Why is freezing water extremely biologically relevant?

The following image is of a diatom. it lives in water and gets food from photosynthesis. it is encased in a hard shell made of something similar to glass or sand . a diatom is a(n) because it has a) multi-celled organism; specialized parts. b) vertebrate; a skeleton. c) insect; an exoskeleton. d) single-called organism; only one cell.

What is the answer for the complicated molecules that make up living things usually contain carbon. why is carbon so important in these molecules?

Which part of cellular respiration must occur before any of the other steps can occur