Water in Living Systems
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Questions and Answers

What percentage of the human body is composed of water?

  • 50-60%
  • 60-70% (correct)
  • 80-90%
  • 70-80%

    • What is the primary function of water in the human body?

  • To transport oxygen to the cells
  • To maintain a constant environment for cells
  • To act as a solvent for essential substances (correct)
  • To regulate body temperature

    • What is the term for maintaining a constant environment for cells?

  • Acid-base regulation
  • Thermoregulation
  • Osmoregulation
  • Homeostasis (correct)

    • What is the term for a solution that resists change in pH when small quantities of an acid or base are added to it?

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

    What is an acidic buffer solution typically made from?

    <p>A weak acid and one of its salts</p> Signup and view all the answers

    What happens to the position of equilibrium when a sodium salt is added to an acidic buffer solution?

    <p>It shifts to the left</p> Signup and view all the answers

    What is the role of water in regulating body temperature?

    <p>It helps to regulate body temperature</p> Signup and view all the answers

    What is the term for the movement of molecules into and out of cellular compartments?

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

    What happens to the pH of a buffer solution when an acid is added?

    <p>The pH will not change very much</p> Signup and view all the answers

    What is the role of CH3COO- ions in a buffer solution when an acid is added?

    <p>They react with H+ ions to form CH3COOH</p> Signup and view all the answers

    What happens to the equilibrium position when an alkali is added to an acidic buffer solution?

    <p>The equilibrium position shifts to the right</p> Signup and view all the answers

    What is the composition of an alkaline buffer solution?

    <p>A weak base and its conjugate acid</p> Signup and view all the answers

    What happens to the equilibrium position when an acid is added to an alkaline buffer solution?

    <p>The equilibrium position shifts to the left</p> Signup and view all the answers

    What is the definition of a chemical equilibrium?

    <p>A state where the rate of forward reaction equals the rate of reverse reaction</p> Signup and view all the answers

    What does an equilibrium constant (K) greater than 10^2 indicate?

    <p>The products are favored in the equilibrium reaction</p> Signup and view all the answers

    What does an equilibrium constant (K) less than 10^-2 indicate?

    <p>The reactants are favored in the equilibrium reaction</p> Signup and view all the answers

    What is the major buffer system in blood?

    <p>Carbonic acid - bicarbonate system</p> Signup and view all the answers

    What happens to the concentration of H+ when a strong acid is added to the blood?

    <p>It increases</p> Signup and view all the answers

    What is the condition known as when the pH of blood drops to 7.1?

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

    What is the result of increased excretion of H+ and retention of HCO3 by kidneys?

    <p>Acidic urine</p> Signup and view all the answers

    What happens to the concentration of H+ ions when a base is added to the blood?

    <p>It decreases</p> Signup and view all the answers

    What is the condition known as when the pH of blood increases to 7.8?

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

    What is the result of hypoventilation?

    <p>Decrease in CO2 exhalation</p> Signup and view all the answers

    What is the purpose of the bicarbonate buffer system in blood?

    <p>To maintain the pH of blood</p> Signup and view all the answers

    What happens to the concentration of H+ when an acid is added to blood?

    <p>It increases</p> Signup and view all the answers

    Which of the following is regulated by the kidneys?

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

    What is the acid component of the bicarbonate buffer system?

    <p>H2CO3</p> Signup and view all the answers

    What happens to the rate of breathing when an acid is added to blood?

    <p>It increases</p> Signup and view all the answers

    What is the function of the enzyme carbonic anhydrase?

    <p>To catalyze the reaction between CO2 and H2O</p> Signup and view all the answers

    What happens to the concentration of carbonic acid when an alkali is added to blood?

    <p>It decreases</p> Signup and view all the answers

    What is the effect of increased partial pressure of CO2 in the gas phase in the lungs?

    <p>Increased rate of breathing</p> Signup and view all the answers

    What is the ultimate dependent variable in the bicarbonate buffer system?

    <p>Partial pressure of CO2 in the gas phase</p> Signup and view all the answers

    What is the primary reason for the bicarbonate buffer system's effectiveness?

    <p>Its ability to equilibrate with a large reserve of gaseous carbon dioxide</p> Signup and view all the answers

    At what pH is the bicarbonate buffer system most effective as a buffer?

    <p>6.1</p> Signup and view all the answers

    What is the principle enzyme that catalyzes the generation of HCO3-?

    <p>Carbonic anhydrase</p> Signup and view all the answers

    What happens to the ratio of bicarbonate to carbonic acid when carbonic anhydrase activity decreases?

    <p>It tends to fall</p> Signup and view all the answers

    What is the primary function of the kidney in the phosphate buffer system?

    <p>To remove excess HPO4- and H2PO4- from the body</p> Signup and view all the answers

    What happens to the reaction H2PO4- ↔ HPO4- when a strong acid is added?

    <p>The reaction shifts to the left</p> Signup and view all the answers

    Study Notes

    Water in Living Systems

    • Water is the most abundant chemical compound in living systems, making up 60-70% of the human body.
    • 2/3 of the total body water is intracellular, with the rest being interstitial fluid (25%) and blood plasma (25%).
    • Water acts as a solvent for essential substances such as Na+, K+, glucose, ATP, and proteins.
    • The body regulates both the volume and pH of water to maintain a constant environment for cells (homeostasis).
    • Water helps regulate body temperature and is a reactant and product in many chemical reactions in the living system.
    • It plays a crucial role in transporting oxygen and nutrients to cells and carrying away waste products.
    • Water is a medium for the movement of molecules into and out of cellular compartments.
    • Water is essential for the structure and function of biomolecules.

    Buffers

    • A buffer is a solution that resists changes in pH when small quantities of acid or base are added.
    • Acidic buffers have a pH less than 7, while basic buffers have a pH greater than 7.
    • Buffer solutions are made from a weak acid and its salt (e.g., ethanoic acid and sodium ethanoate) or a weak base and its salt (e.g., ammonia solution and ammonium chloride).

    How Buffer Solutions Work

    • Acidic buffers: When an acid is added to a buffer, the buffer removes most of the new hydrogen ions by combining with the weak acid to form a weak acid.
    • Basic buffers: When an alkali is added to a buffer, the OH- ions react with the weak base and its conjugate acid, shifting the equilibrium to the right.

    Chemical Equilibrium

    • A chemical reaction is in equilibrium when the rate of the forward reaction equals the rate of the reverse reaction.
    • The equilibrium constant (K) is a measure of the ratio of products to reactants at equilibrium.
    • When K is greater than 10^2, the products are favored, and when K is less than 10^-2, the reactants are favored.

    Buffer Systems in the Body

    • The major buffer system in blood is the carbonic acid-bicarbonate system.
    • This system helps regulate pH by buffering excess H+ or OH- ions.
    • When an acid is added, the system shifts to the left, forming more carbonic acid, which can be removed from the blood through exhalation.
    • When an alkali is added, the system shifts to the right, forming more bicarbonate, which can be removed through increased excretion by the kidneys.

    Regulation of pH in the Body

    • The body has several mechanisms to regulate pH, including:
      • Increasing or decreasing breathing rate to expel or retain CO2.
      • Increasing or decreasing excretion of H+ or HCO3- by the kidneys.
      • Increasing or decreasing the concentration of carbonic acid or bicarbonate in the blood.

    Bicarbonate Buffer

    • The bicarbonate buffer is a conjugate acid-base pair that helps regulate pH in the blood.
    • It is regulated by the kidneys and lungs.
    • The acid component (H2CO3) is generated from dissolved CO2 and water, while the base component (HCO3-) is regulated by the kidneys.
    • The buffer system is highly effective due to its equilibration with a large reserve of gaseous CO2 in the air space of the lungs.

    Phosphate Buffer

    • The phosphate buffer system is another buffer active mainly within cells.
    • It helps regulate pH by buffering excess H+ or OH- ions.
    • The kidneys remove excess HPO4-2 and H2PO4- from the body to maintain pH homeostasis.

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