Glycolysis Flashcards
To lose one pound of weight, ones caloric intake should decrease by approximately how many calories?
1500
2000
2500
3000
3500
3500
In order to maintain his/her current weight, hw many calories will a 70 kg sedentary individual require daily?
1550
1850
2150
2450
2750
2150
(70 x 24 x 1.3 = 2150)
Under fasting conditions, which of the following is true?
Muscle glycolysis is inhibited
Liver glycolysis is inhibited
Muscle glycogen degradation is inhibited (it can be turned on
Liver glycogen degradation is inhibited
Liver glycolysis is inhibited (Muscle glycolysis won’t be inhibited under fasting conditions)
Still under initial fasting conditions which statement is correct (initial fasting conditions)?
Muscle glycogen synthesis increases
Adipocyte fate content increases
Urea synthesis increases
Lactate utilization by RBC increases
Urea synthesis increases (AA are now used as energy source and their waste is in urea)
What is diabetes?
Type 1?
Type 2?
What are you looking for?
A type 1 diabetic has just eaten, but forgot to take insulin. Which of the following will occur as a result?
Fatty acid degradation in the liver will increase
Glycogen degradation in the liver will decrease
Gluconeogenesis in the liver will continue
RBC’s will increase their oxidation of fatty acids
Gluconeogenesis in the liver will continue (In absence of insulin gluconeogenesis will continue. But glucose levels will actually continue to rise because insulin is required for glucose uptake by the muscle and the adipose tissue and liver still pumps out glucose via gluconeogenesis. Insulin is required to stimulate glycogen synthesis.)
(RBC’s have no mitochondria and therefore cannot oxidize FA)
(RBC’s have no mitochondria and therefore cannot oxidize FA)
Overview of Glycolysis
Two pathways of Glycolysis — Anaerobic and Aerobic
In order to generate Triglyceride we need to go through glycolysis.
Excess glucose goes through glycogen biosynthesis.
Glycolysis in Muscle vs. Liver
What type of metabolism is used when sprinting
Sprinting — Anaerobic Metabolism
Glucokinase is found…
Glucokinase — liver and pancreas.
Hexokinase is found…
In every other tissue but the liver and the pancreas
Glucose-1-Phosphate is Isomerized into…
Glucose 1 phosphate is isomerated into Glucose-6-P
What is the first committed step in glycolysis?
Phosphofructokinase 1 (PFK1) — Irreversible. Committed Step. Regulated Step.
How many ATP’s are used to get to the point of having two triose’s?
2 ATP
How does NAD become NADH?
Is this oxidization or reduction?
NAD+ accepts two electrons and a proton to become NADH
What is a mutase?
Whenever we move a phosphate from one functional group to another.
What is the function of dehydration?
Dehydration creates very high energy bond — about twice the energy of a high energy bond in ATP — ATP is 7kcal/mol where as the enolated phosphate is about 14 kcal/mol (which is doubled).
Which enzyme regenerates NAD so it can be reused?
Lactate Dehydrogenase regenerates NAD by converting NADH so it can be reused.
The Hexokinase Reaction
The Phosphohexose Isomerase Step
The Phosphofructokinase-1 Reaction (PFK-1)
Difference between Bisphosphate vs. Diphosphate
The Aldolase Reaciton
The triose phosphate isomerase reaction most closely resembles which other reaction?
Glucose to G6P
G6P to F6P
F6P to F1,6BP
F1,6BP to G3P and Dhap
G6P to F6P
When a compound is oxidized, it:
Loses water
Loses electrons
Gains electrons
Gains water
Loses electrons
Generation of a High Energy Bond
What is NAD+
Pellagra
The phosphoglycerate kinase reaction
What makes a reaction freely reversible vs. Irreversible?
Energy in high energy bond in the reactants is the same energy level as ATP in the product so overall energy is the same on both sides of the reactions which makes it reversible.
Substrate Level Phosphorylation
Substrate Level Phosphorylation — In the absence of Oxygen
Oxidative Phosphorylation
Oxidative Phosphorylation — Requires Oxygen.
Phosphoglycerate Mutase Step
Formation of ATP by Pyruvate Kinase
What are the 3 Irreversible Steps of Glycolysis?
PFK-1
Inhibitors of PFK1
Activators of PFK-1
ATP’s role in PFK-1
ATP = Key Inhibitor — Indicates high energy levels.
Where does glycolysis occur?
Glycolysis — Occurs in the Cytoplasm
Where is Citrate Made?
Citrate is made in the Mitochondria
Explain Citrate’s Role in Glycolysis
When Energy levels are high in the Mitochondria citrate accumulates and leaves mitochondria. When it leaves and goes into the cytoplasm it tells Glycolysis to slow down because we have lots of energy.
What’s AMP Role’s in Glycolysis
AMP tells glycolysis to speed up
Storing Energy
Can’t store ATP because if we stored energy as ATP it would feedback inhibit ATP production. That’s why we store as creatine phosphate in muscle.
F-2,6-BisPhosphate’s role in Glycolysis?
Fructose 2,6 Bisphosphate is a major activator of PFK-1 which activates glycolysis.
Where does F2,6BP come from?
What is velocity?
The rate at which the product of the reactoin is formed.
How does F-2,6-BP Effect the Activity Profile of
PFK-1?
F-2,6-BP reduces substrate concentration required for enzyme to reach 1/2 maximal velocity.
The Maximum velocity does not change but the amount of substrate required to reach that velocity is decreased.
Which curve is more active and which is more inhibited?
More active curve is to the left — enzyme is active at lower substrate concentrations.
More inhibited curve to the right
What are ATP’s two roles with PFK-1?
ATP has two roles in this enzyme — at low ATP conc. it allows it to proceed because its a substrate. But as we increase the ATP it starts to be an inhibitor. That’s why we see the curve go up then down.
Mixed allosteric function. First as a substrate then once too it becomes too much it becomes inhibited.
The glycolytic rate can be increased by which one of the following?
Increasing G6P levels
Increasing ATP levels
Increasing citrate levels
Increasing pyruvate levels
Increasing NAD+ levels
Increasing G6P levels (We increase g6p we’ll make more F6P which will increase substrate and increase the rate)
Increasing NAD+ levels — won’t allow glycolysis to increase rate unless we also increase the substrate in that specific enzyme.
A key difference between liver and muscle glycolysis is which one of the following?
F2,6 bp is not Important in muscle
Lactate formation Is exclusive to liver
Glucokinase vx. Hexokinase
Amp only actives in muscle
Muscle will not slow down glycolysis in presence of ATP
Lactate formation Is exclusive to liver
What hormone is released when blood glucose levels drop?
Insulin
Glucagon
Vitamin D
Acetylcholine
Glucagon
Hormonal Regulation of PFK-2 in Liver
R is regulatory subunit
C is catalytic subunit
Why don’t muscle cells respond to low blood sugar?
Muscle cells do not have glucagon receptors. Muscle cells don’t respond to low blood glucose.
When PFK2 is NOT phosphorylated
When PFK2 is not phosphorylated it acts as a kinase
When PFK2 is phosphorylated…
When PFK2 is phosphorylated it acts as a phosphatase
By phosphorylating PFK2
By phosphorylating PFK2 we are destroying F 2,6 BP.
Skeletal Muscle Isozyme of PFK-2…
Skeletal Muscle Isozyme of PFK2 never gets phosphorylated. PFK2 in skeletal muscle is only regulated allosterically.
More on PFK-2
Skeletal muscle does have protein kinase A but…
Skeletal muscle does have protein kinase A but it does not phosphorylate PFK2 because in the skeletal muscle it’s not a substrate for that enzyme.
PFK-2 Regulation in the Liver vs. Muscle
Heart PFK-2
Regulation of Hexokinase vs. Glucokinase
G6P’s effect on Glucokinase vs. Hexokinase
G6p is an allosteric inhibitor of Hexokinase. G6p is not however a regulator of Glucokinase.
3 Forms of Pyruvate Kinase
L-Form of Pyruvate Kinase
M-Form of Pyruvate Kinase
Explain the Role of cAMP dependent protein kinase in the liver
Which one of these correctly describes the activity state of key glycolytic enzymes if you go for a run after waking up without eating breakfast.
Muscle and liver pfk1 are active
Only liver pfk1 is active
Muscle and liver pfk2 are active (kinase activity)
Only liver Pfk2 is active (kinase activity)
Only muscle PFK-1 and PFK2 kinase activities are active
Only muscle PFK-1 and PFK2 kinase activities are active
Muscle and liver pfk2 are active (kinase activity) — no in the liver its the phosphatase activity
Only liver Pfk2 is active (kinase activity) — no again it’s phosphatase activity is active
Allosteric Regulation vs. Covalent Modification
Regulation of Liver vs. Skeletal Muscle
Where does the liver get its energy for its own function when blood glucose is low?
Liver gets its own energy from the Fatty Acids which are released when glucagon is present.
Arsenic poisoning is due to the presence of arsenate and arsenite in the toxin arsenal was as a phosphate analog but arseon-anhydride bonds are unstable and rapidly hydrolyzed in water which glycolytic enzyme catalyzers a reaction that would be most affected by the presence of arsenate:
Glucokinase
PFK -1
PFK-2
Glyceraldehyde 3-phosphate dehydrogenase
Pyruvate Kinase
Lactate dehydrogenase
Glyceraldehyde 3-phosphate dehydrogenase (only enzyme that uses a free inorganic phosphate so it will be affected)
Fluoride inhibits enolase, and is used in water and toothpaste to keep oral bacteria from growing and creating dental caries. Red blood cell pyruvate kinase deficiency can lead to mild anemia. which of the following glycolytic intermediates would accumulate in common in both of these conditions?
Pyruvate only
Glucose only
Pep only
3-phosphoglycerate only
2-phosphoglycerate only
Glyceraldehyde 3-phosphate only
1, 2, 3
4, 5, 6
1, 3, 5
2, 4, 6
Pyruvate only
Glucose only
Pep only
3-phosphoglycerate only
2-phosphoglycerate only
Glyceraldehyde 3-phosphate only
1, e, 3
4, 5, 6
1, 3, 5
2, 4, 6
Differential Regulation
Describe the Cori Cycle
Why Enzyme Kinetics?
Enzyme Kinetics