QCHP exam preparation (Qatar) – page 15

HDL performs reverse cholesterol transport, taking cholesterol from peripheral tissues to the liver. Chylomicrons carry dietary triglyceride and LDL delivers cholesterol to tissues.

The five classic fractions are albumin, alpha-1, alpha-2, beta and gamma globulins.

Immunoglobulins, especially IgG, make up most of the gamma region, which moves least toward the anode at pH 8.6.

CRP is a positive acute-phase protein synthesised by hepatocytes, mainly in response to IL-6. It rises quickly in infection and inflammation.

NADH and NADPH absorb strongly at 340 nm, whereas NAD+ and NADP+ do not, so the reaction is followed by absorbance change at 340 nm.

ALP hydrolyses phosphate esters with a pH optimum around 9–10, so assays are run at alkaline pH.

UDP-glucuronyltransferase is an endoplasmic reticulum enzyme, so bilirubin conjugation takes place there before secretion into bile.

Amino acid nitrogen is converted to ammonia and then to urea in the liver. Purines give uric acid and creatine phosphate gives creatinine.

In humans, the purine bases adenine and guanine are broken down to uric acid. Pyrimidines are degraded to soluble products such as beta-alanine.

Chloride is the most abundant extracellular anion, followed by bicarbonate. Phosphate and proteins are the main intracellular anions.

The adult reference range for serum potassium is about 3.5–5.0 (to 5.1) mmol/L, so values below 3.5 mmol/L are hypokalemia.

The bicarbonate–carbonic acid system is the major extracellular buffer because CO2 is controlled by the lungs and bicarbonate by the kidneys. Hemoglobin is the main buffer in red cells.

Blood gas syringes contain heparin, usually dry (lyophilised) and balanced for electrolytes. EDTA, citrate and fluoride alter pH or electrolyte results.

When ventilation is inadequate, CO2 accumulates, raising carbonic acid and lowering pH. Hyperventilation causes respiratory alkalosis.

The primary change in metabolic alkalosis is a rise in bicarbonate. Changes in pCO2 as the first event define respiratory disorders.

In respiratory disorders, the kidneys compensate by adjusting bicarbonate reabsorption and acid excretion. The lungs compensate for metabolic disorders.

Prolactin from the anterior pituitary stimulates milk production by the breast. Oxytocin causes uterine contraction and milk ejection.

ADH is made in the hypothalamus and stored in and released from the posterior pituitary (neurohypophysis).

Transferrin carries iron in the blood to tissues such as the bone marrow. Ferritin and hemosiderin are storage forms and haptoglobin binds free hemoglobin.

hCG is produced by trophoblastic tissue, so it is the marker for gestational trophoblastic disease, including choriocarcinoma and hydatidiform mole.