DAILY QUIZ 19

Which of the following best describes isoenzymes?

• Enzymes that catalyze different reactions but have similar structures

• Enzymes that catalyze the same reaction but differ in amino acid sequence

• Enzymes that have identical amino acid sequences but different activities

• Enzymes that catalyze similar reactions and have the same structure

Which pair of enzymes is an example of isoenzymes?

• Glucokinase and hexokinase

• Trypsin and chymotrypsin

• Pepsin and trypsin

• Sucrase and lactase

Isoenzymes are particularly important in clinical diagnostics because they:

• Have the same kinetic properties

• Are present in different tissues at different concentrations

• Are inactivated by the same inhibitors

• Have the same temperature and pH optima

Which of the following is NOT a method for identifying isoenzymes?

• Electrophoresis

• Immunological techniques

• Chromatography

• Mass spectrometry

Isoenzyme patterns can be differentiated by electrophoresis based on their:

• Molecular weight

• Charge and mobility

• Shape and size

• Substrate affinity

Which technique involves the use of antibodies to detect specific isoenzymes?

• Gel electrophoresis

• Western blotting

• High-performance liquid chromatography (HPLC)

• Polymerase chain reaction (PCR)

Isoenzymes of lactate dehydrogenase (LDH) can be separated and identified by:

• Ultracentrifugation

• Isoelectrofocusing

• Western blot

• Liquid chromatography

The mobility of an isoenzyme on an electrophoretic gel is determined by:

• Its molecular weight alone

• Its net charge at the pH of the buffer

• Its substrate specificity

• The type of gel used

Which identification method involves separating proteins based on their movement in an electric field?

• Immunohistochemistry

• Electrophoresis

• ELISA

• X-ray crystallography

Which isoenzyme of lactate dehydrogenase (LDH) is predominantly found in the heart?

• LDH-1

• LDH-2

• LDH-3

• LDH-4