carbon represents less than 1% of the earth's crust, but is 18% of the composition of living things. why? question 3 options: living organisms sequester carbon to lower its toxicity to their cells. cytoplasm is composed largely of a liquid form of carbon. cell membranes are composed of layers of graphite. the unique bonding properties of carbon allow it to create a huge variety of biological molecules. this is a measure of waste gases like co2 and ch4.