📘 Protein Structure and Function – Expanded Summary Notes
🔬 1. Introduction to Proteins
Proteins are fundamental biological macromolecules composed of amino acid chains.
They are involved in nearly every cellular process, including:
Structural roles (e.g. collagen in connective tissue)
Catalytic activity (enzymes like DNA polymerase)
Transport (hemoglobin carrying oxygen)
Communication (hormones like insulin)
Defense (antibodies in the immune system)
Movement (actin and myosin in muscle contraction)
Key Concept: The functionality of a protein is directly dependent on its 3D structure,
which is determined by its amino acid sequence (primary structure).
🧩 2. Structure–Function Relationship in Proteins
Proteins are asymmetrical molecules that fold into unique three-dimensional shapes.
This asymmetry and specificity allow proteins to perform specialized tasks.
Proteins with very different amino acid sequences can adopt similar 3D folds,
highlighting the evolutionary conservation of essential structural motifs.
Structure governs:
o Substrate specificity in enzymes
o Ligand binding in receptors
, o Mechanical strength in structural proteins
A change in structure—due to mutation, denaturation, or misfolding—can lead to loss of
function or disease.
🫁 3. Hemoglobin vs Myoglobin – Oxygen Binding Proteins
Hemoglobin (Hb):
Structure: A tetramer (4 polypeptide chains – 2 alpha, 2 beta)
Function: Transports oxygen from lungs to tissues
Cooperativity: Binding of O₂ to one subunit enhances binding to others
Oxygen Binding Curve: Sigmoidal, due to cooperative binding
Myoglobin (Mb):
Structure: Monomer (single polypeptide chain)
Function: Stores oxygen in muscle tissues
Affinity: High oxygen affinity even at low O₂ concentrations
Oxygen Binding Curve: Hyperbolic, no cooperativity
Biological Implication: Hb is tuned for oxygen delivery, while Mb is optimized for
oxygen storage.
🔄 4. Cooperativity in Hemoglobin: The Key to Efficient Oxygen Transport
T (tense) state: Low O₂ affinity
R (relaxed) state: High O₂ affinity
🔬 1. Introduction to Proteins
Proteins are fundamental biological macromolecules composed of amino acid chains.
They are involved in nearly every cellular process, including:
Structural roles (e.g. collagen in connective tissue)
Catalytic activity (enzymes like DNA polymerase)
Transport (hemoglobin carrying oxygen)
Communication (hormones like insulin)
Defense (antibodies in the immune system)
Movement (actin and myosin in muscle contraction)
Key Concept: The functionality of a protein is directly dependent on its 3D structure,
which is determined by its amino acid sequence (primary structure).
🧩 2. Structure–Function Relationship in Proteins
Proteins are asymmetrical molecules that fold into unique three-dimensional shapes.
This asymmetry and specificity allow proteins to perform specialized tasks.
Proteins with very different amino acid sequences can adopt similar 3D folds,
highlighting the evolutionary conservation of essential structural motifs.
Structure governs:
o Substrate specificity in enzymes
o Ligand binding in receptors
, o Mechanical strength in structural proteins
A change in structure—due to mutation, denaturation, or misfolding—can lead to loss of
function or disease.
🫁 3. Hemoglobin vs Myoglobin – Oxygen Binding Proteins
Hemoglobin (Hb):
Structure: A tetramer (4 polypeptide chains – 2 alpha, 2 beta)
Function: Transports oxygen from lungs to tissues
Cooperativity: Binding of O₂ to one subunit enhances binding to others
Oxygen Binding Curve: Sigmoidal, due to cooperative binding
Myoglobin (Mb):
Structure: Monomer (single polypeptide chain)
Function: Stores oxygen in muscle tissues
Affinity: High oxygen affinity even at low O₂ concentrations
Oxygen Binding Curve: Hyperbolic, no cooperativity
Biological Implication: Hb is tuned for oxygen delivery, while Mb is optimized for
oxygen storage.
🔄 4. Cooperativity in Hemoglobin: The Key to Efficient Oxygen Transport
T (tense) state: Low O₂ affinity
R (relaxed) state: High O₂ affinity
