In the five-kingdom classification, the kingdom Protista includes: MCQ with Answer and Explanation

Explanation:
Molecular oxygen (O₂) accepts electrons at the end of the electron transport chain, combining with protons to form water (metabolic water). Without oxygen, the chain backs up, stopping ATP production. This is why oxygen is vital for aerobic respiration. NAD⁺ and FAD are electron carriers, cytochrome c a component.

Explanation:
The cell cycle consists of interphase (G1, S, G2) and M phase. DNA synthesis or replication occurs during the S (synthesis) phase, resulting in each chromosome having two sister chromatids. G1 is for cell growth and RNA/protein synthesis; G2 is for preparation for mitosis. M phase includes mitosis and cytokinesis. Accurate DNA replication in S phase is crucial for genetic continuity.

Explanation:
Amylase (ptyalin in saliva, pancreatic amylase in intestine) hydrolyzes starch (a polysaccharide) into maltose (a disaccharide) and dextrins. Lactase breaks lactose, lipase digests lipids, protease digests proteins. Salivary amylase works at neutral pH, pancreatic amylase in the small intestine. Maltase then breaks maltose into two glucose molecules.