The fluid mosaic model describes the structure of which cellular component? MCQ with Answer and Explanation

Explanation:
The Sinoatrial (SA) node, located in the right atrium, is the natural pacemaker because its cells are autorhythmic; they can spontaneously generate action potentials without external neural input. Crucially, the SA node has the highest intrinsic rate of depolarization (about 70-80 beats per minute) compared to other autorhythmic tissues like the AV node or Purkinje fibers. Therefore, it sets the pace for the entire heart, overriding slower pacemakers.

Explanation:
Cutin, along with waxes, forms the cuticle on the epidermis of leaves and stems, reducing water loss and providing protection. Lignin strengthens cell walls, cellulose is the wall polysaccharide, suberin is in cork cells and root endodermis.

Explanation:
The ozone layer, which absorbs harmful UV radiation, is located in the stratosphere. Chlorofluorocarbons (CFCs) release chlorine atoms in the stratosphere that catalytically destroy ozone molecules. Global warming is primarily driven by the greenhouse effect due to excess carbon dioxide and other greenhouse gases, not oxygen. Thus, statements 1 and 2 are correct.