MLT GlobeMOH exam preparation (UAE) – page 2
700 practice MCQs for the MOH medical laboratory exam. Level: Basic to intermediate.
Intrinsic factor, required for vitamin B12 absorption in the terminal ileum, is:
Parietal cells secrete intrinsic factor, which binds B12 in the duodenum for ileal uptake; autoantibodies against it cause pernicious anaemia. Haptocorrin binds B12 earlier and is removed by pancreatic proteases.
β-Oxidation of palmitate takes place mainly in the:
Fatty acid oxidation occurs in the mitochondrial matrix in most tissues, yielding acetyl-CoA, NADH and FADH2. The cytosol is the site of fatty acid synthesis, which uses NADPH.
An adult has bone pain, low serum calcium and phosphate, raised alkaline phosphatase and low 25-hydroxyvitamin D. The likely diagnosis is:
Vitamin D deficiency after growth plates close causes defective mineralisation, i.e. osteomalacia; in children it is rickets. Osteoporosis usually shows normal calcium, phosphate and ALP.
Glycogen is best classified as a:
Glycogen contains only glucose, in α-1,4 chains with α-1,6 branches every 8–12 residues. Linear glucose polymers are amylose and cellulose; GAGs contain amino sugars and uronic acids.
After digestion of dietary starch and disaccharides, carbohydrate is used by body cells mainly in the form of:
Digestion yields monosaccharides; fructose and galactose are largely converted to glucose in the liver. Disaccharides are not absorbed intact and must be hydrolysed at the brush border.
The α cells of the pancreatic islets secrete:
α cells secrete glucagon, β cells insulin, δ cells somatostatin and PP cells pancreatic polypeptide.
Humans cannot digest cellulose because its glucose units are joined by:
Human enzymes hydrolyse α-glycosidic bonds only; cellulose's β-1,4 bonds need cellulase from gut microbes. α-1,4 and α-1,6 bonds occur in starch and glycogen; α1–β2 in sucrose.
Which peptidase is an exopeptidase that removes amino acids one at a time from the N-terminus?
Aminopeptidases act at the free amino end of peptides. Trypsin, chymotrypsin and pepsin are endopeptidases that cut bonds within the chain.
Allosteric enzymes, which do not follow Michaelis–Menten kinetics, give what shape of velocity versus substrate curve?
Cooperative binding between subunits produces an S-shaped curve. Hyperbolic curves are typical of Michaelis–Menten enzymes.
How many classes of heavy-chain constant region (isotypes) define the human immunoglobulin classes?
The γ, α, μ, δ and ε heavy chains define IgG, IgA, IgM, IgD and IgE. Two is the number of light-chain types (κ and λ).
Activation of the complement cascade proceeds mainly by:
Each activated component is a protease that cleaves the next (e.g. C3 convertase splits C3 into C3a and C3b), amplifying the cascade, much like coagulation. Kinase-type phosphorylation is not involved.
Mature human red blood cells lack which of the following?
Having lost their mitochondria, mature red cells cannot run the Krebs cycle and rely on glycolysis for ATP and the HMP shunt for NADPH.
Which of these is a trace element (daily requirement well below 100 mg)?
Copper is needed in milligram amounts, for example in ceruloplasmin and cytochrome oxidase. Calcium, phosphorus and magnesium are macrominerals needed in hundreds of milligrams daily.
The Na+/K+-ATPase is best classified as a(n):
It uses ATP directly to pump 3 Na+ out and 2 K+ in, i.e. two ions in opposite directions. Symporters move solutes the same way; channels allow passive flow.
D-glucose and L-glucose are non-superimposable mirror images. They are best described as:
Mirror-image stereoisomers are enantiomers. Diastereomers, including epimers, are stereoisomers that are not mirror images; anomers differ only at the anomeric carbon.
Bleeding gums and poor wound healing in scurvy reflect defective synthesis of:
Vitamin C is needed by prolyl and lysyl hydroxylases; underhydroxylated collagen forms weak triple helices and fragile vessels. Prothrombin depends on vitamin K.
The 'S' in the amniotic fluid L/S ratio is a choline-containing sphingolipid. It is:
Sphingomyelin contains phosphocholine attached to ceramide; lecithin (phosphatidylcholine) is the 'L'. Phosphatidylserine and phosphatidylethanolamine contain no choline.
Which vitamin deficiency presents mainly with night blindness and xerophthalmia rather than neurological disease?
Vitamin A deficiency affects the retina and epithelia. B12 deficiency causes subacute combined degeneration, B6 deficiency neuropathy and seizures, and thiamine deficiency dry beriberi and Wernicke encephalopathy.
Which tissue converts glucose into galactose in large amounts to synthesise lactose?
UDP-glucose 4-epimerase forms UDP-galactose, which lactose synthase joins to glucose in the lactating breast. The intestine absorbs galactose but does not make lactose.
Raised plasma homocysteine can result from deficiency of several vitamins. Which vitamin deficiency does NOT raise it?
Folate and B12 are needed to remethylate homocysteine, and B6 is needed for transsulfuration. Vitamin C plays no part in homocysteine metabolism.