Recording-2025-03-08T12:06:22.157Z

Overview of Proteins

• Proteins are essential macromolecules found in all cells, constituting approximately 50% of the dry mass of cells.

• They are crucial for dynamic functions in living organisms; life is impossible without them.

• Humans possess tens of thousands of distinct proteins, all composed of 20 different amino acids.

Protein Functions

• Major Functions of Proteins:

  • Enzymes: Proteins that accelerate chemical reactions, such as digestive enzymes that break down food into monomers.

  • Defense (Antibodies): Proteins that protect the body against diseases, e.g., COVID-19 antibodies.

  • Storage: Certain proteins store essential materials (e.g., iron).

  • Transport: Proteins transport substances across cell membranes, including charged molecules and hemoglobin for oxygen transport.

  • Hormones: Some hormones, like insulin, are proteins that regulate bodily functions.

  • Receptors: Proteins in cell membranes that detect and respond to external chemical changes.

  • Contraction/Motility: Muscle proteins (actin and myosin) that enable movement.

  • Structural: Proteins provide shape and support to cells (e.g., keratin in hair and nails, collagen in connective tissues).

  • Gene Regulation: Proteins help regulate gene expression, determining which genes are activated in cells.

Amino Acids and Protein Structure

• Building Blocks:

  • Proteins are polymers made from amino acids linked by peptide bonds.

  • There are 20 different amino acids, categorized by their side chains:

    • Nonpolar (Hydrophobic): e.g., glycine and valine.

    • Polar (Hydrophilic): e.g., serine and cysteine.

    • Charged (Ionic): e.g., acidic (negative charge) and basic (positive charge) amino acids.

Properties of Amino Acids

• Zwitterions: Amino acids can exist in a form that carries both a positive and negative charge yet is overall neutral, which can change with pH levels.

Protein Structure Levels

• Primary Structure: The specific sequence of amino acids in a protein.

• Secondary Structure: Localized folding patterns, such as alpha helices and beta sheets, held together by hydrogen bonds.

• Tertiary Structure: The overall 3D shape of a protein, determined by interactions between side chains.

• Quaternary Structure: The structure formed by multiple polypeptide chains aggregating; not all proteins exhibit this structure.

The Importance of Protein Folding

• Proper protein folding is crucial for function.

• Chaperonins assist in protein folding, ensuring proteins reach their functional conformations.

• Misfolding can lead to diseases (e.g., Alzheimer’s, Parkinson’s), highlighting the importance of correct protein conformation.

Effects on Protein Structure

• Changes in pH, temperature, or ionic strength can denature proteins, altering their shape and functionality, often irreversibly.

• Denaturation examples include cooking eggs, where egg proteins lose their structure and become opaque.

Nucleic Acids and Proteins

• Nucleic acids (DNA and RNA) encode the amino acid sequence in proteins, serving as the genetic blueprint.

• Genes within DNA direct protein synthesis through messenger RNA (mRNA), embodying the flow of genetic information (DNA > RNA > Protein).

Genomics and Proteomics

• Advances in sequencing technologies have accelerated the study of genomes and proteins, revealing vast amounts of data that require computational analysis through bioinformatics to interpret genomic differences across species.