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BIOL 201 Lecture Notes - Lecture 6: Protein Phosphatase, Glycogen Phosphorylase, Adenylyl Cyclase

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crimsonjackal99
25 Feb 2013
School
McGill University
Department
Biology (Sci)
Course
BIOL 201
Professor
Greg Brown

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Document Summary

The enzymes are not active simultaneously, to prevent wasting energy. Conditions that favor glycolysis inhibit gluconeogenesis and vice versa. Citrate promote gluconeogenesis, through f1,6pase high amp levels would promote glycolysis by promoting f6p into. During exercise, pyruvate is made faster than it could be oxidized. Lactate is then produced from fermentation and enters the blood towards the liver. The liver then convert lactate into glucose through gluconeogenesis, the cori cycle. Glycogen can be converted to g6p as well. Skeletal muscle is not rich in mitochondria, but cardiac muscle is. Some of the lactate from the blood is taken by the cardiac muscle. The lactate from the blood is then processed by the cardiac muscle into pyruvate. Synthesized from a glucose derivative called udp-glucose (uracil diphosphate). Transfer glucose from udp-glucose to a pre-existing chain of glucose, creating a chain and a free udp. A free pi could be added to a glycogen chain to get a g1p out.

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Related Questions

16. Muscle glycogen cannot contribute directly to blood glucose levels because:

A. Muscle glycogen cannot be converted to glucose-6-phosphate

B. Muscle lacks glucose-6-phosphatase

C. Muscle contains no glycogen phosphoyrlase

D. Muscle lacks phophoglucoisomerase

_____17. Which of one of the following tissues requires insulin for glucose transport into the cell?

A. Brain

B. Liver

C. Skeletal muscle

D. Red blood cells

_____18. The mobilization of triaclyglycerol-bound fatty acids from adipose tissue and their subsequent oxidation by muscle mitochondria require all of the following compounds except:

A. Serum albumin

B. Carnitine

C. Acetyl CoA carboxylase

D. Hormone sensitive lipase

_____19. Which one of the following reactions is unique to gluconeogenesis?

A. Lactate ® pyruvate

B. Phosphoenolpyruvate® pyruvate

C. Oxalacetate® Phosphoenolpyruvate

D. 1,3bisphosphoglycerate ® 3-phosphoglycerate

_______20. A newborn vomits after each feeding of milk-based formula and doesn’t gain weight. Biochemical testing reveals a sever deficiency of galactose-1-phosphate uridyltransferase. If this condition goes untreated, which of the following is the likely outcome for this patient?

A. Benign disease except for cataract formation

B. Chronic emphysema appearing in early adulthood

C. Chronic renal failure appearing in adolescence

D. Death in infancy

E. Gastrointestinal symptoms that remit with puberty

(BIOCHEMISTRY QUESTION)

A. Gluconeogenesis is not just the reverse of glycolysis. Briefly describe one of the steps catalyzed by different enzymes in glycolysis and gluconeogenesis.

B. Explain how a biochemist might dicover that a certain enzyme is allosterically regulated.

C. What are the regulatory implications for the cell with regard to ATP & AMP, given the relative concentrations of ATP & AMP in a cell?

D. Describe the function of fructose 2,6-bisphosphate in overriding the control of gycolysis and gluconeogenesis in liver cells in response to lowered blood glucose levels.

E. The human disease beriberi is caused by a deficiency of thiamine in the diet. People with severe beriberi have higher than normal levels of pyruvate in their blood & urine. Explain this observation in terms of specific enzymatic reaction(s).

My Responses: Could you tell me if these are correct? If not, could you provide the correct answer and explanation?

A. Its a cellular process in which glucose is produced from pyruvate, amino acids, lactate, and other biogenic precursors.

B. They might learn that an enzyme is allosterically regulated if that protein or enzyme undergoes a conformational change modulated by the binding of one or more modulators/effectors to alternate sites on the protein, resulting in a change in its activity. And they usually have more than one polypeptide chain.

C. The regulatory implications for the cell would be that all activity would increase and concentrations would go up unless bound to PFK-1 and then the overall activity would drop.

D. Low blood glucose is when glucagon signals the liver to produce and release more glucose (gluconeogenesis) and stop consumption. Fructose 2, 6-bisphosphate mediates rapid hormonal regulation of glycolysis and gluconeogenesis.

E. Pyruvate is the product of both carbohydrate and amino acid catabolism that enters cellular respiration in the mitochondria when converted to acetyl-CoA catalyzed by the PDH complex. The first step in the PDH complex reaction is a decarboxylation reaction that cannot be catalyzed without the enzyme thiamine pyrophosphate (TPP). This coenzyme is a derivative of thiamine or vitamin B1.

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