Q-221. Vitamin K is required for:
a) Carboxylation
b) Hydroxylation
c) Chelation
d) Transamination
Answer: Carboxylation
Explanation:
Gamma-glutamyl carboxylase is an enzyme that catalyzes the posttranslational modification of vitamin K-dependent proteins.
Many of these vitamin K-dependent proteins are involved in coagulation so the function of the encoded enzyme is essential for hemostasis.
Vitamin K is involved in the carboxylation of certain glutamate residues in proteins to form gamma-carboxy-glutamate (Gla) residues.
Q-222. Proteins which are different in peptide sequence but have a similar structure in the process of evolution are said to be:
a) Convergent
b) Divergent
c) Opportunistic
d) Incidental
Answer: Convergent
Explanation:
Proteins undergoing functional convergence:
Unrelated proteins have similar functions with different structure.
Proteins undergoing structural convergence:
Unrelated proteins have similar tertiary structures but different amino acid sequence or functions.
Whole protein structural convergence is not thought to occur but some convergence of pockets and secondary structural elements have been documented.
Q-223. Hemoglobin estimation is done by all except:
a) Drabkin’s method
b) Sahli’s method
c) Spectro-photometry
d) Wintrobe’s method
Answer: Wintrobe’s method
Explanation:
Methods of Hemoglobin Estimation:
Sahli’s method (Acid-Hematin Method)-Least accurate
Alkaline-Hematin Method
Drabkin’s method (Cyano-methmoglobin Method)
Oxy-hemoglobin Method- Simplest and quickest
Spectro-photometry- Most accurate
Q-224. Nephelometry is based on the principle of:
a) Light attenuated in intensity by scattering
b) Reduced transmission of light
c) Refraction of light
d) Filtration of solutes by kidney
Answer: Light attenuated in intensity by scattering
Explanation:
Turbidimetry is the measurement of the degree of attenuation of a radiant beam incident on particles suspended in a medium, the measurement being made in the directly transmitted beam.
Nephelometry is the measurement of the light scattered by suspended particles, the measurement usually being made perpendicularly to the incident beam.
(Ref: http://apps.who.int/phint/en/p/docf/)
Q-225. All are involved in fast axonal transport, except
a) Kinesin
b) Dynein
c) Myosin
d) Neuro-filaments
Answer: Neuro-filaments
Explanation:
Axonal Transport: Transport is bi-directional
Antero-grade:
Fast (Motor: Kinesin complex proteins)
Slow
Retrograde:
Fast (Motor: Dynactin complex proteins)
Slow
Molecular motor proteins- Kinesin, Dynein and Myosin
The transport of vesicles in neurons is a highly regulated process, with vesicles moving either anterogradely or retrogradely depending on the nature of the molecular motors, Kinesin and Dynein, respectively, which propel vesicles along microtubules (MTs).
Q-226. Collagen of which type is found in hyaline cartilage
a) Type I
b) Type II
c) Type III
d) Type IV
Answer: Type II
Explanation:
Type of collagen:
Fibril Forming Collagens:
Collagens Type I– Bone, Tendon, Skin, Cornea and Blood Vessels
Collagens Type II– Cartilage, Inter-vertebral Disk, Vitrous Body
Collagens Type III-Blood Vessels and Fetal skin
Network Forming Collagens:
Collagens Type IV– Basement membrane
Collagens Type VII– Beneath stratified squamous epithelia
Fibril Associated Collagens:
Collagens Type IX– Cartilage
Collagens Type XII- Tendon, Ligament
Q-227. Which Vitamin is required for carboxylation clotting factors?
a) Vitamin A
b) Vitamin D
c) Vitamin E
d) Vitamin K
Answer: Vitamin K
Explanation:
Gamma-glutamyl carboxylase is an enzyme that catalyzes the posttranslational modification of vitamin K-dependent proteins.
Vitamin K is involved in the carboxylation of certain glutamate residues in proteins to form gamma-carboxy-glutamate (Gla) residues.
The modified residues are often (but not always) situated within specific protein domains called Gla domains.
Gla residues are usually involved in binding calcium, and are essential for the biological activity of all known Gla proteins.
At this time, 16 human proteins with Gla domains have been discovered, and they play key roles in the regulation of following physiological processes:
Blood coagulation: prothrombin (factor II), factors VII, IX, and X, and proteins C, S, and Z
Bone metabolism: Osteocalcin, also called bone Gla protein (BGP), matrix Gla protein (MGP), periostin, and the recently discovered Gla-rich protein (GRP).
Q-228. Which of the following metabolic pathways does not generate ATP?
a) Glycolysis
b) TCA cycle
c) Fatty acid oxidation
d) HMP pathway
Answer: HMP pathway
Explanation:
The pentose phosphate pathway or hexose mono-phosphate shunt is an alternative route for metabolism of glucose.
No ATP is directly consumed or produced in the hexose mono-phosphate shunt.
Q-229. In which of the following tissues is glycogen incapable of contributing directly to blood glucose:
a) Liver
b) Muscle
c) Both
d) None
Answer: Muscle
Explanation:
In muscles, enzyme glucose-6-phosphatase is absent. This enzyme removes the phosphate from glucose-6-phosphate.
Free glucose can therefore not form in muscle directly, hence glycogenolysis in muscle dose not contribute directly to blood glucose.
Important points:
This glucose-6-phosphate can enter the glycolytic cycle and form pyruvate and lactic acid.
Indirectly, lactic acid may go to glucose formation in liver.
Q-230. Phosphorylase b is maintained in an inactivated state by
a) ATP
b) c-AMP
c) Calcium
d) Insulin
Answer: Insulin
Explanation:
Factors maintaining phosphorylase in its active form (Phosphorylase a):
c-AMP
Calcium
ATP
Factors maintaining phosphorylase in its inactive form (Phosphorylase b):
Insulin
Protein phosphatase
Glucose-6-phosphate