Quiz: Amino Acids, Fatty Acids and Lipids Quiz 1
This quiz follows Lesson 3: Amino Acids, Fatty Acids and Lipids from the BIOMOLECULES course. It tests your understanding of amino acids as substituted methanes, the role of the α-carbon and R group, the twenty proteinaceous amino acids, and the classification into acidic, basic, neutral and aromatic types. You will also be tested on the zwitterionic form, fatty acids, glycerol, glycerides, fats and oils, and phospholipids.
What to expect
- 15 medium-difficulty questions on amino acids and lipids.
- Questions on glycine, alanine, serine, glutamic acid, lysine, valine, tyrosine, phenylalanine and tryptophan.
- Questions on palmitic acid, arachidonic acid, glycerol, triglycerides, lecithin and phospholipids.
- Clear explanations for every answer.
Tip: Recall that amino acids are built on a methane skeleton with four substituents: hydrogen, carboxyl, amino and the variable R group. Keep the carbon counts of palmitic acid (16) and arachidonic acid (20) in mind.
Q1. Amino acids are described in the lesson as substituted methanes because:
Amino acids are substituted methanes: the four valency positions of the methane carbon carry hydrogen, a carboxyl group, an amino group and a variable R group.
Q2. The carbon atom that carries both the amino group and the acidic group in an amino acid is called the:
The amino group and the acidic group are substituents on the same carbon, designated the α-carbon, so the molecules are called α-amino acids.
Q3. Which set correctly lists the three constant substituents on the α-carbon of an amino acid?
Three substituents are constant across the family: a hydrogen atom, a carboxyl group and an amino group. The fourth position carries the variable R group.
Q4. How many types of amino acids occur in proteins, according to the lesson?
Although many amino acids are possible because the R group can vary, those that occur in proteins are of only twenty types.
Q5. In glycine, the R group is:
When the R group is simply a hydrogen atom, the amino acid is glycine, the smallest of the set.
Q6. Alanine is the amino acid in which the R group is:
When the R group is a methyl group, the amino acid is alanine.
Q7. Serine is formed when the R group of the amino acid is:
When the R group is a hydroxymethyl group, the amino acid is serine.
Q8. Which of the following is given in the lesson as an example of an acidic amino acid?
Based on the number of amino and carboxyl groups, glutamic acid is cited as an acidic amino acid, lysine as basic and valine as neutral.
Q9. Lysine is classified in the lesson as:
The lesson classifies lysine as a basic amino acid, glutamic acid as acidic and valine as neutral.
Q10. Which group of amino acids is correctly described as aromatic?
The lesson lists tyrosine, phenylalanine and tryptophan as the aromatic amino acids.
Q11. The zwitterionic form of an amino acid arises because of the:
A particular property of amino acids is the ionizable nature of the –##\ce{NH2}## and –COOH groups, so in solutions of different pH the structure changes and the zwitterionic form appears.
Q12. Palmitic acid contains how many carbon atoms, including the carboxyl carbon?
The lesson states that palmitic acid has 16 carbons including the carboxyl carbon.
Q13. Arachidonic acid contains how many carbon atoms, including the carboxyl carbon?
Arachidonic acid has 20 carbon atoms including the carboxyl carbon.
Q14. Glycerol is described in the lesson as:
Another simple lipid is glycerol, which the lesson describes as trihydroxy propane.
Q15. Which statement about phospholipids is correct according to the lesson?
Some lipids have phosphorus and a phosphorylated organic compound in them; these are phospholipids, found in cell membranes, and lecithin is one example.