Q-241. All of the following enzymes are involved in oxidation-reduction reactions except
a) Dehydrogenase
b) Hydrolase
c) Oxygenase
d) Peroxidase
Answer: Hydrolase
Explanation:
Enzymes involved in oxidation-reduction reactions or oxido-reductase:
Dehydrogenase
Hydro-peroxidase- Peroxidase and catalase
Oxygenase
Oxidase
Q-242. Which of the following side chains is least polar group?
a) Methyl
b) Carboxyl
c) Amino
d) Phosphate
Answer: Methyl
Explanation:
Methyl side chains and methylene side chains are non polar side chains associated with non polar amino acids.
Q-243. Which of the following statements about facilitated diffusion is true?
a) It is a form of active transport
b) It requires a carrier protein
c) Rate of transport is proportionate to the concentration gradient
d) Requires creatine phosphate
Answer: It requires a carrier protein
Explanation:
Facilitated diffusion is the process of spontaneous passive transport of molecules or ions across a biological membrane via specific trans-membrane integral proteins.
Important points:
Facilitated diffusion is a form of passive transport.
Rate of transport in facilitated diffusion is proportionate to concentration gradient only at low concentrations, before the carrier protein becomes saturated.
Q-244. After overnight fasting, levels of glucose transporters are reduced in
a) Brain cells
b) Hepatocytes
c) Adipocytes
d) RBCs
Answer: Adipocytes
Explanation:
Glucose transporters that are dependent on insulin for their expression are reduced in fasting state when insulin level is low.
Such insulin dependent transporters (GLUT-4) are specially found in adipose tissue and skeletal muscle.
Glucose transporters in hepatocytes, brain cells and RBCs are insulin independent.
Q-245. Acetyl CoA can be converted into all of the following except
a) Glucose
b) Fatty acids
c) Cholesterol
d) Ketone bodies
Answer: Glucose
Explanation:
Fates of Acetyl-Co-A:
Synthetic pathway: Lipogenesis, Ketogenesis, cholesterologenesis and steroidogenesis
Oxidative pathway: Enters the citric acid cycle to generate ATP
Substrates for gluconeogenesis:
Glucogenic amino acids
Lactate
Pyruvate
Glycerol
Propionic acid in ruminants
Important point:
Acetyl-Co-A is not a substrate for gluconeogenesis.
Q-246. All of the following statements about lipoprotein lipase are true Except
a) Found in adipose tissue
b) Found in myocytes
c) Deficiency leads to hyper-triacylglycerolemia
d) Does not require CII as cofactor
Answer: Does not require CII as cofactor
Explanation:
Lipoprotein lipase is found in adipose tissue, skeletal and cardiac muscles.
Lipoprotein lipase requires apo-protein CII as cofactor and deficiency causes Type-I Hyper-lipoproteinemia with accumulation of chylomicrons in the plasma.
Q-247. The gaps between segments of DNA on the lagging strand produced by restriction enzymes are rejoined/ sealed by
a) DNA ligase
b) DNA Helicase
c) DNA topoisomerase
d) DNA phosphorylase
Answer: DNA ligase
Explanation:
DNA ligases close nicks in the phosphodiester backbone of DNA. DNA ligases are essential for the joining of Okazaki fragments on lagging strand during replication, and for completing short-patch DNA synthesis occurring in DNA repair process.
Q-248. Splicing activity is a function of
a) m-RNA
b) sn-RNA
c) r-RNA
d) t-RNA
Answer: sn-RNA
Explanation:
Small Nuclear RNAs:
One important subcategory of small regulatory RNAs consists of the molecules known as small nuclear RNAs (sn-RNAs).
These molecules play a critical role in gene regulation by way of RNA splicing.
Sn-RNAs are found in the nucleus and are typically tightly bound to proteins in complexes called sn-RNPs (small nuclear ribonucleoproteins, sometimes pronounced “snurps”).
The most abundant of these molecules are the U1, U2, U5, and U4/U6 particles, which are involved in splicing of pre-mRNA to give rise to mature mRNA.
Q-249. CAP in Lac Operon is an example of
a) Positive regulator
b) Negative regulator
c) Constitutive expression
d) Attenuation
Answer: Positive regulator
Explanation:
Regulatory proteins in Lac Operon:
CAP: Catabolite gene activator protein (Positive regulator)
Lac I gene or repressor protein (Negative regulator)
Q-250 (a). All of the following are true about sickle cell disease except
a) Single nucleotide change results in change of glutamine to Valine
b) RFLP results from a single base change
c) Sticky patch is generated as a result of replacement of a non polar residue with a polar residue
d) HbS confers resistance against malaria in heterozygotes
Answer: Sticky patch is generated as a result of replacement of a non polar residue with a polar residue
Explanation:
Sickle cell disease:
Sticky patch is generated as a result of replacement of a polar glutamate residue (Normal amino acid in position 6 of the beta chain) with a non-polar valine residue due to single nucleotide replacement.
Replacement of a polar glutamate residue with a non-polar valine residue leads to altered solubility of HbS.
Primary patho-physiological event in sickling is intra-cellular polymerization of deoxy HbS due to its markedly reduced solubility.
Q-250 (b). Sickling in ‘HbS’ disease is primarily caused by
a) Decreased Solubility
b) Decreased Stability
c) Altered Function
d) Altered O2 Binding capacity
Answer: Decreased Solubility
Explanation: See above explanation