IB Bio: Unit 2-Cell Membrane Transport

Chapter 1: Introduction

  • Cells and Their Origins

    • The first cells originated from primordial soup in a hot atmosphere with the correct elements for life's molecules: proteins, lipids, nucleic acids, and carbohydrates.

    • Lightning strikes contributed to the combination of these elements, forming monomers such as saccharides, nucleotides, triglycerides, and phospholipids, which eventually created cell membranes through hydrophilic and hydrophobic interactions.

    • Membrane folding allowed for chemical reactions and increased internal concentrations, leading to the formation of membrane-bound organelles.

  • Types of Cells

    • Prokaryotic Cells ("before nuclei")

      • Characteristics: No membrane-bound organelles, very simple structure (e.g., bacteria).

      • Features include flagella for movement and a capsule for protection.

      • Contains a cell wall, cell membrane, small 70S ribosomes, and free-floating circular DNA (plasmids).

    • Eukaryotic Cells

      • Characteristics: Contains membrane-bound organelles; examples include human and plant cells.

      • Key organelles include the nucleus (with nucleolus), endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and peroxisomes, responsible for protein and lipid synthesis, storage, and cellular cleanup.

      • Example: Insulin is produced in the rough ER and then secreted through vesicles.

Chapter 2: Shape of Cell

  • Cell Nutrient Transport

    • Cells need to transport substances such as water, oxygen, carbon dioxide, nutrients, and ions through the cell membrane.

    • Diffusion is important: substances move from areas of high concentration to low concentration.

    • Concentration Gradient:

      • Active Transport: Movement against the concentration gradient requiring ATP energy.

      • Passive Transport: Movement down the concentration gradient without energy.

  • Types of Transport

    • Passive Transport:

      • Simple Diffusion: Movement of small/nonpolar molecules (e.g., O2, CO2) through the phospholipid bilayer.

      • Facilitated Diffusion: Proteins assist in moving substances across the membrane through carrier proteins or channels.

      • Osmosis: Movement of water through aquaporins (water channels).

      • Ion Channels: Special channels allow ions (charged particles) to pass through; facilitated via concentration gradients.

    • Active Transport: Uses ATP to move substances against their concentration gradients.

      • Primary Active Transport: Pumps molecules using energy to transport them against the gradient.

      • Secondary Active Transport: Energy from primary transport creates gradients for subsequent transport.

Chapter 3: The Right Side

  • Diffusion Overview

    • Molecules spread out over time until equilibrium is achieved (e.g., oxygen diffusion).

    • Size and charge affect a molecule's ability to cross the membrane: small, nonpolar molecules pass easily, while larger or polar molecules cannot.

  • Importance of Ion Channels

    • Ions such as sodium and potassium require channels and carry electrical signals essential for nerve and muscle function.

  • Electrolyte Role in Physical Activity

    • Replacements such as sports drinks replenish ions and maintain muscle functionality and coordination during exertion.

Chapter 4: Real Protein Right

  • Facilitated Vs. Simple Diffusion

    • Facilitated Diffusion: Membrane proteins assist larger/polar molecules pass through; includes carrier and channel proteins that don't require energy.

    • Understanding Osmosis: Movement of water; involves three types of solutions (hypertonic, hypotonic, isotonic), affects cell shape and survival.

Chapter 5: Cell and Cell

  • Osmosis Explained

    • Hypertonic: Solutions that cause cells to lose water; cells shrivel.

    • Hypotonic: Solutions that cause cells to gain water; cells swell and may burst.

    • Isotonic: Balanced solute concentration; cells maintain shape and function normally.

  • Real-Life Examples

    • Plants wilt in hypertonic solutions and recover in hypotonic solutions; isotonic solutions ensure cellular health in IVs and eye drops.

Chapter 6: Primary Active Transport Energy

  • Mechanics of Active Transport

    • Primary Active Transport: Moves substances against their gradients using ATP.

    • Sodium-Potassium Pump: Exchanges sodium (out) and potassium (in) crucial for nerve and muscle function.

    • Secondary Active Transport: Utilizes the concentration gradient established by primary transport to facilitate the entrance of other molecules.

Chapter 7: Cell Drinking

  • Vesicular Transport:

    • Endocytosis: Bulk intake of materials (phagocytosis for solids, pinocytosis for liquids); involves vesicle formation to bring substances in.

    • Exocytosis: Release of substances (e.g., hormones) through vesicles merging with the membrane.

    • The cell’s ability to change shape enables material uptake and release effectively.

Chapter 8: Conclusion

  • Reflection on Transport Mechanisms

    • Active and passive transport mechanisms are vital for cellular function.

    • Understanding these processes helps explain how cells maintain homeostasis, interact with their environments, and respond to changes.