BIOL2171 Lecture Notes - Lecture 5: Phosphoglycerate Kinase, Oxidative Phosphorylation, Chemiosmosis

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Topic 5: Glycolysis Regulation

Enzymes

Hexokinase

• Is an important step to trap glucose inside cells

• There are two isoforms of this enzyme, namely glycokinase and hexokinase

• Hexokinase is an example of an enzyme undergoing an induced fit

• This means not only the substrate conformation is changed to the transition stage, but also

the enzyme adapts to the transition state

Aldolase

• The most energy consuming step in glycolysis is splitting a six carbon molecule into two units

of three-carbon molecules

• Under stadard oditios this reatio is highly ufavorale ΔG0 ’ = +.9 kJ/ol.

• This is offset by the use of ATP in the prior reactions. Under physiological conditions in the cell

the reaction is in fact at equilibrium.

Glyceraldehyde-3-phosphate dehydrogenase

• In this reaction the energy released by the oxidation is captured in the form of NADH.

• At the same time the substrate is phosphorylated forming 1,3- Bisphosphoglycerate which

prepares for the generation of ATP in the next step.

Phosphoglycerate kinase

• here are two ways to produce ATP in the human body: substrate level phosphorylation (of

ADP) and chemiosmotic ATP synthesis.

• During glycolysis, substrate-level phosphorylation generates ATP by transfer of a substrate-

bound phosphate to ADP.

• The majority of ATP Glycolysis is produced in the mitochondria by a different chemiosmotic

mechanism, which makes use of proton gradients (see lectures on oxidative phosphorylation).

Pyruvate kinase

• Although the enzyme is called pyruvate kinase it rather uses phosphoenolpyruvate to

phosphorylate ADP to form ATP and pyruvate (substrate-level phosphorylation).

• The energy for the ATP generation comes from the interconversion of the enol-form of

pyruvate to the keto-form.

• The ketoform is the preferred conformation, which is released when the phosphate is

transferred to ADP forming ATP.

• Pyruvate can enter the mitochondria where it is oxidized in the TCA cycle. In the absence of

oxygen or when oxygen is low, most cells can switch to the production of lactate.

• This step consumes the NADH that was produced by Glyceraldehyde-3-phosphate

dehydrogenase.

• While NADH is recycled to NAD the net production of 2ATP during glycolysis is preserved.

• Erythrocytes generate energy entirely by using this mechanism.

• NADH can only be oxidized inside mitochondria in the presence of oxygen.

• To accomplish this shuttle, systems exist in the mitochondrial membrane to transfer NADH

generated in the cytosol into the mitochondria. Depending on the cell type, two different

shuttles are used, namely the Glycerol-phosphate shuttle or the malate-aspartate shuttle.

Regulation of glycolysis

• Glycolysis is autoregulated by the availability of ADP and NAD+ .

• In addition it is regulated at two enzymatic steps: the phosphofructokinase reaction and the

pyruvate kinase reaction. ATP and AMP levels strongly influence the speed of glycolysis.

• In addition, glycolysis in the liver is regulated by the allosteric effector fructose-2,6-bis-

phosphate, which will be discussed later.

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Document Summary

Under physiological conditions in the cell the reaction is in fact at equilibrium. In this reaction the energy released by the oxidation is captured in the form of nadh: at the same time the substrate is phosphorylated forming 1,3- bisphosphoglycerate which prepares for the generation of atp in the next step. Phosphoglycerate kinase: here are two ways to produce atp in the human body: substrate level phosphorylation (of. To accomplish this shuttle, systems exist in the mitochondrial membrane to transfer nadh generated in the cytosol into the mitochondria. Depending on the cell type, two different shuttles are used, namely the glycerol-phosphate shuttle or the malate-aspartate shuttle. Regulation of glycolysis: glycolysis is autoregulated by the availability of adp and nad+ . In addition it is regulated at two enzymatic steps: the phosphofructokinase reaction and the pyruvate kinase reaction. Atp and amp levels strongly influence the speed of glycolysis.

Related Questions

i need question number nine please

Case Study Section 2 â glycolysis
Based on âMonday at the Metabolic Clinic, Adventures in Glycolysisâ by Nancy Boury (National Center for Case Study Teaching in Science)

Background:
You have been chosen for a very competitive undergraduate clinical internship at St. Visintainerâs Hospital and Metabolic Clinic working with Dr. Saccharo, an expert in enzyme deficiency disorders related to glycolysis. Before your first day Dr. Saccharo has asked that you review the reactions of glycolysis and the concept of isoenzymes.

Recall that isoenzymes are groups of enzymes that catalyze the same reaction in that they use the same reactants to product the same products. They may have different genes, tissue expression, developmental timing of expression, and affinities for their substrates. As an example, phosphofructokinase-1 has 3 isoenzyme forms: PFK-L is expressed in the liver and the gene is found on chromosome 21; PFK-M is expressed in the muscle and the gene is found on chromosome 12; and PFK-P is expressed in platelets and the gene is found on chromosome 10.

Question 1:
If a person would be deficient in all 3 forms of PFK-1, this person would .
A. Have lower than normal glycogen stores.
B. Have more mitochondrial activity than normal.
C. Be dead.
D. Produce more energy per glucose molecule because glycolysis would be unregulated.

It is now Monday morning and you are ready to start seeing patients with Dr. Saccharo.

Patient 1:
Ann is a teenager and avid golfer who was referred to the clinic after being refused at the blood drive and tiring easily on the high school golf course during practice. Ann is examined and a blood sample was obtained for analysis of a glycolysis related metabolic panel. The results of her panel is below (levels: + = normal, - = decreased; ++= increased):
Blood Metabolic Panel
Blood Glucose +
Glucose-6-phosphate ++
Fructose-6-phosphate ++
Fructose-1,6,bisphosphate ++
Glyceraldehyde-3-phosphate ++
1,3-bisphosphoglycerate ++
Phosphoenolpyruvate ++
Pyruvate -
ATP -
Red Blood Cell Concentration -
Question 2:
Assuming that Dr. Saccharo is correctly assuming that Ann has a defect in glycolysis, what glycolytic enzyme is the most likely to have the defect based on the blood metabolic profile?
A. Hexokinase
B. Phosphofructokinase
C. Triose Phosphate Isomerase
D. Pyruvate Kinase
E. Aldolase

Patient 2:
Marie is a 32-year-old mother of three complaining of fatigue and muscle cramps with exercise. She had always blamed her intolerance to exercise on her sedentary lifestyle. However, she recently joined a gym and after a week of aerobics classes went to her physician, who ordered a series of blood tests. The blood work came back with abnormal results, leading to her muscle biopsy and referral to the metabolic clinic. Marieâs blood was subjected to the same metabolic panel used before with the following results:
Blood Metabolic Panel
Blood Glucose +
Glucose-6-phosphate ++
Fructose-6-phosphate ++
Fructose-1,6,bisphosphate -
Glyceraldehyde-3-phosphate -
1,3-bisphosphoglycerate -
Pyruvate -
ATP -
Red Blood Cell Concentration -

Marieâs muscle biopsy was also analyzed and showed an excess of glycogen.

Question 3:
What is the most likely enzyme deficiency for Marie?
A. Hexokinase
B. Phosphofructokinase
C. Triose Phosphate Isomerase
D. Pyruvate Kinase
E. Aldolase

Question 4:
If you wanted to test the ability of red blood cells to complete glycolysis what compound would you try to detect?
A. Fructose-6-phosphate
B. Aldolase
C. Pyruvate
D. Phosphofructokinase
E. Dihydroxyacetone phosphate

Question 5:
If you used a sample of Marieâs blood for this, what compound could you add to enable these cells to complete glycolysis?
A. Glucose
B. Fructose-1,6-bisphosphate
C. Insulin
D. Glucagon
E. Fructose-6-phosphate

Patient 3:
Leo is a 25-year-old accountant that is not anemic, has perfect teeth, but has experienced two fainting spells recently. One happened after accidentally drinking a non-diet soda; the other after eating ânaturally sweetenedâ fruit salad. His dentist referred him to Dr. Saccharoâs clinic. Dr. Saccharo suspects Leo may have Hereditary Fructose Intolerance (HFI) and has recommended a closely monitored fructose tolerance test.

Hereditary Fructose Intolerance is a recessive disorder where individuals lack a functional copy of one isoform of the enzyme aldolase, specifically Aldolase B (also known as fructose-1-phosphate aldolase). In the liver, fructose is phosphorylated by Fructokinase to fructose-1-phosphate, then is cleaved by Aldolase B to glyceraldehyde and dihydroxyacetone phosphate. Fructose-1-phosphate is also a known allosteric inhibitor of Glycogen Phosphorylase, the primary enzyme responsible for releasing glucose from glycogen.

Question 6:
As compared to a normal individual that consumes fructose, a person with HFI who ingested fructose would have (select all that apply):
A. High levels of blood fructose
B. High levels of blood fructose-1-phosphate
C. High levels of blood glucose
D. Low levels of blood fructose
E. Low levels of blood glucose

That afternoon Leo undergoes the fructose tolerance test with the following results:

Question 7:
Based on the results of the test, what was the effect of giving Leo the intravenous fructose?
A. A rise in blood glucose levels
B. A decrease in blood glucose levels
C. An increase in glycogen stores
D. A rapid drop in blood pressure

However there were complications: Soon after the test Leo orders and drinks a cup of tea, but after half the cup Leo passes out. Dr. Saccharo orders two sequential blood glucose checks. The first was 50 mg/dl and 15 minutes later Leoâs blood glucose was down to 40 mg/dl. With those results Dr. Saccharo injected something into Leoâs IV and within minutes Leo was back to normal.

Question 8:
From these results does it appear that Leo has HFI?
A. Yes
B. No
C. It is unclear from the results

Question 9:
What did Dr. Saccharo inject into Leoâs IV line?
A. Insulin
B. Glucagon
C. Glucose
D. Fructose
E. Phosphofructokinase

Dr. Saccharo puts Leo on a restricted diet and orders follow-up visits.

Question 10:
Which of the following foods/ingredients would Leo NOT be allowed to eat?
A. Artificial sweeteners
B. High starch foods, such as potatoes
C. Sweet tea made with cane sugar
D. Any dairy products

Dr. Saccharo puts Leo on a restricted diet and orders follow-up visits.

Case Study Section 2 â glycolysis
Based on âMonday at the Metabolic Clinic, Adventures in Glycolysisâ by Nancy Boury (National Center for Case Study Teaching in Science)

Question 9:
What did Dr. Saccharo inject into Leoâs IV line?
A. Insulin
B. Glucagon
C. Glucose
D. Fructose
E. Phosphofructokinase

indigolocust876

1. All of the following are/can be products of the pentosephosphate pathway
EXCEPT?
a. NADPH
b. Reducing power
c. Precursor metabolites
d. Ribose 5-phosphate
e. ATP

2. Chelsea is working with the N2 (g)- fixing soil bacteriumAzotobacter. She hopes
to isolate two enzymes from this bacterium: hexokinase and
phosphoglycerokinase. Try as she might, Chelsea cannot isolatehexokinase but
she is incredibly successful in isolating phosphoglycerokinase. Ina sudden
moment of brilliance, Chelsea realizes that this is because
a. hexokinase is a triose-stage enzyme.
b. Azotobacter degrades glucose using the Entner-doudoroff pathwayrather
than the Embden-Meyerhof pathway.
c. Azotobacter cannot degrade organic carbon.
d. hexokinase and phosphoglycerokinase are the same enzyme.

3. After coming to the above realization, Chelsea notes that ascompared to E. coli,
Azotobacter will generate more __________ from the breakdown of oneglucose
molecule to two pyruvate molecules.
a. ATP
b. NADH
c. NADPH
d. CO2

4. Halloween is coming and Mike, Jenna, Ashley H. and Amanda P.decide to brew
some pumpkin Ale. They find a recipe online at The Brew Site.com.They add the
pumpkin, malt, wheat, vanilla, spices and hops. They then add thebrown sugar,
molasses and yeast. Finally, they are ready to ferment and theystarve the yeast of
O2 by placing an air seal on the top of the bottle. Once the O2 isdepleted from the
bottle
a. the fate of pyruvate changes.
b. the yeast utilize alcoholic fermentation in order to regenerateNAD+ and
allow glycolysis to continue running.
c. the yeast can generate only 2 ATP per molecule of glucose.
d. all of the above

5. In the pumpkin ale bottle (above), after O2 is depleted, doesthe TCA cycle
continue to turn? If not, why not? [*Mark all that apply.]
a. Yes
b. No, because the TCA cycle generates so much reducing power that,in the
absence of an externally derived terminal electron acceptor, couldnot be
regenerated.
c. No, because the ETC stops running.
d. No, because there is no reducing power generated in ananaerobic
environment.

6. Which one of the following events occurs during step 1 of theTCA cycle when
the acetyl group from acetyl-CoA is transferred ontooxaloacetate?
a. reducing power is generated.
b. CO2 is produced.
c. a carbon-carbon bond is formed.
d. ATP is generated via substrate-level phosphorylation.

7. In step 4 of the TCA cycle, a-ketoglutarate is converted tosuccinyl-CoA. All of
the following are true for both this step and the transition stepEXCEPT
a. both are catalyzed by dehydrogenases.
b. both involve the incorporation of a cosubstrate.
c. both generate reducing power and fully oxidized carbon.
d. both occur in the mitochondrial matrix of a eukaryoticcell.
e. both occur when fat is catabolized.

8. Succinate dehydrogenase [*Mark all that apply.]
a. requires a prosthetic group.
b. is complex II of the mitochondrial electron transportchain.
c. catalyzes the phosphorylation of GDP.
d. Is fondly called the âWonder Woman Enzymeâ

1. C6H12O6 + 6O2 Ã 6CO2 + 6H2O Glucose is being _____ to _____ and oxygen is being _____ to _____. a. oxidized; carbon dioxide; reduced; water b. oxidized; water; reduced; carbon dioxide Incorrect c. reduced; water; oxidized; carbon dioxide d. reduced; carbon dioxide; oxidized; water

2. Which of the following stages in the breakdown of the piece of toast you had for breakfast generates the most ATP? a. the citric acid cycle Incorrect b. glycolysis c. the digestion of starch to glucose d. oxidative phosphorylation

3. Which of the following is a catabolic pathway? a. gluconeogenesis b. production of starch Incorrect c. glycolysis d. production of glycogen

4. Per molecule, the oxidation of a fatty acid results in _____ energy storage than the oxidation of glucose. a. the same b. less Incorrect c. more d. None of the above; fatty acids cannot be oxidized.

5. Of the eight reactions in the citric acid cycle, how many are oxidation-reduction reactions? a. one b. two c. three d. four e. five

6. The process of glycolysis transfers the energy in sugar molecules into the stored energy of activated carriers such as ATP and NADH. Which statement is true about glycolysis? a. Only eukaryotic organisms do glycolysis. b. The ten reactions of glycolysis are identical in all eukaryotic cells, but are different in prokaryotic cells due to their diverse metabolic strategies. Incorrect c. The ten reactions of glycolysis are identical in almost all living organisms on the planet. d. There are many ways to oxidize glucose and transfer energy into activated carriers; the diversity of organisms on the planet is reflected in the diversity of their mechanisms of glycolysis.

7. Referring to the sentence completed in #13 above, the purpose of the latter reaction (in active muscle cells) is to _____. a. accumulate lactic acid in the cell, which provides additional energy for the production of ATP Incorrect b. slow down glycolysis until oxygen becomes available again c. accelerate the Krebs cycle, which will restore the oxygen supply d. regenerate NAD+ so that glycolysis can continue in the absence of oxygen

8. What are the products of the citric acid cycle? a. carbon dioxide, NADH, FADH2 and GTP b. carbon dioxide, NAD+, FAD and GTP c. NADH, FADH2, and acetyl CoA Incorrect d. carbon dioxide and water

9. Which statement is true about enzymes? a. Enzymes catalyze chemical reactions because they make inherently endergonic reactions exergonic. b. Each enzyme in a cell can catalyze many different chemical reactions involving chemically different substrates. Incorrect c. Enzymes can only catalyze reactions in one direction. d. After catalyzing a reaction, an enzyme is permanently altered and can no longer bind substrate. e. None of the above is true. 1

10. âG measures the change in free energy in a system as it converts reactant (Y) into product (X). When [X] = [Y], âG is equal to _____. a. RT b. ÎGÂ° + RT c. ÎGÂ° d. ln [X]/[Y]

11. The âGÂ° for the hydrolysis of ATP is -7.3 kcal/mol. What conditions in the cell would lead to a âG for ATP hydrolysis of -11 kcal/mol? a. An increase in the ATP/ADP ratio b. An increase in anabolic activity in the cell c. Transport of ATP out of the compartment where the reaction is occurring Incorrect d. A decrease in the ATP/ADP ratio

12. In the first reaction of glycolysis, a phosphate transferred from ATP to a glucose molecule to produce glucose-6-phosphate and ADP. Under conditions existing in the cell, the free energy change for this reaction is -8.0 kcal/mole. Which of the following statements is true? Recall that the âGÂ° for the hydrolysis of ATP is -7.3 kcal/mol. a. Glucose concentrations in the cell are always low, making this reaction more favorable than would be expected. b. This reaction is less favorable than would be expected, given the âGÂ° of ATP hydrolysis. c. Glucose-6-P concentrations in the cell are very low relative to glucose concentrations, making the reaction more favorable than would be expected. d. The âGÂ° for the addition of a phosphate to glucose must be -0.7 kcal/mole.

13. Protein E can bind to two different proteins, S and I. The binding reactions are described by the following equations and values: E + S --> ES Keq for ES = 10 E + I> EI Keq for EI = 2 Given the equilibrium constant values, which one of the following statements is true? a. When S is present in excess, no I molecules will bind to E. b. E binds I more tightly than S. c. The binding energy of the ES interaction is greater than that of the EI interaction. d. Changing an amino acid on the binding surface of I from a basic amino acid to an acidic one will probably make the free energy of association with E more negative.

BIOL2171 Lecture Notes - Lecture 5: Phosphoglycerate Kinase, Oxidative Phosphorylation, Chemiosmosis

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