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Questions and Answers
What is the equilibrium constant, Keq, defined as?
Keq = [H+][OH-]/[H2O]
What is the equilibrium constant, Keq, of water under standard conditions?
In pure water, the concentration of protons ([H+]) is equal to the concentration of hydroxide ions ([OH-]).
True
What is the pH of a solution with a [H+] concentration of 10^-2 M?
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What is the pH of a solution with a [OH-] concentration of 10^-2 M?
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What is biochemistry?
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Which six non-metallic elements constitute more than 97% of the weight of living organisms?
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Water is the most indispensable nutrient for humans.
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Macromolecules are polymers created by joining smaller organic molecules, referred to as ________, via condensation reactions.
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What is the main characteristic underlying the properties of water?
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What is the angle between the two covalent O-H bonds in water?
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What type of bond is formed between the slightly positive hydrogen atom of one molecule and the slightly negative oxygen atom of another molecule?
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What is the heat energy required to disrupt a hydrogen bond in water?
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Which type of molecules are hydrophobic and do not dissolve in water?
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Water is the only molecule capable of establishing hydrogen bonds.
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Study Notes
Introduction to Biochemistry
- Biochemistry is the study of the molecules and biochemical reactions of life.
- It explores the molecular mechanisms that underlie the functioning of living organisms.
Importance of Water
- Water is the most indispensable nutrient, and humans can survive only a few days without it.
- Life is a water-based phenomenon, and water constitutes 60-70% of the mass of cells.
- Water is an excellent solvent, and macromolecules are subdivided according to their water affinity (hydrophilic versus hydrophobic).
Functions of Water
- Transports nutrients and oxygen
- Regulates cell structure
- Aids in regulating the body temperature
- Serves as a shock absorbent
- Serves as a solvent
- Cleanses the blood of waste
Structure of Water
- Water is a polar molecule, with a V-shaped structure and a 104.5o angle between the two covalent O-H bonds.
- Oxygen has 8 electrons, 2 in the inner shell and 6 in the outer shell, which can accommodate 8 electrons in one s and three p orbitals.
- The outer shell electrons occupy 4 sp3 hybrid orbitals, which are pictured as occupying the four corners of a tetrahedron.
Hydrogen Bonding
- Hydrogen bonds are a type of non-covalent attraction between the slightly positive hydrogen atom of one molecule and the slightly negative oxygen atom of another molecule.
- The water molecule contributing the hydrogen is called the hydrogen donor, and the molecule contributing the electronegative atom is called the hydrogen acceptor.
- Hydrogen bonds are weaker than covalent bonds, but are crucial for the structure and function of macromolecules.
Properties of Water
- High melting point of ice due to hydrogen bonding
- Lower density of solid phase compared to liquid phase
- High specific heat/heat capacity
- High heat of vaporization
Non-covalent Interactions
- Hydrogen bonds: between hydrogen donor and hydrogen acceptor
- Charge-charge interactions: electrostatic interactions between two charged molecules
- Van der Waals forces: weak non-covalent interactions between permanent dipoles of two uncharged polarized bonds
- Hydrophobic interactions: the exclusion of non-polar molecules from water, leading to their association with each other
Ionization of Water
- Water can ionize into hydronium (H3O+) and hydroxide (OH-) ions
- The ionization of water is a reversible reaction, and the concentrations of reactants and products reach equilibrium
- The ion product for water (Kw) is 1x10-14 M2
pH and pOH
- pH is a logarithmic scale that measures the concentration of protons in a solution
- pH = -log[H+] = log 1/[H+]
- pOH is a logarithmic scale that measures the concentration of hydroxide ions in a solution
- pOH = -log[OH-] = log 1/[OH-]
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Description
This quiz covers the basics of biochemistry, including the definition and importance of biochemistry, the composition of living organisms, and the functions of water in biological systems.
