MLT GlobeMOH exam preparation (UAE) – page 18
700 practice MCQs for the MOH medical laboratory exam. Level: Basic to intermediate.
Fungal infection of the nails is called:
Onychomycosis is nail infection, most often by dermatophytes; otomycosis affects the ear canal.
Yeasts such as Candida reproduce asexually mainly by:
Yeasts form buds (blastoconidia) that pinch off from the parent cell.
Aflatoxin, a toxin in poorly stored grains and nuts that can cause liver cancer, is produced by:
A. flavus grows on stored crops and produces aflatoxin, a potent liver carcinogen.
A mould whose colony is dark brown to black on both the surface and the reverse, due to melanin in its walls, is described as:
Dematiaceous fungi have melanin in their hyphae and conidia; hyaline moulds are colourless or light-coloured.
Immediately after collection, an EDTA tube should be mixed by:
Gentle inversion mixes the anticoagulant without haemolysing cells; vigorous shaking causes haemolysis.
In a skin puncture, the first drop of blood is usually wiped away because it:
The first drop is diluted with tissue fluid and may contain alcohol residue, which can affect results.
How many microlitres are there in 5 mL?
1 mL = 1000 µL, so 5 mL = 5000 µL.
A haemoglobin result of 14 g/dL expressed in g/L is:
1 L = 10 dL, so multiply by 10: 14 g/dL = 140 g/L.
Before a centrifuge is started, tubes must be placed so that:
An unbalanced rotor vibrates, can damage the centrifuge and may break tubes, creating aerosols.
When reading the volume of a clear aqueous solution in a graduated pipette or cylinder, you should read:
For clear liquids the lowest point of the curved meniscus is read with the eye level with the mark to avoid parallax error.
How do cytotoxic (CD8+) T lymphocytes kill virus-infected cells?
CD8+ T cells recognise antigen on MHC class I and deliver perforin and granzymes that trigger apoptosis. B cells, not T cells, become plasma cells.
The carbon skeleton of glutamate, and through it proline and arginine, comes from which TCA-cycle intermediate?
Reductive amination or transamination of α-ketoglutarate gives glutamate, the parent of glutamine, proline and arginine. Oxaloacetate gives aspartate.
Just after DNA replication, which protein complex holds the two sister chromatids together until anaphase?
Cohesin rings encircle sister chromatids until separase cleaves them at anaphase. Condensins compact chromosomes but do not join sisters.
The degree of ionisation of a weak electrolyte does NOT depend on:
Dissociation depends on solvent dielectric properties, temperature and dilution. Passing current does not change the equilibrium extent of ionisation.
A castor-bean toxin depurinates 28S rRNA and so inactivates the large (60S) ribosomal subunit. The toxin is:
Ricin's A chain is an N-glycosidase acting on 28S rRNA. Diphtheria toxin ADP-ribosylates EF-2; chloramphenicol and tetracycline act on bacterial ribosomes.
Aconitase, which converts citrate to isocitrate in the Krebs cycle, contains which prosthetic group?
Aconitase has a [4Fe–4S] cluster that binds citrate during dehydration–rehydration; fluoroacetate-derived fluorocitrate blocks it. It is not a zinc enzyme.
The H antigen, precursor of the A and B blood group antigens, is formed by adding which sugar to a terminal galactose?
Fucosyltransferase (FUT1) adds L-fucose to make H substance; A and B transferases then add N-acetylgalactosamine or galactose. Fructose is not part of blood group antigens.
Salivary and pancreatic α-amylase hydrolyse which bonds in dietary starch?
α-Amylase cleaves internal α-1,4 links, producing maltose, maltotriose and α-limit dextrins. The α-1,6 branch bonds are removed by brush-border isomaltase; β-1,4 bonds (cellulose) are not digested.
Pulses such as lentils are relatively poor in which amino acid, so they are best combined with cereals?
Pulses are limited in sulfur amino acids (methionine), while cereals are limited in lysine; eaten together they complement each other.
A young adult has exercise-induced cramps and myoglobinuria, and blood lactate does not rise during forearm exercise. Which enzyme is deficient?
McArdle disease (GSD V) affects skeletal muscle only: muscle cannot break down glycogen, so no lactate is produced. Glucose-6-phosphatase deficiency is von Gierke disease; acid α-glucosidase deficiency is Pompe disease.