Q.23 In transmission electron microscopy, electron opacity is greatly enhanced by treating the specimen
with
(A) ferrous ammonium sulfate (B) uranium acetate
(C) sodium chloride (D) basic fuchsin
Transmission electron microscopy (TEM) requires heavy metal stains to enhance electron opacity and contrast in biological specimens. The correct answer is (B) uranium acetate.
Correct Answer
B) uranium acetate.
Uranium acetate serves as a standard heavy metal stain in TEM, binding to cellular components and scattering electrons to produce dark contrast in ultrathin sections.
Post-staining with uranyl acetate followed by lead citrate remains the most common protocol for visualizing ultrastructure.
Option Breakdown
A) Ferrous Ammonium Sulfate
Ferrous ammonium sulfate acts primarily as a reducing agent or mordant in light microscopy and chemical assays.
It lacks sufficient atomic mass for effective electron scattering in TEM, making it unsuitable for enhancing opacity.
C) Sodium Chloride
Sodium chloride functions as a simple electrolyte or osmotic agent but contains light elements (Na, Cl) with low electron density.
These fail to provide the heavy metal contrast needed for TEM imaging of biomolecules.
D) Basic Fuchsin
Basic fuchsin represents a light microscopy dye for staining bacteria or fungi, binding via organic interactions.
Its low atomic number prevents significant electron opacity, limiting use to optical rather than electron microscopy.
TEM Staining Applications
Heavy metal stains like uranium acetate target proteins, lipids, and nucleic acids, enabling visualization of organelles in biotechnology research such as microbial ultrastructure or mammalian cell analysis.
Negative staining with uranyl acetate suits quick virus or protein imaging, while en bloc methods preserve membranes.
