3. Structures of Amino Acids, Peptides, and Proteins

MIT OpenCourseWare・2 minutes read

Lecture focused on proteins, amino acids, peptides, and lipids, discussing lipid structure, membrane permeability, and amino acid properties affecting protein functions, highlighting the significance of understanding collagen structure for disease prevention.

Insights

  • Lipids are molecules rich in carbon-carbon and carbon-hydrogen bonds, which can be hydrophobic or amphipathic, forming semi-permeable membranes with hydrophobic and hydrophilic components. Membranes allow the passage of small hydrophobic molecules but require active mechanisms for charged or large molecules, showcasing the intricate nature of lipid structures and their role in cellular function.
  • Proteins are complex molecules made up of amino acids, with unique properties dictated by their side chains and structures. The order of amino acids in proteins determines their functions, with secondary structures like alpha helices and beta sheets forming distinct patterns. Protein folding, involving maximizing non-covalent forces for stability, can be computationally simulated to understand the thermodynamic interactions leading to stable structures, emphasizing the critical role of protein structure in biological processes and disease prevention.

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Recent questions

  • What are the building blocks of proteins?

    Amino acids

  • How do lipids contribute to cell membranes?

    Form semi-permeable barriers

  • What is the significance of protein folding?

    Maximizes stability through non-covalent forces

  • What are the common secondary structures in proteins?

    Alpha helix and beta sheet

  • How do genetic defects in collagen impact human health?

    Lead to collagenopathies like brittle bone syndrome

Related videos

Summary

00:00

Proteins, Lipids, and Amino Acids Explained

  • Lecture on proteins, focusing on amino acids, peptides, and lipids
  • Lipidic molecules rich in carbon-carbon and carbon-hydrogen bonds
  • Lipids can be hydrophobic or amphipathic
  • Phospholipid structure includes long chain fatty acids attached to glycerol
  • Fatty acids can be saturated (no double bonds) or unsaturated (with double bonds)
  • Double bonds in lipids can be trans or cis, affecting shape
  • Phospholipids form semi-permeable membranes with hydrophobic and hydrophilic components
  • Membranes allow passage of small hydrophobic molecules but need active mechanisms for charged or large molecules
  • Membranes are self-healing, closing holes made by poking
  • Amino acids are building blocks of proteins, with different properties based on side chains and structures

15:12

Amino acids and proteins: structure and function

  • Lysine's amine is likely charged, while arginine's quanidinium group is charged.
  • Histidine and side chains with carboxylate are negatively charged.
  • Amino acids with polar uncharged side chains exist.
  • Polymers of amino acids are heteropolymers with a defined sequence.
  • Proteins' functions are dictated by the order of amino acids.
  • Glycine, proline, and cysteine are unique amino acids with distinct properties.
  • Amino acids are assembled in a unique linear polymer of defined order.
  • Peptides are shorter sequences of amino acids.
  • Peptide bonds have restricted rotation, influencing protein tertiary structure.
  • Protein folding involves maximizing non-covalent forces for stability.

31:08

Protein Structures: From Bonds to Folds

  • Secondary structure in proteins is formed by interactions between peptide bonds in the peptide backbone.
  • The alpha helix is a common secondary structure in proteins, formed by hydrogen bonding in the peptide backbone.
  • Another secondary structure is the anti-parallel beta sheet, where stretched out strands of peptides align in the folded structure.
  • Beta turns are another secondary structure element where the peptide sequence goes through a chain reversal.
  • Proteins fold hierarchically, starting with elements of secondary structure like helices and turns.
  • Tertiary structure in proteins involves interactions between side chains of amino acids and the backbone, like electrostatic and hydrophobic forces.
  • Protein folding can be computationally simulated to understand the thermodynamic interactions that lead to stable structures.
  • Proteins can have complex structures with combinations of secondary structures like alpha helices and beta sheets.
  • Quaternary structure involves multiple units of folded motifs coming together through non-covalent forces.
  • Collagen is a structural protein that provides mechanical support for tissues, a topic to be covered in the next class.

46:09

Collagen: Key Protein in Bone Health

  • Collagen is the most abundant protein in the human body, serving as a structural protein in various body parts like bone, tendon, and cartilage, each with subtle mechanical differences to suit their functions.
  • A single amino acid change in collagen's primary sequence can lead to structural destabilization, causing collagenopathies like osteogenesis imperfecta, also known as brittle bone syndrome, where bones are fragile and prone to breaking easily.
  • Collagen's tertiary structure consists of a polyproline helix forming a three-helix bundle, which then combines into fibrils and bundles to create the macromolecular collagen structure, with genetic defects propagating through all strands.
  • Genetic defects in collagen, like a glycine to alanine change, can lead to structural bulges and decreased mechanical stability, resulting in weakened bones due to improper collagen formation, highlighting the importance of understanding collagen structure for disease prevention.
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