Study Guide

Biomolecules and the Chemistry of Life - Test Your Knowledge!

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Test Your Knowledge!

Chemistry Questions

  1. Potassium (K) has an atomic number of 19. How many protons does it have? How many electrons does it have? 

  2. Magnesium (Mg) has two electrons in its outer shell, which can hold up to eight electrons. In its ion form, therefore, Mg has a charge of +2 since it loses both of those outer electrons. If Mg2+ binds with chlorine ions (Cl-), what will the ratio between them be? 

  3. If two nitrogen atoms want to form a covalent bond, how many pairs of electrons will they need to share? Hint: each nitrogen atom has five electrons in its outer shell, but desires eight. 

  4. Stomach acid has a pH number around 1. Lemon juice has a pH number around 2. Stomach acid is _______ times as acidic as lemon juice. 

Biological Molecules Questions

  1. What is the monomer of a polypeptide chain? What is the monomer of a polysaccharide?

  2. What are the three kinds of lipids? How do their structures differ? 

  3. List three differences between DNA and RNA. 

  4. Which biomolecules can be used for structural support?

Chemistry Answers

  1. Answer: Potassium has 19 protons and 19 electrons. How were you supposed to know that? A quick peek at the periodic table should help you out.

  2. Answer: One magnesium ion will bind with two chloride ions to balance the charge. This comes out to a ratio of 1:2. The compound formula is MgCl2.

  3. Answer: The two nitrogen atoms will share three pairs of electrons in a triple covalent bond.

  4. Answer: Because differences in whole number pH units are tenfold, stomach acid is ten times as acidic as lemon juice.

Biological Molecules Answers

  1. Answer: The monomer of a polypeptide chain is an amino acid. The monomer of a polysaccharide is a monosaccharide.

  2. Answer: The three kinds of lipids are: i) fats, oils, and waxes, where three fatty acids bind to a glycerol; ii) phospholipids, where two fatty acids and a phosphate group bind to a glycerol; and iii) steroids, where four carbon rings stick together.

  3. Answer: Three differences between DNA and RNA are that DNA is i) double-stranded, ii) has thymine instead of uracil as a base, and iii) is the molecule of heredity. RNA is i) single-stranded, ii) has uracil instead of thymine as a base, and iii) is involved in protein synthesis.

  4. Answer: Carbohydrates and proteins are the biomolecules that can be used for structural support.

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