The 'P' wave in a standard ECG represents: MCQ with Answer and Explanation

Explanation:
Approximately 97% of O₂ is transported bound to hemoglobin (as oxyhemoglobin), while only 3% is dissolved in plasma. Each hemoglobin molecule can bind four O₂ molecules cooperatively. CO₂ is mainly transported as bicarbonate (70%), carbaminohemoglobin (23%), and dissolved (7%). The affinity of hemoglobin for O₂ is influenced by pH, CO₂, and temperature (Bohr effect).

Explanation:
Excretion is the elimination of nitrogenous waste products (urea, uric acid, ammonia) and other metabolic wastes from the body, primarily by the kidneys. Digestion is breakdown of food, circulation is transport, respiration is gas exchange and energy release. Excretion maintains homeostasis of body fluids and prevents toxic accumulation.

Explanation:
SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) denatures proteins and coats them with negative charge, allowing separation by molecular weight in an electric field. PCR amplifies DNA, sequencing determines base order, ELISA detects antigens/antibodies. SDS-PAGE is a fundamental biochemistry technique.