Proteins and Nucleic Acids: Structure, Function, and Biological Information

Proteins: Structure and Function

Amino Acids: Building Blocks of Proteins

Proteins are polymers made from amino acids, which are organic molecules containing both an amino group and a carboxyl group. The sequence and properties of amino acids determine protein structure and function.

• Amino Acid Structure: Each amino acid has a central carbon (alpha carbon) bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable side chain (R group).

• Peptide Bonds: Amino acids are linked by peptide bonds formed through dehydration synthesis between the carboxyl group of one amino acid and the amino group of another.

• Polypeptides: Chains of amino acids linked by peptide bonds are called polypeptides; proteins may consist of one or more polypeptide chains.

• Side Chains: The R group determines the chemical nature (polar, nonpolar, acidic, basic) of each amino acid.

Example: Hemoglobin is a protein composed of multiple polypeptide chains, each with a specific sequence of amino acids that enables oxygen transport.

Levels of Protein Structure

• Primary Structure: The linear sequence of amino acids in a polypeptide.

• Secondary Structure: Local folding patterns such as alpha helices and beta sheets, stabilized by hydrogen bonds.

• Tertiary Structure: The overall three-dimensional shape of a polypeptide, determined by interactions among R groups.

• Quaternary Structure: The association of multiple polypeptide chains into a functional protein complex.

Additional info: Protein structure is critical for biological function; misfolded proteins can lead to diseases such as Alzheimer's.

Nucleic Acids: Storage and Transmission of Hereditary Information

Nucleic Acid Structure

Nucleic acids are polymers of nucleotides, which store and transmit genetic information in cells.

• Nucleotide Structure: Each nucleotide consists of a five-carbon sugar (ribose or deoxyribose), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, guanine, or uracil).

• Phosphodiester Bonds: Nucleotides are linked by phosphodiester bonds between the phosphate group of one nucleotide and the sugar of the next.

• Polynucleotide Chains: Nucleic acids (DNA and RNA) are long chains of nucleotides.

Example: DNA is the genetic material in most organisms, while RNA plays roles in protein synthesis and gene regulation.

DNA vs. RNA: Comparison

DNA and RNA differ in structure, function, and types of nitrogenous bases.

Feature	DNA	RNA
Strands	Double-stranded	Single-stranded
Sugar	Deoxyribose	Ribose
Bases	A, T, C, G	A, U, C, G
Function	Genetic information storage	Protein synthesis, gene regulation

Additional info: DNA's double helix structure is stabilized by hydrogen bonds between complementary bases (A-T, C-G).

Chargaff's Rule

• Base Pairing: In DNA, the amount of adenine (A) equals thymine (T), and the amount of cytosine (C) equals guanine (G).

• Formula: $[A] = [T]$ and $[C] = [G]$

Genomics and Proteomics: Biological Inquiry and Applications

Genomics

Genomics is the study of whole sets of genes and their interactions within and between species.

• Human Genome Project: Sequencing and mapping all human genes to understand genetic diseases and evolution.

• Bioinformatics: Use of computational tools to analyze and compare genetic data.

Proteomics

Proteomics involves the large-scale study of proteins, their structures, and functions.

• Applications: Identifying protein functions, understanding disease mechanisms, and developing new therapies.

Recap: Macromolecules in Biology

Macromolecule	Examples	Functions
Proteins	Enzymes, hemoglobin, antibodies	Catalyze reactions, transport, defense, structure
Nucleic Acids	DNA, RNA	Store and transmit genetic information

Additional info: Other macromolecules include carbohydrates (energy storage, structure) and lipids (membranes, energy storage).