2/9/24, 3:52 PM Medical Biochemistry 1 basic notes that are well arranged
• Medical Biochemistry
HNS 2113
• Dr. Otsyula Munyekenye
• Introduction
• Biochemistry is the study of the chemistry of life processes.
• Biochemistry asks how properties of living organisms arise from the thousands of different
biomolecules.
• Biochemistry describes how the collections of inanimate molecules that constitute living
organisms interact to maintain and perpetuate life governed solely by the physical and chemical
laws that govern the nonliving universe
• Water
• Water is the most abundant substance in living systems, making up 45 - 70% or more of the
weight of most organisms.
• We will describe the physical and chemical properties of water, to which all aspects of cell
structure and function are adapted.
• Hydrogen bonds between water molecules provide the cohesive forces that make water a liquid
at room temperature and a crystalline solid (ice) with a highly ordered arrangement of
molecules at cold temperatures.
• Water
• Polar biomolecules dissolve readily in water because they can replace water-water interactions
with more energetically favorable water-solute interactions.
• In contrast, nonpolar biomolecules are poorly soluble in water because they interfere with
water-water interactions but are unable to form water-solute interactions.
• Water
• As the biological solvent, water plays a major role in all aspects of metabolism: absorption,
transport, digestion, and excretion of inorganic and organic substances, as well as maintenance
of body temperature.
• The unique properties of water are inherent in its structure.
• Water has a higher melting point, boiling point, and heat of vaporization than most other
common solvents.
• Water
• It is the hydrogen bonding that give water its unusual properties.
• These unusual properties are a consequence of attractions between adjacent water molecules
that give liquid water great internal cohesion.
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, 2/9/24, 3:52 PM Medical Biochemistry 1 basic notes that are well arranged
• In the electron structure of the H2O molecule each hydrogen atom of a water molecule shares
an electron pair with the central oxygen atom.
• Water
• The oxygen nucleus attracts electrons more strongly than does the hydrogen nucleus (a proton)
this makes oxygen more electronegative.
• The result of this unequal electron sharing is two electric dipoles in the water molecule, one
along each of the H—O bonds.
• Each hydrogen atom bears a partial positive charge, and the oxygen atom bears a partial
negative charge equal in magnitude to the sum of the two partial positives.
• See Fig 1 below
• Fig 1: Structure of Water
• Water
• As a result, there is an electrostatic attraction between the oxygen atom of one water molecule
and the hydrogen of another called hydrogen bond.
• See Fig 2
• The sum of all the hydrogen bonds between H2O molecules confers great internal cohesion on
liquid water.
• The nearly tetrahedral arrangement of the orbitals about the oxygen atom allows each water
molecule to form hydrogen bonds with as many as four neighboring water molecules.
• Fig 2: H-Bond
• Water
• In liquid water at room temperature and atmospheric pressure, water molecules are
disorganized and in continuous motion, so that each molecule forms hydrogen bonds with an
average of only 3.4 other molecules.
• In ice, on the other hand, each water molecule is fixed in space and forms hydrogen bonds with
a full complement of four other water molecules to yield a regular lattice structure.
• Water
• Hydrogen bonds account for the relatively high melting point of water, because much thermal
energy is required to break a sufficient proportion of hydrogen bonds to destabilize the crystal
lattice of ice
• Physical properties
• Properties of water that are important to biological systems include :
• Melting point
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• Medical Biochemistry
HNS 2113
• Dr. Otsyula Munyekenye
• Introduction
• Biochemistry is the study of the chemistry of life processes.
• Biochemistry asks how properties of living organisms arise from the thousands of different
biomolecules.
• Biochemistry describes how the collections of inanimate molecules that constitute living
organisms interact to maintain and perpetuate life governed solely by the physical and chemical
laws that govern the nonliving universe
• Water
• Water is the most abundant substance in living systems, making up 45 - 70% or more of the
weight of most organisms.
• We will describe the physical and chemical properties of water, to which all aspects of cell
structure and function are adapted.
• Hydrogen bonds between water molecules provide the cohesive forces that make water a liquid
at room temperature and a crystalline solid (ice) with a highly ordered arrangement of
molecules at cold temperatures.
• Water
• Polar biomolecules dissolve readily in water because they can replace water-water interactions
with more energetically favorable water-solute interactions.
• In contrast, nonpolar biomolecules are poorly soluble in water because they interfere with
water-water interactions but are unable to form water-solute interactions.
• Water
• As the biological solvent, water plays a major role in all aspects of metabolism: absorption,
transport, digestion, and excretion of inorganic and organic substances, as well as maintenance
of body temperature.
• The unique properties of water are inherent in its structure.
• Water has a higher melting point, boiling point, and heat of vaporization than most other
common solvents.
• Water
• It is the hydrogen bonding that give water its unusual properties.
• These unusual properties are a consequence of attractions between adjacent water molecules
that give liquid water great internal cohesion.
about:blank 1/13
, 2/9/24, 3:52 PM Medical Biochemistry 1 basic notes that are well arranged
• In the electron structure of the H2O molecule each hydrogen atom of a water molecule shares
an electron pair with the central oxygen atom.
• Water
• The oxygen nucleus attracts electrons more strongly than does the hydrogen nucleus (a proton)
this makes oxygen more electronegative.
• The result of this unequal electron sharing is two electric dipoles in the water molecule, one
along each of the H—O bonds.
• Each hydrogen atom bears a partial positive charge, and the oxygen atom bears a partial
negative charge equal in magnitude to the sum of the two partial positives.
• See Fig 1 below
• Fig 1: Structure of Water
• Water
• As a result, there is an electrostatic attraction between the oxygen atom of one water molecule
and the hydrogen of another called hydrogen bond.
• See Fig 2
• The sum of all the hydrogen bonds between H2O molecules confers great internal cohesion on
liquid water.
• The nearly tetrahedral arrangement of the orbitals about the oxygen atom allows each water
molecule to form hydrogen bonds with as many as four neighboring water molecules.
• Fig 2: H-Bond
• Water
• In liquid water at room temperature and atmospheric pressure, water molecules are
disorganized and in continuous motion, so that each molecule forms hydrogen bonds with an
average of only 3.4 other molecules.
• In ice, on the other hand, each water molecule is fixed in space and forms hydrogen bonds with
a full complement of four other water molecules to yield a regular lattice structure.
• Water
• Hydrogen bonds account for the relatively high melting point of water, because much thermal
energy is required to break a sufficient proportion of hydrogen bonds to destabilize the crystal
lattice of ice
• Physical properties
• Properties of water that are important to biological systems include :
• Melting point
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