Cell Membrane Function and Temperature Effects
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Questions and Answers

What is the primary energy source required for active transport?

  • Glucose breakdown
  • Hydrolysis of ATP (correct)
  • Cellular respiration
  • Fermentation
  • What role do carrier proteins play in active transport?

  • They store energy for future use
  • They change shape to facilitate molecule transport (correct)
  • They increase the size of the molecules
  • They prevent passage of any ions
  • Which process describes the bulk transport of liquids into a cell?

  • Exocytosis
  • Pinocytosis (correct)
  • Diffusion
  • Phagocytosis
  • What happens to a phagosome after it forms during phagocytosis?

    <p>It fuses with a lysosome for digestion</p> Signup and view all the answers

    In which scenario is active transport particularly beneficial over simple diffusion?

    <p>When moving polar molecules against their concentration gradient</p> Signup and view all the answers

    What is a key characteristic of active transport systems?

    <p>They move substances only in one direction as required</p> Signup and view all the answers

    What is the primary role of the cell membrane in cellular functions?

    <p>Acts as a barrier between cytoplasm and external environment</p> Signup and view all the answers

    What happens to membrane proteins at high temperatures?

    <p>They denature and lose their function</p> Signup and view all the answers

    Which process allows for the selective movement of substances across the membrane?

    <p>Both passive and active transport</p> Signup and view all the answers

    What is the effect of high temperature on a cell membrane?

    <p>Leads to membrane leakage and loss of function</p> Signup and view all the answers

    Which molecules can freely diffuse across the phospholipid bilayer?

    <p>Non-polar lipid-soluble molecules</p> Signup and view all the answers

    What type of transport is osmosis classified as?

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

    What is the role of glycoproteins and glycolipids in the cell membrane?

    <p>Cell signaling and stability</p> Signup and view all the answers

    What is the main characteristic of simple diffusion?

    <p>It is a passive process driven by concentration gradients</p> Signup and view all the answers

    Which statement about phospholipids is correct?

    <p>They provide the foundation of the cell membrane and allow selective permeability</p> Signup and view all the answers

    Which factor has the greatest impact on the rate of diffusion for larger molecules?

    <p>Size of the molecule</p> Signup and view all the answers

    What occurs to an animal cell placed in a hypotonic solution?

    <p>The cell swells and may burst.</p> Signup and view all the answers

    What type of proteins facilitate the transport of polar molecules across the cell membrane?

    <p>Channel and carrier proteins</p> Signup and view all the answers

    What effect does increasing the surface area of a cell have on diffusion?

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

    What primarily determines the movement of water through a partially permeable membrane during osmosis?

    <p>Osmotic concentration of solutes</p> Signup and view all the answers

    Which condition is characteristic of isotonic solutions?

    <p>Equal water potential inside and outside the cell</p> Signup and view all the answers

    What happens to plant cells in a hypertonic solution?

    <p>Cells undergo plasmolysis.</p> Signup and view all the answers

    What is the primary role of aquaporins in osmosis?

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

    How does temperature affect the rate of diffusion?

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

    What is the significance of the concentration gradient in facilitated diffusion?

    <p>It determines the direction and rate of molecule movement.</p> Signup and view all the answers

    Study Notes

    Cell Membrane Function

    • The cell membrane acts as a barrier separating the cytoplasm from the external environment.
    • It controls the entry and exit of substances into and out of the cell.
    • The membrane contains receptors for cell signaling substances like hormones and neurotransmitters.
    • It acts as a cell surface antigen, allowing for cell recognition and preventing cell destruction.
    • Glycoproteins and glycolipids on the membrane surface form hydrogen bonds with water, contributing to its stability.
    • The membrane has a flexible nature, allowing for changes in cell shape, such as during phagocytosis.
    • It provides a location for enzymes and serves as a site for many chemical processes, including some respiration reactions on the inner mitochondrial membrane.

    Effects of High Temperature on Cell Membrane

    • High temperatures can damage the cell membrane by denaturing proteins.
    • This denaturation leads to loss of tertiary structure, a change from globular shape, and breakage of ionic, hydrogen, and hydrophobic interactions.
    • Consequences of protein denaturation include the loss of functionality, preventing the reception of cell signals and the transport of polar molecules.
    • The membrane becomes more leaky, losing its partially permeable nature and disrupting its ability to regulate substance entry and exit.
    • The interaction between proteins and the phospholipid bilayer is disrupted.

    Phospholipid Bilayer Significance

    • Forms the foundation of the cell membrane.
    • Creates a selectively permeable barrier, allowing the diffusion of small polar molecules (water), non-polar lipid-soluble molecules, and gases.
    • Contributes to the fluidity of the cell membrane.

    Mechanisms of Substance Entry and Exit

    • Passive Transport requires no energy input:
      • Simple diffusion: Movement of non-polar molecules from an area of high concentration to low concentration.
      • Facilitated diffusion: Movement of polar molecules through protein channels or carriers down their concentration gradient.
        • Channel proteins: Allow specific types of molecules to pass, based on size and charge.
        • Carrier proteins: Bind to specific molecules and change shape to facilitate transport.
      • Osmosis: Movement of water molecules from an area of high water potential to an area of low water potential through a semi-permeable membrane.
    • Active Transport requires energy input (ATP):
      • Active transport: Movement of molecules against their concentration gradient using carrier proteins and energy from ATP.
      • Bulk transport: Movement of large quantities of substances through:
        • Endocytosis: Engulfing substances into the cell (phagocytosis for solids and pinocytosis for liquids).
        • Exocytosis: Releasing substances from the cell.

    Factors Affecting Simple Diffusion Rate

    • Concentration Gradient: A steeper concentration gradient increases the rate of diffusion.
    • Temperature: Higher temperatures increase kinetic energy, leading to faster diffusion.
    • Molecule Size and Polarity: Larger and polar molecules diffuse slower.
    • Surface Area: A larger surface area increases the number of protein transporters and diffusion rate.

    Osmosis and Its Effects on Cells

    • Osmotic concentration: Measures the concentration of solutes affecting osmosis.

    • Osmotic pressure: Measures a solution's tendency to absorb pure solvent by osmosis.

    • Effects on Animal Cells:*

    • Hypotonic solution: Water moves into the cell, causing it to swell and potentially burst.

    • Isotonic solution: No net movement of water, maintaining the cell's size.

    • Hypertonic solution: Water moves out of the cell, causing it to shrink.

    • Effects on Plant Cells:*

    • Hypotonic solution: Cell becomes turgid, with the cytoplasm pushing against the cell wall, generating hydrostatic pressure.

    • Isotonic solution: No net movement of water, maintaining the cell's size.

    • Hypertonic solution: Water leaves the cell, causing plasmolysis—the cell membrane pulls away from the cell wall.

    Active Transport

    • Requires energy from ATP to move molecules against their concentration gradient using carrier proteins.
    • The movement of substances is directional, meeting the cell's specific needs.
    • Active transport can move substances faster than simple diffusion.

    Endocytosis

    • Phagocytosis ("cell eating"): Engulfing solid particles (e.g., bacteria) into the cell.
    • Pinocytosis ("cell drinking"): Taking in extracellular fluid containing dissolved substances.

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    Description

    Explore the critical functions of the cell membrane, including its role as a barrier and in cell signaling. Learn how high temperatures can impact membrane proteins and overall cellular integrity. This quiz covers essential concepts relevant to cell biology and membrane dynamics.

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