Facilitated Diffusion in Cell Biology
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Questions and Answers

Which statement correctly describes the orientation of DNA strands?

  • Strands have neither polarity nor direction.
  • One strand runs 3′–5′ while the other runs 5′–3′. (correct)
  • Both strands run from 5′ to 3′ direction.
  • Strands run parallel to each other in the same direction.

    • Which type of facilitated diffusion allows the movement of ions across the membrane through specific channels?

  • Channel-mediated facilitated diffusion (correct)
  • Simple diffusion
  • Carrier-mediated facilitated diffusion
  • Active transport

    • What is the result when the N-terminal ends of histones undergo reversible covalent modifications?

  • They directly alter the nucleotide sequence of DNA.
  • They erase all gene expression patterns permanently.
  • They influence the binding affinity of histones to DNA. (correct)
  • They cause the DNA to become a double helix.

    • Which of the following base pairings is correct according to the rules of complementary base pairing?

    <p>Adenine pairs with Thymine.</p> Signup and view all the answers

    What characterizes ligand-gated channels in channel-mediated facilitated diffusion?

    <p>They open when a ligand binds to the channel.</p> Signup and view all the answers

    Why is diffusion of ions through channels generally slower than diffusion through the lipid bilayer?

    <p>Channels occupy a smaller fraction of the lipid membrane's surface area.</p> Signup and view all the answers

    During DNA replication, what is the primary role of DNA?

    <p>To carry the genetic material and ensure its transmission.</p> Signup and view all the answers

    Which statement accurately describes RNA's location and function?

    <p>RNA primarily exists in the cytoplasm and is involved in protein synthesis.</p> Signup and view all the answers

    Which substances typically utilize carrier-mediated facilitated diffusion?

    <p>Glucose, fructose, and amino acids</p> Signup and view all the answers

    What is the main characteristic of osmosis?

    <p>It involves the movement of water through a semipermeable membrane.</p> Signup and view all the answers

    In carrier-mediated facilitated diffusion, what occurs when the solute binds to the carrier protein?

    <p>The shape of the carrier protein changes.</p> Signup and view all the answers

    What is the nature of the movement in facilitated diffusion?

    <p>Solutes move down their concentration gradient.</p> Signup and view all the answers

    Which type of channels remain closed until a specific event occurs?

    <p>Gated channels</p> Signup and view all the answers

    What characterizes a competitive irreversible antagonist?

    <p>It forms a covalent bond with the active site.</p> Signup and view all the answers

    How do non-competitive antagonists exert their effect?

    <p>By binding to a different site and blocking receptor activation.</p> Signup and view all the answers

    Which modality of antagonism involves the formation of an inactive complex?

    <p>Chemical antagonism.</p> Signup and view all the answers

    What is the main difference between potency and efficacy in drug selection?

    <p>Efficacy is the drug's effectiveness in achieving a response, whereas potency measures the dosage required.</p> Signup and view all the answers

    What is the role of physiological antagonism?

    <p>Inducing different effects through different receptors.</p> Signup and view all the answers

    Which type of antagonist has no affinity for the agonist's active site?

    <p>Non-competitive antagonist.</p> Signup and view all the answers

    What must occur for the effect of a competitive irreversible antagonist to cease?

    <p>New receptors must be synthesized by the body.</p> Signup and view all the answers

    In terms of drug safety, monitoring quantal dose-frequency curves is important for what reason?

    <p>To assess the toxicity levels and effective responses.</p> Signup and view all the answers

    How do non-competitive antagonists affect receptor activity?

    <p>They stabilize the receptor in an inactive state.</p> Signup and view all the answers

    Which antagonist type relies on a different pharmacological pathway to achieve its effect?

    <p>Physiological antagonist.</p> Signup and view all the answers

    What is the primary reason plasma has a different protein concentration than interstitial fluid?

    <p>Presence of a permeability barrier at the capillary wall</p> Signup and view all the answers

    What effect does hyponatremia have on extracellular fluid (ECF) volume?

    <p>Decreases ECF volume</p> Signup and view all the answers

    Which of the following describes osmolality?

    <p>Total concentration of all particles free in a solution</p> Signup and view all the answers

    How does osmotic pressure relate to the solute concentration in a solution?

    <p>Osmotic pressure increases with higher solute concentration</p> Signup and view all the answers

    What happens during osmosis when solute concentrations are equal on both sides of a membrane?

    <p>Water diffusion stops</p> Signup and view all the answers

    Which of the following ions is primarily responsible for osmotic activity in extracellular fluid (ECF)?

    <p>Na+</p> Signup and view all the answers

    Which statement about osmolarity is true?

    <p>It is measured in osmoles per liter of solution.</p> Signup and view all the answers

    What occurs when hypernatremia is present in the body?

    <p>Expansion of ECF volume</p> Signup and view all the answers

    What does the term 'particle bound to macromolecules' imply in relation to osmolality?

    <p>Does not contribute at all to osmolality</p> Signup and view all the answers

    In what situation would water movement across a membrane be prevented?

    <p>By applying mechanical pressure to the concentrated solution</p> Signup and view all the answers

    What occurs during the G2 phase of the cell cycle?

    <p>RNA and proteins necessary for cell division are synthesized.</p> Signup and view all the answers

    What defines nucleic acids in terms of their structure?

    <p>Nucleotides, consisting of a 5-carbon sugar, phosphoric acid, and nitrogenous bases, are the building blocks of nucleic acids.</p> Signup and view all the answers

    In which phase do cells analyze DNA replication for possible errors?

    <p>G2 phase</p> Signup and view all the answers

    What type of cells typically enter the G0 phase of the cell cycle?

    <p>Highly differentiated neurons and muscle cells</p> Signup and view all the answers

    Which statement about nucleotides is true?

    <p>Each nucleotide consists of a 5-carbon sugar, a nitrogenous base, and a phosphoric acid.</p> Signup and view all the answers

    What is one key function of nucleic acids in living organisms?

    <p>Encoding and storing genetic information.</p> Signup and view all the answers

    Which of the following correctly describes how DNA differs from RNA?

    <p>RNA contains uracil, while DNA contains thymine as a nitrogenous base.</p> Signup and view all the answers

    What happens to cells that are highly differentiated after mitosis?

    <p>They may exit the cell cycle and enter G0 phase.</p> Signup and view all the answers

    What is the primary role of the G2 phase in the cell cycle?

    <p>To repair any DNA errors and prepare for mitosis.</p> Signup and view all the answers

    Which of the following is a characteristic of the G0 phase?

    <p>Cells are in a resting stage and may re-enter the cell cycle under certain conditions.</p> Signup and view all the answers

    What is the primary distinction between active and passive transport across the cell membrane?

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

    In facilitated diffusion, what role do membrane channels play?

    <p>They allow selective movement of specific ions across the membrane.</p> Signup and view all the answers

    Which of the following substances would most likely pass through the lipid bilayer via simple diffusion?

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

    What distinguishes channel-mediated facilitated diffusion from simple diffusion?

    <p>It occurs through specific membrane proteins, allowing for selective ion transport.</p> Signup and view all the answers

    What is a key characteristic of gated channels in channel-mediated facilitated diffusion?

    <p>They can open or close in response to specific signals or stimuli.</p> Signup and view all the answers

    Which scenario describes secondary active transport?

    <p>Sodium ions move out of a cell while glucose moves in against its concentration gradient.</p> Signup and view all the answers

    What differentiates simple diffusion from facilitated diffusion?

    <p>Facilitated diffusion occurs through channels for small molecules, whereas simple diffusion does not.</p> Signup and view all the answers

    In the context of passive transport, what does the term 'electrochemical gradient' refer to?

    <p>The combined influence of concentration gradient and electrical charge on ion movement.</p> Signup and view all the answers

    What distinguishes voltage-gated channels from ligand-gated channels?

    <p>Voltage-gated channels open in response to ligand binding.</p> Signup and view all the answers

    Which substances typically require carrier-mediated facilitated diffusion to cross the plasma membrane?

    <p>Glucose and amino acids</p> Signup and view all the answers

    How do molecules move during osmosis?

    <p>From low solute concentration to high solute concentration</p> Signup and view all the answers

    What is a primary characteristic of active transport?

    <p>It requires energy to move substances against their gradient.</p> Signup and view all the answers

    Which processes are involved in the transport of water during osmosis?

    <p>Through passive diffusion and aquaporins</p> Signup and view all the answers

    What triggers the opening of voltage-gated channels?

    <p>Change in electrical potential across the membrane</p> Signup and view all the answers

    Which of the following best describes the role of carrier proteins in facilitated diffusion?

    <p>They bind to solutes and change shape to facilitate transport.</p> Signup and view all the answers

    What type of diffusion does osmosis fall under?

    <p>Passive transport of solvents through a membrane</p> Signup and view all the answers

    What is the main characteristic of primary active transport?

    <p>It utilizes energy derived from hydrolysis of ATP.</p> Signup and view all the answers

    Which process involves the movement of Na+ along its electrochemical gradient to drive the transport of another substance?

    <p>Secondary Active Transport</p> Signup and view all the answers

    Which of the following accurately describes the sodium-potassium pump?

    <p>It requires ATP and is a form of primary active transport.</p> Signup and view all the answers

    What is the primary source of energy for secondary active transport?

    <p>Gradient energy from another substance</p> Signup and view all the answers

    What is the result of ATP hydrolysis in primary active transport?

    <p>It causes a conformational change in the carrier protein.</p> Signup and view all the answers

    In what way does active transport differ from passive transport?

    <p>Active transport moves substances against a concentration gradient.</p> Signup and view all the answers

    Which of the following correctly describes the role of a carrier protein during secondary active transport?

    <p>It binds to both Na+ and another substance to transport them simultaneously.</p> Signup and view all the answers

    What regulates the operation of the sodium-potassium pump at the cellular level?

    <p>ATP availability and sodium-potassium ratios</p> Signup and view all the answers

    Study Notes

    Facilitated Diffusion

    • Channel-mediated facilitated diffusion: Solutes move down their concentration gradient through membrane channels, integral proteins that allow the passage of small, inorganic ions.
    • Selective permeability: Channels are specific for the ions they allow to pass through.
    • Leak channels: Remain open continuously.
    • Gated channels: Only open when required; types include voltage-gated and ligand-gated.
      • Voltage-gated channels: Open and close in response to changes in membrane potential.
      • Ligand-gated channels: Open and close in response to binding of a specific molecule.
    • Carrier-mediated facilitated diffusion: Larger solutes, such as glucose, fructose, and amino acids, move down their concentration gradient with the help of carrier proteins.
      • Binding: The solute binds to the carrier protein, causing a conformational change.
      • Transport: The conformational change moves the solute through the membrane.

    Osmosis

    • Movement of water: Osmosis is the net movement of water across a semipermeable membrane from a region of high water concentration to a region of low water concentration.
    • Passive process: Osmosis does not require energy expenditure.
    • Osmotic pressure: The pressure that needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
    • Osmolality: The total concentration of osmotically active particles (solute) in a solution, expressed as osmoles per kilogram of water.
    • Osmolarity: The total concentration of osmotically active particles (solute) in a solution, expressed as osmoles per liter of solution.

    Osmosis and Tonicity

    • Tonicity: Describes the osmotic pressure difference between two solutions.
      • Isotonic: Two solutions have the same osmotic pressure.
      • Hypertonic: A solution has a higher osmotic pressure than another solution.
      • Hypotonic: A solution has a lower osmotic pressure than another solution.
    • Water movement: In osmosis, water moves from a hypotonic solution to a hypertonic solution to achieve an isotonic state.

    ECF (Extracellular Fluid) Composition

    • Na+ concentration: Na+ is the dominant cation in the ECF, accounting for nearly all of the osmotic activity.
    • ECF volume: Factors affecting Na+ concentration influence the ECF volume.
      • Hyponatremia (low Na+): Leads to hypovolemia (low ECF volume).
      • Hypernatremia (high Na+): Leads to hypervolemia (high ECF volume).

    Competitive Antagonism

    • Competitive reversible antagonist: Binds to the active site of a receptor, preventing agonist binding. The effect can be overcome by increasing the concentration of the agonist.
    • Competitive irreversible antagonist: Forms a permanent covalent bond with the active site, making the receptor inactive. This effect is not reversible by increasing the agonist concentration.

    Non-Competitive Antagonism (Allosteric Antagonism)

    • Allosteric site: Antagonist binds to a site other than the active site, preventing agonist binding or activation.
    • No impact on agonist binding: The antagonist does not compete directly with the agonist for the active site.
    • Irreversible: This type of antagonism is not overcome by increasing the agonist concentration.

    Other Modalities of Antagonism

    • Physiological antagonism: Achieved by two agents acting on different receptors to produce opposing effects.
    • Chemical antagonism: Occurs when two agents react chemically to form an inactive complex.

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    Related Documents

    Cell Biology Lecture Notes PDF
    Transport Across Biomembranes Lecture Notes PDF

    Description

    This quiz explores the mechanisms of facilitated diffusion, focusing on channel-mediated and carrier-mediated processes. Learn about the roles of different types of channels, including gated, voltage-gated, and ligand-gated channels. Test your understanding of how solutes move across the cell membrane.

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