The 'Hormone Resistin' is secreted primarily by adipose tissue in humans (and by macrophages in rodents). Its primary function is to: MCQ with Answer and Explanation

Explanation:
Autotrophs (self-feeders) include photoautotrophs (plants, algae, cyanobacteria) and chemoautotrophs (some bacteria). They produce organic matter from CO₂. Heterotrophs depend on others, saprotrophs decompose dead matter, parasites live on hosts.

Explanation:
Syphilis is caused by the spirochete bacterium Treponema pallidum, typically transmitted through sexual contact. It progresses through primary, secondary, latent, and tertiary stages, potentially causing severe neurological and cardiovascular damage if untreated. Gonorrhea is by Neisseria gonorrhoeae, herpes by HSV, chlamydia by Chlamydia trachomatis. Penicillin is an effective treatment.

Explanation:
The lac operon in E. coli is a classic example of an inducible operon. It is normally 'off' (repressed) because the lac repressor protein, produced by the 'i' gene, binds to the operator, preventing transcription of the structural genes (z, y, a) needed for lactose metabolism. However, when lactose is present in the environment, it is converted to allolactose, which acts as an inducer. Allolactose binds to the repressor, changing its shape and preventing it from binding to the operator, thus 'inducing' or allowing transcription to occur.