SEPTEMBER 2023

BIOPHYSICAL
CHEMISTRY
Department of Biochemistry

Presented by GROUP 2
 TABLE
of contents
01. Introduction

02. Properties of H2O of Biological Importance 05. Colloidal State

03.Properties of Solution 06. Optical Activity

04. Hydrogen Ion - Concentration 07. Isotopes

Biophysical Chemistry

Biophysical Chemistry is an interdisciplinary field, combining elements of

biology, chemistry, and physics.

It focuses on understanding fundamental biological processes by studying the

fundamental physical and chemical principles that govern them.
Biophysical Chemistry
In summary, biochemistry explores how biological macromolecules,
such as proteins, nucleic acids, and lipids, interact with each other as
well as how they respond to physical forces and environmental
conditions.

It is concerned with the study of molecular structure, dynamics and

thermodynamics, with particular emphasis on the relationship between
structure and function.
 SEPTEMBER 2023

PROPERTIES OF H2O OF
BIOLOGICAL IMPORTANCE

Presented by GROUP 2
Properties of H2O of Biological Importance

Water or H2O
universal solvent
invaluable life-sustaining force
Regulates body temperature.
helps cells transport and use substances
Chemical Structure of Water

two hydrogen atoms and one

oxygen atom
The three atoms make an angle;
the H-O-H angleis approximately
104.5 degrees.
Chemical Structure of Water

Electronegativity
I. Hydrogen atom: 2.20
II. Oxygen atom: 3.44
*Hydrogen has only 2 electrons
while oxygen has 8 electrons
Chemical Structure of Water
Because oxygen is more electronegative than
hydrogen, the hydrogen atoms end up with a partial
positive charge, and the oxygen atom with a partial
negative charge. This separation of charge produces
a net dipole moment on the molecule. This results to
a polar covalent bond which is why water is a polar
molecule.
Chemical Structure of Water
Chemical Structure of Water
This molecular structure leads to hydrogen
bonding which is a stabilized structure in which a
hydrogen atom is in a line between the oxygen
atom on its own molecule and the oxygen on
another molecule. These hydrogen bonds, with
their extra attractive energy, are the cause of
many of the unusual properties of water.
PROPERTIES OF WATER
I. Surface Tension: Water
molecules want to cling to
each other. At the
surface, however, there
are fewer water molecules
to cling to since there is
air above (thus, no water
molecules).
PROPERTIES OF WATER
This results in a stronger bond between those molecules
that actually do come in contact with one another, and a
layer of strongly bonded water. This surface layer (held
together by surface tension) creates a considerable
barrier between the atmosphere and the water. In fact,
other than mercury, water has the greatest surface
tension of any liquid.
PROPERTIES OF WATER
II. Cohesion: Cohesion
refers to the attraction of
molecules for other
molecules of the same kind,
and water molecules have
strong cohesive forces
thanks to their ability to
form hydrogen bonds with
one another.
PROPERTIES OF WATER
Water is highly cohesive—it is the highest of the non-
metallic liquids. Water is sticky and clumps together into
drops because of its cohesive properties, but chemistry
and electricity are involved at a more detailed level to
make this possible. More precisely, the positive and
negative charges of the hydrogen and oxygen atoms that
make up water molecules makes them attracted to each
other.
PROPERTIES OF WATER
In a water molecule, the two hydrogen atoms align
themselves along one side of the oxygen atom, with the
result being that the oxygen side has a partial negative
charge and the side with the hydrogen atoms has a partial
positive charge. Thus when the positive side on one water
molecule comes near the negative side of another water
molecule, they attract each other and form a bond making
them cohesive in nature.
PROPERTIES OF WATER
III. Adhesion: Adhesion is the binding or attraction of
water to dissimilar molecules, atoms, surfaces, or
substances. The molecular concept of adhesion in
water is the same as the cohesion in water wherein
the attraction will depend if the "other molecules" of
a material are polar like in this example.
PROPERTIES OF WATER
The water molecules are more strongly
attracted to the glass than they are to
other water molecules (because glass
molecules are even more polar than
water molecules). You can see this by
looking at the image below: the water
extends highest where it contacts the
edges of the tube, and dips lowest in
the middle. The curved surface formed
by a liquid in a cylinder or tube is called
a meniscus.
PROPERTIES OF WATER
IV. High Heat Capacity: Water’s
high heat capacity is a property
caused by hydrogen bonding
among water molecules. When
heat is absorbed, hydrogen
bonds are broken and water
molecules can move freely.
When the temperature of water
decreases, the hydrogen bonds
are formed and release a
considerable amount of energy.
PROPERTIES OF WATER
Water has the highest specific heat capacity of any
liquid. It means that water needs a large amount of heat
to increase in temperature. As a result, it takes water a
long time to heat and a long time to cool. In fact, the
specific heat capacity of water is about five times more
than that of sand. This explains why the land cools
faster than the sea.
PROPERTIES OF WATER
V. High Heat of Vaporization:
This is an effect of the water's
high heat capacity which makes
it another property of water. In
order for water to heat up , it
needs to absorb large amounts
of heat. If that happens then
hydrogen bonds are in pieces.
Evaporation will only occure if
MANY hydrogen bonds are
broken down.
IONIZATION OF WATER
Ionization is defined as the process by which an atom or molecule
gains or loses a positive or negative charge as a result of chemical
changes. An ion is an electrically charged atom or molecule that
results. If the ion has a negative charge, it is called an anion; if it has
a positive charge, it is called a cation.

The basic ionisation reaction can be represented as follows:

M → M+ + e–
IONIZATION OF WATER

Ionization can occur as a result of the loss of an

electron in collisions with subatomic particles,
collisions with other atoms, molecules, and ions,
or interactions with electromagnetic radiation.
Amphiprotic Nature of Water

Due to its highly polar structure, liquid water can

either act as an acid (by donating a proton to a
base) or a base (by using a lone pair of electrons
to accept a proton).
Amphiprotic Nature of Water
As bases:
When a strong acid like HCl dissolves in water, it separates into
chloride ions (Cl–) and protons (H+). In turn, the proton reacts with
a water molecule to form the hydronium ion (H3O+). The acid in
this reaction is HCl, and the base is water, which accepts an H+ ion.

As acids:
Water can also act as an acid. H2O donates a proton to NH3, which
acts as a base, in this equilibrium reaction:
Self-Ionization of Water
Water will self-ionize to a very small extent under normal
conditions. The reaction in which a water molecule donates
one of its protons to a neighboring water molecule, either in
pure water or in an aqueous solution
PROPERTIES OF
SOLUTION
 OUTLINE
types of solutions
the solution process
solubility
concentration terms
colligative properties of solutions
BUT FIRST,
calculations of mass percent and molarity
electrolytes
water as solvent
mole fraction
dalton's law
intermolecular forces
polarizability
vapor pressure of liquids
 SOLUTION
a homogeneous mixture in which a solute dissolves
in a solvent, and the separate particles occur as
individual atoms, ions, or molecules.
most common type of mixture; exists as one phase
as no boundaries separate its components.
all particles are individual atoms, ions, or molecules.
an aqueous solution is a solution with water as the
solvent
 TYPES OF SOLUTIONS
Ion-dipole, ion–induced dipole, and dipole-induced dipole forces occur in solutions,
in addition to all the intermolecular forces that also occur in pure substances.
If similar intermolecular forces occur in solute and solvent, they replace each other
when the substances mix and a solution is likely to form ("like dissolves like").
When ionic compounds dissolve in water, the ions become surrounded by hydration
shells of H-bonded water molecules.
Solubility of organic molecules in various solvents depends on the relative sizes of
their polar and nonpolar portions.
The solubility of nonpolar gases in water is low because of weak intermolecular
forces. Gases are miscible with one another, and they dissolve in solids by fitting
into spaces between the closely packed particles.
Solid-solid solutions include alloys (some of which are formed by mixing molten
components) and waxes.
 THE SOLUTION PROCESS
In a thermochemical solution cycle, the heat of solution is the sum of the
endothermic separations of solute and of solvent and the exothermic mixing of
their particles.
In water, the combination of solvent separation and mixing with solute particles is
hydration. For ions, heats of hydration depend on the ion's charge density but
are always negative because ion-dipole forces are strong. Charge density exhibits
periodic trends.
Systems naturally increase their entropy (distribute their energy in more ways). A
gas has higher entropy than a liquid, which has higher entropy than a solid, and
a solution has higher entropy than the pure solute and solvent.
Relative sizes of the enthalpy and entropy changes determine solution formation.
 SOLUBILITY
A solution that contains the maximum amount of
dissolved solute in the presence of excess undissolved
solute is saturated. A saturated solution is in
equilibrium with excess solute, because solute particles
are entering and leaving the solution at the same rate.
Most solids are more soluble at higher temperatures.
Henry's law says that the solubility of a gas is directly
proportional to its partial pressure above the solution.
CONCENTRATION TERMS
The concentration of a solution is independent of the quantity of
solution and can be expressed as molarity (mol solute/L solution),
molality (mol solute/kg solvent), parts by mass (mass solute/mass
solution), parts by volume (volume solute/volume solution), or
mole fraction [mol solute/(mol solute + mol solvent)].
Molality is based on mass, so it is independent of temperature; the
mole fraction gives the proportion of dissolved particles.
If, in addition to the quantities of solute and solution, the solution
density is known, the various ways of expressing concentration are
interconvertible.
COLLIGATIVE PROPERTIES OF SOLUTION
Colligative properties arise from the number, not the type, of solute particles.
Compared to pure solvent, a solution has lower vapor pressure (Raoult's law),
elevated boiling point, and depressed freezing point, and it gives rise to osmotic
pressure.
Colligative properties are used to determine solute molar mass; osmotic pressure
gives the most precise measurements.
When solute and solvent are volatile, each lowers the vapor pressure of the other,
with the vapor pressure of the more volatile component greater. When the vapor is
condensed, the new solution is richer in that component than the original solution.
Calculating colligative properties of electrolyte solutions requires a factor (i) that
adjusts for the number of ions per formula unit. These solutions exhibit nonideal
behavior because charge attractions effectively reduce the concentration of ions.
HYDROGEN ION-
CONCENTRATION
 DEFINITION OF
HYDROGEN-ION CONCENTRATION
This is a measure of the acidity or alkalinity of a
substance. When acid and alkaline substances
dissociate in water, hydrogen ions (H+) and
hydroxyl ions (OH–) are released. Acidity and
alkalinity are associated with the relative
concentrations of H+.
THE pH SCALE
The pH scale is a measure of how acidic
or alkaline (basic) a substance is. It
ranges from 0 to 14, with 7 being
neutral.
 MEASURING pH
It is a fundamental technique for assessing the
acidity or alkalinity of a solution, and it's done
using indicators or pH meters that detect the
concentration of hydrogen ions in the solution
 IMPORTANCE IN CHEMISTRY
chemistry is at the core of understanding and
manipulating hydrogen-ion concentration, as
expressed by pH. It is a fundamental concept in
chemistry with broad applications in various fields,
including biology, environmental science, analytical
chemistry, and materials science. pH measurements
and control are essential for ensuring the desired
outcomes in many chemical and biological processes.
SUMMARY OF HYDROGEN-ION
CONCENTRATION
The hydrogen-ion concentration, often measured
by pH, is a crucial factor in various chemical and
biological processes. In conclusion, maintaining
the appropriate pH level is essential for the
functioning of living organisms and many
industrial processes. pH values below 7 are acidic,
while values above 7 are basic (alkaline). Accurate
measurement and control of hydrogen-ion
The Colloidal State
In biophysical chemistry, the term
"colloidal state" refers to a state
of matter in which particles are
dispersed throughout a medium
in a colloidal suspension.
Colloids
are heterogeneous mixtures with particle sizes between
those of true solutions and suspensions. In the context
of biological systems, colloids play a significant role.
Y
Colloids

Colloids have particles smaller than those in

suspensions and larger than those in solutions.

These intermediate-sized particles cannot be retained

by filter paper as are the larger particles of a suspension.
They do not settle out with time.
Examples of Colloids
1. Protein Colloids - Proteins, such as albumin and
globulins, can exist in a colloidal state in biological
fluids like blood and interstitial fluid. They help
transport molecules and maintain osmotic pressure.

2. Lipid Colloids - Lipids, such as phospholipids

in cell membranes, can form colloidal structures,
like micelles and liposomes, which are crucial for
cellular processes and drug delivery.
Examples of Colloids
3. Nanoparticles - Engineered nanoparticles,
including liposomes, nanoparticles, and
nanocapsules, are used in drug delivery
systems and have colloidal properties that
are important in biophysics.
4. DNA Colloids- DNA molecules can form
colloidal suspensions when they are in a
dispersed state. Understanding these
colloidal properties is essential for
biophysical studies.
Examples of Colloids

5. Cell Colloids - Cells themselves can be

considered colloidal particles, with complex
internal structures and interactions with the
surrounding medium.
Suspension
What is the difference between a
suspension and a solution?
A suspension is a mixture from which particles
settle out upon standing.
A solution is a homogeneous mixture.
Suspensions are heterogeneous because at
least two substances can be clearly identified.
Suspension

A suspension differs from a solution because the

particles of a suspension are much larger and do not
stay suspended indefinitely.
Tyndall Effect

The scattering of visible light by colloidal

particles is called the Tyndall effect.
Suspensions also exhibit the Tyndall effect.
The particles in solutions are too small to
scatter light.
Brownian Motion

The chaotic movement of colloidal

particles, which was first observed by
the Scottish botanist Robert Brown
(1773–1858), is called Brownian motion.
Brownian Motion

Brownian motion is caused by collisions of the

molecules of the dispersion medium with the
small, dispersed colloidal particles.

These collisions help prevent the

colloidal particles from setting.
Emulsion
An emulsion is a colloidal
dispersion of a liquid in a liquid.

An emulsifying agent is essential for

the formation of an emulsion and for
maintaining the emulsion’s stability.
Key Concepts

A suspension differs from a solution because the

particles of a suspension are much larger and do
not stay suspended indefinitely.
Colloids have particles smaller than those in
suspensions and larger than those in solutions.
Glossary Terms

Suspension: a mixture from which some of the particles

settle out slowly upon standing.
Colloid: a mixture whose particles are intermediate in size
between those of a suspension and a solute solution.
Glossary Terms
Tyndall Effect: scattering of light by particles in a colloid or
suspension, which causes a beam of light to become visible.
Brownian Motion: the chaotic movement of colloidal
particles, caused by collision with particles of the solvent in
which they are dispersed.
Emulsion: the colloidal dispersion of one liquid in another.
 OPTICAL ACTIVITY
Optical activity, often known as optical rotation, is a
phenomenon that describes rotational capacity. The ability
of a compound to rotate the plane of polarized light is
known as optical activity, The optical activity of some
materials corresponds to their ability to rotate the plane of
polarization of light waves.
WHAT IS PLANE POLARIZED LIGHT?
plane of polarized light are known as optically active materials.
consists of waves having vibration in the same direction for all
waves. Light is an electromagnetic wave. It contains an electric
and magnetic field. The electric field vectors are limited to single
plane, then light is referred to plane or linearly polarized.
Optically Active Substances are Classified
in Two Type:

1. Dextrorotatory Substances: The dextrorotatory substances are also known as

the right substances. Dextrorotatory Substances are those optically active
substances that rotate the plane of polarization of the light towards ther right
and are known as right-handed or dextrorotatory. In other words, if a substance
rotates the plane-polarized light to the right or clockwise direction, such
substances are known as the Dextrorotatory substances.
2. Laevorotatory Substances: Laevorotatory Substances are the type of
substances that rotate the plane of polarization of the light toward the left and
are known as left-handed or Levorotatory. The Levorotatory substances are
those optically active substances that rotate the plane of polarization of the light
toward the left are known as left-handed. In other words, if a substance rotates
the plane-polarized light to the left or counterclockwise direction, such
substances are known as the Dextrorotatory substances.