Assertion (A): The Krebs cycle occurs in the mitochondrial matrix. Reason (R): The enzymes for the Krebs cycle are soluble in the matrix. MCQ with Answer and Explanation

Explanation:
Implantation occurs about 6-7 days after fertilization, when the blastocyst embeds into the endometrium. Fertilization is sperm-egg fusion, ovulation egg release, menstruation shedding.

Explanation:
The spleen, located in the upper left abdomen, filters blood, removes senescent or damaged red blood cells, stores platelets and white blood cells, and mounts immune responses. The liver processes nutrients and toxins, kidneys filter blood to produce urine, pancreas secretes enzymes/hormones.

Explanation:
The tricuspid valve has three cusps and prevents backflow of blood from the right ventricle to the right atrium during contraction. The mitral (bicuspid) valve is on the left side. Semilunar valves are at the ventricular outlets.