Cell Membrane Structure and Function
43 Questions
6 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary reason that the hydrophobic portions of phospholipid molecules arrange themselves in the middle of the cell membrane?

  • They desire to increase permeability of the membrane.
  • They facilitate signaling between cells.
  • They are attracted to water molecules.
  • They are repelled by water and attracted to each other. (correct)

    • Which substances can readily pass through the lipid bilayer of a cell membrane?

  • Glucose
  • Sodium ions
  • Oxygen (correct)
  • Urea

    • What role do integral proteins play in the cell membrane?

  • They form channels for selective diffusion. (correct)
  • They are solely responsible for signal transmission.
  • They provide structural support only.
  • They do not interact with water-soluble substances.

    • How do peripheral proteins differ from integral proteins in the cell membrane?

    <p>They penetrate only one side of the membrane.</p> Signup and view all the answers

    What is the main function of cholesterol within the cell membrane?

    <p>To help control membrane fluidity.</p> Signup and view all the answers

    Which type of lipid is described as having both hydrophobic and hydrophilic groups and is commonly found in cell membranes?

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

    What is NOT a function of sphingolipids in cell membranes?

    <p>Nutrient transport across the membrane</p> Signup and view all the answers

    Which characteristic is true of water-soluble substances with respect to the cell membrane?

    <p>They require integral proteins for passage.</p> Signup and view all the answers

    What is the primary reason that water movement across the red blood cell membrane typically results in zero net movement?

    <p>The volume of water diffusing in both directions is equal.</p> Signup and view all the answers

    Which statement accurately describes a hypotonic solution in relation to a cell's internal environment?

    <p>It has a lower solute concentration, causing the cell to swell.</p> Signup and view all the answers

    In the process of osmosis, what primarily determines the direction of water movement across a membrane?

    <p>The concentration gradient of water molecules.</p> Signup and view all the answers

    Which scenario correctly illustrates the concept of active transport?

    <p>Glucose molecules moving into a cell against their concentration gradient.</p> Signup and view all the answers

    What occurs when a cell is placed in a hypertonic solution?

    <p>Water exits the cell, resulting in cell shrinkage.</p> Signup and view all the answers

    What is the primary role of peripheral proteins in the cell membrane?

    <p>They act primarily as enzymes or controllers of substance transport.</p> Signup and view all the answers

    Which of the following correctly describes the glycocalyx?

    <p>It forms a protective layer on the outer surface and involves glycoproteins and glycolipids.</p> Signup and view all the answers

    What is a key characteristic of the carbohydrate moieties attached to the outer surface of cells?

    <p>Many have a negative electrical charge which affects cell interactions.</p> Signup and view all the answers

    What distinguishes the extracellular fluid from the intracellular fluid regarding ion concentrations?

    <p>Extracellular fluid has a high concentration of sodium and chloride, while intracellular fluid has higher potassium.</p> Signup and view all the answers

    Which function is NOT associated with membrane carbohydrates?

    <p>Facilitating the transport of lipids across the membrane.</p> Signup and view all the answers

    What type of proteins facilitate the free movement of molecules and ions across the cell membrane?

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

    How does the binding of glycocalyx to another cell influence cellular behavior?

    <p>It allows cells to adhere to each other.</p> Signup and view all the answers

    What distinguishes the composition of intracellular fluid from extracellular fluid concerning phosphates?

    <p>Intracellular fluid contains considerably more phosphates.</p> Signup and view all the answers

    In relation to hormone interactions, what significant role do glycoproteins play within cell membranes?

    <p>They serve as major receptors for hormone binding.</p> Signup and view all the answers

    Which membrane component is primarily involved in forming pores for substance transport?

    <p>Integral proteins.</p> Signup and view all the answers

    What is the role of carrier proteins in membrane transport?

    <p>They bind with molecules and undergo conformational changes to transport substances.</p> Signup and view all the answers

    What primarily distinguishes active transport from passive transport?

    <p>Active transport requires energy to move substances against a gradient.</p> Signup and view all the answers

    Which statement about diffusion is accurate?

    <p>Diffusion represents random molecular movement in gases and liquids.</p> Signup and view all the answers

    What is true regarding simple diffusion?

    <p>It occurs through membranes without protein interaction.</p> Signup and view all the answers

    What defines the driving force behind passive transport processes?

    <p>The kinetic energy of molecular motion.</p> Signup and view all the answers

    Which characteristic applies to channel proteins?

    <p>They transport ions selectively through a central pore.</p> Signup and view all the answers

    What is one result of increased molecular motion in diffusion?

    <p>Higher likelihood of collisions among particles.</p> Signup and view all the answers

    What distinguishes carrier proteins from channel proteins in terms of transport?

    <p>Carrier proteins undergo shape changes for transport, while channel proteins do not.</p> Signup and view all the answers

    How does passive transport differ from active transport concerning concentration gradients?

    <p>Active transport involves movement against concentration gradients using energy.</p> Signup and view all the answers

    In terms of molecular behavior, what does temperature influence in a solution?

    <p>The kinetic energy and motion of molecules within that solution.</p> Signup and view all the answers

    What happens to sodium gates when the inside of the cell membrane loses its strong negative charge?

    <p>They open suddenly allowing sodium to enter the cell.</p> Signup and view all the answers

    What is the primary mechanism by which acetylcholine channel operates?

    <p>It requires the binding of a chemical ligand.</p> Signup and view all the answers

    How does facilitated diffusion differ from simple diffusion?

    <p>Facilitated diffusion has a maximum rate known as Vmax.</p> Signup and view all the answers

    What is primarily transported through facilitated diffusion?

    <p>Charged or large particles such as glucose and amino acids.</p> Signup and view all the answers

    What is the diameter of the pore provided by the acetylcholine channel?

    <p>0.65 nanometers.</p> Signup and view all the answers

    What does the process of chemical gating primarily involve?

    <p>Conformational changes in protein channels due to ligand binding.</p> Signup and view all the answers

    What is the effect of concentration on the rate of facilitated diffusion?

    <p>It plateaus once Vmax is reached.</p> Signup and view all the answers

    What type of molecules can pass through the acetylcholine channel?

    <p>Positive ions and uncharged molecules smaller than 0.65 nanometers.</p> Signup and view all the answers

    What role do membrane carrier proteins play in facilitated diffusion?

    <p>They facilitate the diffusion of substances across the membrane.</p> Signup and view all the answers

    What is the primary function of ion channels in nerve signal transmission?

    <p>To allow specific ions to enter or exit the cell rapidly.</p> Signup and view all the answers

    Study Notes

    Cell Membrane Structure

    • The cell membrane is composed of a phospholipid bilayer.
    • The hydrophobic tails of phospholipids face inwards, forming the inside of the membrane.
    • The hydrophilic heads face outwards, interacting with the intracellular and extracellular fluids.
    • The membrane is impermeable to water-soluble substances like ions, glucose, and urea.
    • The membrane is permeable to fat-soluble substances like oxygen, carbon dioxide, and alcohol.

    Sphingolipids

    • Sphingolipids are derived from the amino alcohol sphingosine.
    • They contain both hydrophobic and hydrophilic groups.
    • They are present in small amounts in cell membranes, especially in nerve cells.
    • Functions of sphingolipids include protection from environmental factors, signal transmission, and adhesion sites for extracellular proteins.

    Cholesterol

    • Cholesterol has a steroid nucleus, making it highly fat-soluble.
    • It is interspersed within the phospholipid bilayer.
    • It helps regulate membrane permeability to water-soluble substances.
    • Cholesterol affects membrane fluidity.

    Cell Membrane Proteins

    • There are two types of cell membrane proteins: integral and peripheral.
    • Integral proteins span the entire membrane.
    • Peripheral proteins are attached to one surface of the membrane.

    Integral Protein Functions

    • Form channels for water and water-soluble substances (especially ions).
    • Act as carrier proteins for transporting substances across the lipid bilayer.
    • Function as enzymes.
    • Serve as receptors for molecules that cannot easily penetrate the membrane.

    Peripheral Protein Functions

    • Primarily function as enzymes or regulators of substance transport through membrane pores.

    Membrane Carbohydrates (Glycocalyx)

    • Attached to membrane proteins (glycoproteins) or lipids (glycolipids).
    • Located exclusively on the external surface of the cell.
    • Form a protective layer called the glycocalyx.

    Glycocalyx Functions

    • Contribute to the negative electrical charge of cells.
    • Facilitate cell-to-cell adhesion.
    • Act as receptors for hormones (e.g., insulin).
    • Participate in immune reactions.

    Transport of Substances Through Cell Membranes

    • Extracellular fluid has high sodium and chloride concentrations, while intracellular fluid has high potassium and phosphate concentrations.
    • Membrane proteins create alternative pathways through the cell membrane.

    Lipid-Soluble Substances

    • Move through the membrane directly.

    Transport Proteins

    • Facilitate the movement of substances across the membrane.
    • Channel proteins allow free movement of water, ions, and molecules.
    • Carrier proteins bind with transported molecules and undergo conformational changes to move substances across the membrane.

    Membrane Transport Mechanisms

    • Diffusion: Random molecular movement of substances down their concentration gradient.
      • Simple diffusion occurs through membrane openings or intermolecular spaces without carrier proteins.
      • Facilitated diffusion involves carrier proteins.
    • Active Transport: Moves substances against their concentration gradient, requiring energy.

    Diffusion

    • Molecules and ions in body fluids are in constant motion.
    • Diffusion is the random movement of molecules among one another in liquids or gases.

    Diffusion Through the Cell Membrane

    • Simple diffusion: Movement through membrane openings or intermolecular spaces without carrier proteins.
    • Facilitated diffusion: Requires carrier proteins, but transport is still down the concentration gradient. Most glucose and amino acids are transported this way.

    Facilitated Diffusion Characteristics

    • Facilitated diffusion approaches a maximum rate (Vmax) as the concentration of the diffusing substance increases.

    Osmosis

    • Net movement of water across a membrane due to a water concentration difference.
    • Occurs if:
      • There is a concentration difference of water.
      • The membrane is not permeable to the solute.

    Tonicity

    • The ability of an extracellular solution to make water move into or out of a cell by osmosis.
    • Isotonic: Equal solute concentration compared to the cell interior.
    • Hypotonic: Lower solute concentration than the cell, causing water to enter the cell and potentially lead to swelling.
    • Hypertonic: Higher solute concentration than the cell, causing water to leave the cell and potentially lead to shrinking.

    Active Transport

    • Movement of solutes against their electrochemical gradient (uphill).
    • Requires energy to move molecules or ions uphill.
    • Crucial for maintaining cellular function.

    Summary of Key Concepts

    • The cell membrane is a complex structure that controls what enters and exits the cell.
    • Phospholipids, cholesterol, and proteins contribute to the membrane's structure and function.
    • Membrane transport mechanisms include diffusion, facilitated diffusion, and active transport.
    • Osmosis is a special type of diffusion that involves the movement of water across a membrane.
    • Tonicity describes the effect of a solution on the volume of a cell.
    • Active transport is essential for maintaining the appropriate intracellular environment.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Membrane Physiology - Cellular Transport PDF

    Description

    Explore the intricate structure of the cell membrane, including the roles of phospholipids, sphingolipids, and cholesterol. Understand how these components influence membrane permeability and function, especially in nerve cells. This quiz is essential for anyone studying cell biology.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser