Assertion (A): Lysosomes are known as the 'suicidal bags' of the cell. Reason (R): They contain hydrolytic enzymes that can digest the cell’s own components. MCQ with Answer and Explanation

Explanation:
Syphilis is caused by the spirochete Treponema pallidum and is curable with antibiotics. Hepatitis B and HIV are viral, genital herpes is caused by herpes simplex virus. Gonorrhea and chlamydia are other bacterial STDs. Early diagnosis and treatment prevent serious complications like neurological damage and congenital syphilis.

Explanation:
Phycoerythrin is a red pigment found in red algae (Rhodophyta), masking the green chlorophyll. Fucoxanthin is brown (brown algae), chlorophyll is green, carotene is orange/yellow. Phycoerythrin absorbs blue light, allowing red algae to live in deeper waters.

Explanation:
In the lac operon, the 'i' gene (regulatory gene) constitutively produces a repressor protein. In the absence of lactose (the inducer), this active repressor binds specifically to the operator region of the operon. The operator overlaps with the promoter, physically blocking RNA polymerase from binding to the promoter or moving forward to transcribe the structural genes (z, y, a). When lactose is present, it binds to the repressor, inactivating it and allowing transcription.