Carbohydrates and Glycogen Metabolism

Question 1

What is the difference between Epimers and Enantiomers?

Answer 1

Epimers: Isomer that differ in
configuration only one carbon atom
Enantiomers: The groups attached to the
asymmetric carbon atom can be
arranged to form two different isomers
that are mirror images of each other
are not superimposable.

Question 2

Which is of the following is true?
A. The new stereocenter of the cyclic form is referred to as the anomeric carbon.
B. If the OH group on the anomeric carbon is axial DOWN, anomeric carbon is α
C. In solution, OH group on the anomeric carbon spontaneously changes from α to β position through a process called mutarotation
D. If the OH group on the anomeric carbon is equatorial up, anomeric carbon is β
E. All

Answer 2

E

Question 3

Which of the following is wrong?
A. If the anomeric carbon is not linked to another molecule, the ring can open and sugar act as a reducing sugar.
B. All monosaccharides are reducing sugar
C. 1,6 glycosidic bonds forms linear, 1,4 glycosidic bonds forms branched poly saccharides
D. Sucrose is a non reducing sugar while maltose and lactose are reducing sugar.

Answer 3

C
1,4 - linear
1,6 - branched

Question 4

Which of the following enzyme is correctly matched with its function
A. glycoside hydrolases (glycosidases) hydrolyze glycosidic bonds in poly-and oligo-saccharides
B. Glycogen Synthase makes α(1-4) glycosidic bonds using a fragment of glycogen as primer
C. Disaccharidases hydrolyze tri-and
di-saccharides into their reducing sugars.
D. All
E. None

Answer 4

D

Question 5

Wat is the most common digestive enzyme deficiency?

Answer 5

Lactose intolerance

Question 6

The glycogen is degraded to glucose by the process of…………..

Answer 6

glycogenolysis

Question 7

Which of the following is False?
A. When there is excess of glucose, it is used to synthesize glycogen in a process called glycogenesis.
B. specific tissues synthesize glucose de novo, using amino acids from the body’s proteins as primary source of carbons via gluconeogenesis.
C. Gluconeogenesis is a slow process
D. Dietary glucose is a constant source of energy for the human body
E. None

Answer 7

D

Dietary glucose is not always constant source

Question 8

Glycogen has……
A. only one anomeric carbon
B. Reducing end attached to the protein glycogenin by glycosidic bond.
C. 1/3 of glycogen is water
D. Branches occur more frequently in the center
E. A and B
F. All except C

Answer 8

F

2/3 of glycogen is water

Question 9

Which of the following is true about glycogen storage?
A. Glycogen gets broken to Glucose6-P and never leaves the muscle cell.
B. 400 g of glycogen is stored in liver while 100g is stored in muscle.
C. Muscle glycogen is not affected by short periods of fasting time while Liver glycogen can maintain blood glucose only for 18 h.
D. Pyruvate and lactate are produced in the liver
E. A and C
F. B and C

Answer 9

E
400g- muscle
100g- liver
Pyruvate and lactate are produced in muscle

Question 10

Why body store most of energy in the form of adipose tissue not as glycogen?

Answer 10

1. fats are hydrophobic so they take less place than glycogen
2. fats have high ATP production so they are only used for emergencies.

Question 11

Choose the correct one
I. In order glycogen to be synthesized, glucose has to be linked to high energy molecule, UDP. (UDP-glucose pyrophosphorylase)
II. In the absence of glycogen synthase, protein called glycogene serves as an acceptor of glucose.
III. Branches are made by
branching enzyme amylo- α(1-6) -> α(1-4)
transglucosidase
IV. Glycogen Synthase makes α(1-4) glycosidic bonds using a fragment of glycogen as primer
A. I, II, III B. II, III IV
C. I, III, IV D. I, II, IV

Answer 11

D.
Branches are made by
branching enzyme amylo- α(1-4) -> α(1-6)
transglucosidase

Question 12

Where does Glycogenesis occur?

Answer 12

cytosol

Question 13

What is the purpose of Glycogen

phosphorylase in glycogenolysis?

Answer 13

sequentially cleaves the α(1-4) glycosidic

bonds by simply phosphorylation and producing glucose1-phosphate

Question 14

What is the correct pathway of glycogenolysis?

Answer 14

GLYCOGEN- Debranching enzyme- GLUCOSE( small amount)- glycogen phosphorylase- GLUCOSE 1-PHOSPHATE - GLUCOSE 6-PHOSPHATE- glucose 6-phosphotase - GLUCOSE

Question 15

What is the correct pathway of glycogenesis?

Answer 15

GLUCOSE- hexokinase/glucokinase- GLUCOSE 6-PHOSPHATE- phosphoglucomutase- GLUCOSE 1-PHOSPHATE- UDP-glucose pyrophosphorylase- UDP-G- glycogen synthase( branching enzyme) - GLYCOGEN

Question 16

Which of the following is wrongly matched with its function
A. Insulin’s :increase glucose levels in blood
B. Epinephrine’s :elicit a short term release of glucose from stores
C. Cortisol’s action: to stimulate make of glucose from proteins.
D. Glucagon’s :stimulate the release of
glucose from stored glycogen

Answer 16

A
Insulin reduce the level of sugar in blood
Insulin stimulate storage of fuel while the rest stimulate release of fuel.

Question 17

Fill in the blank
In muscle during exercise, After the production of pyruvate from glucose 6-phosphate,
lactate is formed in………….
CO2 is formed in……………..

Answer 17

Anerobic (fast)

Aerobic (slow)

Question 18

Which of the following is true
I. In liver, while fasting- glucagon increase
- Insulin decrease
II. In muscle during exercise- Epinephrine
decrease
III. In liver, after meal - glucagon decrease
- Insulin increase
IV. In muscle after meal - insulin increase
V. while fasting - glycogenesis increase
- glycogenolysis decrease
A. I, II, III, B. I, III, IV
C. II, IV, V D. III, IV, V

Answer 18

B
In muscle during exercise- Epinephrine
increase
while fasting - glycogenesis decrease
- glycogenolysis increase

Question 19

Glycogen synthase is activated by………..
inhibited by…………
Glycogen phosphorylase is activate by……..
inhibited by……

Answer 19

a. insulin and glucose
b. glucagon and epinephrine
c. glucagon and epinephrine, AMP
d. insulin, ATP

Question 20

Which of the following are glycogen storage diseases?
A. Pompe disease
B. Corin disease
C. McArdle syndrome
D. Von Gierke disease
E. All

Answer 20

E

Question 21

What are the two basic classification of monosaccharides?

Answer 21

Aldose - COH

Ketose - CO