Question

1. what is the key structural difference between rna and dna? (1.6)

a. dna contains ribose sugar, while rna contains deoxyribose sugar.
b. rna contains thymine, while dna contains uracil.
c. dna is typically double - stranded, while rna is typically single - stranded.
d. rna is composed of amino acids, while dna is composed of nucleotides.

1. you are given a protein with the following amino acid sequence: methionine (nonpolar)-glycine (nonpolar)-serine (polar)-alanine (nonpolar). if an amino acid substitution occurred in this polypeptide chain, predict which would have a significant impact on the structure and function of the protein. (1.5)

a. serine is replaced by tryptophan (nonpolar).
b. glycine is replaced by alanine (nonpolar).
c. alanine is replaced by leucine (nonpolar).
d. lysine is replaced by arginine (polar).

1. nitrogen is an important element in building both: (1.2)

a. proteins and lipids
b. nucleic acids and lipids
c. proteins and nucleic acids
d. carbohydrates and proteins

1. which of the following functional groups is found in all nucleotides?

a. -cooh
b. -po4
c. -sh
d. -ch3

Explanation:

1. DNA contains deoxyribose sugar and thymine, is double - stranded, while RNA contains ribose sugar and uracil, is typically single - stranded. Option c is correct.
2. Serine is polar and its replacement by non - polar tryptophan can change the protein's structure and function due to changes in hydrophobicity and hydrogen - bonding potential. Option a is correct.
3. Proteins contain nitrogen in their amino - group and nucleic acids have nitrogen in their nitrogenous bases. Option c is correct.
4. Nucleotides have a phosphate group (-PO₄). Option b is correct.

Answer:

1. c. DNA is typically double - stranded, while RNA is typically single - stranded.
2. a. Serine is replaced by tryptophan (nonpolar).
3. c. Proteins and nucleic acids
4. b. -PO₄