Clinical Biochemistry: Enzymology, Electrolytes, and Endocrine Flashcards

Flashcards covering vocabulary and key laboratory methods for clinical enzymology, electrolyte balance, endocrinology, and toxicology as found in the lecture notes.

Enzymology

The study of biochemical catalysts that speed up biological reactions by lowering the free energy needed for a reaction to take place.

Michaelis-Menten Hypothesis

A hypothesis stating that the rate of substrate conversion to product is determined by substrate concentration and the rate of dissociation of the enzyme-substrate complex.

Holoenzyme

A whole, active enzyme composed of an apoenzyme (the protein portion) and a cofactor (coenzyme or activator).

Zymogen

The inactive form of an enzyme, also known as a proenzyme.

Isoenzyme

An enzyme with the same chemical activity as another but with different characteristics or structural properties.

Active Site

The specific site on an enzyme where substrates attach and undergo a chemical reaction.

Allosteric Site

A site on an enzyme opposite to the active site where regulatory molecules attach.

First-order Kinetics

A reaction rate that is proportional to the substrate concentration.

Zero-order Kinetics

A reaction rate that depends on enzyme concentration because the substrate is present in excess and all enzymes are bound (Saturation point or $V_{max}$).

$K_m$ (Michaelis constant)

The substrate concentration at which the reaction velocity is half-maximum ($1/2 V_{max}$).

Competitive Inhibition

A type of inhibition where the inhibitor and the enzyme substrate compete for the same binding site.

International Unit (IU)

The amount of enzyme that catalyzes the conversion of $1\,mmol$ of substrate per minute ($\mu mol/min$).

Katal

The amount of enzyme that catalyzes the conversion of $1\,mole$ of substrate per second ($mol/sec$).

De Ritis Ratio

The ratio of AST to ALT; a ratio $>2$ suggests alcoholic hepatitis or non-viral hepatocarcinoma, while a ratio $<1$ suggests viral hepatitis.

Wacker Method

A laboratory method for LDH that utilizes the lactate-to-pyruvate reaction to produce a blue-purple color at pH $8.3-8.9$.

Wroblewski Ladue

The preferred method for measuring LDH, utilizing the reverse reaction of pyruvate to lactate at pH $7.1-7.4$.

Oliver-Rosalki Assay

The preferred method for CK measurement, involving the reverse reaction where creatine phosphate is converted to creatine at pH $6.8$.

Bessey-Lowry-Brock

A rapid endpoint or kinetic method for measuring ALP using p-Nitrophenylphosphate as a substrate.

Bowers-McComb Method

The reference method for ALP measurement that uses p-Nitrophenol and requires Magnesium ($Mg^{2+}$) and Manganese ($Mn^{2+}$) as activators.

TRAP (Tartrate Resistant Acid Phosphatase)

A form of Acid Phosphatase (ACP) found in the serum of patients with hairy cell leukemia that is not inhibited by tartrate.

Amyloclastis Method

A laboratory method for Amylase (AMS) that measures the disappearance of the starch substrate, resulting in a reduction of blue color intensity.

Cherry-Crandal Method

The reference titrimetric method for Lipase (LPS) that measures liberated fatty acids using an olive oil substrate after a $24\,hour$ incubation.

Anion Gap

The difference between the sums of concentrations of the principal unmeasured cations and anions; calculated as $Na^+ - (HCO_3^- + Cl^-)$, with a reference range of $7-16\,mmol/L$.

Osmolal Gap

The difference between measured osmolality and calculated osmolality; values greater than $10$ may indicate poisoning with ethanol or methanol.

Chloride Shift

The reversible exchange process between Chloride and Bicarbonate in RBCs which maintains the buffer capacity of blood.

Pilocarpine Iontophoresis

The method used for sweat collection to test for Chloride levels in the diagnosis of various conditions.

Cretinism

A condition characterized by severe mental retardation caused by low levels of $T_3$ and $T_4$ in the fetus.

Acromegaly

A disorder resulting from pathologic or autonomous Growth Hormone (GH) excess in adults, often due to a pituitary tumor.

SIADH (Syndrome of Inappropriate ADH)

A condition involving sustained production of ADH in the absence of stimuli, leading to dilutional hyponatremia and low serum electrolytes.

Grave's Disease

An autoimmune condition of hyperthyroidism where thyroglobulin reflects thyroid mass and receptor stimulation.

Pheochromocytoma

The most common tumor of the adrenal medulla (90%), arising from chromaffin cells and causing hypertension through catecholamine overproduction.

Pharmacokinetics

The study of the relationship between drug dose and drug blood level as a function of absorption, distribution, metabolism, and excretion.

Bioavailability

The extent to which a drug can be successfully absorbed from the GI tract and become therapeutically active.

Steady State

The condition where drug intake balances drug inactivation and excretion, typically reached after $5$ to $7$ doses.

Reinsch Test

A screening test for heavy metals (Arsenic, Mercury, etc.) based on the ability of these metals to deposit on and plate elemental copper.