Biology Pre Lab - Macromolecules

Lab 5: The Chemistry of Life

Pre-Lab Questions

1. Nitrogen fixation is a natural process by which inert or unreactive forms of nitrogen are transformed into usable nitrogen. Why is this process important to life?

Answers: Nitrogen fixation, natural and synthetic, is a process of combining atmospheric nitrogen with other elements to form useful compounds, which is relatively inert. It is important for all forms of life because most organisms cannot use nitrogen that is not combined with other elements. Nitrogen is required for DNA, RNA and protein and all amino acids contain nitrogen. Nitrogen is fixed naturally by some micro-organism and by lighting. Nitrogen is important to the continuation of life on earth. Fixed, or combined, nitrogen is also necessary for the manufacture of many substances, including explosive and commercial fertilizer.

2. Given what you have learned about the hydrogen bonding shared between nucleic acids in DNA, which pair is more stable under increasing heat: adenine and thymine, or cytosine and guanine? Explain why.

Answer: Cytosine (C) and guanine (G) are more stable under increasing heat because C and G have three hydrogen bonds whereas Adenine (A) and Thymine (T) have only two Hydrogen bonds. The more hydrogen bonds there are the more stable the nucleotides are. Greater bond stability requires more heat energy to dissociate the bonds, and since G≡C have more hydrogen bonds than A=T, they are consequently more stable under increasing heat.

3. Which of the following is not an organic molecule; Methane (CH4), Fructose (C6H12O6), Rosane (C20H36), or Ammonia (NH3)? How do you know?

Answer: Methane (CH4), Fructose (C6H12O6) and Rosane (C20H36) are organic molecules since they have the presence of carbon, which carbon is a building block of all organic molecules. Ammonia (NH3) is not an organic molecule because it has nitrogen and hydrogen in it but does not contain carbon and would be considered an inorganic molecule.

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