Which of these is a central purpose of steroids in mammals? choose the correct answer. a)they form protective coatings. b)they serve as chemical messengers. c)they provide most of the energy for a cell. d)they break down bonds in polymers by adding water.

Ans.

Steroids are defined as active organic bio-molecules, having four rings with a specific molecular configuration. Steroids play role in two major functions: as hormones or signaling molecules and as structural components of plasma membrane.  

Examples of steroid hormones are estrogen, progesterone, and cortisol. Thus, the correct answer is 'option b). they serve as chemical messengers.'

They serve as chemical messengers.

Explanation:

Steroid may be defined as the molecule that are made of large number of non polar molecules and are hydrophobic in nature. The cholesterol is an important steroid present in mammals.

Steroids as a precursor for the formation of the important hormones. Steroidal hormones plays an important role in the growth and metabolism of the organisms. The sex hormone are also made of steroids. They regulate the chemical messages in the body.

Thus, the correct answer is option (b).

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: