26. Reactive proteins include
a. Enzymes
b. Hormones
c. Globulins of blood
d. All
Correct answer: d. All
These protein groups actively participate in chemical and physiological reactions, making all of them reactive proteins.
27. Lipids include
a. Triglycerides
b. Waxes
c. Prostaglandins
d. All
Correct answer: d. All
All listed substances are classified as lipids based on their chemical nature and biological roles.
28. RNA is intimately associated with synthesis of which constituent of the cell
a. Carbohydrates
b. Proteins
c. Lipids
d. Inorganics
Correct answer: b. Proteins
RNA acts as the functional template and machinery (mRNA, rRNA, tRNA) for protein synthesis.
29. How much percentage of inorganic material is contained in bones
a. 35%
b. 45%
c. 55%
d. 65%
Correct answer: d. 65%
Around 65% of bone mass is made of inorganic hydroxyapatite crystals, responsible for hardness.
30. Which mineral is an essential part of thyroxin?
a. Fe
b. Mg
c. Iodine
d. Na
Correct answer: c. Iodine
Iodine is required for the production of thyroid hormones T3 and T4.
31. Smooth endoplasmic reticulum is involved in the synthesis of
a. Glycogen
b. Lipids
c. Steroids
d. All
Correct answer: d. All
Smooth ER is the site for lipid, phospholipid, and steroid synthesis and is also involved in glycogen metabolism.
32. Oxidase enzymes responsible for producing H₂O₂ are present in
a. Mitochondria
b. Ribosomes
c. Peroxisomes
d. Polysomes
Correct answer: c. Peroxisomes
Peroxisomes house oxidase enzymes that generate hydrogen peroxide during metabolic detoxification.
33. Microfilaments may assist
a. In the movement of fibroblasts in heart
b. Growth of axons
c. Contraction of all muscle
d. All
Correct answer: d. All
Microfilaments (actin) support cell motility, axonal extension, and muscle contraction.
34. Centriole consists of how many paired filaments
a. 5
b. 7
c. 9
d. 11
Correct answer: c. 9
Each centriole contains nine triplets of microtubules arranged cylindrically.
35. The life span of RBC is
a. 80 days
b. 100 days
c. 120 days
d. 140 days
Correct answer: c. 120 days
Normal erythrocytes circulate for approximately 120 days before removal.
36. Pyrimidine thymine occurs only in
a. RNA
b. DNA
c. Both
d. All
Correct answer: b. DNA
Thymine is a DNA-specific pyrimidine, replaced by uracil in RNA.
37. Pyrimidine uracil occurs only in
a. RNA
b. DNA
c. Both
d. None
Correct answer: a. RNA
Uracil is found only in RNA and never in DNA.
38. Adenine is always paired with
a. Guanine
b. Cytosine
c. Thymine
d. Uracil
Correct answer: c. Thymine
In DNA, adenine forms two hydrogen bonds with thymine.
39. Guanine is always paired with
a. Adenine
b. Cytosine
c. Thymine
d. Uracil
Correct answer: b. Cytosine
Guanine pairs with cytosine through three hydrogen bonds.
40. During starvation of cell, the amount of following may decrease
a. RNA
b. Protein
c. Both
d. None
Correct answer: c. Both
Starvation reduces cellular protein synthesis and RNA content because anabolic activity declines.
41. The following are neurotransmitters in the autonomic ganglia
a. GABA
b. Noradrenaline
c. Acetylcholine
d. 5-HT
Correct answer: c. Acetylcholine
Autonomic ganglia use acetylcholine acting on nicotinic receptors.
42. True statements about the pH of the extracellular fluid
a. In healthy people it is maintained between 7.4 and 7.5
b. Is increased in hypovolemic shock
c. Increases following a cardiac arrest
d. Influences the binding of drugs to plasma proteins
Correct answer: d. Influences the binding of drugs to plasma proteins
ECF pH alters protein ionization and affects drug-binding affinity.
43. The following occur in the proximal tubules of the nephron
a. Reabsorption of all glucose
b. Reabsorption of most water
c. Active reabsorption of sodium
d. All of these
Correct answer: d. All of these
The proximal tubule reabsorbs all filtered glucose, most water, and actively transports sodium.
44. Cytochrome P450 is
a. Involved in phase I metabolic reactions
b. Found in lysosomes
c. Found in ribosomes
d. Found in mitochondria
Correct answer: a. Involved in phase I metabolic reactions
Cytochrome P450 enzymes oxidize drugs mainly in the smooth endoplasmic reticulum.
45. Actions of angiotensin II include
a. Increases the release of aldosterone
b. Reduces renin release from the kidney
c. Promotes microalbuminuria
d. All of these
Correct answer: d. All of these
Angiotensin II stimulates aldosterone, suppresses renin, and contributes to glomerular injury.
46. In a normal nephron
a. ADH increases the permeability of collecting ducts to water
b. All the filtered glucose is reabsorbed in the proximal tubule
c. Nearly all the filtered protein is reabsorbed in the proximal convoluted tubule
d. All of these
Correct answer: a. ADH increases the permeability of collecting ducts to water
ADH acts specifically on the collecting ducts; the other statements are partly true but not absolute.
47. The release of acetylcholine is blocked by
a. Hemicholinium
b. Venom of black widow spider
c. Cocaine
d. None
Correct answer: a. Hemicholinium
Hemicholinium blocks choline uptake, preventing acetylcholine synthesis and release.
48. Antidiuretic hormone
a. Decreases the osmolarity of urine
b. Decreases the volume of urine
c. Increases the reabsorption of water in the proximal tubules
d. Is synthesized in the posterior pituitary gland
Correct answer: a & b (but single best: a. Decreases the osmolarity of urine)
ADH concentrates urine and reduces its volume. It works on collecting ducts, not proximal tubules, and is synthesized in the hypothalamus.
49. Insulin secretion
a. Is inhibited by atropine
b. Is decreased by vagal stimulation
c. Is inhibited by amino acids
d. Is stimulated by beta agonists
Correct answer: d. Is stimulated by beta agonists
Beta-adrenergic stimulation increases insulin release; vagal stimulation and amino acids increase insulin, not decrease it.
50. Prolactin secretion
a. Is higher in female than male
b. Is inhibited by dopamine
c. Is increased in patients taking phenothiazines
d. All above
Correct answer: d. All above
Females have higher prolactin; dopamine inhibits prolactin; phenothiazines block dopamine receptors, increasing prolactin.