Chapter 104 – MCQs for Lab (Biochemistry)

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Cahpter 104 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.

5151 to 5200 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 104 (Biochemistry)

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Questions 5151 to 5200

MHC class II proteins are present on the surface of:
  • a) All cells
  • b) B lymphocytes only
  • c) Macrophages only
  • d) Macrophages and B lymphocytes
Explanation: MHC class II molecules are expressed specifically on Professional Antigen-Presenting Cells (APCs), which include macrophages, B lymphocytes, and dendritic cells. They play a crucial role in presenting exogenous antigens to Helper T cells (CD4+).
Why other options are incorrect:
  • • All cells: Most nucleated cells express MHC class I, but only specific immune cells express MHC class II.
  • • B lymphocytes only: While they do express MHC II, they are not the only cells to do so; macrophages and dendritic cells also possess them.
  • • Macrophages only: Similar to B cells, macrophages are just one type of APC that expresses MHC II.
MHC Class II proteins, in conjunction with antigens, are recognised by:
  • a) Cytotoxic T cells
  • b) Helper T cells
  • c) Suppressor T cells
  • d) Memory T cells
Explanation: MHC Class II molecules present processed exogenous antigens to Helper T cells (CD4+). The CD4 receptor on the helper T cell specifically binds to the invariant region of the MHC class II molecule.
Why other options are incorrect:
  • • Cytotoxic T cells: These cells (CD8+) recognize antigens presented by MHC Class I molecules, which are found on almost all nucleated cells.
  • • Suppressor T cells: Also known as Regulatory T cells; while they modulate the immune system, the primary recognition of MHC II for immune activation is the hallmark of Helper T cells.
  • • Memory T cells: These are long-lived cells that can be either CD4+ or CD8+, but they are defined by their persistence after an infection rather than the specific MHC class they recognize during initial presentation.
CD 8 is a transmembrane glycoprotein present in:
  • a) Cytotoxic T cells
  • b) Helper T cells
  • c) Suppressor T cells
  • d) Memory T cells
Explanation: CD8 (cluster of differentiation 8) is a transmembrane glycoprotein that serves as a co-receptor for the T cell receptor (TCR). It is a specific marker for Cytotoxic T cells and allows them to bind to MHC Class I molecules.
Why other options are incorrect:
  • • Helper T cells: These cells are characterized by the presence of CD4 glycoproteins, which interact with MHC Class II molecules.
  • • Suppressor T cells: While some suppressor (regulatory) cells can be CD8+, the primary and most common textbook definition for the CD8 marker is the Cytotoxic T lymphocyte.
  • • Memory T cells: Memory cells can be either CD4+ or CD8+ depending on whether they originated from helper or cytotoxic lineages; therefore, CD8 is not a universal marker for all memory T cells.
CD 4 is a transmembrane glycoprotein present in:
  • a) Cytotoxic T cells
  • b) Helper T cells
  • c) Suppressor T cells
  • d) Memory T cells
Explanation: CD4 (cluster of differentiation 4) is a glycoprotein found on the surface of immune cells such as Helper T cells. It serves as a co-receptor that assists the T cell receptor (TCR) in communicating with antigen-presenting cells by binding to MHC Class II molecules.
Why other options are incorrect:
  • • Cytotoxic T cells: These cells are characterized by the presence of CD8 glycoproteins, which interact with MHC Class I molecules.
  • • Suppressor T cells: While some regulatory cells express CD4, the term “Suppressor T cells” in a classical context is often associated with the CD8 lineage, though modern immunology classifies most regulatory T cells (Tregs) as a subset of CD4+ cells. However, “Helper T cell” is the primary definition for CD4.
  • • Memory T cells: Like other memory cells, they can be either CD4+ or CD8+ depending on their origin; CD4 is not a marker for all memory cells.
CD 3 complex and p 56lck proteins are present in:
  • a) Cytotoxic T cells
  • b) Helper T cells
  • c) Both (Cytotoxic T cells) and (Helper T cells)
  • d) None of these
Explanation: The CD3 complex is a defining marker for all mature T lymphocytes; it is the signaling component of the T-cell receptor (TCR). p56lck (Lck) is a tyrosine kinase essential for T-cell activation that is associated with both CD4 and CD8 co-receptors. Therefore, both are present in both types of T cells.
Why other options are incorrect:
  • • Cytotoxic T cells: While they do contain these proteins, they are not the only cells to have them.
  • • Helper T cells: Similarly, these proteins are standard for the helper lineage but not exclusive to it.
  • • None of these: This is incorrect because these proteins are fundamental components of the T-cell signaling machinery.
Cytotoxic T cells release:
  • a) Perforins
  • b) Interleukins
  • c) Colony stimulating factors
  • d) Tumour necrosis factor
Explanation: Perforins are cytolytic proteins found in the granules of Cytotoxic T cells and Natural Killer (NK) cells. When released, they create pores in the target cell’s membrane, leading to osmotic lysis or allowing granzymes to enter and trigger apoptosis.
Why other options are incorrect:
  • • Interleukins: These are primarily secreted by Helper T cells (CD4+) to signal and regulate other immune cells.
  • • Colony stimulating factors: These are glycoproteins that stimulate the bone marrow to produce more white blood cells.
  • • Tumour necrosis factor: While some T cells can produce TNF, it is primarily a cytokine produced by macrophages to regulate immune cells and induce inflammation.
Helper T cells release:
  • a) Interleukins
  • b) Colony stimulating factors
  • c) Tumour necrosis factor
  • d) All of these
Explanation: Helper T cells (CD4+) are the orchestrators of the immune system. They function by secreting a variety of signaling proteins called cytokines that coordinate the activities of other immune cells like B cells, cytotoxic T cells, and macrophages.
Why all options are correct:
  • • Interleukins: They secrete many types, such as IL-2 (for T-cell proliferation), IL-4, and IL-5 (for B-cell activation).
  • • Colony stimulating factors: They release factors like GM-CSF to stimulate the production of granulocytes and macrophages in the bone marrow.
  • • Tumour necrosis factor: They produce TNF-alpha and TNF-beta (lymphotoxin) to help mediate inflammation and cellular immune responses.
MHC Class III proteins include:
  • a) Immunoglobulins
  • b) Components of complement system
  • c) T cells receptors
  • d) CD4 and CD8 proteins
Explanation: Unlike MHC Class I and II, which are membrane-bound molecules involved in antigen presentation, MHC Class III molecules are secreted proteins. They include several components of the complement system (such as C2, C4, and Factor B), as well as inflammation-related cytokines like Tumor Necrosis Factor (TNF).
Why other options are incorrect:
  • • Immunoglobulins: These are antibodies produced by B-cells/plasma cells, not encoded by the MHC Class III region.
  • • T cell receptors: These are specific receptors found on the surface of T lymphocytes for antigen recognition.
  • • CD4 and CD8 proteins: These are co-receptors (glycoproteins) located on T cells that assist in binding to MHC Class II and Class I respectively.
Human immunodeficiency virus (HIV) destroys:
  • a) Cytotoxic T cells
  • b) Helper T cells
  • c) B cells
  • d) Plasma cells
Explanation: The Human Immunodeficiency Virus (HIV) specifically targets and destroys Helper T cells (CD4+ T cells). It does this by binding to the CD4 molecule on the cell surface. As the count of these cells drops, the immune system weakens, leading to Acquired Immunodeficiency Syndrome (AIDS).
Why other options are incorrect:
  • • Cytotoxic T cells: These are CD8+ cells. While they are eventually affected by the lack of “help” from Th cells, they are not the primary target of the HIV virus.
  • • B cells: HIV does not infect B cells directly. However, B cell function is impaired because they require Helper T cells to become fully activated.
  • • Plasma cells: These are mature B cells that secrete antibodies. Like B cells, they are not the primary host cells for HIV replication.
In allergic diseases, the concentration of the following is increased in plasma:
  • a) IgA
  • b) IgG
  • c) IgD
  • d) IgE
Explanation: IgE (Immunoglobulin E) is the antibody type specifically associated with allergic reactions (Type I hypersensitivity) and parasitic infections. It binds to allergens and triggers mast cells and basophils to release histamine, causing allergic symptoms.
Why other options are incorrect:
  • • IgA: Primarily found in mucosal secretions like saliva, tears, and breast milk; it provides localized defense at body surfaces.
  • • IgG: The most abundant antibody in the plasma; it provides long-term immunity and is the only antibody that crosses the placenta.
  • • IgD: Found mainly on the surface of B cells where it acts as an antigen receptor; its concentration in the plasma is very low.
IgE has a tendency to attach to:
  • a) Basophils
  • b) Mast cells
  • c) Both (Basophils) and (Mast cells)
  • d) None of these
Explanation: IgE molecules have a high-affinity receptor (FcεRI) specifically located on the membranes of both mast cells (found in tissues) and basophils (found in the blood). When an allergen cross-links the IgE bound to these cells, it triggers the release of histamine and other inflammatory mediators.
Why other options are incorrect:
  • • Basophils: While IgE does attach to basophils, it is not restricted to them; it also binds to mast cells.
  • • Mast cells: Similarly, IgE binds to mast cells, but focusing only on them ignores the role of basophils in systemic reactions.
  • • None of these: This is incorrect because the binding to these specific cells is the fundamental mechanism of Type I hypersensitivity (allergic) reactions.
Reaginic antibody is:
  • a) IgA
  • b) IgG
  • c) IgD
  • d) IgE
Explanation: IgE is also known as the reaginic antibody. This name stems from its ability to mediate “reagin-type” hypersensitivity (Type I hypersensitivity), which includes conditions like asthma, hay fever, and anaphylaxis.
Why other options are incorrect:
  • • IgA: Known as the secretory antibody, found in body fluids like saliva, tears, and milk.
  • • IgG: The primary antibody of the secondary immune response and the most abundant in serum.
  • • IgD: Primarily serves as a surface receptor on mature B-cells and is not involved in reaginic activity.
Active immunity can be produced by administration of
  • a) Killed bacteria or viruses
  • b) Live attenuated bacteria or viruses
  • c) Toxoids
  • d) All of these
Explanation: Active immunity develops when an individual’s immune system is stimulated to produce its own antibodies and immune memory. Vaccines containing killed microorganisms, live attenuated microorganisms, or toxoids can all induce active immunity.
Why other options are correct:
  • • Killed bacteria or viruses: Inactivated vaccines stimulate the body’s own immune response.
  • • Live attenuated bacteria or viruses: Attenuated organisms can produce a strong active immune response.
  • • Toxoids: Inactivated bacterial toxins, such as tetanus toxoid, stimulate active immunity.
Passive immunity can be produced by administration of:
  • a) Pure antigens
  • b) Immunoglobulins
  • c) Toxoids
  • d) Killed bacteria or viruses
Explanation: Passive immunity is the transfer of pre-formed antibodies (immunoglobulins) or sensitized lymphocytes from an immune individual to a non-immune one. It provides immediate, but short-term protection because the recipient’s body does not produce its own memory cells.
Why other options are incorrect:
  • • Pure antigens: Administering antigens triggers Active immunity, where the body’s own immune system must work to produce antibodies.
  • • Toxoids: These are used in vaccines to stimulate the body to produce its own antitoxins, which is a form of Active immunity.
  • • Killed bacteria or viruses: These are components of “inactivated” vaccines which stimulate Active immunity by teaching the body to recognize and fight the pathogen.
Helper T cells release all the following except:
  • a) Interleukins
  • b) Colony stimulating factors
  • c) Perforins
  • d) Tumour necrosis factor
Explanation: Helper T cells (CD4+) function as the “commanders” of the immune response by secreting cytokines (Interleukins, CSFs, and TNF) to activate other cells. Perforins, however, are pore-forming proteins secreted by Cytotoxic T cells (CD8+) and Natural Killer (NK) cells to directly destroy infected or cancerous cells.
Why other options are incorrect:
  • • Interleukins: Helper T cells produce various interleukins (like IL-2, IL-4, and IL-5) to signal other immune cells.
  • • Colony stimulating factors: Th cells secrete factors like GM-CSF to stimulate the bone marrow to produce more white blood cells.
  • • Tumour necrosis factor: Th1 cells produce TNF-beta (lymphotoxin) and TNF-alpha as part of the inflammatory response.
IgG cleaved by papain into:
  • a) Two light and two heavy chains
  • b) Two Fab and one Fc fragments
  • c) Two pairs of one light and one heavy chain each
  • d) One Fab and two Fc fragments
Explanation: The enzyme papain cleaves the IgG molecule at the hinge region, just above the inter-heavy chain disulfide bonds. This results in three separate fragments: two identical Fab (Fragment antigen-binding) fragments and one Fc (Fragment crystallizable) fragment.
Why other options are incorrect:
  • • a) & c) Chains/Pairs: Separation into individual light and heavy chains occurs through the use of reducing agents (like mercaptoethanol) which break disulfide bonds, not proteolytic enzymes like papain.
  • • d) One Fab and two Fc: This is structurally impossible. One IgG molecule consists of two Fab “arms” and one Fc “stem.” Papain separates these three components.
Bence-Jones protein is:
  • a) An immunoglobulin
  • b) A dimer of heavy chains
  • c) A dimer of light chains
  • d) A dimer of one heavy and one light chains
Explanation: Bence-Jones proteins are monoclonal globulins composed of free immunoglobulin light chains (either kappa or lambda). In clinical conditions like Multiple Myeloma, these light chains are produced in excess and typically occur as dimers.
Why other options are incorrect:
  • • a) An immunoglobulin: While light chains are parts of an immunoglobulin, Bence-Jones proteins specifically refer to the *free* light chains, not the complete four-chain antibody molecule.
  • • b) A dimer of heavy chains: Heavy chain fragments are associated with “Heavy Chain Disease,” not Bence-Jones proteinuria.
  • • d) A dimer of one heavy and one light chains: This structure describes a “half-antibody” molecule, whereas Bence-Jones proteins consist strictly of light chains.
Bence-Jones proteins possess all the following properties except:
  • a) They are dimers of light chains
  • b) Their amino acids sequences are identical
  • c) Their N-terminal halves have variable amino acid sequences
  • d) Their C-terminal halves have constant amino acid sequences
Explanation: Bence-Jones proteins are monoclonal globulins consisting of free immunoglobulin light chains (kappa or lambda). While they are identical within a single patient (monoclonal), their sequences are not identical across different cases because the variable region (N-terminal) differs from one patient to another depending on the plasma cell clone.
Why other options are incorrect:
  • • a) They are dimers: This is a true property; they usually exist as dimers of light chains linked by disulfide bonds.
  • • c) N-terminal variable: This is a true property; the N-terminal half corresponds to the V-region (variable) of the light chain.
  • • d) C-terminal constant: This is a true property; the C-terminal half corresponds to the C-region (constant) of the light chain.
A Zwitterion is
  • a) Positive ion
  • b) Negative ion
  • c) Both (Positive ion) and (Negative ion)
  • d) None of these
Explanation: A zwitterion is a molecule that contains both a positively charged group and a negatively charged group simultaneously, while having an overall net charge of zero. Amino acids commonly exist as zwitterions at physiological pH.
Why other options are incorrect:
  • • Positive ion: A zwitterion contains a positive charge but is not solely a positive ion.
  • • Negative ion: A zwitterion also contains a negative charge but is not solely a negative ion.
  • • None of these: Incorrect because a zwitterion contains both positive and negative charges.
After accounting for SDA, the net gain of energy from 25 gm of proteins is about:
  • a) 70 kcal
  • b) 100 kcal
  • c) 130 kcal
  • d) 200 kcal
Explanation: The Specific Dynamic Action (SDA), also known as the Thermic Effect of Food, is the energy required for the digestion, absorption, and metabolism of nutrients. For proteins, the SDA is very high, approximately 30%.

Calculation:
  • 1. Gross Energy: 25g protein × 4 kcal/g = 100 kcal.
  • 2. SDA “Tax” (30%): 30% of 100 kcal = 30 kcal.
  • 3. Net Energy Gain: 100 kcal – 30 kcal = 70 kcal.
Why other options are incorrect:
  • • 100 kcal: This is the total potential energy of 25g of protein before accounting for the energy lost during metabolism (SDA).
  • • 130 kcal: This would imply a negative SDA or a higher caloric value per gram than protein actually possesses.
  • • 200 kcal: This would assume protein provides 8 kcal/g, which is incorrect (it provides 4 kcal/g).
After accounting for SDA, the net gain of energy from 25 gm of proteins is about:
  • a) 70 kcal
  • b) 100 kcal
  • c) 130 kcal
  • d) 200 kcal
Explanation: The gross energy value of protein is 4 kcal/gm. For 25g, that equals 100 kcal. However, Protein has a high Specific Dynamic Action (SDA) of approximately 30%. This means 30% of the energy is used for its own metabolism.

Calculation: 100 kcal – (30% of 100) = 70 kcal.
Why other options are incorrect:
  • • 100 kcal: This is the total (gross) caloric value of 25g of protein before subtracting the energy required for metabolism (SDA).
  • • 130 kcal: This value is mathematically incorrect as SDA results in an energy loss, not a gain.
  • • 200 kcal: This would imply a caloric value of 8 kcal/gm, which is incorrect for protein (which is 4 kcal/gm).
After accounting for SDA, the net gain of energy from 100 gm of fat is about:
  • a) 600 kcal
  • b) 780 kcal
  • c) 900 kcal
  • d) 1020 kcal
Explanation: The gross energy value of fat is 9 kcal/gm. For 100g, the total energy is 900 kcal. However, after accounting for the Specific Dynamic Action (SDA) of fat (which is approximately 13% in metabolic calculations), the net energy available to the body is reduced.

Calculation: 900 kcal – (13% of 900) ≈ 780 – 783 kcal.
Why other options are incorrect:
  • • 600 kcal: This value is too low; it would imply an SDA of over 30%, which is characteristic of proteins, not fats.
  • • 900 kcal: This is the total gross energy. It does not account for the energy lost during the processing/metabolism (SDA) of the fat.
  • • 1020 kcal: This is higher than the total energy available in 100g of fat, making it physiologically impossible.
If proteins, carbohydrates and fats are consumed together:
  • a) The total SDA is the sum of individual SDAs of proteins, carbohydrates and fats
  • b) The total SDA is more than the sum of individual SDAs of proteins, carbohydrates and fats
  • c) Carbohydrates and fats lower the SDA of proteins
  • d) Proteins raise the SDA of carbohydrates and fats
Explanation: When proteins, carbohydrates, and fats are consumed together, their specific dynamic actions (SDA), also called the thermic effects of food, are essentially additive. Therefore, the total SDA is approximately the sum of the individual SDAs of the three nutrients.
Why other options are incorrect:
  • • More than the sum: There is no significant synergistic increase beyond the individual SDAs.
  • • Carbohydrates and fats lower protein SDA: Their presence does not lower the specific dynamic action of protein.
  • • Proteins raise SDA of carbohydrates and fats: Protein does not increase the individual SDA of carbohydrates or fats.
After calculating the energy requirement of a person:
  • a) 10% kcal are subtracted on account of SDA
  • b) 10% kcal are added on account of SDA
  • c) 20% kcal are subtracted on account of SDA
  • d) 20% kcal are added on account of SDA
Explanation: Specific Dynamic Action (SDA), also known as the Thermic Effect of Food (TEF), is the energy expended by the body to process food (digestion, absorption, and storage). For a standard mixed diet, this is estimated to be about **10%** of the total energy intake. Therefore, when calculating a person’s total daily energy requirement, 10% must be added to the sum of the Basal Metabolic Rate (BMR) and physical activity to ensure the body has enough energy to cover the cost of digestion.
Why other options are incorrect:
  • • Option a & c: Subtraction is incorrect because SDA is an additional energy expenditure. If you subtract it, the person would be in a caloric deficit.
  • • Option d: 20% is generally considered too high for a normal mixed diet. While pure protein has an SDA of nearly 30%, a balanced diet of carbohydrates, fats, and proteins averages out to approximately 10%.
The recommended energy intake for an adult sedentary Indian man is:
  • a) 1,900 kcal/day
  • b) 2,400 kcal/day
  • c) 2,700 kcal/day
  • d) 3,000 kcal/day
Explanation: According to standard nutritional guidelines in India (ICMR-NIN), an adult man with a sedentary lifestyle requires approximately 2,400 kcal/day (specifically cited as 2,320–2,425 kcal in various editions).

Why other options are incorrect:
  • • 1,900 kcal/day: This range is generally recommended for an adult sedentary Indian woman (approx. 1,660–1,900 kcal).
  • • 2,700 kcal/day: This is closer to the requirement for a man engaged in moderate physical activity.
  • • 3,000 kcal/day: This level of energy intake is required for men engaged in heavy or strenuous physical work.
The recommended energy intake for an adult sedentary Indian woman is:
  • a) 1,900 kcal/day
  • b) 2,200 kcal/day
  • c) 2,400 kcal/day
  • d) 2,700 kcal/day
Explanation: According to the ICMR (Indian Council of Medical Research) standards, an adult Indian woman with a sedentary lifestyle requires approximately 1,900 kcal/day (specifically 1,875 – 1,900 kcal in older charts).

Why other options are incorrect:
  • • 2,200 kcal/day: This is generally the requirement for an Indian woman engaged in moderate physical activity.
  • • 2,400 kcal/day: This is the recommended intake for a sedentary Indian man.
  • • 2,700 kcal/day: This is the requirement for a woman engaged in heavy or strenuous physical work.
During pregnancy, the following should be added to the calculated energy requirement:
  • a) 300 kcal/day
  • b) 500 kcal/day
  • c) 700 kcal/day
  • d) 900 kcal/day
Explanation: During pregnancy, additional energy is required to support the growth of the fetus, the placenta, and maternal tissues (like the uterus and breasts), as well as the increased metabolic demands. The standard recommendation is an additional 300 kcal/day over the woman’s pre-pregnancy requirement (specifically during the 2nd and 3rd trimesters).
Why other options are incorrect:
  • • 500 kcal/day: This is the approximate additional energy requirement for a lactating mother (specifically during the first 6 months of breastfeeding).
  • • 700 kcal/day & 900 kcal/day: These values are excessively high for a normal pregnancy and could lead to unhealthy maternal weight gain and associated complications like gestational diabetes.
During the first six months of lactation, the following increment in energy intake is recommended:
  • a) 200 kcal/day
  • b) 300 kcal/day
  • c) 550 kcal/day
  • d) 1,000 kcal/day
Explanation: Energy requirements are highest during the first six months of lactation due to the high metabolic cost of breast milk production. The ICMR-NIN recommends an additional 550 to 600 kcal/day for the first six months to ensure adequate milk supply without depleting maternal energy stores.
Why other options are incorrect:
  • • 200 kcal/day: This is insufficient to meet the energy demands of exclusive breastfeeding.
  • • 300 kcal/day: This is the recommended additional intake for pregnancy, not lactation.
  • • 1,000 kcal/day: This is an excessive amount that would likely lead to unnecessary maternal weight gain.
The proximate principles of diet are:
  • a) Vitamins and minerals
  • b) Proteins
  • c) Carbohydrates and fats
  • d) Carbohydrates, fats and proteins
Explanation: The proximate principles of diet refers to the macronutrients that are required in large quantities by the body to provide energy and building blocks for growth and repair. These include Carbohydrates, Fats, and Proteins.
Why other options are incorrect:
  • • Vitamins and minerals: These are known as protective principles or micronutrients because they are required in small amounts to regulate body processes and protect against diseases.
  • • Option b & c: These options are incomplete. While proteins, carbohydrates, and fats are all proximate principles, all three must be grouped together to define the term correctly.
The limiting amino acid in wheat is:
  • a) Leucine
  • b) Lysine
  • c) Cysteine
  • d) Methionine
Explanation: A limiting amino acid is an essential amino acid that is present in a food in the lowest amount relative to the body’s requirements. For wheat (and most other cereals), the primary limiting amino acid is Lysine.
Why other options are incorrect:
  • • Leucine: Wheat contains sufficient amounts of leucine; it is rarely the limiting factor in cereal grains.
  • • Cysteine: This is a non-essential amino acid (though it can be synthesized from methionine) and is not the primary limiting factor in wheat.
  • • Methionine: This is the limiting amino acid in pulses (legumes). This is why a combination of cereals (low in lysine) and pulses (low in methionine) provides a complete protein profile.
The limiting amino acid in pulses is:
  • a) Leucine
  • b) Lysine
  • c) Tryptophan
  • d) Methionine
Explanation: Pulses are excellent sources of protein, but they are deficient in sulfur-containing amino acids. The primary limiting amino acid in pulses is Methionine.

This is why mutual supplementation (eating cereals and pulses together, like rice and dal) is nutritionally beneficial; cereals are low in lysine but rich in methionine, while pulses are low in methionine but rich in lysine.
Why other options are incorrect:
  • • Leucine: Pulses generally contain adequate amounts of leucine.
  • • Lysine: Pulses are actually rich in Lysine. This makes them a perfect complement to cereals, which are deficient in Lysine.
  • • Tryptophan: While present in varying amounts, Tryptophan is specifically known as the limiting amino acid in Maize (Corn).
Maize is poor in:
  • a) Lysine
  • b) Methionine
  • c) Tryptophan
  • d) Lysine and tryptophan
Explanation: Maize (corn) is unique among cereals because it is significantly deficient in two essential amino acids: Lysine and Tryptophan.

The deficiency of Tryptophan is particularly important because Tryptophan is a precursor for Niacin (Vitamin B3). This is why populations that rely solely on maize as a staple food are at a high risk of developing Pellagra.
Why other options are incorrect:
  • • Option a & c: While maize is indeed poor in both Lysine and Tryptophan, selecting only one would be an incomplete answer.
  • • Methionine: Maize is actually a relatively good source of sulfur-containing amino acids like Methionine, especially when compared to pulses.
The percentage of ingested protein/ nitrogen absorbed into blood stream is known as:
  • a) Net protein utilisation
  • b) Protein efficiency ratio
  • c) Digestibility coefficient
  • d) Biological value of protein
Explanation: The Digestibility Coefficient specifically measures how much of the nitrogen (protein) consumed is actually absorbed by the digestive tract. It is calculated as:
(Nitrogen Absorbed / Nitrogen Ingested) × 100.
Why other options are incorrect:
  • • Net Protein Utilisation (NPU): This is the proportion of ingested nitrogen that is actually retained in the body. It takes into account both digestibility and biological value.
  • • Protein Efficiency Ratio (PER): This measures the weight gain of a subject per gram of protein consumed. It is a biological assay usually done on growing rats.
  • • Biological Value (BV): This measures the percentage of absorbed nitrogen that is retained by the body. Unlike the Digestibility Coefficient, it does not care about what was lost in feces, only what happened to the protein once it reached the blood.
Biological value of a protein is:
  • a) The percentage of ingested protein/nitrogen absorbed into circulation
  • b) The percentage of ingested protein/nitrogen in the body
  • c) The percentage of absorbed nitrogen retained/utilised for protein synthesis in the body
  • d) The gain in body weight (gm) per gm of protein ingested
Explanation: The Biological Value (BV) of a protein is a measure of the proportion of absorbed nitrogen that is retained by the body for maintenance and growth. It essentially tells us how efficient the body is at using the protein it actually absorbs.
Formula: (Nitrogen Retained / Nitrogen Absorbed) × 100.
Why other options are incorrect:
  • • Option a: This is the definition of the Digestibility Coefficient.
  • • Option b: This is a vague statement and does not represent a standard nutritional index.
  • • Option d: This is the definition of Protein Efficiency Ratio (PER), which is usually determined by animal growth studies.

Net protein utilisation depends upon:
  • a) Protein efficiency ratio
  • b) Digestibility coefficient
  • c) Digestibility coefficient and protein efficiency ratio
  • d) Digestibility coefficient and biological value
Explanation: Net Protein Utilisation (NPU) is a product of both how well a protein is digested and how well the absorbed nitrogen is retained.

Mathematically: NPU = Digestibility Coefficient × Biological Value.

While Biological Value (BV) only considers nitrogen that has already entered the blood, NPU considers the nitrogen lost in feces as well, providing a more complete picture of the protein’s nutritional quality.
Why other options are incorrect:
  • • Protein Efficiency Ratio (PER): This is a separate measure based on weight gain in animal models; it is not a direct mathematical component used to calculate NPU.
  • • Option b: While the Digestibility Coefficient is one part of the equation, it only measures absorption, not the subsequent retention/utilization.
  • • Option c: This incorrectly pairs the absorption metric (DC) with the weight gain metric (PER).
The gain in body weight (gm) per gm of protein ingested is known as:
  • a) Net protein utilisation
  • b) Protein efficiency ratio
  • c) Digestibility coefficient
  • d) Biological value of protein
Explanation: The Protein Efficiency Ratio (PER) is a measure of protein quality based on the weight gain of a test subject (traditionally growing rats) relative to its protein intake.

Formula: PER = Weight Gain (gm) / Protein Consumed (gm).
Why other options are incorrect:
  • • Net Protein Utilisation (NPU): This measures the percentage of nitrogen retained in the body compared to the nitrogen intake.
  • • Digestibility Coefficient: This measures the percentage of nitrogen absorbed into the blood, not the resulting weight gain.
  • • Biological Value (BV): This measures how efficiently the body uses absorbed nitrogen for synthesis, expressed as a percentage of retention.
The following is considered as reference standard for comparing the nutritional quality of proteins:
  • a) Milk proteins
  • b) Egg proteins
  • c) Meat proteins
  • d) Fish proteins
Explanation: Egg protein is considered the “Reference Protein” or the “Gold Standard” in nutrition. This is because it contains all the essential amino acids in the most ideal proportions for human needs and has a Biological Value (BV) and Net Protein Utilisation (NPU) of nearly 100.
Why other options are incorrect:
  • • Milk proteins: While very high in quality (BV ~85-90), milk is slightly lower than egg in terms of overall amino acid balance and utilization.
  • • Meat & Fish proteins: These are high-quality animal proteins (BV ~75-80), but they do not reach the near-perfect 100% efficiency score that egg protein achieves in biological assays.
Biological value of egg proteins is about
  • a) 70 %
  • b) 80 %
  • c) 86 %
  • d) 94 %
Explanation: Egg protein has a very high biological value because it contains all the essential amino acids in proportions that closely match human requirements. Its biological value is approximately 94%.
Why other options are incorrect:
  • • 70 %: This is lower than the biological value of egg protein.
  • • 80 %: This is below the approximate biological value of egg protein.
  • • 86 %: This is lower than the commonly cited value of approximately 94% for whole egg protein.
The following has the highest protein efficiency ratio (PER):
  • a) Milk proteins
  • b) Egg proteins
  • c) Meat proteins
  • d) Fish proteins
Explanation: The Protein Efficiency Ratio (PER) measures weight gain relative to protein intake. Since Egg proteins have the most balanced amino acid profile (containing all essential amino acids in ideal proportions), they result in the highest growth/weight gain per gram consumed. Egg protein typically has a PER of about 3.9, which is the highest among common food sources.
Why other options are incorrect:
  • • Milk proteins: While very high (Casein has a PER of approx. 2.5), it is used as a standard benchmark but is lower than the value for whole egg.
  • • Meat & Fish proteins: These have high PER values (typically between 2.7 and 3.0), but they do not reach the peak efficiency of egg protein.
The following has the lowest protein efficiency ratio:
  • a) Maize proteins
  • b) Wheat proteins
  • c) Milk proteins
  • d) Rice proteins
Explanation: Maize protein has a low protein efficiency ratio (PER) because it is deficient in essential amino acids, particularly lysine and tryptophan. Therefore, among the given options, maize protein has the lowest PER.
Why other options are incorrect:
  • • Wheat proteins: Have a relatively low PER but generally higher than maize protein.
  • • Milk proteins: Have a high PER because of their excellent essential amino acid profile.
  • • Rice proteins: Have a relatively good amino acid quality compared with maize and wheat proteins.
Protein content of egg is about:
  • a) 10%
  • b) 13%
  • c) 16%
  • d) 20%
Explanation: The protein content of a whole chicken egg is approximately 13%. For a standard egg weighing about 50–60 grams, this equates to roughly 6 to 7 grams of high-quality protein.

Nutritional composition of a whole egg:
  • Protein: ~13%
  • Fat: ~11%
  • Water: ~74%
  • Minerals/Carbs: ~2%
Why other options are incorrect:
  • • 10%: This is slightly lower than the actual protein density of an egg; 10% is closer to the protein content of some cereals like wheat.
  • • 16%: This is higher than the average protein content found in whole eggs.
  • • 20%: This percentage is more characteristic of lean meats (like chicken breast) or certain types of fish, rather than eggs.
Protein content of meat is about:
  • a) 10%
  • b) 13%
  • c) 16%
  • d) 20%
Explanation: The protein content of lean meat (such as beef, mutton, or chicken) is approximately 18% to 22%, making 20% the standard representative value.

Nutritional composition of lean meat:
  • Protein: ~20%
  • Fat: ~3–5% (varies by cut)
  • Water: ~70–75%
  • Minerals/Glycogen: ~1%
Why other options are incorrect:
  • • 10%: This is the average protein content of cereals (like wheat or maize).
  • • 13%: This is the specific protein content of a whole egg.
  • • 16%: While some types of processed meats or fatty fish may fall into this range, pure muscle meat is generally denser in protein (closer to 20%).
Protein content of rice is about:
  • a) 7%
  • b) 12%
  • c) 15%
  • d) 20%
Explanation: Among all common cereals, rice has the lowest protein content, which is approximately 6% to 7%. However, it is important to note that although the quantity is low, the quality of rice protein (Oryzenin) is superior to other cereals because it has a higher Biological Value.
Why other options are incorrect:
  • • 12%: This is the average protein content of wheat.
  • • 15%: This is a high value for cereals and is closer to the protein content of some varieties of oats or specialized grains.
  • • 20%: This is the protein content of meat, fish, or pulses (like dal), which are much richer in protein than rice.
The calorific value of wheat is about:
  • a) 2.5 kcal/gm
  • b) 3.5 kcal/gm
  • c) 4.5 kcal/gm
  • d) 5.5 kcal/gm
Explanation: Most cereals, including wheat and rice, provide approximately 340 to 350 kcal per 100 grams. When converted to a per-gram basis, this is approximately 3.5 kcal/gm.

This energy comes primarily from its high carbohydrate content (approx. 70%), along with protein (approx. 12%) and a small amount of fat.
Why other options are incorrect:
  • • 2.5 kcal/gm: This value is too low for a dry grain; such a value might be found in cooked grains (which contain high water weight) but not in the raw grain itself.
  • • 4.5 kcal/gm: This is higher than the energy provided by pure carbohydrates or proteins (4 kcal/gm) and would imply a much higher fat content.
  • • 5.5 kcal/gm: This is an extremely high energy density, usually characteristic of high-fat nuts or oilseeds, not cereals.
For vegetarians, pulses are an important source of:
  • a) Carbohydrates
  • b) Proteins
  • c) Fat
  • d) Iron
Explanation: Pulses (legumes) are considered the “meat of the poor” or the primary protein source for vegetarians. They contain about 20% to 25% protein, which is roughly double the amount found in cereals. They are essential for providing lysine, an amino acid that is often missing in cereal-based diets.
Why other options are incorrect:
  • • Carbohydrates: While pulses do contain carbohydrates (55-60%), the main source of carbohydrates in a vegetarian diet is usually cereals (wheat, rice).
  • • Fat: Pulses are generally very low in fat (usually less than 1.5%), making them a lean source of nutrients.
  • • Iron: Although pulses contain non-heme iron, their most significant nutritional contribution to a balanced vegetarian diet is their high protein content.
The amino acids present in pulses can supplement the limiting amino acids of:
  • a) Cereals
  • b) Milk
  • c) Fish
  • d) Nuts and beans
Explanation: This is known as Mutual Supplementation. Cereals (like wheat and rice) are deficient in the amino acid Lysine but rich in Methionine. Conversely, pulses are rich in Lysine but deficient in Methionine. When eaten together (e.g., Rice and Dal), they provide a complete and balanced amino acid profile.
Why other options are incorrect:
  • • Milk & Fish: These are animal proteins that are already “complete” proteins. They contain all essential amino acids in the right proportions and do not require supplementation from pulses.
  • • Nuts and beans: These generally share a similar amino acid profile to pulses (often being low in sulfur-containing amino acids). Therefore, they do not effectively supplement the specific deficiencies found in pulses.
Milk is a good source of all of the following except:
  • a) Essential amino acids
  • b) Vitamin C
  • c) Galactose
  • d) Calcium and phosphorous
Explanation: Milk is often described as a “complete food,” but it is notoriously poor in Vitamin C and Iron. Processing methods like pasteurization or boiling further reduce the already small amount of Vitamin C present in raw milk.
Why other options are incorrect:
  • • Essential amino acids: Milk contains high-quality proteins (casein and whey) that provide all the essential amino acids required by the body.
  • • Galactose: This is a primary component of Lactose (milk sugar), which is a disaccharide made of glucose and galactose.
  • • Calcium and phosphorous: Milk is one of the best dietary sources for these minerals, which are vital for bone and dental health.
Milk is poor in:
  • a) Cholesterol
  • b) Retinol
  • c) Calcium
  • d) Iron
Explanation: While milk is an excellent source of many nutrients, it is notoriously deficient in Iron and Vitamin C. Prolonged exclusive milk feeding in infants beyond the age of six months without introducing iron-rich solid foods can lead to “milk anemia” (iron-deficiency anemia).
Why other options are incorrect:
  • • Cholesterol: As an animal-derived product, whole milk contains cholesterol (found within the milk fat).
  • • Retinol: Milk is actually a good source of Vitamin A (retinol), provided it is whole milk or fortified skim milk.
  • • Calcium: Milk is considered one of the best dietary sources of calcium for humans.
Egg is rich in all of the following except:
  • a) Cholesterol
  • b) Saturated fatty acids
  • c) Ascorbic acid
  • d) Calcium
Explanation: Eggs are an incredibly nutrient-dense food, often called “nature’s multivitamin,” but they contains zero Ascorbic acid (Vitamin C). Just like milk, eggs lack this specific vitamin entirely.
Why other options are incorrect:
  • • Cholesterol: Eggs are very rich in cholesterol, containing approximately 186mg per large egg, concentrated entirely in the yolk.
  • • Saturated fatty acids: Egg yolks contain a significant amount of fats, including about 1.6 grams of saturated fatty acids per egg.
  • • Calcium: While the shell is the primary source of calcium, the edible portion of the egg still contains small amounts of calcium (approx. 25-50mg). While not as “rich” as milk, it is present, whereas Vitamin C is completely absent.
A phosphoprotein present in egg is:
  • a) Casein
  • b) Albumin
  • c) Ovoglobulin
  • d) Ovovitellin
Explanation: Ovovitellin is the primary phosphoprotein found in the egg yolk. Phosphoproteins are conjugated proteins where phosphoric acid is chemically bonded to the protein molecule.
Why other options are incorrect:
  • • Casein: This is a well-known phosphoprotein, but it is found in milk, not eggs.
  • • Albumin (Ovalbumin): This is the main protein found in egg white. While it is the most abundant protein in eggs, it is classified as a glycoprotein.
  • • Ovoglobulin: These are globulin proteins present in the egg white which contribute to the foaming properties of eggs, but they are not the primary phosphoproteins.

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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