Physiology LE 1: Cell Membrane + Transport
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Questions and Answers

What is the fluid-like portion of cytoplasm that contains dissolved substances?

  • Lipid bilayer
  • Cytosol (correct)
  • Granules
  • Plasma membrane

    • What is the function of the plasma membrane?

  • To store genetic material
  • To act as a selectively permeable barrier (correct)
  • To synthesize proteins
  • To allow the passage of all substances

    • What type of proteins penetrate through the plasma membrane?

  • Receptor proteins
  • Carrier proteins
  • Peripheral proteins
  • Integral proteins (correct)

    • What is the main component of the lipid bilayer?

    <p>Phospholipids, sphingolipids, and cholesterol</p> Signup and view all the answers

    What is the effect of double bonds in the lipid bilayer?

    <p>It makes the bilayer more flexible</p> Signup and view all the answers

    Which substances can pass through the plasma membrane?

    <p>Gases, alcohol, and small, nonpolar substances</p> Signup and view all the answers

    What is the purpose of water channels in the plasma membrane?

    <p>To allow the passage of water</p> Signup and view all the answers

    What type of proteins are attached only to one surface of the plasma membrane?

    <p>Peripheral proteins</p> Signup and view all the answers

    What is the direction of movement of water in osmosis?

    <p>From higher to lower water concentration</p> Signup and view all the answers

    What is the effect of increasing molecular weight on diffusion?

    <p>Decreases diffusion</p> Signup and view all the answers

    What is the effect of increasing temperature on diffusion?

    <p>Increases diffusion</p> Signup and view all the answers

    What is the effect of increasing concentration gradient on diffusion?

    <p>Increases diffusion</p> Signup and view all the answers

    What is the effect of increasing lipid solubility on diffusion?

    <p>Increases diffusion</p> Signup and view all the answers

    What is the effect of increasing resistance on diffusion?

    <p>Decreases diffusion</p> Signup and view all the answers

    What is osmotic pressure (π) related to?

    <p>The amount of pressure required to stop osmosis</p> Signup and view all the answers

    What determines the osmotic pressure (π) of a solution?

    <p>The number of osmotically active particles</p> Signup and view all the answers

    What is the primary driving force behind the movement of substances from one point to another in a system?

    <p>Concentration difference</p> Signup and view all the answers

    What type of gradients can contribute to the flow of substances?

    <p>Concentration and electrical gradients</p> Signup and view all the answers

    What is the basis for diffusion?

    <p>Energy gradient</p> Signup and view all the answers

    What determines the rate of diffusion?

    <p>Resistance of flow</p> Signup and view all the answers

    What is the equation that describes the rate of diffusion?

    <p>𝐽 =− 𝐷𝐴 ∆𝐶 ∆𝑋</p> Signup and view all the answers

    What type of movement is described by Fick's Law of Diffusion?

    <p>Constant, random movement</p> Signup and view all the answers

    What is the term for the movement of substances through the cell membrane?

    <p>Diffusion</p> Signup and view all the answers

    What determines the direction of diffusion?

    <p>Concentration gradient</p> Signup and view all the answers

    What is the direction of transport of K+ ions in the figure?

    <p>Against the concentration gradient</p> Signup and view all the answers

    Why does H+ ion concentration move against the gradient in the figure?

    <p>Because it is more abundant in the lumen</p> Signup and view all the answers

    What is the characteristic of primary active transport?

    <p>Pumps molecules against the concentration gradient</p> Signup and view all the answers

    What is the function of an antiporter?

    <p>Transports substances in opposite directions</p> Signup and view all the answers

    What is the correct statement about the cell membrane?

    <p>It is a selectively permeable barrier that regulates the transport of molecules</p> Signup and view all the answers

    What is false about the rate of osmosis?

    <p>It is affected only by the pressure gradient</p> Signup and view all the answers

    Which statement is false about passive transport?

    <p>It moves solutes against their concentration gradient</p> Signup and view all the answers

    What is the correct statement about the sodium-potassium pump?

    <p>It requires integral proteins</p> Signup and view all the answers

    What is a characteristic of the cell membrane?

    <p>It is selectively permeable</p> Signup and view all the answers

    What is the result of double-bonded fatty acids in the lipid bilayer?

    <p>Increased flexibility of the membrane</p> Signup and view all the answers

    What is a type of transport mechanism that requires energy input?

    <p>Active transport</p> Signup and view all the answers

    What is an example of a transport mechanism that does not require energy input?

    <p>Simple diffusion</p> Signup and view all the answers

    What is a way to classify transport mechanisms?

    <p>By number of solutes transported</p> Signup and view all the answers

    What is the function of the smooth ER?

    <p>Lipid synthesis</p> Signup and view all the answers

    What is a characteristic of passive transport?

    <p>Does not require energy input</p> Signup and view all the answers

    What is the result of active transport?

    <p>Movement of solutes with energy input</p> Signup and view all the answers

    What is an example of a transport mechanism that moves solutes against their concentration gradient?

    <p>Active transport</p> Signup and view all the answers

    What is a characteristic of the lipid bilayer?

    <p>Contains double-bonded fatty acids</p> Signup and view all the answers

    Study Notes

    Cytoplasm Components

    • Cytosol: Jelly-like fluid containing dissolved substances such as proteins, ions, and glucose.
    • Granules: Storage for various substances like fats and glycogen.
    • Organelles: Specialized structures within the cytoplasm.

    Plasma Membrane Structure

    • Selective Permeability: Regulates what enters and exits the cell; allows gases, alcohol, and small nonpolar substances; restricts water-soluble substances like ions and glucose.
    • Lipid Bilayer: Thin double-layer composed of phospholipids, sphingolipids, and cholesterol; contains unsaturated fatty acids that introduce flexibility.
    • Membrane Proteins:
      • Integral Proteins: Span the membrane, including ion channels, carrier proteins, and receptors.
      • Peripheral Proteins: Attached to one side of the membrane, not embedded.

    Membrane Transport Mechanisms

    • Primary Active Transport: Moves molecules against their concentration gradient using energy (e.g., sodium-potassium pump).
    • Antiporter Mechanism: Transports substances in opposite directions.

    Osmosis and Osmotic Pressure

    • Osmosis: Net diffusion of water across selectively permeable membranes, moving from high to low water concentration, often through aquaporins.
    • Osmotic Pressure: The pressure required to halt osmosis, depends on the solute concentration and the number of osmotically active particles in the solution.

    Factors Affecting Diffusion

    • Molecular Weight: Higher molecular weight decreases diffusion rate.
    • Temperature: Increased temperature raises kinetic energy and diffusion rate.
    • Concentration Gradient: Greater concentration differences enhance diffusion.
    • Lipid Solubility: High lipid solubility promotes diffusion through membranes.
    • Resistance: Increased resistance diminishes diffusion.

    Diffusion Overview

    • Random Movement: Molecules collide and move, causing diffusion across membranes.
    • Types of Diffusion:
      • Simple Diffusion: Movement along the concentration gradient directly through the membrane.
      • Facilitated Diffusion: Assistance from proteins to move substances across the membrane.

    Fick's Law of Diffusion

    • Describes the rate of diffusion (J) based on diffusion coefficient (D), area (A), concentration difference (ΔC), and distance (ΔX).

    Summary of Membrane Transport

    • Passive Transport Mechanisms: Move solutes without energy input, include simple diffusion, facilitated diffusion, and osmosis.
    • Active Transport Mechanisms: Require energy input including primary and secondary active transport.
    • Transport Mechanisms Classification:
      • Uniport: Movement of one solute.
      • Symport: Movement of two solutes in the same direction.
      • Antiport: Movement of two solutes in opposite directions.

    Common Misconceptions

    • The cell membrane is flexible, not rigid.
    • Specificity in membrane functions is crucial; primary functions include selective transport and maintenance of homeostasis.

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