1. which elements are most abundant in living organisms?
hydrogen, carbon, calcium, potassium, oxygen, and phosphorus
oxygen, calcium, phosphorus, sodium, hydrogen, and carbon
carbon, potassium, iron, magnesium, hydrogen, and nitrogen
oxygen, nitrogen, carbon, hydrogen, sulfur, and phosphorus

2. why is carbon so abundant in living things when oxygen is the most abundant element on earth?
carbon atoms can bond with one another to make chains and cyclic structures whereas oxygen atoms cannot form chains or cyclic structures.
carbon atoms are found in compounds that are solids at room temperature whereas oxygen atoms are found in compounds that form gases
carbon atoms have lower mass than oxygen atoms, which keeps the masses of living things within desirable limits.
carbon atoms are more stable than oxygen atoms, which allows living things to have more stable compositions.

3. how is a protein different from a complex carbohydrate?
the monomers that make up a protein vary whereas the monomers that make up a complex carbohydrate are all the same.
proteins function as energy storage polymers whereas complex carbohydrates function to control rates of metabolic reactions.
proteins can be described as a linear polymer chain whereas complex carbohydrates cannot.
proteins contain very little carbon whereas complex carbohydrates contain mostly carbon.

4. suppose an alien form of life is discovered on mars. which of the following macromolecules would have to be discovered in this creature before scientists could suggest that life on earth and life on mars have similar methods for storing and transmitting genetic information?
lipid
complex carbohydrate
protein
polynucleotide

5. a sample of biological origin was analyzed for its elemental composition and found to contain only carbon and hydrogen. which type of macromolecule might it be?
polynucleotide
complex carbohydrate
lipid
protein