Biology Chapter: Water and Its Importance
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Questions and Answers

What characteristic of water contributes to its ability to resist temperature changes?

  • High thermal conductivity
  • Increased heat capacity (correct)
  • Low heat of fusion
  • High pH level

    • Which of the following describes water's role in living organisms?

  • It acts solely as a solid medium.
  • It is primarily a waste product.
  • It has no role in cellular processes.
  • It serves as a transport system. (correct)

    • Which property of water facilitates the dissipation of heat in biological systems?

  • Low specific heat
  • High viscosity
  • Increased thermal conductivity (correct)
  • Reactivity with acids

    • What is meant by the term 'universal solvent' in reference to water?

    <p>It can dissolve a wide range of solutes.</p> Signup and view all the answers

    How does water contribute to maintaining homeostasis in living organisms?

    <p>Through its participation in acid-base reactions.</p> Signup and view all the answers

    What property of water allows it to dissolve polar molecules effectively?

    <p>Formation of hydrogen bonds</p> Signup and view all the answers

    Which factor does NOT influence water intake?

    <p>Body temperature</p> Signup and view all the answers

    How is osmolality primarily regulated in the body?

    <p>By adjusting total body water</p> Signup and view all the answers

    Which electrolyte concentration is commonly used to assess water balance disorders?

    <p>Serum sodium</p> Signup and view all the answers

    What effect does high latent heat of evaporation in water have on the body?

    <p>It aids in temperature regulation.</p> Signup and view all the answers

    What is the role of the dipolar nature of water?

    <p>It allows water to form hydrogen bonds.</p> Signup and view all the answers

    Which of the following factors does NOT affect total body water content?

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

    How much water is typically lost through urine per day?

    <p>1500 mL</p> Signup and view all the answers

    Why do females typically have lower body water content than males?

    <p>They have higher fat content.</p> Signup and view all the answers

    What is the bond angle of a water molecule?

    <p>104.3°</p> Signup and view all the answers

    What is cohesion in the context of water's properties?

    <p>Attraction between particles of water.</p> Signup and view all the answers

    How does the amount of fat in the body affect water content?

    <p>Higher fat content leads to decreased water content.</p> Signup and view all the answers

    Which of the following is a major source of daily water intake?

    <p>Drinking water</p> Signup and view all the answers

    What is the primary function of a Bronsted-Lowry acid?

    <p>Donates a proton</p> Signup and view all the answers

    Which statement accurately describes a Lewis acid?

    <p>Accepts an electron pair</p> Signup and view all the answers

    How do buffers help maintain pH levels in a solution?

    <p>By reacting with conjugate bases to minimize pH change</p> Signup and view all the answers

    What components make up a typical buffer system?

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

    What role does the Henderson-Hasselbalch equation serve in biochemistry?

    <p>Computes the pH of a buffer solution</p> Signup and view all the answers

    Which of the following best describes a Bronsted-Lowry base?

    <p>Accepts a proton</p> Signup and view all the answers

    Why is the logarithmic scale used for pH and pOH measurements?

    <p>Because ion concentrations vary greatly</p> Signup and view all the answers

    What happens when a weak acid is added to a buffered solution?

    <p>It reacts with the conjugate base to stabilize pH</p> Signup and view all the answers

    What is the pH of pure water at 25°C?

    <p>7</p> Signup and view all the answers

    What does a higher osmolarity indicate?

    <p>Higher solute content</p> Signup and view all the answers

    Which equation represents the dissociation constant of water?

    <p>Kw = [H+][OH-]</p> Signup and view all the answers

    What is the relationship of osmolality to the amount of solute?

    <p>It measures solute per kilogram of solvent.</p> Signup and view all the answers

    According to Arrhenius, what defines an acid?

    <p>A substance that increases hydronium ion concentration.</p> Signup and view all the answers

    Which of the following is true regarding the pOH of pure water?

    <p>It equals 7.</p> Signup and view all the answers

    What is represented by the variable Keq in the dissociation of water?

    <p>The equilibrium constant for the dissociation of water.</p> Signup and view all the answers

    What is the value of Kw at 25°C?

    <p>$1 \times 10^{-14}$</p> Signup and view all the answers

    Study Notes

    Water

    • Predominant chemical component of a living organism
    • Forms an essential part of body cell and body fluids
    • The matrix of many living reactions
    • “Universal solvent”
    • Medium in intracellular and extracellular processes
    • Transport system
    • Important in maintain homeostasis

    Distribution of Body Water

    • Total amount of body water is 45-80%
    • Water content is dependent on:
      • Body weight
      • Age
      • Sex
      • Amount of fat
    • Younger people have higher water content
    • Obese persons have less water content
    • Females have less water content because they have higher fat content

    Water Balance

    • Average intake and output per day is 2750mL

    Chemical Structure of Water

    • Consists of 2 atoms of H and 1 atom of O
    • Dipolar nature (both with partial + and – ends) allows it to form hydrogen bonds
    • Responsible for its solvent property
    • Can act as H+ donor and H+ acceptor simultaneously
    • Has 2 unshared electron pairs that form an electron-densed cloud
    • A bent molecule with a bond angle of 104.3°

    Properties of Water

    • Liquid at room temperature
    • Has a high surface tension
    • Cohesion: attraction between particles of same substance (e.g. surface tension which enables insect to walk in water)
    • Adhesion: attraction between two different substances
    • High conductivity
    • High latent heat of evaporation

    Water as a Solvent

    • Dissolution (because H2O forms bonds and electrostatic interactions)
    • Hydrogen bonds are strong enough to dissolve polar molecules in water and to separate charges

    Osmosis

    • Water distribution is dependent on solute concentration in the body
    • It is proportional to the total concentration of all dissolved molecules
    • Osmolality and Osmolarity:
      • A measure of osmotic pressure
      • A total concentration of dissolved particles in a solution
      • Osmolarity: number of particles of solute per liter of solution
      • Osmolality: number of particles of solute per kilogram of solvent
    • The higher the osmolarity, the higher the solute content

    Regulation of Osmolality

    • Osmolality is regulated by changing the total body water and not by changing body solutes
    • Measurement of osmolality in one compartment will reflect the osmolality in all compartments
    • The serum sodium concentration, being a measure of body osmolality, is used to diagnose disorders of water balance

    Dissociation of Water

    • Forms H+ and OH- at 0.0000001M or 10-7mol/L
    • pH of water= -log[𝐻 +] = 7
    • pOH of water= 7
    • Acts as partly acid and base
    • Dissociation constant:
      • Keq: [𝐻 +][𝑂𝐻 −]/ 𝐻2𝑂 [ ]
      • Kw=[𝐻 +][𝑂𝐻 −]= 1×10-14
      • pKa= -log 1×10-14 = 14

    Acids and Bases

    • Arrhenius:
      • Acids increase the concentration of hydronium ions when added to solutions, and base increases the concentration of hydroxide ions.
    • Bronsted-Lowry:
      • Acid is a substance that donates a proton (hydrogen ion), and a base is a substance that accepts a proton
    • Lewis:
      • Lewis acid is a substance that accepts an electron pair and a Lewis base is a substance that donates an unshared electron pair

    PH and POH

    • Due to the enormous range in the concentrations of hydronium and hydroxide ions, we usually use a logarithmic scale to express these concentrations.

    Buffers

    • Certain solutions can resist drastic changes in pH when small quantities of acids and base are added to them
    • Mixtures of a weak acid and a salt containing its conjugate base or a weak base and a salt containing its conjugate acid
    • Buffers maintain homeostasis in the body

    Henderson-Hasselbalch Equation

    • The pH of the buffer solution is computed through the Henderson-Hasselbalch equation

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    Description

    Explore the critical role of water in living organisms through this quiz. Delve into its chemical structure, the distribution of body water, and the concept of water balance. Test your knowledge on how water influences bodily functions and homeostasis.

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