PGMEE Biochemistry MCQs 231-240

Q-231. Which of the following groups of proteins assist in the folding of other proteins?
a) Proteases
b) Proteosomes
c) Templates
d) Chaperones

Answer: Chaperones
Explanation:
Certain proteins called chaperons play a role in the assembly and proper folding of the synthesized protein so that its biological activity.
Many chaperones are heat shock proteins, that is, proteins expressed in response to elevated temperatures or other cellular stresses.
Human chaperone proteins:
General chaperones: GRP78/BiP
Lectin chaperones: Calnexin and Calreticulin
Non-classical molecular chaperones: HSP47 and ERp29
Folding chaperones:
Protein disulfide isomerase (PDI)
Peptidyl prolyl cis-trans-isomerase (PPI)
ERp57

Q-232. Proteins are sorted by
a) Golgi bodies
b) Mitochondria
c) Ribosomes
d) Nuclear membrane

Answer: Golgi bodies
Explanation:
The Golgi apparatus is involved in glycosylation and sorting proteins.

Q-233. All of the following are trypsin inhibitors except
a) Alpha-1 antitrypsin
b) Alpha-1 anti-proteinase
c) Entero-kinase
d) Egg White

Answer: Entero-kinase
Explanation:
Activators of trypsin:
Enterokinase
Calcium
Trypsin itself
Inhibitors of trypsin:
Alpha-1 anti-proteinase or Alpha-1 antitrypsin
Egg White
Di-isopropyl fluro-phosphate (DFP)
Raw soya beans
Human and bovine colostrum

Q-234. All of the following statements about apo-proteins are true except
a) Apo-protein A-I activates LCAT
b) Apo-protein C-I activates lipoprotein lipase
c) Apo-protein C-II inhibits lipoprotein lipase
d) Apo-protein C-II activates lipoprotein lipase

Answer: Apo-protein C-II inhibits lipoprotein lipase
Explanation:
Lipoprotein lipase, located on the capillary endothelium of extra-hepatic tissues, catalyzes the rate-limiting step in the hydrolysis of triglycerides from circulating chylomicrons and very low density lipoprotein.
Functions of Apo-lipoproteins:
Lipoprotein lipase activators: Apo-protein C-II and Apo-protein C-I
Lipoprotein lipase inhibitors: Apo-protein C-III and Apo-protein A-II
Lecithin cholesterol acyl transferase (LCAT) activators: Apo-protein A-I

Q-235. Which of the following types of hyper-triglyceridemia is associated with an increase in chylomicrons and VLDL remnants?
a) Type I
b) Type IIa
c) Type III
d) Type IV

Answer: Type III
Explanation:
Frederickson Classification of Lipid Disorders:
Type and Elevated particles:
Type-I: Chylomicrons
Type-IIa: LDL
Type-IIb: LDL and VLDL
Type-III: Chylomicrons and VLDL remnants
Type-IV: VLDL
Type-VI: Chylomicrons and VLDL

Q-236. Okazaki fragments are formed during the synthesis of
a) ds-DNA
b) ss-DNA
c) m-RNA
d) t-RNA

Answer: ds-DNA
Explanation:
Okazaki fragments are short, newly synthesized DNA fragments that are formed on the lagging template strand during process of replication of a ds-DNA.
They are complementary to the lagging template strand, together forming short double-stranded DNA sections.

Q-237. Which of the following is a water soluble vitamin?
a) Folic acid
b) Vitamin A
c) Vitamin K
d) Linolenic acid

Answer: Folic acid
Explanation:
Fat soluble vitamins:
Vitamin A
Vitamin D
Vitamin E
Vitamin K
Water soluble vitamins:
B-complex
Vitamin C

Q-238. Which of the following is considered the active form of calcium?
a) Ionized calcium
b) Albumin bound calcium
c) Phosphate bound calcium
d) Protein bound calcium

Answer: Ionized calcium
Explanation:
About 50 % total calcium is ionized and ionized calcium is physiologically active form of calcium.
Remaining 50 % of total calcium is bound, mainly to albumin.

Q-239. Neutral molecules are transported by
a) Porin channels
b) Ionophores
c) Simple diffusion
d) None of the above

Answer: Simple diffusion
Explanation:
Neural molecules are usually transported freely across plasma membrane by simple diffusion as a free diffusion or through channel proteins.

Q-240. Normal role of micro RNA is
a) Gene regulation
b) RNA splicing
c) Initiation of translation
d) DNA conformational change

Answer: Gene regulation
Explanation:
A micro RNA (miRNA) is a small non-coding RNA molecule, which functions in transcriptional and post-transcriptional regulation of gene expression.
A micro RNAs are transcribed from different genomic locations as long primary transcripts (pri-miRNA) by RNA polymerase II. They are embedded in either independent non-coding RNAs or the introns of protein-coding genes.
A micro RNAs function via base-pairing with complementary sequences within mRNA molecules, usually resulting in gene silencing via translational repression or target degradation.
Micro RNA is involved in several cancer-types such as Glioblastoma, Astrocytoma and chronic lymphocytic leukemia.