MLT GlobeDHA exam preparation (Dubai)
700 practice MCQs for the DHA medical laboratory exam. Level: Basic to intermediate.
Subject mix: Chemistry 17%, Hematology 16%, Bacteriology 14%, Blood Banking 12%, Immunology & Serology 10%, Parasitology 7%, Laboratory Operations 7%, Urinalysis & Body Fluids 7%, Mycology 5%, Virology 5%
A patient is group O, RhD-negative. Which red cell unit is fully compatible?
Group O plasma has anti-A and anti-B, so only group O cells are ABO-compatible. An RhD-negative recipient should receive RhD-negative cells to avoid anti-D sensitisation.
Neutrophils engulfing bacteria at a wound within minutes, without prior exposure, illustrates which arm of immunity?
Phagocytosis by neutrophils is non-specific and needs no previous sensitisation, so it belongs to innate immunity. Adaptive responses depend on antigen-specific lymphocytes and take days to develop.
In an emergency when the recipient's group is unknown, red cells of which ABO/RhD group are given?
O RhD-negative red cells lack A, B and D antigens, so they are not destroyed by recipient anti-A, anti-B or anti-D. AB patients are the universal plasma donors instead.
Which statement about the ABO blood group system is correct?
Group O red cells lack A and B antigens, and the plasma carries naturally occurring anti-A and anti-B. Group AB has neither antibody and is the universal red-cell recipient.
HIV infection progressively lowers which lymphocyte population, monitored by flow cytometry?
HIV binds CD4 with CCR5 or CXCR4 co-receptors and destroys helper T cells. A CD4 count below 200 cells/uL defines AIDS.
Methane (MW 16) is a gas at room temperature, while water (MW 18) is a liquid. What mainly accounts for this difference?
Each water molecule can hydrogen-bond with up to four neighbours, holding them together as a liquid. Methane has only weak van der Waals forces.
Triacylglycerols can be stored as anhydrous droplets in adipocytes because they are:
Esterification of all three glycerol hydroxyls removes charged groups, so TAGs are hydrophobic and stored without water, giving about 9 kcal/g.
Non-standard base pairing between codon and anticodon is allowed at which codon position?
Crick's wobble hypothesis: the 3′ codon base pairs loosely with the 5′ anticodon base, so one tRNA can read several codons.
Butter stored too long develops a sour odour as lipases release free fatty acids from triglycerides. This change is called:
Hydrolysis of ester bonds (often microbial lipase) frees volatile short-chain acids such as butyric acid. Oxidative rancidity involves peroxidation of double bonds.
Prostacyclin (PGI2), which inhibits platelet aggregation, is produced mainly by:
Endothelial prostacyclin synthase makes PGI2, which opposes platelet thromboxane A2 to keep vessels patent.
Which drug reduces prostaglandin formation by irreversibly acetylating cyclooxygenase?
Aspirin acetylates a serine in COX-1 and COX-2. Fluoride inhibits enolase and cyanide cytochrome oxidase.
The VDRL and RPR tests for syphilis use which phospholipid as antigen?
Cardiolipin (diphosphatidylglycerol) is antigenic; antibodies to it (reagin) appear in syphilis and form the basis of non-treponemal tests.
Which disaccharide is synthesised by the mammary gland and occurs naturally only in milk?
Lactose (galactose β-1,4 glucose) is made by lactose synthase in the lactating breast. Maltose comes from starch digestion, sucrose from plants, and trehalose from fungi and insects.
Breaking down glycogen to carbon dioxide and water with release of energy is an example of:
Catabolic pathways degrade complex molecules and release energy. Anabolism, including gluconeogenesis and other biosynthesis, consumes energy to build molecules.
In osmosis across a semipermeable membrane, what moves and in which direction?
Osmosis is net water movement toward higher solute concentration, since solute cannot cross. Solute movement down its gradient is ordinary diffusion.
Which sugar is an aldopentose found in RNA?
Ribose has five carbons and an aldehyde group. Erythrulose is a ketotetrose, fructose a ketohexose, and glyceraldehyde an aldotriose.
At pH 7.4, which amino acid carries a negatively charged side chain?
Aspartate's side-chain carboxyl (pKa about 3.9) is ionised at physiological pH. Lysine is positive, histidine is mostly uncharged (pKa ~6), and proline's side chain is non-polar.
Which dietary protein has the highest protein efficiency ratio and is often used as the reference protein?
Whole egg protein has an ideal essential amino acid pattern and near-complete digestibility, giving the highest PER and biological value. Milk, meat and fish proteins are high quality but rank slightly lower.
Which function is carried out chiefly by the Golgi apparatus?
The Golgi completes glycosylation, packages proteins into vesicles and directs them to their destinations. ATP synthesis is mitochondrial, translation ribosomal, and autophagic digestion lysosomal.
An inactive enzyme protein combines with its required coenzyme. The active complex formed is called the:
Apoenzyme plus cofactor equals holoenzyme. A zymogen is an inactive precursor activated by cleavage, isoenzymes are different forms of one enzyme, and ribozymes are catalytic RNA.