General Biochemistry MODULE
Biochemistry
1
Notes
GENERAL
BIOCHEMISTRY
1.1 INTRODUCTION
Solutions of chemical reagents are a big part of biochemistry, biological and
chemical based work. For a beginner of experimental procedure making
solutions can also be the most frustrating part. Preparation and handling
solutions are essential part of experimental biochemistry. Thus any of new
science graduates should be clear in preparing reagents, buffers, and accuracy
in pipeting.
The concentration of a dissolved salt in water refers to the amount of salt (solute)
that is dissolved in water (solvent). Solutes are the substance of interest to be
dissolved and the term solvent denotes the material in which the solute is
dissolved.
Solution is a mixture that contains solute and a solvent. Solute can be denoted
as the component of a solution present in the lesser amount and the solvent is
the component of a solution present in the greater amount. Concentration can
be written as the amount of a solute present in a solution per amount of solvent.
OBJECTIVES
After reading this lesson, you will be able to:
z describe the importance of solution preparation in biochemistry
z explain different concentration units
z describe different terms of percent solutions
BIOCHEMISTRY 1
, MODULE General Biochemistry
Biochemistry
1.2 UNITS OF CONCENTRATION
z There are many ways to express concentrations. Concentration may be
expressed several different ways and some of the more common concentration
units are:
1. Equivalent weight
2. Molarity
Notes 3. Molality
4. Normality
5. Percent solution (weight/weight)
6. Percent solution (weight/volume)
7. Percent solution (volume/volume)
1.2.1 Equivalent Weight
The equivalent weight is determined by dividing the atomic or molecular weight
by the valence. A major use of the concept of equivalents is that one equivalent
of an ion or molecule is chemically equivalent to one equivalent of a different
ion or molecule. The mass of a substance especially in grams is chemically
equivalent to eight grams of oxygen or one gram of hydrogen : the atomic or
molecular weight divided by the valence
Valance could be determined as
1. The absolute value of ion charge
2. The number of H+ or OH– that a species can react with
3. The absolute value of change in charge on a species when undergoing a
chemical reaction.
1.2.1.1 Preparation of NaOH
Solutions of NaOH can be prepared by either dissolving solid NaOH pellets in
water or by diluting a concentrated solution of NaOH. However, the exact
concentration of the solution prepared by these methods cannot be calculated
from the weighed mass or using the dilution equation for two reasons:
1. Solid sodium hydroxide is hygroscopic (“water-loving”). Pellets of NaOH
exposed to air will increase in mass as they become hydrated so the actual
mass of pure NaOH is not accurately known.
2. Sodium hydroxide in solution reacts with carbonic acid and its concentration
decreases over time. The acid is formed when small amounts of CO2 gas
(which is always present in air) dissolves in solution.
ZZX H2O + Na+(aq) + HCO3–(aq)
H2CO3(aq) + NaOH(aq) YZZ
2 BIOCHEMISTRY
Biochemistry
1
Notes
GENERAL
BIOCHEMISTRY
1.1 INTRODUCTION
Solutions of chemical reagents are a big part of biochemistry, biological and
chemical based work. For a beginner of experimental procedure making
solutions can also be the most frustrating part. Preparation and handling
solutions are essential part of experimental biochemistry. Thus any of new
science graduates should be clear in preparing reagents, buffers, and accuracy
in pipeting.
The concentration of a dissolved salt in water refers to the amount of salt (solute)
that is dissolved in water (solvent). Solutes are the substance of interest to be
dissolved and the term solvent denotes the material in which the solute is
dissolved.
Solution is a mixture that contains solute and a solvent. Solute can be denoted
as the component of a solution present in the lesser amount and the solvent is
the component of a solution present in the greater amount. Concentration can
be written as the amount of a solute present in a solution per amount of solvent.
OBJECTIVES
After reading this lesson, you will be able to:
z describe the importance of solution preparation in biochemistry
z explain different concentration units
z describe different terms of percent solutions
BIOCHEMISTRY 1
, MODULE General Biochemistry
Biochemistry
1.2 UNITS OF CONCENTRATION
z There are many ways to express concentrations. Concentration may be
expressed several different ways and some of the more common concentration
units are:
1. Equivalent weight
2. Molarity
Notes 3. Molality
4. Normality
5. Percent solution (weight/weight)
6. Percent solution (weight/volume)
7. Percent solution (volume/volume)
1.2.1 Equivalent Weight
The equivalent weight is determined by dividing the atomic or molecular weight
by the valence. A major use of the concept of equivalents is that one equivalent
of an ion or molecule is chemically equivalent to one equivalent of a different
ion or molecule. The mass of a substance especially in grams is chemically
equivalent to eight grams of oxygen or one gram of hydrogen : the atomic or
molecular weight divided by the valence
Valance could be determined as
1. The absolute value of ion charge
2. The number of H+ or OH– that a species can react with
3. The absolute value of change in charge on a species when undergoing a
chemical reaction.
1.2.1.1 Preparation of NaOH
Solutions of NaOH can be prepared by either dissolving solid NaOH pellets in
water or by diluting a concentrated solution of NaOH. However, the exact
concentration of the solution prepared by these methods cannot be calculated
from the weighed mass or using the dilution equation for two reasons:
1. Solid sodium hydroxide is hygroscopic (“water-loving”). Pellets of NaOH
exposed to air will increase in mass as they become hydrated so the actual
mass of pure NaOH is not accurately known.
2. Sodium hydroxide in solution reacts with carbonic acid and its concentration
decreases over time. The acid is formed when small amounts of CO2 gas
(which is always present in air) dissolves in solution.
ZZX H2O + Na+(aq) + HCO3–(aq)
H2CO3(aq) + NaOH(aq) YZZ
2 BIOCHEMISTRY
