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Glucose 6-phosphate is in a pivotal position in metabolism. Depending on conditions, glucose 6-phosphate follows one of several pathways. Under what conditions do the following occur?

A. Glycolysis

when either ribose 5-phosphate or the reduced coenzyme NADPH is needed
when the body needs energy and the supply of glucose is adequate
when free glucose is needed in cells in other parts of the body
when the concentration of glucose in the blood is high and the body doesn’t need glucose for energy production

B. Hydrolysis to free glucose

when free glucose is needed in cells in other parts of the body
when the concentration of glucose in the blood is high and the body doesn’t need glucose for energy production
when either ribose 5-phosphate or the reduced coenzyme NADPH is needed
when the body needs energy and the supply of glucose is adequate

C.Pentose phosphate pathway

when either ribose 5-phosphate or the reduced coenzyme NADPH is needed
when free glucose is needed in cells in other parts of the body
when the concentration of glucose in the blood is high and the body doesn’t need glucose for energy production
when the body needs energy and the supply of glucose is adequate

D. Glycogenesis

when either ribose 5-phosphate or the reduced coenzyme NADPH is needed
when the concentration of glucose in the blood is high and the body doesn’t need glucose for energy production
when free glucose is needed in cells in other parts of the body
when the body needs energy and the supply of glucose is adequate

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28 Sep 2019

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Related questions

1. Pyruvic acid is produced in __________, and is the starting point for __________.

a. the Krebs cycle; the electron transport chain .

b. The Prep step; Glycolysis.

c. The Krebs cycle; Glycolysis.

d. The electron transport chain; The Prep step.

e. Glycolysis; The Prep step.

2. Which process enables glycolysis to continue to run by generating needed reactants without oxygen?

a. Aerobic respiration

b. Electron transport chain

c. Krebs cycle

d. Fermentation

e. All of the above

3. When water is oxidized by green plants, what is produced?

a. oxygen

b. carbon dioxide

c. sulfur granules

d. hydrogen sulfide

4. In cyclic photophosphorylation, the electrons

a. return to chlorophyll in PS I.

b. are used to make ATP & NADPH.

c. are energized in both PSI and PSII.

d. are converted to glucose.

5. In the Calvin-benson cycle:

a. oxygen is used to synthesize sugars.

b. carbon dioxide is used to synthesize

sugars.

c. ATP is formed.

d. light is required.

6. Light dependent reaactions:

a. capture the energy of sunlight with chlorophyll in PS I & PS II

b. make ATP & NADPH using electron transport chains

c. energize electrons in both PSI & PSII

d. include both cyclic and noncyclic pathways

e. all of the above

7. The five-carbon sugars of nucleotides are

derived from either the ______ or ______.

a.pentose phosphate pathway; Entner-Doudoroff pathway

b. pentose phosphate pathway; the Krebs cycle

c. Entner-Doudoroff pathway; glycolysis

d. glycolysis; the Krebs cycle

8. The pentose phosphate pathway provides a means to break down glucose and synthesize

a. DNA

b. six-carbon sugars.

c. peptidoglycan

d. galactose.

i need question number nine please

Case Study Section 2 – glycolysis
Based on “Monday at the Metabolic Clinic, Adventures in Glycolysis” 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. Visintainer’s 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. Marie’s 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 -

Marie’s 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 Marie’s 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 “naturally sweetened” fruit salad. His dentist referred him to Dr. Saccharo’s 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 Leo’s blood glucose was down to 40 mg/dl. With those results Dr. Saccharo injected something into Leo’s 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 Leo’s 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 – glycolysis
Based on “Monday at the Metabolic Clinic, Adventures in Glycolysis” 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. Visintainer’s 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 9:
What did Dr. Saccharo inject into Leo’s IV line?
A. Insulin
B. Glucagon
C. Glucose
D. Fructose
E. Phosphofructokinase

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

11. The ∆G° for the hydrolysis of ATP is -7.3 kcal/mol. What conditions in the cell would lead to a ∆G 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 ∆G° 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 ∆G° 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 ∆G° 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.

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