Chapter 101 – MCQs for Lab (Biochemistry)

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Chapter 101 of 5000 Plus MCQs for Lab Technician and Technologists are designed to test the knowledge and proficiency of laboratory professionals who work in the field of clinical laboratory science.

5001 to 5050 MCQs for Lab Technician and Technologist Exam Preparation

5000 Plus MCQs for Lab Technician and Technologists are designed to test the knowledge and proficiency of laboratory professionals who work in the field of clinical laboratory science. These questions cover a wide range of topics related to laboratory science, including anatomy, physiology, microbiology, chemistry, and hematology.

MCQs Chapter 101 (Biochemistry)

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Questions 5001 to 5050

The amino acids involved in the synthesis of creatine are:
  • a) Arginine, glycine, active methionine
  • b) Arginine, alanine, glycine
  • c) Glycine, lysine, methionine
  • d) Arginine, lysine, methionine
Explanation: Creatine is synthesized in a two-step process primarily in the kidneys and liver. It requires three specific amino acids: Glycine, Arginine, and Methionine (in its active form, S-adenosylmethionine, which provides the methyl group).
Why other options are incorrect:
  • • Option B: Contains Alanine, which is not involved in the pathway for creatine production.
  • • Option C: Contains Lysine. While lysine is an essential amino acid, it is not a precursor for creatine.
  • • Option D: Also incorrectly includes Lysine instead of Glycine.
Chemical score of egg proteins is considered to be:
  • a) 100
  • b) 60
  • c) 50
  • d) 40
Explanation: The Chemical Score (or Amino Acid Score) is a method of evaluating protein quality by comparing its essential amino acid content to a reference protein. Egg protein is considered the “ideal” or “reference” protein because it contains all essential amino acids in the proportions required by the human body, giving it a score of 100.
Why other options are incorrect:
  • • 60, 50, 40: These lower scores are typical for plant-based proteins (like wheat, pulses, or maize) that are deficient in one or more essential amino acids, such as lysine or methionine.
Chemical score of milk proteins is:
  • a) 70
  • b) 65
  • c) 60
  • d) 40
Explanation: The Chemical Score of a protein is a measure of its quality based on its most limiting essential amino acid compared to a reference protein (usually egg protein, which is 100). Milk protein typically has a chemical score of 60, with sulfur-containing amino acids (methionine and cysteine) being the limiting factors.
Why other options are incorrect:
  • • 70: This value is more common for animal proteins like meat or fish, which have slightly higher chemical scores than milk.
  • • 65: While close, 60 is the standard textbook value cited for cow’s milk chemical score in nutritional science.
  • • 40: This represents a lower-quality protein, typical of wheat or certain cereals that are severely limited by lysine.
Chemical score of proteins of bengal gram is:
  • a) 70
  • b) 60
  • c) 44
  • d) 42
Explanation: The Chemical Score of Bengal gram (chana) is approximately 44. This score is significantly lower than animal-based proteins because legumes like Bengal gram are deficient in sulfur-containing amino acids, primarily Methionine and Cysteine.
Why other options are incorrect:
  • • 70: This is a higher score, closer to animal proteins or high-quality plant isolates like soy.
  • • 60: This is the typical chemical score for milk proteins.
  • • 42: While very close, 44 is the standard value cited in most biochemistry and nutrition textbooks for Bengal gram.
Chemical score of protein gelatin is:
  • a) 0
  • b) 44
  • c) 57
  • d) 60
Explanation: The chemical score of gelatin is 0 because it is an incomplete protein. It completely lacks the essential amino acid tryptophan. Since the chemical score is based on the most limiting amino acid, a total absence results in a score of zero.
Why other options are incorrect:
  • • 44: This is a typical chemical score for certain plant-based proteins like wheat (which is limited by lysine).
  • • 57: This value is closer to the chemical score of pulses or legumes.
  • • 60: This represents a moderate protein quality score found in various cereal-based diets, but not gelatin.
Chemical score of protein zein is:
  • a) 0
  • b) 57
  • c) 60
  • d) 70
Explanation: The Chemical Score of Zein (the primary protein found in maize/corn) is 0. Similar to gelatin, zein is an incomplete protein because it is severely deficient in the essential amino acids Lysine and Tryptophan.
Why other options are incorrect:
  • • 57: This is the approximate chemical score for rice protein.
  • • 60: This is the chemical score for milk protein.
  • • 70: This is a higher score typical of high-quality plant proteins like soy or certain animal proteins like fish.
Biological value of egg white protein is:
  • a) 94
  • b) 83
  • c) 85
  • d) 77
Explanation: The Biological Value (BV) measures how efficiently the body utilizes protein consumed in the diet. Egg white protein (albumen) has a very high BV of approximately 94, making it one of the most high-quality protein sources available for human nutrition.
Why other options are incorrect:
  • • 83 – 85: These values are typically associated with Cow’s Milk or certain fish proteins.
  • • 77: This is a common biological value for Rice protein or some pulses.
Net protein utilisation (NPU) of egg protein is:
  • a) 75%
  • b) 80%
  • c) 91%
  • d) 72%
Explanation: Net Protein Utilisation (NPU) is a product of Biological Value (BV) and the Digestibility Coefficient (NPU = BV × Digestibility / 100). For a whole egg, the NPU is approximately 91%. It is considered the gold standard for protein quality because it is both highly digestible and contains an ideal balance of amino acids.
Why other options are incorrect:
  • • 75% – 80%: These values are typical for high-quality animal proteins like milk (around 75-80%) or meat/fish (around 72-80%).
  • • 72%: This is closer to the NPU value for meat or certain high-quality soy products.
Net protein utilization (NPU) of milk protein is:
  • a) 75%
  • b) 80%
  • c) 86%
  • d) 91%
Explanation: Net Protein Utilization (NPU) is the ratio of amino acids converted to proteins to the ratio of amino acids supplied. For cow’s milk, the NPU is approximately 80%, indicating high digestibility and efficient amino acid profile.
Why other options are incorrect:
  • • 75%: This is often the NPU value for Casein (the main protein in milk) specifically, but whole milk protein as a whole is slightly higher.
  • • 86%: This value is closer to the Biological Value (BV) of milk protein, which is typically higher than the NPU.
  • • 91%: This high value is usually associated with the NPU of whole eggs, which is considered the “gold standard” for protein quality.
A limiting amino acid is an essential amino acid:
  • a) That is most deficient in proteins
  • b) That is most excess in proteins
  • c) That which increases the growth
  • d) That which increases the weight gain
Explanation: A limiting amino acid is the essential amino acid found in the shortest supply relative to the amounts needed for human protein synthesis. If one essential amino acid is missing or deficient, the body cannot utilize the other amino acids for protein synthesis, effectively “limiting” the process.
Why other options are incorrect:
  • • Option B: An excess amino acid does not limit protein synthesis; it is usually deaminated and used for energy or stored.
  • • Options C & D: While having a complete profile of amino acids (without a limiting one) supports growth and weight gain, the term “limiting” specifically refers to the deficiency that prevents these processes.
The limiting amino acid of rice is:
  • a) Lysine
  • b) Tryptophan
  • c) Phenylalanine
  • d) Tyrosine
Explanation: Rice, like most cereals, is primarily deficient in the essential amino acid Lysine. Although rice has a better balance of amino acids compared to other grains (like wheat or corn), Lysine remains its first limiting amino acid, meaning it is the one present in the lowest amount relative to human needs.
Why other options are incorrect:
  • • Tryptophan: While some cereals like maize are deficient in tryptophan, it is generally not the primary limiting amino acid in rice.
  • • Phenylalanine & Tyrosine: These are aromatic amino acids usually found in adequate amounts in most cereal proteins.
The limiting amino acid of fish proteins is
  • a) Tryptophan
  • b) Cysteine
  • c) Lysine
  • d) Threonine
Explanation: Tryptophan is considered the limiting amino acid in fish proteins in the context of this nutritional protein-quality classification.
Why other options are incorrect:
  • • Cysteine: Fish proteins generally provide adequate amounts relative to the reference amino acid pattern.
  • • Lysine: Fish protein is relatively rich in lysine and is not usually the limiting amino acid.
  • • Threonine: It is present in fish proteins in sufficient amounts and is not the limiting amino acid here.
Pulses are deficient in:
  • a) Lysine
  • b) Threonine
  • c) Methionine
  • d) Tryptophan
Explanation: Pulses (legumes) are generally deficient in sulfur-containing amino acids, with Methionine being the primary limiting amino acid. However, they are rich in Lysine, which is why they are often eaten in combination with cereals (which are rich in methionine but low in lysine) to provide a complete protein profile.
Why other options are incorrect:
  • • Lysine: Pulses are actually a great source of lysine; this is the limiting amino acid in cereals, not pulses.
  • • Threonine: This is the limiting amino acid in fish proteins.
  • • Tryptophan: This is the limiting amino acid in maize (corn) and gelatin.
A trace element deficient in the milk is:
  • a) Magnesium
  • b) Copper
  • c) Zinc
  • d) Chloride
Explanation: Milk is often described as a “nearly perfect food,” but it is notoriously deficient in two specific minerals: Iron and Copper. Because of this deficiency, infants who are exclusively fed milk for too long without starting solid foods (complementary feeding) are at risk of developing nutritional anemia.
Why other options are incorrect:
  • • Magnesium: Milk contains a reasonable amount of magnesium (about 10–12 mg per 100g).
  • • Zinc: Zinc is present in milk and is generally well-absorbed from breast milk.
  • • Chloride: This is an electrolyte (major mineral), not a trace element, and is found in significant quantities in milk.
A conjugated protein present in the egg yolk is:
  • a) Vitellin
  • b) Livetin
  • c) Albuminoids
  • d) Ovo-mucoid
Explanation: Vitellin is the major protein found in egg yolk. It is a conjugated protein, specifically a phosphoprotein (protein combined with phosphoric acid). It usually exists in the yolk as a lipoprotein complex called lipovitellin.
Why other options are incorrect:
  • • Livetin: Although found in egg yolk, it is a simple globular protein, not a conjugated one.
  • • Albuminoids: These are fibrous structural proteins (like keratin or collagen) found in connective tissues, not egg yolk.
  • • Ovo-mucoid: This is a glycoprotein, but it is found in the egg white (albumen), not the yolk.
The chief protein of cow’s milk is:
  • a) Albumin
  • b) Vitellin
  • c) Livetin
  • d) Casein
Explanation: Casein is the principal protein in cow’s milk, accounting for about 80% of the total protein content. The remaining 20% consists of whey proteins (such as lactalbumin and lactoglobulin). Casein is a phosphoprotein and is responsible for the white, opaque appearance of milk.
Why other options are incorrect:
  • • Albumin: In the context of milk (Lactalbumin), this is a whey protein and makes up a much smaller percentage compared to casein.
  • • Vitellin & Livetin: These are proteins found in egg yolk, not in milk.
A water soluble vitamin deficient in egg is:
  • a) Thiamin
  • b) Riboflavin
  • c) Ascorbic acid
  • d) Cobalamin
Explanation: Eggs are often called “nature’s multivitamin” because they contain almost every essential vitamin and mineral required by the human body, with one major exception: Vitamin C (Ascorbic acid). Eggs contain zero Vitamin C.
Why other options are incorrect:
  • • Thiamin (B1): Found in significant amounts in the egg yolk.
  • • Riboflavin (B2): Eggs are one of the best dietary sources of Riboflavin; it is found in both the white and the yolk.
  • • Cobalamin (B12): Being an animal product, eggs are a good source of Vitamin B12, which is essential for nerve function and blood formation.
Pulses are rich in:
  • a) Lysine
  • b) Methionine
  • c) Tryptophan
  • d) Phenylalanine
Explanation: Pulses (legumes) are an excellent source of the essential amino acid Lysine. In nutritional science, pulses and cereals are considered “complementary proteins” because pulses provide the Lysine that cereals lack, while cereals provide the Methionine that pulses lack.
Why other options are incorrect:
  • • Methionine: This is actually the limiting (deficient) amino acid in pulses.
  • • Tryptophan: While present, it is not found in high enough concentrations to be considered the “rich” characteristic of pulses.
  • • Phenylalanine: This is generally found in adequate amounts in most plant proteins, but Lysine is the specific amino acid pulses are most famous for providing.
Milk is deficient in:
  • a) Vitamin B1
  • b) Vitamin B2
  • c) Sodium
  • d) Potassium
Explanation: While milk is a nutrient-dense food, it is relatively poor in Vitamin B1 (Thiamin). It is also well-known for being deficient in Vitamin C and Iron. Thiamin is also heat-sensitive, meaning levels can decrease further during pasteurization or boiling.
Why other options are incorrect:
  • • Vitamin B2 (Riboflavin): Milk is an excellent source of Riboflavin; it is one of the primary dietary sources for this vitamin.
  • • Sodium: Milk contains a natural and significant amount of sodium.
  • • Potassium: Milk is considered a rich source of potassium, which is vital for heart and muscle function.
Milk is deficient in:
  • a) Calcium
  • b) Iron
  • c) Sodium
  • d) Potassium
Explanation: Milk is notoriously deficient in Iron. While it provides many essential nutrients, the iron content in milk (both cow’s and human milk) is very low. This is why prolonged exclusive breast or bottle feeding without the introduction of iron-rich solid foods (weaning) can lead to iron-deficiency anemia, often called “milk anemia.”
Why other options are incorrect:
  • • Calcium: Milk is one of the richest and most common dietary sources of calcium.
  • • Sodium & Potassium: Milk contains significant quantities of these essential electrolytes.
When net protein utilization (NPU) is low, the requirements for proteins are:
  • a) High
  • b) Moderate
  • c) Low
  • d) Supplementary
Explanation: There is an inverse relationship between protein quality (NPU) and protein requirement. Since NPU measures the percentage of dietary protein actually retained by the body, a low NPU means the protein is poorly utilized. Consequently, a larger quantity (high requirement) of that protein must be consumed to meet the body’s nitrogen and essential amino acid needs.
Why other options are incorrect:
  • • Moderate/Low: If NPU is low, consuming only low or moderate amounts would result in a protein deficiency, as the body isn’t absorbing enough usable amino acids.
  • • Supplementary: While poor-quality proteins can be “supplemented” with other proteins to improve the overall score, the physical *requirement* for that specific low-quality protein remains high if it is the sole source.
Protein content of human milk is about:
  • a) 1.4%
  • b) 2.4%
  • c) 3.4%
  • d) 4.4%
Explanation: Human milk contains significantly less protein than cow’s milk, typically ranging between 1.1% and 1.4%. While the quantity is lower, the quality is ideally suited for human infants, with a higher ratio of whey protein to casein compared to animal milks, making it easier for infants to digest.
Why other options are incorrect:
  • • 2.4%: This is higher than the standard protein concentration in human milk.
  • • 3.4%: This is the approximate protein content of Cow’s milk (~3.3% to 3.5%).
  • • 4.4%: This is a very high protein concentration, more typical of sheep’s milk or concentrated dairy products.
Protein content of cow’s milk is about:
  • a) 2.5%
  • b) 3.5%
  • c) 4.5%
  • d) 5.5%
Explanation: The protein content of cow’s milk typically ranges from 3.3% to 3.5%. This is nearly three times the concentration found in human milk. The majority of this protein (about 80%) is casein, while the remaining 20% is composed of whey proteins.
Why other options are incorrect:
  • • 2.5%: This is lower than the standard protein concentration for whole cow’s milk.
  • • 4.5% – 5.5%: These values are too high for standard cow’s milk, though some other species (like sheep or buffalo) may have protein levels in this higher range.
Protein content of soyabean is about:
  • a) 30%
  • b) 40%
  • c) 50%
  • d) 60%
Explanation: Soybeans are among the richest plant-based sources of protein, containing approximately 40% protein by weight (dry). Unlike many other plant proteins, soy protein is considered a “complete” protein because it contains all the essential amino acids in sufficient quantities for human needs.
Why other options are incorrect:
  • • 30%: This is lower than the actual protein density of soybeans, though some other legumes might fall in this range.
  • • 50% – 60%: These high percentages are typically found only in processed soy products like Soy Protein Isolate or defatted soy flour, but not in the whole soybean itself.
Lipid content of egg white is
  • a) 12%
  • b) 33%
  • c) 10–11%
  • d) Traces
Explanation: Egg white (albumen) consists of approximately 90% water and 10% protein. It contains almost no fat; the lipids of an egg are concentrated almost entirely in the yolk.
Why other options are incorrect:
  • • 12%: This is roughly the protein content percentage of a whole egg.
  • • 33%: This is the approximate lipid (fat) content of the egg yolk.
  • • 10–11%: This is the approximate protein concentration of the egg white, not the lipid content.
The recommended daily allowance (RDA) of proteins for an adult man is
  • a) 70 gms
  • b) 50 gms
  • c) 40 gms
  • d) 30 gms
Explanation: The Recommended Daily Allowance (RDA) for protein is generally calculated as 0.8 to 1.0 gram of protein per kilogram of body weight. For a “reference” adult man weighing 70 kg, the requirement is approximately 70 grams per day.
Why other options are incorrect:
  • • 50 gms: While this might be closer to the RDA for an adult woman or a man with very low body weight, it is generally considered insufficient for a standard 70kg adult male.
  • • 40 gms & 30 gms: These values are significantly below the physiological requirements needed to maintain nitrogen balance and muscle mass in a healthy adult male.
The basic amino acids are
  • a) Lysine
  • b) Bile acids
  • c) Glycine
  • d) Alanine
Explanation: Basic amino acids have side chains that contain nitrogen and can be positively charged (basic) at physiological pH. The three primary basic amino acids are Lysine, Arginine, and Histidine.
Why other options are incorrect:
  • • Bile acids: These are not amino acids; they are steroid acids found in the bile that help in the digestion of fats.
  • • Glycine: This is the simplest amino acid and is classified as a neutral/non-polar amino acid.
  • • Alanine: This is an aliphatic, neutral, and non-polar amino acid.
The daily caloric requirement for the normal adult female is about
  • a) 1500
  • b) 2100
  • c) 2500
  • d) 2900
Explanation: On average, a healthy adult female with a moderate activity level requires approximately 2000 to 2200 calories per day to maintain her weight. Therefore, 2100 is the most accurate estimate among the choices.
Why other options are incorrect:
  • • 1500: This is generally considered a “weight loss” calorie level for most women and is below the maintenance level for a normal adult.
  • • 2500: This is the average daily caloric requirement for a normal adult male.
  • • 2900: This level is typically reserved for individuals with very high physical activity levels, such as athletes or those performing heavy manual labor.
In the total proteins, the percentage of albumin is about
  • a) 20–40
  • b) 30–45
  • c) 50–70
  • d) 80–90
Explanation: Albumin is the most abundant protein in human blood plasma. In a healthy adult, total serum protein is about 6.0–8.3 g/dL, and albumin specifically accounts for about 3.5–5.0 g/dL, which represents roughly 50% to 70% of the total protein.
Why other options are incorrect:
  • • 20–40 / 30–45: These percentages are too low for albumin; this range is more typical for the total “globulin” fraction of blood proteins.
  • • 80–90: This is too high; while albumin is the majority, other proteins like globulins and fibrinogen must also be present in significant amounts for blood clotting and immunity.
In the total proteins percentage of α1 globulin is about
  • a) 0.2–1.2%
  • b) 1.2–2.0%
  • c) 2.4–4.4%
  • d) 5.0–10.0%
Explanation: Serum protein electrophoresis separates proteins into groups. The α1 (Alpha-1) globulin fraction, which includes proteins like α1-antitrypsin and α1-acid glycoprotein, normally accounts for approximately 2.4% to 4.4% of total serum protein.
Why other options are incorrect:
  • • 0.2–1.2% & 1.2–2.0%: These values are lower than the standard reference range for a healthy individual.
  • • 5.0–10.0%: This higher range is more characteristic of the α2-globulin or Beta-globulin fractions rather than the α1 fraction.
In the total proteins the percentage of γ globulin is about
  • a) 2.4–4.4%
  • b) 10.0–21.0%
  • c) 6.1–10.1%
  • d) 1.2–2.0%
Explanation: Gamma (γ) globulins consist mainly of immunoglobulins (antibodies). In a normal serum protein electrophoresis, the γ globulin fraction is the largest of the globulin groups, typically accounting for about 10% to 21% of the total protein.
Why other options are incorrect:
  • • 2.4–4.4%: This is the typical range for the α1-globulin fraction.
  • • 6.1–10.1%: This range is more characteristic of the α2-globulin fraction.
  • • 1.2–2.0%: This value is far too low for the gamma globulin fraction in a healthy adult.
Most frequently the normal albumin globulin ratio (A : G) is
  • a) 1.0 : 0.8
  • b) 1.5 : 1.0
  • c) 2.0 : 1.0
  • d) 2.4 : 1.0
Explanation: The Albumin-Globulin (A/G) ratio is a calculation used to compare the levels of these two major protein types in the blood. In a healthy person, the normal range for the A/G ratio is typically between 1.2 and 2.2. A value of 1.5:1 is frequently cited as a standard clinical average.
Why other options are incorrect:
  • • 1.0 : 0.8: This ratio is too low; it suggests that the globulin level is nearly equal to albumin, which is often a sign of liver disease or inflammation.
  • • 2.0 : 1.0: While this is within the high-normal range, 1.5:1 is a more common “textbook” baseline for general assessments.
  • • 2.4 : 1.0: This represents a very high level of albumin compared to globulin, which is less common and usually indicates dehydration or extreme high-protein intake.
In Thymol turbidity test the protein involved is mainly
  • a) Albumin
  • b) α1-Globulin
  • c) α2-Globulin
  • d) β Globulin
Explanation: The Thymol Turbidity test is an older liver function test used to detect abnormal serum protein patterns. The turbidity or precipitation occurs primarily due to the interaction of the thymol reagent with β-globulin (beta-globulin) and gamma-globulin, often in the presence of lipids.
Why other options are incorrect:
  • • Albumin: Albumin actually tends to inhibit the turbidity in this test; hence, a low albumin level often makes the test result more positive.
  • • α1-Globulin & α2-Globulin: These fractions do not play a significant role in the precipitation reaction characteristic of the thymol turbidity test.
In quaternary structure, subunits are linked by
  • a) Peptide bonds
  • b) Disulphide bonds
  • c) Covalent bonds
  • d) Non-covalent bonds
Explanation: The quaternary structure of a protein involves the assembly of multiple polypeptide chains (subunits). These subunits are primarily held together by non-covalent bonds, including hydrogen bonds, ionic bonds (salt bridges), and hydrophobic interactions.
Why other options are incorrect:
  • • Peptide bonds: These are covalent bonds that link amino acids together to form the primary structure of a single polypeptide chain.
  • • Disulphide/Covalent bonds: While some proteins (like antibodies or insulin) use disulfide bridges to link chains, the general defining feature of quaternary assembly across most proteins is non-covalent interaction.
Molecular weight of human albumin is about
  • a) 156,000
  • b) 90,000
  • c) 69,000
  • d) 54,000
Explanation: Human Serum Albumin is a single polypeptide chain with a molecular weight of approximately 66,500 to 69,000 Daltons. Its relatively small size and high concentration make it the primary contributor to the oncotic pressure of plasma.
Why other options are incorrect:
  • • 156,000: This is roughly the molecular weight of Gamma Globulin (IgG), which is much larger than albumin.
  • • 90,000: This is not the standard weight for albumin; proteins like Haptoglobin or Plasminogen fall closer to this range.
  • • 54,000: This value is significantly lower than the actual molecular weight of human serum albumin.
At isoelectric pH, an amino acid exists as
  • a) Anion
  • b) Cation
  • c) Zwitterion
  • d) None of these
Explanation: The isoelectric point (pI) is the specific pH at which an amino acid has a net electrical charge of zero. At this pH, the molecule exists as a Zwitterion (a dipolar ion), containing both a positive charge (NH3+) and a negative charge (COO-) that cancel each other out.
Why other options are incorrect:
  • • Anion: An amino acid becomes an anion (negatively charged) in an alkaline medium where the pH is higher than the isoelectric point.
  • • Cation: An amino acid becomes a cation (positively charged) in an acidic medium where the pH is lower than the isoelectric point.
  • • None of these: This is incorrect because the Zwitterion state is the standard chemical definition of an amino acid at its isoelectric point.
A disulphide bond can be formed between
  • a) Two methionine residues
  • b) Two cysteine residues
  • c) A methionine and a cysteine residue
  • d) All of these
Explanation: Disulphide bonds (S-S bonds) are covalent bonds formed by the oxidation of the sulfhydryl (-SH) groups of two cysteine residues. When two cysteines are linked this way, the resulting unit is called cystine.
Why other options are incorrect:
  • • Two methionine residues: Although methionine contains sulfur, its sulfur is part of a thioether group (C-S-C) and does not have a free sulfhydryl (-SH) group required to form a disulphide bridge.
  • • A methionine and a cysteine residue: For the same reason as above, methionine cannot participate in disulphide bond formation.
  • • All of these: This is incorrect because only cysteine has the chemical structure necessary to form these specific covalent cross-links in proteins.
A coagulated protein is
  • a) Insoluble
  • b) Biologically non-functional
  • c) Unfolded
  • d) All of the above
Explanation: Protein coagulation is an irreversible process (like cooking an egg white) that typically follows denaturation. During this process, the protein loses its specific 3D shape, aggregates, and precipitates out of solution.
Why all options are correct:
  • • Unfolded: Denaturation breaks the hydrogen and ionic bonds, causing the protein to lose its secondary and tertiary structure.
  • • Insoluble: As the protein unfolds, hydrophobic internal groups are exposed to water, causing the molecules to clump together and become insoluble.
  • • Biologically non-functional: Since a protein’s function is strictly dependent on its specific shape (conformation), unfolding and clumping renders it unable to perform its biological role.
At a pH below the isoelectric point, an amino acid exists as
  • a) Cation
  • b) Anion
  • c) Zwitterion
  • d) Undissociated molecule
Explanation: When the pH is below the isoelectric point (pI), the solution is acidic and rich in hydrogen ions (H+). These protons attach to the amino acid, neutralizing the carboxyl group (COO- becomes COOH) while the amino group remains protonated (NH3+). This results in a net positive charge, making the molecule a cation.
Why other options are incorrect:
  • • Anion: An amino acid becomes an anion (negatively charged) only when the pH is above the isoelectric point (alkaline conditions).
  • • Zwitterion: This state, where the net charge is zero, occurs specifically at the isoelectric point, not below it.
  • • Undissociated molecule: In aqueous solution, amino acids always exist in an ionized form (as cations, anions, or zwitterions) due to their amphoteric nature.
An amino acid having a hydrophilic side chain is
  • a) Alanine
  • b) Proline
  • c) Methionine
  • d) Serine
Explanation: Serine is a polar amino acid because its side chain contains a hydroxyl (-OH) group. This group can form hydrogen bonds with water, making the amino acid hydrophilic (water-loving).
Why other options are incorrect:
  • • Alanine: Contains a simple methyl group (-CH3) as a side chain, which is non-polar and hydrophobic.
  • • Proline: Has a cyclic aliphatic side chain that is rigid and non-polar, making it hydrophobic.
  • • Methionine: Although it contains sulfur, its side chain is an aliphatic thioether, which is non-polar and hydrophobic.
An amino acid that does not take part in α helix formation is
  • a) Histidine
  • b) Tyrosine
  • c) Proline
  • d) Tryptophan
Explanation: Proline is known as a “helix breaker.” Because its side chain is cyclic and bonded to the nitrogen of the amino group, it lacks the necessary hydrogen atom to participate in the hydrogen bonding required to stabilize an α-helix. Its rigid structure also introduces a “kink” or bend in the polypeptide chain.
Why other options are incorrect:
  • • Histidine: This is a polar amino acid that can readily fit into the geometry of an α-helix.
  • • Tyrosine & Tryptophan: While these are large aromatic amino acids that can sometimes destabilize a helix due to steric hindrance, they are still capable of forming part of a helical structure, unlike Proline.
A protein rich in cysteine is
  • a) Collagen
  • b) Keratin
  • c) Haemoglobin
  • d) Gelatin
Explanation: Keratin, especially the “hard” keratin found in hair, nails, and horns, is very rich in the sulfur-containing amino acid cysteine. The cysteine residues form extensive disulfide bridges that provide the protein with its characteristic strength, rigidity, and resistance to degradation.
Why other options are incorrect:
  • • Collagen: This is the most abundant protein in the body, but it is primarily rich in Glycine, Proline, and Hydroxyproline, with very little cysteine.
  • • Haemoglobin: While it contains some cysteine residues, it is a globular transport protein and is not characterized by a high cysteine content.
  • • Gelatin: Gelatin is produced by the partial hydrolysis of collagen; therefore, it shares collagen’s lack of cysteine (and tryptophan).
Primary structure of proteins can be determined by the use of
  • a) Electrophoresis
  • b) Chromatography
  • c) Ninhydrin
  • d) Sanger’s reagent
Explanation: The primary structure of a protein is the specific linear sequence of its amino acids. Sanger’s reagent (1-fluoro-2,4-dinitrobenzene) is a classical chemical used for N-terminal amino acid analysis, which was the foundational method for sequencing proteins like insulin.
Why other options are incorrect:
  • • Electrophoresis: This technique separates proteins based on their size and electrical charge, but it cannot determine the specific sequence of amino acids.
  • • Chromatography: While used to separate and purify amino acids or proteins from a mixture, it is not a direct tool for determining the primary sequence.
  • • Ninhydrin: This is a reagent that reacts with all free amino acids to produce a purple color (Ruhemann’s purple). It is used for detection and quantification, not sequencing.
Electrostatic bonds can be formed between the side chains of
  • a) Alanine and leucine
  • b) Leucine and valine
  • c) Aspartate and glutamate
  • d) Lysine and aspartate
Explanation: Electrostatic bonds, also known as salt bridges, occur between amino acids with side chains of opposite electrical charges. Lysine has a positively charged side chain (basic), while Aspartate has a negatively charged side chain (acidic), allowing them to attract each other.
Why other options are incorrect:
  • • Alanine, Leucine, and Valine: These are non-polar, hydrophobic amino acids. They interact through Van der Waals forces or hydrophobic interactions, not electrostatic bonds.
  • • Aspartate and Glutamate: Both of these amino acids are negatively charged. Since like charges repel each other, they cannot form an electrostatic bond with one another.
Sanger’s reagent contains
  • a) Phenylisothiocyanate
  • b) Dansyl chloride
  • c) 1-Fluoro-2, 4-dinitrobenzene
  • d) Ninhydrin
Explanation: Sanger’s reagent is chemically known as 1-Fluoro-2, 4-dinitrobenzene (DNFB). It reacts with the free amino group at the N-terminal end of a polypeptide chain to form a stable dinitrophenyl (DNP)-amino acid derivative, allowing for the identification of the first amino acid in a protein sequence.
Why other options are incorrect:
  • • Phenylisothiocyanate: This is Edman’s reagent, used in the Edman degradation method for sequencing amino acids one by one from the N-terminus.
  • • Dansyl chloride: While also used for N-terminal analysis (producing highly fluorescent derivatives), it is not referred to as Sanger’s reagent.
  • • Ninhydrin: This is a general reagent used to detect amino acids by producing a purple color (Ruhemann’s purple) but is not used for specific sequence determination.
The most abundant protein in mammals is
  • a) Albumin
  • b) Haemoglobin
  • c) Collagen
  • d) Elastin
Explanation: Collagen is the most abundant protein in the animal kingdom and in mammals. it makes up approximately 25% to 35% of the total protein content in the body, acting as a key structural component of connective tissues like skin, bones, tendons, and ligaments.
Why other options are incorrect:
  • • Albumin: While it is the most abundant protein in blood plasma, it does not match the total body mass of collagen.
  • • Haemoglobin: This is highly concentrated in red blood cells for oxygen transport, but its total volume in the body is less than that of structural collagen.
  • • Elastin: Though essential for providing elasticity to tissues like arteries and lungs, it is found in much smaller quantities compared to collagen.
Folding of newly synthesized proteins is accelerated by
  • a) Protein disulphide isomerase
  • b) Prolyl cis-trans isomerase
  • c) Chaperonins
  • d) All of these
Explanation: Protein folding is a complex process assisted by various specialized molecules. Protein disulphide isomerase manages the correct placement of sulfur bonds, Prolyl cis-trans isomerase speeds up the slow rotation of proline bonds, and Chaperonins provide a protected environment to ensure the protein folds without aggregating.
Why all options are correct:
  • • Protein disulphide isomerase: It catalyzes the formation and shuffling of disulfide bonds, which is essential for stabilizing the 3D structure.
  • • Prolyl cis-trans isomerase: It facilitates the interconversion of cis and trans isomers of peptide bonds involving proline, which is often a rate-limiting step in folding.
  • • Chaperonins: These act as “molecular cages” that help unfolded polypeptides reach their native state by preventing them from clumping with other proteins.
Primary structure of a protein is formed by
  • a) Hydrogen bonds
  • b) Peptide bonds
  • c) Disulphide bonds
  • d) All of these
Explanation: The primary structure refers to the linear sequence of amino acids in a polypeptide chain. These amino acids are linked together by covalent peptide bonds, which form the “backbone” of the protein.
Why other options are incorrect:
  • • Hydrogen bonds: These are primarily responsible for the secondary structure (such as alpha-helices and beta-pleated sheets) of a protein.
  • • Disulphide bonds: These covalent linkages between cysteine residues help stabilize the tertiary and quaternary structures, rather than defining the initial sequence.
  • • All of these: While all these bonds are found in proteins, only the peptide bond defines the primary structure.
α-Helix is formed by
  • a) Hydrogen bonds
  • b) Hydrophobic bonds
  • c) Electrostatic bonds
  • d) Disulphide bonds
Explanation: The α-helix is a common secondary structure of proteins. It is stabilized by hydrogen bonds that form between the oxygen of a carbonyl group (C=O) and the hydrogen of an amino group (N-H) located four amino acid residues further down the chain.
Why other options are incorrect:
  • • Hydrophobic bonds: These interactions primarily drive the folding of the protein into its 3D (tertiary) shape to hide non-polar side chains from water.
  • • Electrostatic bonds: These (also called salt bridges) occur between oppositely charged side chains and help stabilize the tertiary or quaternary structures.
  • • Disulphide bonds: These are strong covalent links between cysteine residues that stabilize the overall 3D folding (tertiary structure) rather than the helical coil.
Glutelins are present in
  • a) Milk
  • b) Eggs
  • c) Meat
  • d) Cereals
Explanation: Glutelins are a group of simple proteins that are insoluble in water or neutral salt solutions but soluble in dilute acids and alkalis. They are found predominantly in cereals; a well-known example is glutenin found in wheat and oryzenin in rice.
Why other options are incorrect:
  • • Milk: The primary proteins in milk are Caseins and whey proteins (like Lactalbumin).
  • • Eggs: Egg proteins mainly consist of Albumins (Ovalbumin) and Globulins (Ovoglobulin).
  • • Meat: Muscle tissue is composed primarily of Actin and Myosin, which are structural and contractile proteins.

Answer Key Summary

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The questions are typically designed to assess the technical skills and knowledge required for the laboratory profession, including the ability to analyze laboratory test results, perform laboratory procedures, and maintain laboratory equipment.

To prepare for these MCQs, candidates should have a thorough understanding of the key concepts and principles of laboratory science. They should also be familiar with common laboratory equipment and procedures, as well as laboratory safety protocols.

Candidates may also benefit from studying specific laboratory science textbooks or taking online courses that cover the material tested in the MCQs. Additionally, practicing sample MCQs and reviewing the answers can help candidates identify areas where they may need to improve their knowledge or skills.

Overall, the MCQs for lab technologists are designed to be challenging and comprehensive, requiring candidates to demonstrate a high level of proficiency in the field of laboratory science.

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The website covers a wide range of lab tests, including blood tests, urine tests, stool tests, and imaging tests such as X-rays and CT scans. It also provides information about different health conditions and diseases, as well as tips for maintaining good health.

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