Which of the following is a correct statement about a typical bacterium? MCQ with Answer and Explanation

Explanation:
P700, a specialized chlorophyll a, is the reaction center of photosystem I, absorbing far-red light (700 nm). P680 is the reaction center of photosystem II. Chlorophyll b and xanthophyll are accessory pigments.

Explanation:
Mitochondria and chloroplasts contain circular DNA and 70S ribosomes, enabling them to transcribe and translate some proteins independently, though they rely on nuclear genes for most proteins. This partial autonomy supports the endosymbiotic origin hypothesis. The presence of their own genetic material and protein synthesis machinery qualifies them as semi-autonomous. Thus, both assertion and reason are correct, and the reason correctly explains the assertion.

Explanation:
Oxytocin, released from the posterior pituitary, stimulates uterine smooth muscle contractions during parturition (childbirth) and milk ejection during lactation. Prolactin stimulates milk production. Estrogen and progesterone regulate reproductive cycle and maintain pregnancy. Oxytocin is also known as the 'love hormone' and functions through positive feedback during labor.