More transport..?

Important Announcements

  • The instructor reminded students that there is no class on the upcoming Tuesday.
  • A take-home quiz will be posted on Canvas on Friday morning, due by midnight on the following Tuesday.
    • The quiz will consist of 5 questions, regarding a topic discussed in class.
  • Students are encouraged to complete the quiz within the four days provided, although it shouldn't take that long.
  • Class will resume on the 27th, when additional take-home quizzes will be discussed.

Grading and Exam Review

  • Students can pick up their exams at the end of the lecture.
  • For any grading questions, students should attend office hours the following Wednesday.

Lecture Overview: Membrane Transport

  • The lecture will focus on membrane transport, including passive and active transport as well as bulk transport.
  • Cell membranes are selectively permeable, allowing specific molecules to pass while restricting others.
    • This regulation is achieved through:
    • Phospholipid bilayer
    • Transport proteins
    • Specialized channels
Types of Molecules and Membrane Transport

  • Simple Diffusion

    • Small nonpolar molecules can cross the membrane by passing between phospholipids (e.g., oxygen, carbon dioxide, nitrogen).
    • Passive process: Continues until equilibrium is reached, relying on concentration gradients.

  • Transport Proteins

    • Larger polar and charged molecules cannot pass through the bilateral and require transport proteins (channel proteins or carrier proteins).
    • Examples include ions, which need specialized channels to move across the membrane.
Factors Affecting Diffusion
  • Concentration Gradient: Molecules move from high to low concentration until equilibrium.
  • Steepness of Gradient: More significant difference leads to faster diffusion.
  • Temperature: Higher temperatures increase molecular motion, accelerating diffusion.
  • Molecular Size: Smaller molecules diffuse faster than larger ones.
  • Permeability of the Membrane: More permeable membranes allow for faster diffusion.
Osmosis
  • Definition: Diffusion of water across a selectively permeable membrane from a lower solute concentration to a higher solute concentration.
  • Equilibrium: Desired state where solute and solvent concentrations are balanced on both sides.
  • Types of Solutions:
    • Hypotonic: Lower solute concentration outside the cell, water moves inside, causing cell swelling.
    • Isotonic: Equal solute concentration inside and outside, no net movement.
    • Hypertonic: Higher solute concentration outside; water moves out, causing cell shrinkage.
Facilitated Diffusion
  • Molecules (like glucose or ions) can cross the membrane with the help of transport