501. Which statement best describes the source and action of hormones?
ⓐ. They are secreted by glands and act on target tissues.
ⓑ. They are stored sugars that release glucose on hydrolysis.
ⓒ. They are structural fibres made from \(\beta\)-D-glucose.
ⓓ. They are nucleotide chains that pair with bases in DNA.
Correct Answer: They are secreted by glands and act on target tissues.
Explanation: Hormones are chemical messengers produced by specialised glands or tissues. They are carried to target cells where they produce specific regulatory effects. Their action depends on recognition by target tissues rather than on direct energy release. Storage sugars, structural polysaccharides, and nucleotide chains belong to different biomolecule classes.
502. Which statement best distinguishes hormones from vitamins?
ⓐ. Hormones are always glucose polymers, while vitamins are always proteins.
ⓑ. Hormones act as chemical messengers, while vitamins are dietary micronutrients.
ⓒ. Hormones are nucleotides, while vitamins are amino-acid residues.
ⓓ. Hormones are always non-reducing sugars, while vitamins are always reducing sugars.
Correct Answer: Hormones act as chemical messengers, while vitamins are dietary micronutrients.
Explanation: Hormones regulate body processes by carrying chemical signals between cells or tissues. Vitamins are organic micronutrients needed in small amounts for normal metabolism and health. Both may be needed in small quantities, but their roles are different. Hormones are produced in the body, while vitamins generally need to be supplied through diet in adequate amounts.
503. Which hormone is most closely associated with lowering blood glucose level?
ⓐ. Adrenaline
ⓑ. Thyroxine
ⓒ. Insulin
ⓓ. Glucagon
Correct Answer: Insulin
Explanation: Insulin is a peptide hormone secreted by the pancreas. It helps reduce blood glucose level by promoting uptake and storage of glucose. This regulatory role is why insulin is strongly associated with blood sugar control. Glucagon has an opposite broad effect by helping raise blood glucose level.
504. Which hormone generally acts opposite to insulin in blood glucose regulation?
ⓐ. Glucagon
ⓑ. Estrogen
ⓒ. Thyroxine
ⓓ. Calcitonin
Correct Answer: Glucagon
Explanation: Insulin helps lower blood glucose level. Glucagon generally acts in the opposite direction by helping increase blood glucose level when needed. Both are hormones involved in metabolic regulation. Their opposite effects help maintain glucose balance within a suitable range.
505. Which statement best describes adrenaline?
ⓐ. A storage polysaccharide found in liver and muscles
ⓑ. A hormone involved in stress response
ⓒ. A disaccharide formed from glucose and fructose
ⓓ. A nucleic acid base used only in RNA
Correct Answer: A hormone involved in stress response
Explanation: Adrenaline is a hormone associated with rapid body responses during stress or emergency conditions. It helps prepare the body for quick action by affecting functions such as heart activity and energy mobilisation. This is different from the storage role of glycogen or the structural role of nucleic-acid bases. Adrenaline is a signalling molecule, not a carbohydrate.
506. Thyroxine is most closely associated with which broad role?
ⓐ. Formation of glycosidic bonds in starch
ⓑ. Regulation of metabolic activity
ⓒ. Storage of hereditary information
ⓓ. Hydrolysis of peptide bonds only
Correct Answer: Regulation of metabolic activity
Explanation: Thyroxine is a hormone associated with regulation of metabolic activity. It helps control the rate of several body processes. Its function is regulatory and signalling-based rather than structural or storage-based. DNA stores hereditary information, while glycosidic and peptide bond reactions belong to carbohydrate and protein chemistry.
507. Which element is especially associated with thyroxine?
ⓐ. Sodium
ⓑ. Calcium
ⓒ. Iodine
ⓓ. Silicon
Correct Answer: Iodine
Explanation: Thyroxine is an iodine-containing hormone. Iodine is therefore important for the normal formation of this hormone. Since thyroxine helps regulate metabolic activity, iodine deficiency can disturb normal thyroid-related functions. This association separates thyroxine from peptide hormones such as insulin.
508. Which statement best compares peptide hormones and steroid hormones?
ⓐ. Peptide hormones are amino-acid based, while steroid hormones have steroid frameworks.
ⓑ. Peptide hormones are glucose polymers, while steroid hormones are nucleic acid chains.
ⓒ. Peptide hormones contain only ribose, while steroid hormones contain only phosphate.
ⓓ. Peptide hormones are cellulose fibres, while steroid hormones are disaccharides.
Correct Answer: Peptide hormones are amino-acid based, while steroid hormones have steroid frameworks.
Explanation: Peptide hormones are made from amino-acid units or peptide chains. Insulin is a common example of a peptide hormone. Steroid hormones have steroid-type carbon skeletons and are chemically different from peptide hormones. Both act as signalling molecules, but their chemical structures are not the same.
509. Which statement best explains why insulin is classified as a peptide hormone?
ⓐ. It is made of amino-acid units linked in peptide chains.
ⓑ. It contains only glucose units joined by glycosidic bonds.
ⓒ. It is made of nucleotides joined by phosphodiester bonds.
ⓓ. It is a fat-soluble vitamin stored in body tissues.
Correct Answer: It is made of amino-acid units linked in peptide chains.
Explanation: Insulin is a peptide hormone because its structure is based on amino-acid units. These amino-acid units are connected through peptide linkages. Its biological role is hormonal regulation of blood glucose level. It is not a carbohydrate polymer, nucleic acid, or vitamin.
510. Which pairing is most appropriate?
ⓐ. Insulin — plant cell wall support
ⓑ. Adrenaline — stress response
ⓒ. Thyroxine — DNA base pairing
ⓓ. Glucagon — cellulose digestion
Correct Answer: Adrenaline — stress response
Explanation: Adrenaline is closely linked with stress or emergency responses. Insulin and glucagon are more directly linked with blood glucose regulation. Thyroxine is associated with metabolic regulation. Plant wall support is linked with cellulose, not insulin.
511. Which statement is false about hormones?
ⓐ. They act as chemical messengers.
ⓑ. They are effective in small amounts.
ⓒ. They act on specific target cells or tissues.
ⓓ. They are always storage polysaccharides.
Correct Answer: They are always storage polysaccharides.
Explanation: Hormones are chemical signalling molecules, not storage polysaccharides. They may have different chemical natures, such as peptide or steroid type. They are effective in small amounts because they trigger specific responses in target tissues. Storage polysaccharides such as starch and glycogen belong to carbohydrate chemistry.
512. Which statement correctly separates insulin and thyroxine?
ⓐ. Insulin is peptide-based; thyroxine contains iodine.
ⓑ. Insulin is a nucleic acid, while thyroxine is a disaccharide.
ⓒ. Insulin is cellulose, while thyroxine is starch.
ⓓ. Insulin is vitamin \(C\), while thyroxine is vitamin \(D\).
Correct Answer: Insulin is peptide-based; thyroxine contains iodine.
Explanation: Insulin is a peptide hormone made from amino-acid units. Thyroxine is associated with iodine and regulation of metabolic activity. Both are hormones, but their chemical nature and major recognition features differ. They should not be classified as vitamins, carbohydrates, or nucleic acids.
513. Which assertion-reason pair is correctly evaluated?
Assertion: Hormones can regulate distant organs or tissues.
Reason: Hormones are chemical messengers that can be transported to target sites.
ⓐ. Both are true, and Reason explains Assertion.
ⓑ. Assertion is true, but Reason is false.
ⓒ. Assertion is false, but Reason is true.
ⓓ. Both are true, but Reason is unrelated to Assertion.
Correct Answer: Both are true, and Reason explains Assertion.
Explanation: Hormones are produced at one site and can act at specific target tissues. They function as chemical messengers, so their signal can be carried through body fluids to suitable target cells. The target cells respond because they have appropriate recognition systems. Therefore the reason explains how hormones can regulate distant tissues.
514. Which statement best distinguishes hormones from enzymes?
ⓐ. Hormones are catalysts, while enzymes are always genetic material.
ⓑ. Hormones mainly signal regulation, while enzymes speed up reactions.
ⓒ. Hormones are always carbohydrates, while enzymes are always vitamins.
ⓓ. Hormones break DNA bases, while enzymes form steroid skeletons only.
Correct Answer: Hormones mainly signal regulation, while enzymes speed up reactions.
Explanation: Hormones work mainly as chemical messengers that regulate body processes. Enzymes are biological catalysts that increase the rate of biochemical reactions. Many enzymes are proteins, while hormones can have different chemical natures. Their functions may interact in living systems, but their primary roles are distinct.
515. Which example best represents a hormone with protein or peptide nature?
ⓐ. Insulin
ⓑ. Sucrose
ⓒ. Cellulose
ⓓ. Ribose
Correct Answer: Insulin
Explanation: Insulin is a peptide hormone and is made from amino-acid units. It plays an important role in regulation of blood glucose level. Sucrose, cellulose, and ribose are carbohydrates, not hormones. This makes insulin the suitable example of a protein-related hormone.
516. Which statement gives the most complete summary of hormones?
ⓐ. They are always sugars that provide immediate energy.
ⓑ. They are regulatory chemical messengers.
ⓒ. They are only DNA bases arranged in a double helix.
ⓓ. They are storage polymers made only in plants.
Correct Answer: They are regulatory chemical messengers.
Explanation: Hormones are best understood by their signalling role. They regulate biological processes such as metabolism, growth, stress response, and blood glucose balance. Their structures can vary, including peptide and steroid types. They are not limited to sugars, DNA bases, or plant storage polymers.
517. Which set contains only essential amino acids?
ⓐ. Glycine, alanine, serine, and cysteine
ⓑ. Valine, leucine, lysine, and methionine
ⓒ. Aspartic acid, glutamic acid, glycine, and proline
ⓓ. Alanine, serine, tyrosine, and glutamic acid
Correct Answer: Valine, leucine, lysine, and methionine
Explanation: Essential amino acids are those that the human body cannot synthesise in adequate amounts and must obtain from the diet. Valine, leucine, lysine, and methionine are standard examples of essential amino acids. Glycine, alanine, serine, and glutamic acid are commonly treated as non-essential examples in the usual introductory classification. The distinction is based on dietary requirement, not on whether the amino acid is useful in proteins.
518. Which amino acid is commonly classified as non-essential?
ⓐ. Glycine
ⓑ. Valine
ⓒ. Lysine
ⓓ. Tryptophan
Correct Answer: Glycine
Explanation: Glycine is a common example of a non-essential amino acid. Non-essential does not mean biologically useless; it means the body can normally synthesise it in sufficient quantity. Valine, lysine, and tryptophan are essential amino acids in the usual nutritional classification. The terms essential and non-essential can be misunderstood unless they are connected with dietary requirement.
519. Which pair contains one essential amino acid and one non-essential amino acid respectively?
ⓐ. Alanine and glycine
ⓑ. Leucine and alanine
ⓒ. Serine and cysteine
ⓓ. Glutamic acid and aspartic acid
Correct Answer: Leucine and alanine
Explanation: Leucine is an essential amino acid and must be supplied through diet in adequate amount. Alanine is commonly classified as a non-essential amino acid because the body can synthesise it. A pair containing two non-essential examples would not satisfy the required order. The word respectively means the essential amino acid must come first and the non-essential amino acid second.
520. Which statement correctly identifies lysine?
ⓐ. A non-essential amino acid made from carbohydrate units
ⓑ. A carbohydrate monomer present in starch
ⓒ. A nitrogenous base found in nucleic acids
ⓓ. An essential amino acid required in the diet
Correct Answer: An essential amino acid required in the diet
Explanation: Lysine is an essential amino acid. It is required in the diet because the body cannot make enough of it under normal conditions. It is still an amino acid unit used in proteins, not a carbohydrate or a nucleic-acid base. Its classification depends on nutritional requirement rather than on whether it contains nitrogen.
