Answer:
a) ATP synthase is a molecular machine. This enzyme (protein) is in charge of
making ATP and is used by prokaryotes and eukaryotes. The fact that the same enzyme appears in both groups creates a relationship because the easiest way this could happen is by eukaryotes acquiring this mechanisms from prokaryotes. It is believed that in fact this happened through a process known as endosymbiosis, in which prokaryotic cells engulf other cells establishing a symbiotic relationship. After millions of years it eventually became 1 organism.
b) Since ATP synthase is a type of protein one could expect that the amino acid sequence that creates this enzyme should be similar between prokaryotes and eukaryotes and supporting the idea that eukaryotes evolved from prokaryotes.
