Physiology Chapter 4
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Questions and Answers

Which of the following statements accurately describes the role of GLUT proteins in facilitated diffusion?

  • Some GLUT proteins can transport monosaccharides structurally similar to glucose. (correct)
  • GLUT proteins are exclusively responsible for transporting glucose derivatives.
  • All GLUT proteins are activated by hormones other than insulin.
  • GLUT4 is the only GLUT protein that can increase glucose transport rate significantly.

    • What effect does insulin have on GLUT4 in insulin-sensitive tissues?

  • Insulin can enhance the rate of facilitated diffusion of glucose by 10- to 20-fold. (correct)
  • Insulin decreases the number of GLUT4 proteins on the cell membrane.
  • Insulin permanently alters GLUT4's structural configuration.
  • Insulin inhibits the action of GLUT4 in glucose transport.

    • In facilitated diffusion, which factor is primarily responsible for the movement of glucose across the cell membrane?

  • The electrical potential difference affecting the transport of glucose.
  • The concentration difference of glucose inside and outside the cell. (correct)
  • Pressure difference across the membrane.
  • The structural configuration of membrane-bound proteins.

    • Which of the following statements about facilitated diffusion is incorrect?

    <p>GLUT proteins require ATP to transport glucose.</p> Signup and view all the answers

    What types of substances are primarily transported via the GLUT family of proteins?

    <p>Glucose and similar monosaccharides.</p> Signup and view all the answers

    What is the definition of one osmole?

    <p>One gram molecular weight of osmotically active solute.</p> Signup and view all the answers

    How does the dissociation of a solute affect the osmole count?

    <p>It increases the osmole count based on the number of ions produced.</p> Signup and view all the answers

    What happens to the concentrations of sodium ions inside cells compared to the extracellular fluid?

    <p>They remain low inside the cells despite high concentrations outside.</p> Signup and view all the answers

    What distinguishes active transport from simple diffusion?

    <p>Active transport moves solutes against concentration and other gradients.</p> Signup and view all the answers

    What is the relationship between glucose and osmoles in terms of its molecular weight?

    <p>180 grams of glucose equals 1 osmole.</p> Signup and view all the answers

    In the context of solute dissociation, what is unique about sodium chloride's contribution to osmoles?

    <p>58.5 grams of sodium chloride equals 2 osmoles because of its dissociation.</p> Signup and view all the answers

    What is the primary function of active transport within cells regarding potassium and sodium ions?

    <p>It facilitates the movement of potassium ions into the cell and sodium ions out.</p> Signup and view all the answers

    Which of the following best describes simple diffusion?

    <p>It leads to equal concentrations on both sides of the membrane.</p> Signup and view all the answers

    What triggers net movement of water across a selectively permeable membrane?

    <p>A concentration difference for water across the membrane</p> Signup and view all the answers

    How does osmotic pressure affect the movement of water in a sodium chloride solution?

    <p>It prevents water from moving into the sodium chloride solution</p> Signup and view all the answers

    What happens to the cell when water moves across its membrane during osmosis?

    <p>The cell swells or shrinks depending on the direction of water movement</p> Signup and view all the answers

    What is the defining characteristic of the membrane involved in osmosis?

    <p>It is selectively permeable to water but not solutes</p> Signup and view all the answers

    What occurs when there is zero net movement of water within a cell?

    <p>There is equal water diffusion in both directions</p> Signup and view all the answers

    Which factor can cause osmosis to slow down or stop?

    <p>Application of pressure to the solution</p> Signup and view all the answers

    In the scenario of osmosis illustrated, which chamber includes pure water?

    <p>Chamber B, which contains pure water</p> Signup and view all the answers

    Which statement correctly describes the role of osmosis in cells?

    <p>Osmosis occurs to equalize concentrations on either side of the membrane</p> Signup and view all the answers

    What is the role of ATPase activity in the sodium-potassium pump?

    <p>To cleave ATP and provide energy for ion transport</p> Signup and view all the answers

    How many sodium ions are extruded from the cell during one cycle of the sodium-potassium pump?

    <p>Three sodium ions</p> Signup and view all the answers

    What happens when potassium ions bind to the carrier protein?

    <p>The carrier protein activates ATPase function</p> Signup and view all the answers

    Which ions are involved in the transport process of the sodium-potassium pump?

    <p>Sodium and potassium</p> Signup and view all the answers

    What is the electrochemical gradient's role in active transport?

    <p>It allows for the movement of ions against their concentration gradients</p> Signup and view all the answers

    What conformational change occurs in the carrier protein during ion transport?

    <p>The protein undergoes a chemical alteration to release sodium</p> Signup and view all the answers

    Which of the following correctly describes primary active transport?

    <p>It uses ATP to transport ions against their gradient</p> Signup and view all the answers

    What is the net ion movement during one cycle of the sodium-potassium pump?

    <p>Two potassium ions in and three sodium ions out</p> Signup and view all the answers

    What is the osmotic pressure exerted by a concentration of 1 osmole per liter at 37°C?

    <p>19,300 mm Hg</p> Signup and view all the answers

    How is 1 milliosmole per liter concentration related to osmotic pressure?

    <p>It generates 19.3 mm Hg of osmotic pressure.</p> Signup and view all the answers

    What is the calculated total osmotic pressure of body fluids at a 300-milliosmolar concentration?

    <p>5,790 mm Hg</p> Signup and view all the answers

    Why is the measured osmotic pressure of body fluids lower than the calculated value?

    <p>Ions are attracted to each other, limiting their movement.</p> Signup and view all the answers

    What is the average osmotic pressure of body fluids compared to the calculated value?

    <p>0.93 times the calculated value</p> Signup and view all the answers

    What does the presence of many ions in body fluids imply about osmotic particles?

    <p>They can cluster together, altering effective osmotic pressure.</p> Signup and view all the answers

    What is osmolarity primarily determined by?

    <p>The number of osmotic particles in a solution.</p> Signup and view all the answers

    Which statement accurately describes the effects of temperature on osmotic pressure?

    <p>Normal body temperature allows for a standard osmotic pressure of 5,500 mm Hg.</p> Signup and view all the answers

    Study Notes

    Facilitated Diffusion

    • Facilitated diffusion allows substances like glucose and amino acids to cross cell membranes.
    • At least 14 GLUT (glucose transporter) proteins identified, responsible for glucose transport in various tissues.
    • GLUT proteins can also transport galactose and fructose, which have similar structures to glucose.
    • GLUT4, activated by insulin, can increase glucose transport rates by 10- to 20-fold in insulin-sensitive tissues.

    Osmosis Across Selectively Permeable Membranes

    • Water is the most abundant substance to diffuse through cell membranes.
    • Regular diffusion of water balances in both directions, keeping cell volume constant.
    • A concentration difference can create net water movement across a membrane, affecting cell size—swelling or shrinking.
    • Applying pressure to a sodium chloride solution can slow, stop, or reverse osmosis.

    Osmotic Pressure

    • Osmotic pressure defines how much pressure is needed to prevent water movement into a solution.
    • At 37°C, a concentration of 1 osmol/L can exert approximately 19,300 mm Hg osmotic pressure.
    • Actual osmotic pressure of body fluids averages around 5500 mm Hg, lower than calculated due to ion interactions in fluids.

    Osmolarity and Osmolality

    • Osmolarity expresses solution concentration in terms of particle numbers, measured in osmoles rather than mass.
    • One osmole equals 1 gram molecular weight of a solute; for glucose, this is 180 grams.
    • Dissociated solutes, like sodium chloride, yield more osmoles (e.g., 1 g of NaCl equals 2 osmoles).

    Active Transport

    • Active transport is key in moving ions against their concentration gradients.
    • Sodium-potassium pump is a primary active transport mechanism transporting sodium ions out and potassium ions into cells.
    • Active transport relies on energy, derived from ATP, to shift molecules uphill against gradients.
    • An ATPase function in carrier proteins activates when specific ions are bound, triggering ATP cleavage and ion movement.

    Example of Active Transport

    • Sodium-potassium pump extrudes three sodium ions and brings two potassium ions into the cell, highlighting energy dependency and conformational changes of the carrier protein.

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    Related Documents

    Transport of Substances Through Cell Membranes (Guyton & Hall 14th ed) PDF

    Description

    This quiz explores the postulated mechanisms behind facilitated diffusion, specifically focusing on glucose and amino acids' transport across cell membranes. It also highlights the various GLUT membrane proteins and their roles in transporting these molecules within different tissues.

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