Chapter 6 - Proteins and Nucleic Acids

Amino Acids

Building blocks of proteins.

• A chiral carbon (a carbon bonded to 4 different things) bonded to 4 different groups: amino (-NH2), carboxyl (-COOH), a hydrogen (H) atom, and an R group (varies from protein to another)

Classification of amino acids based on side chains (R-group)

Non-polar: hydrophobic side chains (have hydrogen and carbon only)

Polar: hydrophilic but uncharged side chains (have hydrogen, carbon, AND oxygen)

Acidic: negatively charged side chains

Basic: positively charged side chains

How are polypeptides formed?

Amino acids are linked together through peptide bonds.

• These peptide bonds are formed through dehydration synthesis (a water is removed) and involve the carboxyl group of an amino acid reacting with the amino group of another.

Levels of protein structure (4)

1. Primary: linear sequence of amino acids

2. Secondary: regular structures like alpha-helices and beta-pleated sheets are stabilized by hydrogen bonds.

3. Tertiary: 3D shape due to interaction between side chains (R groups of amino acids)

4. Quaternary: association of multiple polypeptide subunits.

Nucleic Acids

DNA and RNA

Nucleotides

Building blocks (monomers) of nucleic acids (DNA and RNA).

Composed of a phosphate group, a five-carbon sugar, and a nitrogenous base.

DNA vs RNA function

DNA: stores genetic information.

RNA: translates genetic information into proteins.

Five-carbon (pentose) sugar in DNA vs RNA.

DNA: Five-carbon sugar is deoxyribose. Has an extra -H on ‘2 carbon

RNA: Five-carbon sugar is ribose. Has an extra -OH on the ‘2 carbon.

Polynucleotides

Nucleotides bonded together.

• Bonded through phosphodiester bonds.

  • the 3’ hydroxyl group of the sugar of a nucleotide interacts with the 5’ phosphate group of another nucleotide.