Lecture 1/28

Osmosis and Membrane Permeability

• Definition: Membranes are not permeable to solutes, which leads to the process of osmosis.

• Osmosis: The movement of water to equalize solute concentrations on both sides of the membrane.

• Importance: Understanding osmosis is crucial for applying biological concepts both in education and future careers.

Energy Basics

• Energy: The ability to do work, i.e., moving against an opposing force.

  • Potential Energy: Stored energy, not actively doing work.

  • Kinetic Energy: Energy of motion; actively doing work.

• ATP (Adenosine Triphosphate): Primary energy molecule for most eukaryotes.

  • Energy is stored in chemical bonds and released through chemical reactions.

Laws of Thermodynamics

First Law

• Conservation of Energy: Energy is neither created nor destroyed; it only changes form.

  • Example: Sunlight energy is converted into glucose (matter) through photosynthesis.

  • Energy can transform into heat and enter the ecosystem.

Second Law

• Entropy: The universe tends toward disorder (chaos and decay).

  • Example: Converting glucose into ATP results in energy loss (about 40% as heat).

  • The energy released does not remain in the ecosystem; it disperses into the universe.

Energy Conversion in Cells

• Mitochondria: Primary site for ATP production.

• Byproducts: Similar to car emissions - breaking down glucose yields carbon dioxide, water, and heat.

Chemical Reactions

Types of Reactions

• Reactants: Ingredients that undergo a chemical reaction.

• Exergonic Reactions: Release energy; products have less energy than reactants.

  • Example: Energy is captured during processes like cellular respiration.

• Endergonic Reactions: Require an input of energy; products contain more energy than reactants.

  • Cyclic Processes: Often couple exergonic and endergonic reactions to recycle energy.

Activation Energy

• Initial energy needed to begin a reaction.

  • Exergonic and Endergonic Graphs: Show different energy patterns before and after reactions, including activation energy levels.

Role of Enzymes

• Catalysts: Enzymes speed up reactions by lowering activation energy.

• Active Site: Region where substrates bind and reactions occur.

  • Induced Fit: Enzyme changes shape to better accommodate the substrate.

  • Examples: Hydrolysis of sucrose by sucrase.

• Functionality: Enzymes can be reused until denatured, inhibited, or degraded over time.

Enzymatic Environment Requirements

• Enzymes require specific temperatures and pH levels to function optimally.

  • Human Enzymes: Function best around normal body temperature.

  • Bacterial Enzymes: May thrive at higher temperatures due to their origin in hot springs.

  • pH Levels: Stomach enzymes (e.g., pepsin) work in acidic conditions, while others (e.g., trypsin) work better in neutral pH of the small intestine.

Continued Learning

• Encourage further reading on enzymes for deeper understanding.

• Explore practical applications such as food preservation techniques or the effects of enzymes in fruits (e.g., pineapple on proteins in the mouth).