Mcq biochemistry in carbohydrates & cell membrane

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carbohydrates

1. Cyclization of the open chain form of glucose
produces a(n)

a.
acetal.
b.
hemiacetal.
c.
anhydride.
d.
lactone.
e.
aldehyde.
Ans:B
2. From the abbreviated name of the compound
Gal(beta1->4)Glc, we know that

a.
both sugars are beta anomers.
b.
the galactose residue is at the reducing end.
c.
the sugars are joined by a glycosidic bond.
d.
the compound is a D-enantiomer.
e.
the glucose is in its pyranose form.

Ans:C

3. Identify the structure found in N-linked
glycoproteins.

a || b || c || d || e .

Ans:E

4. Methylation (-OH -> -OCH3) of which hydroxyl
group of beta-D-fructose prevents the molecule from mutarotating to
alpha-D-fructose?

a.
C-1
b.
C-2
c.
C-4
d.
C-5
e.
C-6

Ans:B
5. Which of the following sugars cannot exist in a
cyclic form?
a || b || c || d || e .

Ans:E
6.Shown below is the structure of sucrose. Identify
the anomeric carbons.

a.
Cl of fructose; Cl of glucose
b.
C2 of fructose; Cl of glucose
c.
C2 of fructose; C4 of glucose
d.
C5 of fructose; CS of glucose
e.
There are no anomeric carbons in sucrose.
Ans:B

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Cell membrane
1. The fluidity of a phospholipid bilayer increases
when there is a decrease in the

a.
number of cis double bonds present in fatty acyl chains.
b.
content of short chain fatty acyl groups.
c.
van der Waals interactions between adjacent hydrocarbon chains.
d.
temperature.
Ans:C
2. Decreases fluidity of a biological membrane.

a.
Increased temperature
b.
Increased number of cis double bonds in fatty acyl chains
c.
Increased content of short chain fatty acyl group
d.
Increased content of cholesterol
Ans:D
3. The most effective method to solubilize an
erythrocyte membrane protein containing membrane spanning domains is

a.
treatment with a detergent.
b.
hypotonic lysis of the cell in a solution of low osmolarity.
c.
addition of salt.
d.
addition of glycosidase.
e.
addition of monosaccharides.

Ans:A
4.All of the following statements concerning the
erythrocyte cell membrane are correct EXCEPT

a.
It surrounds a protein substructure composed largely of spectrin.
b.
The major amount of its carbohydrate is linked to the protein
glycophorin.
c.
It contains a specific channel for transport of chloride and
bicarbonate.
d.
It is permeable to most small non-polar molecules and water.
e.
Its lipids are distributed symmetrically between the inner and outer
leaflets
Ans:E
5. Spectrin functions in the erythrocyte membrane to

a.
mechanically stabilize the biconcave disk shape of the membrane
skeleton.
b.
act as an anion antiporter for chloride and bicarbonate.
c.
provide large water-filled pores for transport of solvated polar and
charged solutes.
d.
carry the major amount of carbohydrate that forms the extracellular
glycocalyx.
e.
catalyze translocation of phospholipids from the inner leaflet to the
outer leaflet.
Ans:A

6. The extreme toxicity of cyanide results from its
high affinity for the copper and heme-containing protein

a.
pyruvate dehydrogenase.
b.
NADH:Q reductase.
c.
cytochrome oxidase.
d.
cytochrome c reductase.
e.
fumarate reductase.
Ans:C
7.In mitochondria of a patient suffering from severe
cyanide poisoning which of the following cofactors would exist mainly in
the reduced state?
NADH, flavin, Fe/S. heme b, heme c, and heme a.

a.
All
b.
None
c.
NADH, flavin, Fe/S, and heme b, only
d.
Heme c and heme a, only
e.
Flavin, Fe/S, heme b, heme c, and heme a, only
Ans:A

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