Proteins and Their Structures

Proteins

• Macromolecules built from amino acid monomers
• Essential components of cells and tissues
• Water-soluble and large in size
• High molecular weight
• Continuous amino acid supply is necessary for protein synthesis
• Dietary protein is crucial for meeting the body’s amino acid demands

Primary Structure

• Amino acids link through peptide bonds
• Two amino acids form a dipeptide
• Longer chains of amino acids create polypeptides
• The protein’s specific number and sequence of amino acids determines its unique folding pattern.

Fibrous Proteins

• Form elongated structures
• Function as structural and protective components

Globular Proteins

• Compact, spherical structures
• Soluble in water or polar solvents
• Involved in cellular functions

Heteroproteins

• Composed of amino acids combined with other compounds:
  • Glycoproteins: Amino acids + carbohydrates
  • Lipoproteins: Amino acids + lipids
  • Phosphoproteins: Amino acids + phosphates
  • Chromoproteins: Amino acids + pigments
  • Nucleoproteins: Amino acids + nucleic acids

Secondary Structure

• α-Helix: Coils around itself, facilitated by hydrogen bonds between amino acids, forming a helix-like structure
• β-Sheet: Takes on a folded sheet appearance

Tertiary Structure

• Combines amino acid sequences and secondary structures (α-helix and β-sheet)

Functions of Proteins

• Structural: Provide form and support (e.g., collagen in tissues, elastin, keratin)
• Transport: Carry oxygen to cells, transport iron (e.g., hemoglobin)
• Defensive: Strengthen the immune system
• Enzymatic: Accelerate chemical reactions
• Motor: Myosin and actin regulate muscle movements
• Regulatory: Histones and cyclins

Nucleic Acids

• Transmit hereditary information, determining the proteins produced by a cell
• DNA (deoxyribonucleic acid)
• RNA (Ribonucleic acid)
• Polymers constructed from long chains of nucleotide molecules

DNA Structure

• Double helix structure
• Composed of the bases adenine, guanine, cytosine, and thymine
• Guanine pairs with cytosine
• Adenine pairs with thymine
• Connected through hydrogen bonds

Proteins

• Large molecules made from amino acids
• Essential for structure, function, and regulation of cells and tissues
• Soluble in water

Amino Acid Chains

• Amino acids linked by peptide bonds
• Two amino acids = dipeptide
• Longer chains = polypeptide
• Specific amino acid sequence determines protein shape and function

Protein Structures

• Primary Structure: Sequence of amino acids
• Secondary Structure: Folding patterns within the polypeptide chain:
  • Alpha helix: Coiled shape due to hydrogen bonds
  • Beta sheet: Folded sheet structure
• Tertiary Structure: Overall 3D shape of the protein, determined by interactions between amino acids and the environment
• Quaternary Structure: Multiple polypeptide chains interacting to form a functional protein

Protein Types

• Fibrous Proteins: Elongated, structural and protective (e.g., collagen, keratin)
• Globular Proteins: Compact, spherical, involved in cellular processes (e.g., enzymes, antibodies)
• Heteroproteins: Composed of amino acids and other molecules:
  • Glycoproteins: Carbohydrates
  • Lipoproteins: Lipids
  • Phosphoproteins: Phosphates
  • Chromoproteins: Pigments
  • Nucleoproteins: Nucleic acids

Functions

• Structural: Provide support and shape
• Transport: Carry molecules throughout the body
• Defensive: Immune system components
• Enzymatic: Catalyze chemical reactions
• Motor: Movement and contraction
• Regulatory: Control cellular processes

Nucleic Acids

• Carry genetic information and direct protein synthesis
• DNA: Deoxyribonucleic acid
• RNA: Ribonucleic acid
• Polymers composed of nucleotides

DNA Structure

• Double helix structure:
  • Two strands of nucleotides twisted around each other
  • Bases pair: Adenine (A) with Thymine (T), Guanine (G) with Cytosine (C)
  • Hydrogen bonds connect base pairs
• Contains genetic code for protein synthesis
• Located in the nucleus of cells

RNA Structure

• Single strand of nucleotides
• Uses Uracil (U) instead of Thymine (T)
• Involved in protein synthesis and other cellular processes

This quiz covers the essential components of proteins, including their macromolecular structure and functions. Learn about the primary structure, fibrous proteins, globular proteins, and heteroproteins. Test your knowledge on how these molecules interact within biological systems.