Myoglobin_default

Midterm Exam Overview

• Recordings Available: Two tutorial recordings posted covering material for midterm (Chapters 1-5).

• Session Purpose: Next session will be a Q&A about exam content; expect discussion on key topics.

• Exam Details:

  • Date: Next Saturday, 1:00 PM

  • Location: Health Science 1150 or Arts 143

  • Format: 50 multiple choice questions, reflecting lecture emphasis.

Key Topics for Midterm

• Distribution of Questions:

  • Chapter 1 will have minimal emphasis.

  • Expect at least 3 questions on amino acids; approximately 8 on titration curves.

Structural Proteins

• Silk Structure:

  • Primary Structure: Repeats of glycine and alanine.

  • Secondary Structure: Formation of beta sheets.

  • Importance: Combines strength and flexibility via hydrogen bonds in a three-dimensional arrangement.

• Non-Covalent Interactions:

  • Hydrogen bonds contribute to the flexibility and packing (van der Waals and hydrophobic interactions).

Protein Folding Paradigm

• Discussion of challenges to the paradigm that one polypeptide folds into one specific conformation.

• Prion Diseases Context:

  • Examples: Alzheimer’s, ALS.

  • Book Recommendation: "Fatal Flaws" by Jay Ingram.

Chapter Five: Oxygen Transport

• Core Concept: Understanding protein structure and function using oxygen transport as a vehicle.

• Protein Dynamics:

  • Proteins display dynamic structures and can adopt multiple conformations.

  • Ligand-biding specificity is crucial.

  • Induced Fit Mechanism: Binding of ligands alters protein conformation, illustrated through hemoglobin and 2,3-bisphosphoglycerate interactions.

Biological Demand for Oxygen

• Metabolism requires oxygen for energy production.

• Larger organisms face a challenge in oxygen transport to cells further from lungs.

  • Example: Study indicates that increased atmospheric oxygen may correlate with larger insect sizes.

Hemoglobin and Myoglobin

• Hemoglobin:

  • Quaternary structure with four subunits, binds up to four oxygen molecules.

  • Dynamic affinity towards oxygen depending on the state (T state: low affinity; R state: high affinity).

• Myoglobin:

  • Tertiary structure, binds a single oxygen molecule with high affinity, primarily located in muscles.

  • P50 value for myoglobin is around 3 Torr; higher affinity than hemoglobin (P50 ~30 Torr).

Oxygen Binding Curves

• Hemoglobin exhibits cooperative binding; sigmoidal curve indicates that once one oxygen binds, it is easier for others to bind.

• Myoglobin has a hyperbolic curve since it can only bind one molecule, demonstrating high affinity even at lower oxygen pressures.

Importance of Regulation in Hemoglobin Function

• Allosteric Regulation: Hemoglobin functions as an allosteric protein; its oxygen-binding affinity can be affected by environmental factors (e.g., pH, carbon dioxide levels).

  • Allosteric Effectors:

    • Activators: Increase oxygen affinity (e.g., oxygen itself).

    • Inhibitors: Stabilize the T state, decreasing affinity (e.g., 2,3-bisphosphoglycerate).

Key Takeaways for Exam Preparation

• Review protein structures, including polypeptides, hemoglobin, and myoglobin.

• Understand the dynamics of protein-ligand interactions and concepts of induced fit.

• Familiarize with oxygen transport mechanisms in relation to organism size.

• Be prepared to discuss allosteric regulation and its impact on protein function.