Biochemistry Top 25 Most Important Questions and Answers
Biochemistry Top 25 Most Important Questions and Answers
Biochemistry Top 25 Most Important Questions and Answers
• Importance:
➢ Biochemistry deals with study of living system and its working
➢ Biochemistry is involved in the study of nature and working of molecules.
➢ Diagnosis of various metabolic disorders
➢ Biochemistry is involved in study of various deficiency diseases.
➢ Biochemistry helps in synthesizing new molecules.
2. Define carbohydrates and classify them with examples?
Ans.
• Definition: Carbohydrates can be defined as organic compounds which are polyhydroxy aldehydes
or polyhydroxy ketones. Carbohydrates are also called as saccharides or sugar.
• Classification:
A. Glycans: Sweet tasting carbohydrates.
1) Monosaccharides:
➢ Biose: E.g. glycoaldehyde,
➢ Triose: E.g. glyceraldehyde
➢ Pentose: E.g. ribose
➢ Hexose: E.g. glucose, fructose
➢ Heptose: E.g. pseudoheptulose
2) Oligosaccharides: Example: Sucrose (glucose + fructose), Lactose (glucose + galactose)
1) Benedict Test: Simple and quick test for detecting reducing sugars.
➢ Detects: All reducing sugars.
➢ Reaction: Heating sugar with Benedict's reagent forms brick red precipitate for monosaccharides.
2) Fehling Test: Similar to Benedict's test but uses different reagents.
➢ Detects: All reducing sugars.
➢ Reaction: Boiling sugar with Fehling solution produces brick red precipitate for reducing sugars.
3) Barfoed Test: Specifically distinguishes monosaccharides from disaccharides.
➢ Detects: Monosaccharides.
➢ Reaction: Heating with Barfoed reagent forms red precipitate for monosaccharides.
4) Seliwanoff Test: Differentiates between aldose and ketose sugars.
➢ Detects: Ketose sugars.
➢ Reaction: Boiling with Seliwanoff reagent produces cherry-red color for ketose sugars.
5) Iodine Test: Identifies presence of starch and related polysaccharides.
➢ Detects: Starch and related carbohydrates.
➢ Reaction: Starch + Iodine gives blue-violet color; Dextrin gives pink; Glycogen gives brown;
Amylose gives deep blue.
6) Molisch Test: General test for detecting presence of any carbohydrate.
➢ Detects: All carbohydrates.
➢ Reaction: Carbohydrates + Conc. H2SO4 produce blue-violet ring with α-naphthol.
7) Mucic Acid Test: Highly specific for detecting galactose and lactose.
➢ Detects: Galactose and lactose.
➢ Reaction: Galactose treated with HNO3 forms mucic acid crystals resembling broken glass.
8) Tollen Mirror Test: Also known as silver mirror test due to formation of shiny silver mirror.
➢ Detects: Reducing disaccharides.
➢ Reaction: Heating with Tollen reagent produces silver mirror for aldoses.
Ans.
• Definition: Amino acids are the monomers of proteins having an amino and carboxyl group attached to
the same carbon atom.
• Classification:
A. By Chemical Properties
Neutral amino acids: Glycine, Alanine, Valine, Leucine, Serine
Basic amino acids: Lysine, Arginine, Histidine
Acidic amino acids: Aspartic acid, Glutamic acid
B. By Chemical Structure:
Aliphatic amino acids: Glycine, Alanine
Aromatic amino acids: Phenylalanine, Tyrosine, Tryptophan
Sulphur amino acids: Cysteine, Methionine
C. By Dietary Value:
Essential amino acids: Leucine, Isoleucine, Arginine
Nonessential amino acids: Alanine, Glycine, Tyrosine
6. Discuss qualitative test of protein and amino acid?
Ans.
Qualitative test of protein and amino acid
A. Xanthoproteic Test:
➢ Principle: Aromatic amino acids react with concentrated HNO3 to form nitro compounds,
producing a deep yellow or orange color upon addition of alkali.
➢ Significance: Detects proteins containing aromatic amino acids like phenylalanine and tyrosine.
D. Ninhydrin Reaction/Test:
➢ Principle: Free amino groups react with ninhydrin to produce a blue color upon heating.
➢ Significance: Indicates the presence of proteins, peptides, and amino acids; useful in detecting
proteases and peptones.
F. Biuret Test:
➢ Principle: Proteins containing more than one peptide linkage react with CuSO4 in alkaline medium
to produce a violet or deep violet color.
➢ Significance: Detects proteins, proteoses, peptones, and polypeptides based on peptide linkages.
G. Hopkins-Cole Reaction/Test:
➢ Principle: Tryptophan-containing proteins react with Hopkins-Cole reagent (glyoxylic acid) and
H2SO4 to form a violet or purple ring at the liquid junction.
➢ Significance: Indicates the presence of tryptophan in proteins.
C. Nutritional Oedema:
• Causes: Prolonged and significant protein deficiency in adults.
• Symptoms: Weight loss reduced subcutaneous fat, Anaemia, Increased susceptibility to infection,
Lethargy, Watery stools, Inability to sustain work, delayed wound healing, Inability to perform
prolonged hard work. Oedema.
• Treatments: Diet rich in milk, milk products, eggs, and soybeans. Emphasize preventive actions by
regulating daily protein intake.
Ans.
a) Sudan III Test: Mix the sample with Sudan III stain and shake gently. Lipids will form a distinct red layer
on top if present.
b) Paper Chromatography: Apply the lipid sample onto chromatography paper. Allow the paper to run in
a suitable solvent. Lipids will appear as distinct spots on the paper.
c) Emulsion Test: Mix the sample with water and shake vigorously. Lipids will form an emulsion, visible as
a milky or cloudy appearance.
d) Grease Spot Test: Apply a small amount of sample onto filter paper. Allow the paper to dry. Lipids will
leave a translucent spot on the paper.
e) Solubility Test: Test lipid solubility in various solvents like ether, chloroform, or acetone. Lipids are
typically soluble in organic solvents and insoluble in water.
f) Iodine Test: Mix the sample with iodine solution. Lipids will form a brown color if unsaturated, and a
blue-black color if saturated.
g) Acrolein Test: Heat the sample with glycerol and sulfuric acid. Lipids will produce an acrid, pungent
odour characteristic of acrolein.
h) Halphen Test: Mix the sample with bromine water and chloroform. Lipids will form a white precipitate if
present.
i) Ninhydrin Test: Treat the sample with ninhydrin solution and heat. Lipids will produce a purple
coloration if present.
Ans.
A. Introduction:
➢ Most important Primary monohydric or steroid alcohol.
➢ Integral part of bio membranes.
➢ Mainly synthesized in the liver, affected by dietary fat intake.
➢ Abundant in animal tissues, found in membranes with phospholipids.
➢ Precursor for bile salts, sex hormones, corticosteroids, and vitamin D.
B. Structure of cholesterol:
C. Functions/Importance of Cholesterol:
➢ Structural component of bio membranes.
➢ Precursor for bile salt biosynthesis.
➢ Essential for corticosteroid hormone production, aiding in stress relief.
➢ Necessary for sex hormone and prostaglandin biosynthesis.
➢ Chief constituent of gallstones.
11. Define nucleic acid and write component of nucleoside and nucleotides with
examples?
Ans.
Definition: Nucleic acids are very complex, colourless, amorphous compounds made-up of carbon,
hydrogen, oxygen, nitrogenous bases, i.e. purine or pyrimidine, sugar and phosphorous. Example - DNA &
RNA.
• Components of Nucleosides:
a) Effect of Nature and Concentration of Substrate: Increased substrate concentration, with constant
enzyme concentration, increases reaction rate. Initially, reaction rate is directly proportional to substrate
concentration due to active site occupancy. Further increase in substrate concentration increases
catalysis until enzyme saturation.
b) Effect of Nature and Concentration of Enzymes: Enzyme activity directly proportional to enzyme
concentration. Increased velocity requires highest substrate concentration, specific substrate, optimum
pH, and temperature.
c) Effect of Time: Enzyme activity may change over time due to factors like substrate depletion or enzyme
degradation.
d) Effect of Temperature: Enzyme activity increases with temperature up to an optimal point, then
decreases due to denaturation at higher temperatures or reduced activity at lower temperatures.
e) Effect of pH: Enzymes have an optimal pH for maximum activity. Deviations from this pH can affect
enzyme structure and activity, with extreme pH values leading to denaturation.
f) Effect of UV Rays: UV rays denature enzymes, affecting velocity. Damage more pronounced at 2650Å
wavelength. Purity of enzyme affects degree of damage; impurities can absorb UV rays.
g) Effect of Inhibitors: Inhibitors decrease enzyme action and reaction rate.
h) Effect of Activators: Activators increase enzyme activity and reaction rate. Examples: monovalent cations
(K+, Na+), cysteine HCl for papain.
B. Vitamin D (Calciferol):
➢ Rickets: Occur in children Softening and weakening of bones due to inadequate mineralization,
leading to bowed legs and other skeletal deformities.
➢ Osteomalacia: Occur in adult Similar to rickets, but occurring in adults, characterized by weak, soft
bones prone to fractures.
C. Vitamin E (Tocopherol):
➢ Muscle Weakness: Due to oxidative damage to muscle cells.
➢ Neurological Symptoms: Such as impaired reflexes and coordination, due to nerve damage.
➢ Anaemia: Vitamin E deficiency can contribute to haemolytic anaemia.
B. Vitamin B2 (Riboflavin):
Ariboflavinosis: Cracks and sores around the corners of the mouth, inflammation of the tongue and
throat, skin disorders
C. Vitamin B3 (Niacin):
Pellagra: Characterized by the "3 Ds" - dermatitis, diarrhoea, and dementia. Other symptoms include
inflamed mucous membranes, hallucinations, and eventual death if untreated.
E. Vitamin B6 (Pyridoxine):
Peripheral Neuropathy: Numbness, tingling, and weakness in hands and feet.
Anaemia: Due to impaired haemoglobin synthesis.
Dermatitis: Inflammation of the skin.
F. Vitamin B7 (Biotin):
Rare, but symptoms can include hair loss, scaly skin, and neurological symptoms.
G. Vitamin B9 (Folate):
Megaloblastic Anaemia: Characterized by large, immature red blood cells, leading to fatigue and
weakness.
Neural Tube Defects: During pregnancy, folate deficiency can lead to birth defects such as spina bifida
in the developing foetus.
H. Vitamin B12 (Cobalamin):
Pernicious Anaemia: Megaloblastic anaemia due to inability to absorb B12, caused by autoimmune
destruction of intrinsic factor-producing cells in the stomach.
Neurological Symptoms: Such as numbness, tingling, and difficulty walking due to nerve damage.
These are the key deficiency diseases associated with both fat-soluble and water-soluble vitamins.
Reaction:
1) Formation of acetyl-CoA
2) Formation of isocitric acid
3) Formation of oxalosuccinic acid
4) Formation of α-ketoglutaric acid
5) Formation of succinyl-CoA
6) Formation of succinic acid
7) Formation of fumaric acid
8) Formation of malic acid
9) Formation of oxaloacetic acid
➢ Formation of Acetyl-CoA: Pyruvic acid, which is produced during glycolysis, enters the mitochondria
where it undergoes decarboxylation to form acetyl-CoA. This reaction also generates NADH2
(reduced form of NAD+).
➢ Formation of Isocitric Acid: Acetyl-CoA combines with oxaloacetic acid to form citric acid (citrate).
Citrate is then converted to isocitric acid through a series of enzymatic reactions catalysed by
aconitase.
➢ Formation of Oxalosuccinic Acid: Isocitric acid is converted into oxalosuccinic acid by the enzyme
isocitrate dehydrogenase.
➢ Formation of α-Ketoglutaric Acid: Oxalosuccinic acid undergoes oxidative decarboxylation to form α-
ketoglutaric acid.
➢ Formation of Succinyl-CoA: α-ketoglutaric acid is converted into succinyl-CoA through a series of
reactions involving coenzyme A (CoA) and the release of carbon dioxide.
➢ Formation of Succinic Acid: Succinyl-CoA is converted into succinic acid by succinyl-CoA synthetase,
releasing CoA and producing GTP (which can later generate ATP).
➢ Formation of Fumaric Acid: Succinic acid is oxidized to fumaric acid by succinate dehydrogenase,
generating FADH2 (reduced form of FAD).
➢ Formation of Malic Acid: Fumaric acid is hydrated to form malic acid with the help of the enzyme
fumarase.
➢ Formation of Oxaloacetic Acid: Malic acid is oxidized to oxaloacetic acid by malate dehydrogenase,
generating NADH2. Oxaloacetic acid can then combine with another acetyl-CoA to restart the cycle.
One molecule of glucose gives two molecules of pyruvic acid, therefore, total number of ATP formed in
citric acid cycle = 15 × 2 = 30 ATP
Total number of ATP formed in aerobic oxidation.
➢ From TCA cycle—30
➢ From glycolysis—08
Total = 38 ATP
Glycolysis Reactions:
a) Phosphorylation-I: Glucose converts to glucose-6-phosphate with hexokinase, using one ATP.
b) Isomerization: Glucose-6-phosphate turns to fructose-6-phosphate via isomerase.
c) Phosphorylation-II: Fructose-6-phosphate phosphorylates to fructose-1,6-diphosphate with
phosphofructokinase, using ATP.
d) Cleavage: Fructose-1,6-diphosphate splits into phosphoglyceraldehyde (PGAL) and dihydroxy
acetone phosphate (DHAP) with aldolase.
e) Isomerization: DHAP converts to PGAL.
f) Oxidative phosphorylation: PGAL transforms to 1,3-diphosphoglyceric acid with triose phosphate
dehydrogenase, generating 2 NADH2.
g) Dephosphorylation: 1,3-diphosphoglyceric acid becomes 3-phosphoglyceric acid, yielding 2 ATP
and using 2 ADP.
h) Shifting of phosphate group: Phosphate shifts to carbon 2 in 3-phosphoglyceric acid with mutase.
i) Dehydration: 2-phosphoglyceric acid dehydrates to phosphoenol pyruvic acid via enolase.
j) Formation of pyruvic acid: Phosphoenol pyruvic acid converts to pyruvic acid with kinase,
generating 2 ATP.
ATP formed:
Oxidative phosphorylation: 6 ATP.
Dephosphorylation: 2 ATP.
Phosphoenol pyruvic acid to pyruvic acid: 2 ATP.
Total: 10 ATP.
ATP consumed:
Phosphorylation-I: 1 ATP.
Phosphorylation-II: 1 ATP.
Total: 2 ATP.
Classification:
➢ Macrominerals Required in large quantities for daily bodily functions. Examples include Ca, P, Na, K, Mg,
Fe, Zn, etc.
➢ Microelements: Required in trace quantities for daily bodily functions. Examples include Co, Cu, I, Se,
Mn, etc.
Function of minerals:
➢ Minerals provide Maintenance of osmotic pressure of blood.
➢ Minerals helps in transportation of oxygen.
➢ Minerals helps in growth and maintenance of tissues and bones.
➢ Mineral helps in working of nervous system.
➢ Minerals provide muscle contraction.
➢ Minerals maintain electrolyte balance in the body.
➢ Minerals provide acid base balance in the body.
➢ Minerals helps in Blood coagulation.
➢ Minerals also perform Cardiac activity.
➢ Maturation of sperms
➢ Thyroid hormone synthesis
20. Describe distribution and function electrolytes in the body?
Ans.
Distribution of electrolytes in the body:
➢ Electrolytes are evenly distributed in body fluids to maintain osmotic equilibrium and water balance.
➢ Total concentration of cations and anions in each body compartment (extracellular fluid or intracellular
fluid) equals electrical neutrality.
➢ Electrolytes are positively and negatively charged ions present in solution in all body fluids.
➢ Electrolyte concentration is expressed as milliequivalents per liter (mEq/L).
➢ Na and K are the principal extracellular cations.
➢ The difference in concentration of these cations is vital for cell survival, maintained by the Na-K pump.
➢ Body water balance is closely linked to the balance of dissolved electrolytes, with Na and K being most
important.
Symptoms: Dry, hot skin and tongue. Reduced tears and saliva production. Weight loss due to reduced
tissue water. Acid-base balance disturbances. Increased body temperature. Dry, wrinkled skin. Increased
nonprotein plasma content. Decreased urine output. Increased pulse rate and reduced cardiac output.
Elevated packed cell volume.
Treatment: Oral rehydration with plenty of water. Intravenous administration of fluids. Dextrose saline for
energy. Maintaining a cool environment for the patient.
ORT/ORS: Various formulations available, typically containing glucose, sodium chloride, potassium chloride,
and sodium bicarbonate, sometimes with flavouring agents. Dry powdered preparations mixed with water
and taken orally. Provided free of cost by the Government of India, usually available at Primary Health
Centres (PHCs). Common brands include Electrol powder and pediatric powder. Effective first-aid remedy for
conditions such as dysentery, diarrhea, prolonged fever, vomiting, etc.
Composition:
Composition per liter of ORS solution:
➢ Sodium chloride: 3.5 gm
➢ Potassium chloride: 1.5 gm
➢ Sodium citrate: 2.9 gm
➢ Glucose: 20 gm
Objectives of biotechnology:
➢ Understand inheritance and gene expression.
➢ Improve treatment for genetic disorders and diseases.
➢ Enhance agricultural productivity and produce valuable biological molecules economically.
➢ Develop diagnostic test kits for identifying diseases.
➢ Utilize biotechnological techniques for pollution control and biofuel production to maintain ecosystem
health.
Application of biotechnology:
➢ Develop virus-resistant crops and livestock.
➢ Create diagnostic kits for genetic and acquired diseases.
➢ Use gene therapies to treat diseases.
➢ Produce recombinant vaccines for disease prevention.
➢ Aid environmental conservation efforts.
➢ Employ biotechnological techniques in various scientific disciplines.
➢ Improve food quality, quantity, and processing.
➢ Rely on genetic and chemical engineering in modern biotechnology.
➢ Utilize biotechnology for tissue culture, pharmacogenomics, and gene therapy.
➢ Develop microbial biotechnology for biofertilizers, biopesticides, and microbial genomics.
➢ Apply biotechnology in horticulture, enzyme, and textile industries.
➢ Enhance animal breeding through biotechnology.
➢ Utilize biotechnology techniques in detergent manufacturing.
➢ Significantly contribute to the healthcare system.
➢ Support enzyme and leather industries.
Ans. Abnormal constituents of urine are Protein, sugar, ketone, bile, blood, pus.
a) Protein: Presence of proteins in urine is proteinuria. Conditions include nephritis, nephrotic syndrome,
infections, and mercury poisoning. Also observed after exercise, high protein meals, and during
pregnancy.
b) Sugars: Sugar in urine is glycosuria. Seen in diabetes mellitus and renal glycosuria.
c) Ketone Bodies: Ketone bodies in urine, ketonuria, occur due to carbohydrate starvation, pregnancy, or
during anaesthesia.
d) Bile Pigments and Salts: Bile salts and pigments in urine cause a greenish-yellow color. Associated with
defective liver function or bile duct obstruction. Seen in various types of jaundice.
e) Blood: Blood in urine is haematuria, while haemoglobin-only pigment is haemoglobinuria. Conditions
include kidney lesions, enteric fever, malaria, and snake venom poisoning.
f) Pus: Presence of pus in urine is pyuria, caused by inflammation of the urinary bladder, urethra, or kidney
pelvis.