Which substances are responsible for accelerating chemical reactions in cells?
amino acids
enzymes
nucleic acids
lipids

Correct B). Enzymes

The enzymes are the biological catalyst that reduces the activation energy of the chemical reaction and increase the rate of the reaction without being used up in the reaction. The molecules on which the enzymes act are called as substrates and it converts the substrate into different molecules called as products.

Hence, the correct answer would be ''enzymes''.

they float because they are less dense than the water itself

something denser than water, like a rock, will sink to the bottom