyme oxidizes the number _____ carbon aldehyde and then adds a ____________ group. We have an ________ __________ in the product 1,3- bisphophoglycerate -->Remember from bioenergetics that acid anhydrides are high-energy bonds. The phosphate on the number ___ carbon is not a high-energy bond We have used an _______ for the oxidation reaction. The cell has limited amounts of this, so somewhere along the line we have to regenerate it or glycolysis will stop.
phosphoglycerate mutase
Reaction 8 uses the enzyme _____________ ______________ to convert 3PG to 2PG
enolase dehydration high energy bond Fluoride
Reaction 9 uses enzyme __________ to convert 2PG to PEP -this is a ____________ reaction -PEP contains a _________ _______ ________ -This reaction is inhibited by ______________
synthesis hydrolysis
Regulation of F-2,6Bpase and PFK-2 enzyme Phosphorylation causes inactivation of the active site responsible for the __________ of fructose 2,6-bisphosphate and activation of the site responsible for the ___________________. Dephosphorylation has the opposite effect.
hypoxic
Skeletal muscles convert pyruvate to lactic acid ONLY in ______________ conditions- the electron transport chain is dead and this is the only way to maintain glycolysis
traps glucokinase/hexokinase
The 1st step is the irreversible conversion of Glucose to G6P, this __________ glucose in the cell via ______________/______________
NADH NAD+ NADH
The G-3-P DH reaction produces ________, which is normally used in ETC. However, under anaerobic conditions, it is not used in ETC and it builds up in cell. Since ________ is not being regenerated there is a point where the G3P rxn can't go any further. The pyruvate to lactate rxn utilizes __________, which allows for regeneration of NAD+ to be used in the G3P DH rxn.
phosphoglycerate kinase substrate-level phosphorylation both
The first step of energy production is the rxn that uses enzyme: ____________________ _____________ -This rxn coverts 1,3BPG to 3PG and is referred to as ___________ __________ __________ as opposed to oxidative phosphorylation that occurs in mitochondrial ATP production. -We have recovered _______ ATP that were invested. Remember that each glucose gives 2 phosphoglycerate molecules.
glucokinase
The levels of ____________ in the liver of untreated Type 1 diabetics are lower than normal.
phosphoglycerate kinase pyruvate kinase
The only two enzymes involved in producing ATP and substrate level phosphorylation in glycolysis are __________________ ____________ & _____________ ____________
1 3 10
The three reactions of control in glycolysis are _____, ______, and ______
lactate
Tumor cells also use this method to keep glycolysis going. They produce _________ from pyruvate as a mechanism to regenerate NAD+.
1,3BPG PEP
Two high energy molecules in glycolysis are ___________ and ___________
Hexokinase Glucokinase glycogen decreases
Under normal conditions, blood glucose is around 5mM blood glucose, so changes in blood glucose are not really detected by ______________, because it is fully saturated at this level However, ____________ only becomes active when blood levels are very high (w/ high Km). This makes sense because when you have high levels of blood glucose, you can store it as ____________ in the liver- and this is inducible by insulin cAMP ___________ glucokinase levels in the liver
NAD+
Unless ________ is regenerated, glycolysis will stop
glucokinase
Usually allosteric enzymes have multiple subunits with a sigmoidal binding curve. _____________ is a single subunit with a sigmoidal binding curve & is exception
Glycerol-3-phosphate Dehydrogenase
Which enzyme can be inhibited when Niacin is deficient in cell? only one!!
Glycerol-3-phosphate Dehydrogenase Enolase
Which enzymes produce high energy compounds in glycolysis?
All cytoplasm
_____ cells carry out glycolysis • The entire process occurs in ________ Glucose + 2 ADP + 2 NAD+ + 2 Pi -> 2 pyruvate + 2 ATP + 2 NADH + 2H+ + 2H2O
cAMP
_________ is responsible for the regulation of fructose 2,6-bisphosphate levels in liver.
Glucokinase
___________________ mutation causes diabetes b/c B-cells cannot do their fxn of sensing blood glucose increase and secreting insulin. Diabetes
catalytic high RBC ATP pyruvate kinase increase increase right lower left
a. All cells contain a __________ amount of 2,3-BPG. b. Red blood cells contain a ________ concentration of 2,3-BPG (~4mM). It facilitates the release of oxygen from hemoglobin. c. ~20% of glucose goes through this shunt in ______- going from 1,3-BPG to 2,3BPG to 3PG. d. No net _____ is generated if 1,3-BPG is converted to 3-PG via 2,3-BPG. If the entire glycolytic pathway in RBC occurs via the formation of 2,3-BPG, glycolysis will yield no net ATP because the 2 ATP produced by ___________ __________ will be equal to 2 ATP consumed in Phase I of glycolysis. e. 2, 3-BPG levels in erythrocytes _________ in high altitude where partial pressure of oxygen is low. f. Loss-of-function mutations in pyruvate kinase __________ the levels of 2,3-BPG in RBC, thus shifting the sigmoidal curve of oxygen binding to hemoglobin to the __________. If loss-of-function mutations occurs in any of the enzymes upstream of the step involved in the formation of 1,3- BPG, the levels of 2,3-BPG in RBC will be ________ than normal, thus shifting the curve to the ______.
stimulates inhibits decrease stimulates synthesis
cAMP _____________ gluconeogenesis in liver and ____________ glycolysis. cAMP-induced ___________ in fructose 2,6-bisphosphate levels is at least partly responsible for these effects. In some cells, cAMP actually _________ the synthesis of fructose 2,6-bisphosphate (e.g., heart &muscle). In skeletal muscle, cAMP does not affect the _________ of fructose-2,6-bisphosphate.
high
glucokinase only becomes active when blood glucose levels are very _______
hemolytic anemia pyruvate kinase ATP increase bilirubin gallstones
mutations in any enzymes of glycolysis will cause ___________ __________ b/c erythrocytes only get energy from glucose metabolism they cannot metabolize fatty acids or proteins. BUT whenever there is a question about an enzyme in glycolysis and hemolytic anemia the enzyme will always be _______________ ______________- because there is no _________ and 2,3BPG will __________- this causes more hemoglobin to be released-- and _________ levels increase causing jaundice and when it goes to the gallbladder it will cause ____________ in these patients
lactate dehydrogenase
the enzyme responsible for conversion of pyruvate into lactic acid which allows regeneration of NAD+ in anaerobic conditions is ____________ ____________ so if there is none of this enzyme in the cytoplasm, NAD+ will not be regenerated
erythrocytes
the only cells capable of converting glucose to lactic acid all of the time are _________________. They have no mitochondria, so the amount of oxygen is not important- they are actually loaded with oxygen
irreversible F6P-->F-1,6BP ATP 3rd PFK-1
the rate limiting and first commited step to glycolysis is the ________ conversion of _________--> _______ The second _________ is used here This is the _______ reaction in glycolysis The reaction is catalyzed by _______
mitochondria hypoxic
tumor cells have no ____________ but they somehow convert glucose to lactic acid, it is believed this is possible because tumor cells may be _______________- b/c blood cell growth cannot keep up at same pace as tumor cell growth