Biochemistry 1: Importance of Water
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Questions and Answers

What shape does a water molecule resemble?

  • Flat rectangle
  • Perfect tetrahedron
  • Linear and symmetrical
  • Irregular, slightly skewed tetrahedron (correct)

Which atom is at the center of a water molecule?

  • Hydrogen
  • Carbon
  • Nitrogen
  • Oxygen (correct)

How does the shape of a water molecule affect its properties?

  • It makes water a good conductor of electricity.
  • It allows water to be a solid at room temperature.
  • It contributes to its ability to form dipoles. (correct)
  • It enhances water's acidity.

What geometric feature characterizes the structure of a water molecule?

<p>A irregular tetrahedron (D)</p> Signup and view all the answers

What is the significance of the dipole nature of water molecules?

<p>It enables hydrogen bonds to form. (B)</p> Signup and view all the answers

What phenomenon is favored by the hydrogen bonding characteristic of water molecules?

<p>Self-association into ordered arrays (B)</p> Signup and view all the answers

What aspect of water molecules contributes to their ability to self-associate?

<p>Presence of both hydrogen and oxygen atoms (C)</p> Signup and view all the answers

Which characteristic of water molecules is primarily responsible for the formation of ordered arrays?

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

What is the result of the self-association of water molecules due to hydrogen bonding?

<p>Formation of ordered arrays (D)</p> Signup and view all the answers

Which factor does NOT contribute to the self-association of water molecules?

<p>Lack of hydrogen bonds (B)</p> Signup and view all the answers

What type of bond is primarily responsible for the unique properties of water?

<p>Hydrogen bonds (D)</p> Signup and view all the answers

Which statement accurately describes the charges within a water molecule?

<p>The hydrogen atoms carry a partial positive charge, while the oxygen atom carries a partial negative charge. (B)</p> Signup and view all the answers

What characteristic of water is attributed to its polar nature?

<p>Solvent properties (B)</p> Signup and view all the answers

Which of the following best explains why water has a high surface tension?

<p>Strong hydrogen bonds between water molecules (C)</p> Signup and view all the answers

What results from the unshared electrons of the oxygen atom in a water molecule?

<p>The development of a partial negative charge on the oxygen atom (C)</p> Signup and view all the answers

What is primarily responsible for buffering physiological fluids in cells?

<p>Ionization of phosphoric acid (B)</p> Signup and view all the answers

Which ions are formed from the ionization of phosphoric acid (H3PO4)?

<p>Phosphate ions (A)</p> Signup and view all the answers

What role do phosphates play in physiological fluids?

<p>They act as buffers (A)</p> Signup and view all the answers

Which physiological condition is affected by the buffering capacity of phosphates?

<p>pH balance in bodily fluids (A)</p> Signup and view all the answers

Why is phosphoric acid considered essential for cellular functions?

<p>It ionizes to form phosphates that aid in buffering. (D)</p> Signup and view all the answers

What is the general format of the Henderson-Hasselbalch equation?

<p>pH = pK + Log {coo}/{cooH} (A)</p> Signup and view all the answers

Which group in drugs is directly predicted by the Henderson-Hasselbalch equation?

<p>The carboxyl group (cooH) (D)</p> Signup and view all the answers

Why is understanding the degree of ionization of drugs important?

<p>It affects the drug's ability to be absorbed through biological membranes. (B)</p> Signup and view all the answers

What does the 'pK' in the Henderson-Hasselbalch equation represent?

<p>The acid dissociation constant of the acid form (A)</p> Signup and view all the answers

In the context of drug absorption, which form of the drug passes through biological membranes more easily?

<p>The unionized form (D)</p> Signup and view all the answers

What role does the CO2 bicarbonate system play in the body?

<p>It prevents acid or base imbalance. (B)</p> Signup and view all the answers

In which bodily fluids is the CO2 bicarbonate system primarily active?

<p>Plasma and interstitial fluid. (C)</p> Signup and view all the answers

Which of the following best describes the function of the CO2 bicarbonate system?

<p>It buffers changes in pH. (D)</p> Signup and view all the answers

What would happen to the body without the CO2 bicarbonate buffering system?

<p>Risk of acid or base imbalance. (C)</p> Signup and view all the answers

Which of the following systems interacts with the CO2 bicarbonate system to manage acid-base balance?

<p>Respiratory system. (D)</p> Signup and view all the answers

Flashcards

Water molecule shape

A water molecule is an irregular, slightly skewed tetrahedron.

Water molecule center

Oxygen is at the center of the water molecule.

Water molecule structure

Water molecules have an irregular, slightly skewed structure.

Water molecule is a tetrahedron

A water molecule is a 3D geometric shape, like a pyramid with four corners.

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Oxygen in water

Oxygen is located in the center of the water molecule.

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Water molecule features

Water molecules have both positive and negative ends, creating polarity.

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Hydrogen bonding

Attractive forces between water molecules due to their polarity.

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Self-association

Water molecules grouping together due to hydrogen bonding.

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Ordered arrays

The specific arrangement of water molecules.

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Figure 2-2

A diagram showing water molecules arranged in a specific structure.

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Water molecule polarity

Water molecules have a positive and negative end due to uneven electron distribution.

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Hydrogen bonds in water

Weak attractions form between the positive hydrogen end of one water molecule and the negative oxygen end of another.

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What makes water polar?

The oxygen atom attracts electrons more strongly than the hydrogen atoms, creating partial charges.

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Partial charges in water

The oxygen atom has a partial negative charge, while the hydrogen atoms have partial positive charges.

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Hydrogen bond strength

Hydrogen bonds are relatively weak compared to covalent bonds within a water molecule.

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Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical formula used to calculate the pH of a solution containing a weak acid and its conjugate base. It helps predict the degree of ionization of acidic groups in molecules like drugs for absorption.

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pH

A measure of the acidity or alkalinity of a solution. It is a scale from 0 to 14, with 7 being neutral.

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pKa

The negative logarithm of the acid dissociation constant (Ka). It represents the pH at which a weak acid is half ionized.

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Ionized Form

A molecule or part of a molecule that carries an electric charge (positive or negative)

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Unionized Form

A molecule or part of a molecule that does not carry an electric charge

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Phosphate Buffering

The process of maintaining the pH of biological fluids using phosphate ions. This is vital for cellular function and overall well-being.

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Phosphoric Acid (H3PO4)

A weak acid that plays a crucial role in buffering biological fluids. It ionizes to form phosphate ions, which help regulate acidity.

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Phosphate Ions

Charged molecules (PO43-) that are formed from the ionization of phosphoric acid. They are critical for buffering, meaning they help control the pH of fluids.

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Why is phosphate important?

Phosphate ions act as a buffer, helping to maintain the pH of body fluids within a narrow range. This prevents acidity or alkalinity from becoming too extreme, which is essential for healthy cell function.

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How does phosphate buffering work?

Phosphate can donate or accept hydrogen ions (H+), which change the pH of a solution. This allows it to counter shifts in acidity or alkalinity, keeping the pH stable.

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CO2-Bicarbonate System

A critical buffering system in blood plasma and interstitial fluid, preventing dangerous shifts in acidity (pH) levels.

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Buffering

The process of resisting changes in pH by accepting or releasing hydrogen ions (H+).

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Acid-Base Imbalance

A disruption in the body's pH balance, leading to conditions like acidosis (too acidic) or alkalosis (too basic).

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How Does the CO2-Bicarbonate System Work?

It involves a balance between carbon dioxide (CO2), bicarbonate ions (HCO3-), and hydrogen ions (H+). When blood becomes acidic, the system removes H+ by combining with bicarbonate to form CO2. When blood becomes basic, the system releases H+ through the breakdown of bicarbonate.

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Importance of the CO2-Bicarbonate System

This system plays a vital role in maintaining a constant pH level in the blood and interstitial fluid, essential for normal physiological functions and survival.

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Study Notes

Course Information

  • Course: Biochemistry 1
  • Department/Semester: Fourth semester, Fall
  • Lecture: First
  • Instructor: Uda Talha Khujli Abbas
  • Academic Year: 2025-2024

Biomedical Importance of Water

  • Water is the primary chemical component in living organisms.
  • It dissolves various organic and inorganic molecules due to its dipolar structure and ability to form hydrogen bonds.
  • Water is a reactant or product in many metabolic reactions.
  • Water slightly dissociates into hydroxide and proton ions.
  • Buffers maintain extracellular fluid pH between 7.35 and 7.45.
  • Acidosis (blood pH < 7.35) results from conditions like diabetic ketosis and lactic acidosis.
  • Alkalosis (pH > 7.45) can occur due to vomiting of acidic gastric contents.

Water as a Biological Solvent

  • Water is an ideal biological solvent due to its dipole nature.
  • Water molecules are slightly skewed tetrahedrons with oxygen at the center.
  • The oxygen atom is electronegative, pulling electrons away from hydrogen, creating partial positive and negative charges.
  • This polarity allows water to dissolve many charged compounds like salts.

Water Molecules and Hydrogen Bonds

  • Water molecules form hydrogen bonds.
  • Unshielded hydrogen nuclei bonded to electronegative oxygen or nitrogen atoms readily interact with unshared electron pairs in other oxygen or nitrogen atoms, creating hydrogen bonds.
  • Hydrogen bonding causes self-association of water molecules, influencing properties like viscosity, surface tension, and boiling point.
  • Water dissolves many organic biomolecules with functional groups that form hydrogen bonds.

Physical Properties of Water

  • Water is colorless, odorless, and tasteless.
  • Water molecules have intermolecular bonds that result in unique characteristics.
  • Liquid water density is 1.00 g/mL
  • Ice density is 0.92 g/mL

Structure of Liquid Water

  • Liquid water structure is irregular, with continual breakdown and reformation of hydrogen bonds
  • Water molecules act as both hydrogen donors and acceptors.

Self-Ionization of Water

  • Water molecules dissociate into H+ and OH- ions.
  • This dissociation occurs through the breakage of an -OH bond.
  • [H+][OH-] = 10⁻¹⁴ mol²/L² (at 25°C).

pH

  • pH is a measure of hydrogen ion concentration, calculated as -log[H+].
  • pH below 7 is acidic, above 7 is basic.
  • The pH in different compartments of the human body varies.

Acids and Bases

  • Acids release protons (H+) and gain a negative charge (anions).
  • Bases accept protons and gain a positive charge (cations).
  • Amino acids contain both acidic (-COOH) and basic (-NH2) groups, which can ionize depending on the pH.

Ionization of Amino Acids

  • The ionization state of amino acids depends on the pH of the solution.
  • At a specific pH (isoelectric pH), amino acids have no net charge (zwitterions).

The Henderson-Hasselbalch Equation

  • Predicts the ionization state of a weak acid or base based on the pK (acid dissociation constant) and pH.
  • Useful for calculating the degree of ionization of weak acids, such as those in biological molecules.

Buffers

  • Resist pH changes when acids or bases are added.
  • The buffering system in cells and body fluids is vital to maintain a stable pH.
  • Common buffers include phosphates and bicarbonate.

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Bio 1&2: Biomedical Importance of Water (Adalel Almotamyz College of Medical Sciences) PDF

Description

Explore the critical role of water in biochemistry through this quiz. Understand how water acts as a solvent and its significance in metabolic reactions, pH regulation, and more. Test your knowledge on the biochemical properties of water.

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