Structure of Proteins

Page 1

Title: Structure of Proteins

  • Authors: Aure, Mhon Arcel D.R. & Remandaban, Jayzelle C.

  • Introduction to the basic structure of proteins.

Page 2

Introduction to Proteins

  • What are Proteins?

    • Vital macronutrient composed of amino acids.

    • Serve as building blocks for cells, tissues, and organs.

  • Importance of Proteins:

    • Essential for biological processes.

    • Aid in building and repairing tissues.

    • Maintain energy levels and support a healthy immune system.

    • Major component of bones, muscles, cartilage, and skin.

    • Hair and nails are primarily composed of protein.

  • Examples of Protein Sources:

    • Fish, seafood, skinless white-meat poultry, lean beef (tenderloin, sirloin, eye of round), skim or low-fat milk, skim or low-fat yogurt, fat-free or low-fat cheese, eggs.

Page 3

Protein Structure Overview

  • Peptide Bonds:

    • Proteins are formed by the condensation of amino acids.

  • Levels of Protein Structure:

    • Primary Structure, Secondary Structure, Tertiary Structure, Quaternary Structure.

Page 4

Detailed Protein Structures

  • Primary Structure:

    • Exact ordering of amino acids in a chain.

  • Secondary Structure:

    • Local folded structures (α-helix and β-pleated sheet) formed by interactions among backbone atoms.

  • Tertiary Structure:

    • Arrangement of secondary structures and further folding.

  • Quaternary Structure:

    • Spatial arrangement of various tertiary structures, formed by multiple polypeptide chains (sub-units).

Page 5

Amino Acids: Building Blocks of Proteins

  • List of Key Amino Acids:

    1. Alanine

    2. Arginine

    3. Asparagine

    4. Aspartic Acid

    5. Cysteine

    6. Glutamic Acid

    7. Glutamine

    8. Glycine

    9. Histidine

    10. Isoleucine

    11. Leucine

    12. Lysine

    13. Methionine

    14. Phenylalanine

    15. Proline

    16. Serine

    17. Threonine

    18. Tryptophan

    19. Tyrosine

    20. Valine

Page 6

Structure of an Amino Acid

  • Three Important Parts:

    1. α-Carboxyl Group (-COOH)

    2. α-Amino Group (-NH2)

    3. Side Chain (R Group)

      • Unique group of atoms attached to the center carbon atom (α-carbon).

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Classification of Amino Acids

  • Amino acids are classified based on the properties of their R-groups:

    • Nonpolar (Hydrophobic)

    • Polar (Uncharged)

    • Positively Charged (Basic)

    • Negatively Charged (Acidic)

    • Aromatic

Page 8

Essential vs. Non-Essential Amino Acids

  • Essential Amino Acids (EAAs):

    • Cannot be produced by the human body.

  • Non-Essential Amino Acids (NEAAs):

    • Can be produced by the human body.

  • Semi-Essential Amino Acids (SEAA):

    • Conditional amino acids involved in various bodily functions (e.g., Lysine, Cysteine, Tyrosine).

Page 9

Secondary Protein Structures

  • Folding of Polypeptide Chains:

    • Occurs due to interaction between amine and carboxyl groups.

    • Can exist in structures such as α-helix and β-pleated sheet.

  • Hydrogen Bonding:

    • Key factor in holding secondary structures together.

  • Local Folds:

    • Simplified sections of polypeptide chain exhibiting unique shapes (spirals, loops).

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Types of Secondary Structures

  • α-Helix:

    • Twisted right-handed screw, each amino acid residue hydrogen-bonded to adjacent turn of the helix.

  • β-Pleated Sheet:

    • Polypeptide chains laid side by side, held together by intermolecular hydrogen bonds.

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Role of Secondary Structures

  • Functionality of Secondary Structures:

    • Stability of protein structure.

    • Flexibility allowing conformational changes.

    • Creation of binding sites for substrates.

    • Formation of channels and pores for molecular transport.

    • Support for structural proteins.

Page 12

Tertiary Structure of Proteins

  • Overall Folding:

    • Arises from secondary structure folding.

  • Stabilizing Forces:

    • Hydrogen bonds, electrostatic forces, disulfide linkages, van der Waals forces.

  • Shapes of Tertiary Structures:

    • Fibrous and globular forms.

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Types of Bonds in Protein Folding

  • Key Bonds:

    • Hydrogen Bonds

    • Ionic Bonds

    • Disulfide Bonds

    • Hydrophobic Interactions

    • Van der Waals Forces

Page 14

Protein Stability

  • Stability depends on the effectiveness of interactions keeping the structure intact.

  • Factors Disrupting Stability:

    • Heat

    • pH changes

    • Chemical Exposure

Page 15

Clinical Connection: Misfolding Disorders

  • Types of Disorders:

    • Alzheimer’s Disease:

      • Misfolded beta-amyloid proteins cause memory loss.

    • Parkinson’s Disease:

      • Misfolded alpha-synuclein proteins damage nerve cells.

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More Misfolding Disorders

  • Huntington’s Disease:

    • Genetic mutation causes incorrect protein folding, leading to brain cell death.

  • Cystic Fibrosis:

    • Misfolded CFTR protein results in thick mucus buildup in the lungs.

  • Prion Diseases (e.g., Mad Cow Disease):

    • Infectious misfolded proteins spread and damage the brain.

Page 17

Conclusion

  • Thank You for Listening!

  • Overview of protein structure concluded.