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What is the primary characteristic of the plasma membrane?

  • It allows selective permeability for certain substances. (correct)
  • It is completely impermeable to all substances.
  • It always remains in a solid state.
  • It is made only of proteins.

    • What type of molecule are phospholipids primarily considered?

  • Amphipathic molecules. (correct)
  • Hydrophobic molecules.
  • Monosaccharides.
  • Hydrophilic molecules.

    • What does the fluid mosaic model describe regarding cellular membranes?

  • A membrane consists only of lipids.
  • A membrane changes shape frequently and is unstable.
  • A membrane is a fluid structure with a mosaic of proteins embedded within it. (correct)
  • A membrane is a fixed structure with rigid components.

    • How do phospholipids move within the plasma membrane?

    <p>They mainly drift laterally and rarely flip-flop. (D)</p> Signup and view all the answers

    What effect does cholesterol have on membrane fluidity at warm temperatures?

    <p>It restricts movement of phospholipids. (C)</p> Signup and view all the answers

    What is the impact of unsaturated fatty acids on membrane fluidity?

    <p>They enhance the membrane's fluidity. (B)</p> Signup and view all the answers

    As temperatures decrease, what happens to the state of the membrane?

    <p>It transitions from a fluid state to a solid state. (D)</p> Signup and view all the answers

    Which component prevents tight packing of phospholipids at cool temperatures?

    <p>Cholesterol. (A)</p> Signup and view all the answers

    What is the primary direction of molecular movement during diffusion?

    <p>From high concentration to low concentration (A)</p> Signup and view all the answers

    What is mainly responsible for the orientation of membrane proteins?

    <p>The genes that code for the proteins. (D)</p> Signup and view all the answers

    What description best fits the bilayer structure of the plasma membrane?

    <p>It is a stable barrier separating two aqueous compartments. (B)</p> Signup and view all the answers

    What characterizes the process of diffusion at dynamic equilibrium?

    <p>Equal numbers of molecules cross in both directions (C)</p> Signup and view all the answers

    Which of the following statements about passive transport is true?

    <p>It involves the movement down a concentration gradient (B)</p> Signup and view all the answers

    What factors can affect the rate of diffusion?

    <p>Temperature and molecular weight (A)</p> Signup and view all the answers

    What is the direction of water movement during osmosis?

    <p>From areas of low solute concentration to high solute concentration (A)</p> Signup and view all the answers

    Which type of membrane is required for osmosis to occur?

    <p>Selectively permeable membrane (C)</p> Signup and view all the answers

    Why is no work required to move substances down their concentration gradient?

    <p>Molecules possess innate kinetic energy (D)</p> Signup and view all the answers

    Which of the following is NOT a factor that affects the rate of diffusion?

    <p>Presence of electrical charges (D)</p> Signup and view all the answers

    During osmosis, what happens when solute concentrations are equal on both sides of a selectively permeable membrane?

    <p>Net movement of water stops (A)</p> Signup and view all the answers

    What is the significance of the term 'concentration gradient' in diffusion?

    <p>It indicates the direction and rate of molecular movement (C)</p> Signup and view all the answers

    What is the effect of cholesterol on membrane fluidity at moderate temperatures?

    <p>Reduces membrane fluidity (B)</p> Signup and view all the answers

    Which type of membrane protein is embedded within the hydrophobic core of the lipid bilayer?

    <p>Transmembrane protein (A)</p> Signup and view all the answers

    What is one of the major functions of membrane carbohydrates?

    <p>Cell-cell recognition (C)</p> Signup and view all the answers

    What characteristic of the plasma membrane allows it to control molecular traffic effectively?

    <p>Selective permeability (A)</p> Signup and view all the answers

    Which statement accurately describes channel proteins?

    <p>They form hydrophobic channels for ions (D)</p> Signup and view all the answers

    Why can't HIV infect individuals lacking CCR5 co-receptors?

    <p>HIV needs CCR5 to enter the cell (A)</p> Signup and view all the answers

    What process allows for the diffusion of a substance across a membrane without energy investment?

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

    What is the primary role of integral proteins in cell membranes?

    <p>To function as receptors for signaling (B)</p> Signup and view all the answers

    How do glycoproteins function in cellular processes?

    <p>By facilitating cell-cell interactions (C)</p> Signup and view all the answers

    What type of protein changes shape to shuttle molecules across the membrane?

    <p>Carrier protein (D)</p> Signup and view all the answers

    How do peripheral proteins interact with the cell membrane?

    <p>They are bound to the surface (A)</p> Signup and view all the answers

    In what manner do cells modify their lipid composition?

    <p>In response to environmental temperature changes (A)</p> Signup and view all the answers

    What is a key feature of the structure of the plasma membrane?

    <p>Distinct inside and outside faces (D)</p> Signup and view all the answers

    Which molecules can easily pass through the lipid bilayer?

    <p>Hydrophobic molecules (B)</p> Signup and view all the answers

    What describes the effect of a hypertonic solution on a plant cell?

    <p>The cell loses water and undergoes plasmolysis. (D)</p> Signup and view all the answers

    Which type of transport requires energy to move solutes against their concentration gradient?

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

    How does facilitated diffusion differ from active transport?

    <p>Facilitated diffusion is passive and occurs down a concentration gradient. (D)</p> Signup and view all the answers

    What is the primary function of a sodium-potassium pump?

    <p>To create a resting membrane potential. (A)</p> Signup and view all the answers

    What occurs during exocytosis?

    <p>Vesicles fuse with the plasma membrane to release contents outside the cell. (D)</p> Signup and view all the answers

    In which type of osmotic environment does a plant cell become turgid?

    <p>Hypotonic (C)</p> Signup and view all the answers

    What triggers receptor-mediated endocytosis?

    <p>The binding of ligands to specific receptors. (D)</p> Signup and view all the answers

    Which of the following statements about osmotic pressure is true?

    <p>It is the force caused by the presence of solute molecules in a solution. (B)</p> Signup and view all the answers

    What is the role of aquaporins in the cell membrane?

    <p>To facilitate the movement of water molecules. (B)</p> Signup and view all the answers

    What describes the term osmoregulation?

    <p>The control of solute concentrations and water balance. (C)</p> Signup and view all the answers

    What is a primary characteristic of bulk transport?

    <p>It requires energy for transporting large molecules. (C)</p> Signup and view all the answers

    Which statement is true about ion channels?

    <p>They allow selective passage of specific ions. (A)</p> Signup and view all the answers

    Which of the following statements describes pinocytosis accurately?

    <p>It is the intake of extracellular fluid with solutes. (C)</p> Signup and view all the answers

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