Plasma Proteins MCQs

21 MCQs with clinical pearls · MBBS Biochemistry · Prof Jariya

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Topics covered (5)

Immunoglobulins — 10 MCQs
Transport Proteins — 4 MCQs
Acute Phase Proteins — 3 MCQs
Plasma Protein Disorders — 2 MCQs
Albumin — 2 MCQs

Sample MCQs with clinical pearls

The complete heavy chain of IgM (mu chain) consists of which combination of domains?

A) CH1, CH2, CH3

B) CH1, CH2, CH3, CH4

C) VH, CH1, CH2, CH3

D) VH, CH1, CH2, CH3, CH4 ✔

E) VH, CH1, CH3, CH4

IgM mu chain = VH + CH1 + CH2 + CH3 + CH4 (FOUR constant domains). IgE epsilon chain also has 4 constant domains. Both IgM and IgE lack a hinge region — the CH2 domain functionally compensates. IgG, IgA, IgD = 3 constant domains with a hinge region between CH1 and CH2. The extra constant domain in IgM and IgE replaces the absent hinge region. 📹 [VIDEO LINK]

The hinge region of an immunoglobulin molecule confers flexibility and allows both Fab arms to move independently. Between which constant domains is the hinge region located?

A) Between CH1 and CH2 ✔

B) Between CH2 and CH3

C) Between CH3 and CH4

D) Between VH and CH1

E) Between VL and CL

Hinge region = flexible segment BETWEEN CH1 and CH2 of IgG (and IgA, IgD). Rich in proline and cysteine residues → proline provides flexibility, cysteine forms inter-heavy chain disulfide bonds. Hinge region is ABSENT in IgM and IgE (replaced by an extra CH2 domain). Papain cleaves ABOVE the hinge → two Fab fragments + one Fc fragment. Pepsin cleaves BELOW the hinge → one F(ab')2 fragment. [Diagram: IgG structure showing hinge region between CH1 and CH2 on both heavy chains, labelled: Fab arm, Hinge region (proline rich, flexible, disulfide bonds shown), Fc region (CH2 + CH3). Papain cleavage site (above hinge) and Pepsin cleavage site (below hinge) both labelled] 📹 [VIDEO LINK]

A 45-year-old woman with rheumatoid arthritis is started on a biologic therapy that is a monoclonal antibody targeting tumour necrosis factor alpha. Monoclonal antibodies used therapeutically are derived from a single B cell clone and therefore bind:

A) All antigens nonspecifically

B) Multiple epitopes on multiple antigens

C) Multiple epitopes on one antigen

D) One epitope on one specific antigen ✔

E) One epitope on several antigens

MONOCLONAL ANTIBODIES bind ONE SPECIFIC EPITOPE on ONE SPECIFIC ANTIGEN — produced from a single B cell clone (hybridoma technique). Examples: infliximab/adalimumab (anti-TNF-α → RA, IBD), rituximab (anti-CD20 → lymphoma, autoimmune), trastuzumab (anti-HER2 → breast cancer), bevacizumab (anti-VEGF → colorectal cancer). Suffix -mab = monoclonal antibody. Compare: POLYCLONAL antibodies = multiple B cell clones → multiple epitopes → mixture of antibodies (normal serum immunoglobulins, antivenom). 📹 [VIDEO LINK]

These are three of 21 MCQs in this section. Every question carries a clinical pearl explaining the reasoning.

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