Consider the following statements about the circulatory system: 1. Arteries carry blood away from the heart. 2. Veins have valves to prevent backflow. 3. Capillaries are thick-walled vessels. Which of the above is/are correct? MCQ with Answer and Explanation

Explanation:
Platelets (thrombocytes) are small, anucleate cell fragments that adhere to the site of injury, release clotting factors, and aggregate to form a platelet plug, initiating the coagulation cascade. RBCs transport oxygen, WBCs defend against infection, and plasma proteins like albumin maintain osmotic balance. Clotting factors are also present in plasma, but platelets are the primary cellular component.

Explanation:
Photorespiration is a wasteful pathway that occurs when RuBisCO fixes O2 instead of CO2, producing phosphoglycolate. This 2-carbon compound is metabolized through a complex pathway involving three organelles: it is processed in the peroxisome, then the mitochondria, and finally returns to the chloroplast. This process consumes ATP and releases CO2 without producing any sugar.

Explanation:
The QRS complex in an ECG represents the depolarization of the ventricles, which initiates ventricular contraction (systole). The P wave represents atrial depolarization. The T wave represents ventricular repolarization, which leads to ventricular relaxation (diastole). Atrial repolarization is usually masked by the larger QRS complex. Exam tip: P = atrial depolarization; QRS = ventricular depolarization; T = ventricular repolarization.