DOC UY: CARBS REVIEW

Question 1

Explain the biochemical derangement occurring in a patient who is suffering an acute myocardial infarction. What type of glycolysis prevails?

Question 2

Why do you think that a genetic deficiency in muscle glycogen phosphorylase (McArdle disease) is a mere inconvenience, whereas a deficiency of liver glycogen phosphorylase (Hers disease) can be lethal?

Question 3

In an oral glucose tolerance test, an individual in the basal metabolic state ingests a large amount of glucose. If the individual is normal, explain or illustrate biochemical changes that will occur?

Question 4

Consider a type 1 DM patient who has neglected to take his insulin for the last 72 hours and has not been eating much as well. Please describe the activity level of the different hepatic enzymes involved in glycogen metabolism under these condition.

Question 5

Essential fructosuria is a rare and benign genetic disorder caused by a deficiency of the enzyme fructokinase. Why is this disease benign, when a deficiency of aldolase B (hereditary fructose intolerance [HFI]) can be fatal? Why is there severe hypoglycemia in aldolase B deficiency? Explain.

Question 6

Consider a type 1 DM patient who has neglected to take his insulin for the last 72 hours and has not been eating much as well. Please describe the activity level of the different hepatic enzymes involved in glycogen metabolism under these condition.

Answer 6

• glycogenolysis
• gluconeogenesis

Question 7

A patient was started on antibiotic therapy with a combination of trimethoprim and sulfamethoxazole (TMP/sulfa) because he an allergy to penicillin.On the third day of therapy with TMP/sulfa for his infection, he was slightly jaundiced. His hemoglobin level had fallen by 3.5 g/dL from its value at admission, and his urine was red-brown.What is the biochemical derangement in this patient? Why is he jaundiced and why is his urine reddish-brown?

Answer 7

G6PD deficiency

Question 8

Describe the glycolysis pathway

Answer 8

It is a catabolic pathway used by cell to generate ATP from glucose

Question 9

What do anaerobic conditions limit?

Answer 9

ATP production per mole of glucose oxidized

Question 10

Glycolysis is also known as

Answer 10

Embden meyerhoff pathway

Question 11

In anaerobic condition how is glycolytic inhibition prevented?

Answer 11

NADH accumulates in cytoplasm; amount of NAD+ decreases

There’s insufficient NAD+ for G3P dehydrogenase step to proceed. Glycolysis is inhibited.

NAD+ is regenerated. Pyruvate to lactate via LDH.

Question 12

ETC will not work in the absence of ______.

Answer 12

Oxygen

Question 13

NAD+ used in glycolysis must be regenerated in order for glycolysis to continue

Answer 13

to generate reducing equivalents (NADH) for pyruvate dehydrogenase

Question 14

Lactic Acidemia

Answer 14

Blood accumulates up to pH level of 7.2.
NADH/NAD+ ratio increases, leading to lactate formation.

Question 15

T or F: ATP is formed by oxidative phosphorylation

Answer 15

False - Glycolysis synthesizes ATP via substrate-level
phosphorylation

Question 16

Oxidative phosphorylation is found in _____.

Answer 16

areas with a lot of mitochondria such as in the heart

Question 17

T or F: A molecule of pyruvate is formed from the oxidation of one glucose molecule .

Answer 17

False - Two molecules of pyruvate are formed from the oxidation of one glucose molecule .

Question 18

If we start in G3P, how many pyruvate will be formed?

Answer 18

1 pyruvate

Question 19

Pyruvate kinase is the rate-limiting enzyme of glycolysis

Answer 19

PFK

Question 20

Two molecules of ATP are used in the beginning of the pathway

Answer 20

TRUE

• Hexokinase
• PFK-1

Question 21

The net reaction for anaerobic glycolysis

Answer 21

Glucose + 2 ADP + 2 Pi → 2 lactate + 2 ATP + 2 H2O + 2 H

Question 22

2 substrate level phosphorylation in glycolysis

Answer 22

Phosphoglycerate kinase step
Pyruvate kinase step

Question 23

Iodoacetate blocks _____.

Answer 23

G3P dehydrogenase enzyme

In order to inhibit glycolysis.

Question 24

Fluoride blocks ___________.

Answer 24

Enolase

This is to inhibit bacterial growth

Question 25

Arsenic poisoning inhibits _____.

Answer 25

Glycolysis

Question 26

What are the fates of lactate?

Answer 26

- - -

Question 27

Glycolysis and Fate of Lactate in the heart

Question 28

Other functions of Glycolysis

Question 29

dissociation curves shiftts to _______-.

Answer 29

Right

Question 30

The primary control of muscle glycolysis is the energy charge of the cell which is the ____.

Answer 30

the ratio of ATP to AMP

Question 31

Glycolysis is stimulated as the energy charge of the cell ________.

Answer 31

falls-----a signal that the cell needs more ATP.

Question 32

PFK and ATP levels relation

Question 33

PFK and ATP/AMP levels relation

Question 34

PFK and pH levels relation

Question 35

hexokinase vs fructokinase

Answer 35

Hexokinase is inhibited by its product

Question 37

What inhibits PK?

Answer 37

- ATP - Alanine

Question 38

Function of Glycolysis in the Liver

Answer 38

The liver maintains blood glucose: It stores glucose as glycogen when glucose is plentiful, and it releases glucose when the supply is low. uses glucose to generate reducing power for biosynthesis and to synthesize building blocks for other molecules.

Question 39

Glucokinase phosphorylates glucose only when glucose is abundant because _________.

Answer 39

it has a HIGH Km for glucose Its low affinity for glucose in the liver gives the brain and muscles first call for glucose when supply is limited and * It ensures that glucose is not wasted when it is in abundant.

Question 40

Function of pacreatic glucokinase

Answer 40

detect changes in concentrations of glucose in the systemic circulation [note: this is same with hepatic glucokinase].

Question 41

When glucose is increased more glucose is phosphorylated by glucokinase, increasing glycolysis, and leading to increased formation of ATP.

Answer 41

...

Question 42

Explain MODY

Answer 42

mutated glucokinase. km for glucose is above 200, thus moderate hyperglycemia not enough to induce insulin release. [can be mistaken as Type I DM]

Question 43

Fructose 2,6-bisP

Question 44

PFK2

Question 45

High insulin/glucagon ratio causes ____________. to favor glycolysis

Answer 45

decreased cAMP and reduced levels of PFK2 ...... [page 26]

Question 46

PDH is regulated by

Answer 46

rate of ATP utilization

Question 47

However, when tissues do not have an adequate supply of O2 to meet their ATP demands, the increased NADH/NAD ratio inhibits PDH, but AMP activates glycolysis. A proportion of the pyruvate is then reduced to lactate to allow glycolysis to continue.

Question 48

structure of glycogen

Question 49

8 to 10 residues -- amylopectin (starch)

Question 50

glycogenin

Question 51

non-reducing ends

Question 52

Muscle glycogen is a fuel reserved for the production of ATP within that tissue whereas liver glycogen is a glucose reserve for the maintenance of blood concentration

Question 53

resting - fatty acids high demands --> glucose

Question 54

the first and immediate source of glucose for the maintenance of blood glucose levels.

Answer 54

Liver glycogen

Question 55

In the liver, the G6P that is generated from glycogen degradation is hydrolyzed to glucose by glucose 6-phosphatase—an enzyme that is present only in the liver and kidneys.

Question 56

G6-Phosphatase is only present in kidney & liver. What does this imply?

Answer 56

Gluconeogenesis is only possible in kidney and liver

Question 57

Glycogen degradation thus provides a readily mobilized source of blood glucose as dietary glucose decreases, or as exercise increases, the use of blood glucose by muscles.

Question 58

Glycogen synthesis requires the formation of α-1,4-glycosidic bonds to link glucosyl residues in long chains and the formation of an α-1,6-branch every 8 to 10 residues.

Question 59

* Most of glycogen synthesis occurs through the lengthening of the polysaccharide chains of a preexisting glycogen molecule (a glycogen primer) in which the reducing end of the glycogen is attached to the protein glycogenin. To lengthen the glycogen chains, glucosyl residues are added from UDP-G to the nonreducing ends of the chain by glycogen synthase.

Answer 59

GLYCOGEN SYNTAHSE

Answer 60

amylo-4,6-transferase (branching enzyme)

Question 61

glycogen synthase absence

Answer 61

Persistent fasting hypoglycemia

Question 62

T or F: Glycogen synthase cannot form the a -1,6- glycosidic linkages

Answer 62

TRUE

Question 63

T or F: Glycogen has more alpha-1,6 linkages than alpha-1,4 linkages

Answer 63

FALSE

Question 64

T or F: Glycogen synthase form amylose chain then a branching enzyme removes a block of about 7 glucosyl residues from a growing chain and transfer it to another chain to produce an a-1,6 linkage.

Answer 64

TRUE

Question 65

Branching Enzyme Nomenclature

Answer 65

Amylo-4,6-transferase 1,4-a glucan branching enzyme Amylo-(1,4→1,6)-transglycosylase Alpha-1,4-glucan-6-glycosyltransferase Alpha-glucan-branching glycosyltransferase

Question 66

Glycogenolysis doesn't involve hydrolysis reaction but a _____-.

Answer 66

phosphorolysis reaction (breaking of a bond using a phosphate ion as a nucleophile).

Question 67

Why g1P? Glycogen phosphorylase starts at the nonreducing end of a chain and successively cleaves glucosyl residues by adding phosphate to the anomeric carbon of the terminal glycosidic bond, thereby releasing glucose 1-phosphate and producing a free 4α-hydroxyl group on the glucose residue now at the end of the glycogen chain.

Question 68

Two catalytic activities of Glycogenolysis

Answer 68

The debrancher enzyme, which catalyzes the removal of the four residues closest to the branch point, has two catalytic activities: it acts as a transferase and as an α-1,6-glucosidase.

Question 69

One glucose and approximately seven to nine glucose 1-phosphate residues are released for every branch point. [this occurs only in the liver]

Question 70

NOMENCLATURE CONCERNS WITH ENZYMES THAT METABOLIZE GLYCOGEN

Answer 70

Both glycogen phosphorylase and glycogen synthase will be covalently modified to regulate their activity. * When it is activated by covalent modification, glycogen phosphorylase is referred to as glycogen phosphorylase a; when the covalent modification is removed and the enzyme is inactive, it is referred to as glycogen phosphorylase b. * Glycogen synthase, when it is not covalently modified, is active and can be designatedas glycogensynthaseaorglycogensynthaseI. * Whenglycogensynthaseiscovalentlymodified,itisinactiveintheformof glycogen synthase b or glycogen synthase D

Question 71

Skeletal muscle glycogen produces glucose 1- phosphate and a small amount of free glucose.

Question 72

glucagon has no effect in the muscle

Question 73

malignant hyperdermia

Question 74

the effects of Ca in muscle result principally from the release of Ca from the sarcoplasmic reticulum after neural stimulation, and not from epinephrine- stimulated uptake;

Question 75

An increase of glucagon and decrease of insulin during the fasting state initiates a cyclic adenosine monophosphate (cAMP)-directed phosphorylation cascade, which results in the phosphorylation of glycogen phosphorylase to an active enzyme and the phosphorylation of glycogen synthase to an inactive enzyme As a consequence, glycogen degradation is stimulated, and glycogen synthesis is inhibited

Question 76

carb loading

Question 77

orange as a source of glucose