Proteins and Their Functions Class

Types of Proteins

• Collagen: Provides structural support in connective tissues.
• Actin and Myosin: Key proteins in muscle contraction.
• Keratin: Structural protein found in hair, nails, and skin.
• Antibodies: Function as protection proteins; serve as natural defense mechanisms.
• Enzymes: Catalytic proteins that accelerate biochemical reactions.
• Hormones: Chemical messengers that regulate organ and tissue functions through body fluids.

Classification of Proteins by Shape

• Fibrous Proteins: Composed of elongated polypeptide chains, offering structural support (e.g., collagen, keratin).
• Globular Proteins: Spherical proteins, commonly involved in metabolic functions (e.g., enzymes, antibodies).

Peptide Bonds

• Formed through covalent bonding between amino acids.
• Link two amino acids as dipeptides, three as tripeptides, and four as tetrapeptides; longer chains referred to as polypeptides.
• Structure organization ranges from oligopeptides (few amino acids) to polypeptides (many amino acids).

Naming Peptides

• Initiate naming from N-terminal end.
• Modify the first amino acid's ending to '-yl' while maintaining the name of the C-terminal end amino acid.

Characteristics of Peptide Bonds

• Exhibits a partial double bond character, resulting in restricted rotation around the C-N bond.

Characteristics of Amino Acids

• Optical Activity: Dextrorotatory (right) or Levorotatory (left) movement of polarized light.
• Amphoteric Nature: Can act as both acids (COOH) and bases (NH2).
• Zwitterion Formation: Contains both positive and negative charges; COOH can donate a proton, while NH3 accepts it.
• Isoelectric Point: pH at which the zwitterion form is maximized.

Classification of Amino Acids by R-Group

• Neutral Amino Acids: Equal amino and carboxyl groups (e.g., Glycine, Alanine).
• Branched Chain Amino Acids (BCAAs): Have side chains with a central carbon (e.g., Valine, Leucine).
• Acidic Amino Acids: Possess negatively charged R-groups (e.g., Glutamic acid).
• Basic Amino Acids: Feature positively charged R-groups (e.g., Lysine, Arginine).
• Aromatic Amino Acids (Non-polar): Hydrophobic, engage in hydrophobic interactions (e.g., Phenylalanine, Tyrosine).
• Sulfur-containing Amino Acids: Nonpolar, feature a sulfur atom (e.g., Methionine, Cysteine).
• Hydroxy-containing Amino Acids: Exhibit aliphatic hydroxyl groups (e.g., Serine, Threonine).
• Imino Acids: Related to amino acids with a distinct structural difference (e.g., Proline).

R-Group Classification by Polarity

• Aliphatic (Non-polar): Hydrophobic properties (e.g., Glycine, Alanine).
• Polar, Uncharged: More hydrophilic due to functional groups (e.g., Serine, Cysteine).

Classification of Amino Acids by Nutritional Importance

• Essential Amino Acids: Nine amino acids that must be obtained from diet due to inability to be synthesized by the body.
• Non-Essential Amino Acids: Synthesized by the body, not strictly dietary (e.g., Alanine).
• Conditional Amino Acids: Generally non-essential but required during illness or stress.

General Characteristics of Proteins

• Proteins are macromolecules made of amino acids connected by peptide linkages.
• Derived from the Greek word "proteios," meaning "of first importance."
• Vital for the structure, function, and regulation of body's tissues and organs.

Explore the various types of proteins and their essential roles in the body. This quiz covers structural proteins, defense proteins, catalytic proteins, and chemical messengers. Delve into the classification based on conformation and shape to deepen your understanding of protein functions.