Test Your Knowledge!
- Potassium (K) has an atomic number of 19. How many protons does it have? How many electrons does it have?
- Magnesium (Mg) has 2 electrons in its outer shell, which can hold up to 8 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?
- 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.
- 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
- What is the monomer of a polypeptide chain? What is the monomer of a polysaccharide?
- What are the three kinds of lipids? How do their structures differ?
- List three differences between DNA and RNA.
- Which biomolecules can be used for structural support?
- 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.
- 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.
- Answer: The two nitrogen atoms will share three pairs of electrons in a triple covalent bond.
- Answer: Because differences in whole number pH units are tenfold, stomach acid is 10 times as acidic as lemon juice.
Biological Molecules Answers
- Answer: The monomer of a polypeptide chain is an amino acid. The monomer of a polysaccharide is a monosaccharide.
- 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.
- 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.
- Answer: Carbohydrates and proteins are the biomolecules that can be used for structural support.
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