Alexander Fleming discovered the antibiotic penicillin from the fungus: MCQ with Answer and Explanation

Explanation:
The Casparian strip is a waterproof band of suberin and lignin found in the radial and transverse cell walls of the endodermis (the innermost layer of the cortex) in plant roots. It acts as a barrier to the passive flow of water and dissolved minerals through the cell walls (the apoplastic pathway). This forces water and solutes to cross the selectively permeable plasma membrane and enter the symplastic pathway, allowing the plant to control and filter what enters the vascular cylinder (stele).

Explanation:
The sinoatrial node spontaneously depolarizes, setting the rhythm of the heart. The reason correctly explains its role as pacemaker.

Explanation:
Saturated fatty acids have no double bonds between the carbon atoms in their hydrocarbon chain, making them 'saturated' with hydrogen atoms. They are typically solid at room temperature. Palmitic acid and stearic acid are common saturated fats. Oleic, linoleic, and linolenic acids are unsaturated fatty acids, containing one or more double bonds.