Biological Processes and Metabolism Study Notes

Chapter 1: Introduction

• Topics Discussed:

  • Electricity in biological systems

  • Importance of charge difference across membranes

• Definitions:

  • Charge Difference: Refers to the disparity of charged particles, leading to an electrochemical gradient.

  • Electrochemical Gradient: Essentially combines chemical and electrical gradients.

• Key Points:

  • Membrane Charges:

  • High concentration of positively charged molecules outside (e.g., Na⁺)

  • Low concentration inside or high concentration of negatively charged ions (e.g., K⁻)

  • Diffusion of Particles/Ions:

  • Particles tend to diffuse down their electrochemical gradient due to concentration and electrical charges.

• Electrochemical Gradients:

  • Chemical Gradient (defined by concentration):

  • Molecules diffuse from high to low concentration.

  • Electrical Gradient:

  • Moves from areas of high charge concentration to low charge concentration.

• Example Situation:

  • Diffusion of positively charged molecules towards negative areas within the cell.

• Interaction of Electric and Chemical Gradients:

  • Sometimes chemical gradients counteract electrical gradients requiring different transport mechanisms (e.g., coupled transport).

• Electrogenic Pump:

  • A carrier protein that generates a membrane potential.

  • Example: Sodium-Potassium Pump (Na⁺/K⁺):

  • Pumps Na⁺ out and K⁺ into the cell, leading to a high positive charge outside, and negative inside.

• Cotransport:

  • Cooperative transport of two molecules simultaneously.

  • Example: Proton pump pumps H⁺ ions (active transport) with sucrose following (secondary transport).

  • Requires energy from ATP.

Chapter 2: Cool Chemical Gradient

• Facilitated Diffusion:

  • Passive transport does not require energy.

• Active Transport:

  • Energy-requiring transport involved in moving ions across membranes.

• Highlighting Ion Transport:

  • The electrochemical gradient drives diffusion processes primarily involving ions.

• Endocytosis and Exocytosis:

  • Process for transporting large molecules into (endocytosis) and out of (exocytosis) cells.

• Exocytosis Process:

  • Molecules packaged within vesicles (formed by the Golgi apparatus) merge with cell membranes to release substances (e.g., insulin).

• Endocytosis Overview:

  • Cell membrane engulfs large molecules creating pockets, thus pulling them into the cell.

  • Types of Endocytosis:

  • Phagocytosis: Engulfing large particles through pseudopodia.

  • Pinocytosis: Non-selective uptake of small molecules (“cell drinking”).

  • Receptor-mediated Endocytosis:

    • Specific binding of ligands to plasma membrane receptors, followed by direct uptake of those ligands.

Chapter 3: Forms Of Energy

• Metabolism Definition:

  • The totality of chemical reactions occurring in a biological system.

  • Metabolisms can convert food into usable forms of energy and produce byproducts.

• Key Concept: Metabolic Pathway:

  • A sequence of reactions that transform a molecule from one form to another;

  • Byproducts often play a significant role in subsequent chemical processes.

• Enzymes:

  • Biological catalysts that speed up reaction rates.

  • Each step in a metabolic pathway is facilitated by a specific enzyme.

• Metabolic Pathways Groups:

  • Catabolic pathways:

  • Breakdown of complex molecules into simpler ones, releasing energy (e.g., cellular respiration).

  • Anabolic pathways:

  • Synthesis of complex molecules from simpler ones, requiring energy (e.g., protein synthesis).

• Bioenergetics:

  • The study of energy transformations within biological systems and metabolism.

  • Energy is not created or destroyed, merely transformed through metabolic processes.

Chapter 4: Release Of Energy

• Energy Definition:

  • The capacity to cause change within a system; exists in various forms (potential, kinetic, thermal).

• Potential Energy:

  • Associated with an object's position; example is concentration gradients.

• Kinetic Energy:

  • Associated with movement and random motion of particles.

• Thermal Energy:

  • Specifically related to kinetic energy associated with random molecular movement.

• Examples of Energy Transformations:

  • Physical Movement to Position Change (e.g., diver climbing a ladder) illustrating energy transformations between potential and kinetic forms.

Chapter 5: High Potential Energy

• Chemical Energy:

  • A subclass of potential energy, related to energy stored within chemical bonds in molecules.

  • Example: Glucose has high chemical energy due to its structure.

  • Release of this energy can fuel metabolic processes.

Chapter 6: Energy To System

• Thermodynamics:

  • The study of energy transformations; follows two laws regarding the conservation and entropy.

• First Law of Thermodynamics:

  • Energy cannot be created or destroyed; only transformed.

• Second Law of Thermodynamics:

  • Energy transfer increases disorder or entropy within an system (randomness).

  • Example: Energy breakdown and the resulting disorder present.

Chapter 7: Releasing Heat Energy

• Spontaneous Processes:

  • Reactions that occur favorably without energy input and increase disorder.

• Non-spontaneous Processes:

  • Require energy input to occur, often occurring against the disorder tendency.

• Examples of entropy in biological systems, highlighting disorder through natural processes over time.

Chapter 8: Conclusion

• Recap of essential concepts in metabolism, energy transformations, and thermodynamic principles.

• Reminder of interrelated processes that maintain the dynamic function of biological systems.