BIOCHEMISTRY (LAB)
MODULE I. pH of Common Solutions
and Buffer Preparation
M1 Lesson 1 - pH of Common
Solutions
natural water may be either acidic or
basic. Cleaners tend to be basic.
Not All Liquids Have a pH Value, pH
only has meaning in an aqueous
solution (in water). Many chemicals,
including liquids, do not have pH values.
If there's no water, there's no pH. For
example, there is no pH value
for vegetable oil, gasoline, or pure
alcohol.
pH of Common Acids
Learn the pH of Common Solutions
pH is a measure of how acidic or basic a
chemical is when it's in an aqueous
(water) solution. A neutral pH value
(neither an acid nor a base) is 7.
Substances with a pH greater than 7 up
to 14 are considered bases. Chemicals
with a pH lower than 7 down to 0 are
considered acids. The closer the pH is
to 0 or 14, the greater its acidity or
basicity, respectively. Here's a list of the
approximate pH of some common
chemicals.
pH is a measure of how acidic or basic
an aqueous solution is. pH usually
ranges from 0 (acidic) to 14 (basic). A
pH value around 7 is considered neutral.
pH is measured using pH paper or a pH
meter.
Most fruits, vegetables, and body fluids
are acidic. While pure water is neutral,
Fruits and vegetables tend to be acidic.
Citrus fruit, in particular, is acidic to the
point where it can erode tooth enamel.
Milk is often considered to be neutral
since it's only slightly acidic. Milk
becomes more acidic over time. The pH
of urine and saliva is slightly acidic,
around a pH of 6. Human skin, hair, and
nails tend to have a pH of around 5.
pH
Common Acids
0
Hydrochloric Acid (HCl)
1.0
Battery Acid (H2SO4 sulfuric
acid) and stomach acid
2.0
Lemon Juice
2.2
Vinegar
3.0
Apples, Soda
3.0 to
3.5
Sauerkraut
3.5 to
3.9
Pickles
4.0
Wine and Beer
4.5
Tomatoes
4.5 to
5.2
Bananas
around
Acid Rain
5.0
5.0
Milk of Magnesia
11.0
Ammonia
11.5 to
Hair Straightening Chemicals
14
Black Coffee
Neutral pH Chemicals
Distilled water tends to be slightly acidic
because of dissolved carbon dioxide
and other gases. Pure water is nearly
neutral, but rainwater tends to be slightly
acidic. Natural water rich in minerals
tends to be alkaline or basic.
7.0
10.5
-
Pure Water
pH of Common Bases
Many common cleaners are basic.
Usually, these chemicals have a very
high pH. Blood is close to neutral but is
slightly basic.
12.4
Lime (Calcium Hydroxide)
13.0
Lye
14.0
Sodium Hydroxide (NaOH)
Other pH Values
Soil pH ranges from 3 to 10. Most plants
prefer a pH between 5.5 and 7.5.
Stomach acid contains hydrochloric acid
and other substances and has a pH
value of 1.2. While pure water free of
undissolved gases is neutral, not much
else is. However, buffer solutions may
be prepared to maintain a pH near 7.
Dissolving table salt (sodium chloride) in
water does not change its pH.
pH
Common Bases
7.0 to
10
Shampoo
There are multiple ways to test the pH of
substances.
7.4
Human Blood
7.4
Human Tears
7.8
Egg
The simplest method is to use pH paper
test strips. You can make these
yourself using coffee filters and cabbage
juice, use Litmus paper, or other test
strips. The color of the test strips
corresponds to a pH range. Because the
color change depends on the type of
indicator dye used to coat the paper, the
result needs to be compared against a
chart of standard.
around
Seawater
8
8.3
Baking Soda (Sodium
Bicarbonate)
around
Toothpaste
9
How to Measure pH
Another method is to draw a small
sample of a substance and apply drops
of pH indicator and observe the test
change. Many home chemicals
are natural pH indicators.
M1 Lesson 2 - Buffer Preparation
pH test kits are available to test liquids.
Usually, these are designed for a
particular application, like aquaria or
swimming pools. pH test kits are fairly
accurate but may be affected by other
chemicals in a sample.
The most accurate method of measuring
pH is using a pH meter. pH meters are
more expensive than test papers or kits
and require calibration, so they are
generally used in schools and labs.
pH Equation
The equation for calculating pH was
proposed in 1909 by Danish biochemist
Søren Peter Lauritz Sørensen:
pH = -log[H+]
where the log is the base-10 logarithm
and [H+] stands for the hydrogen ion
concentration in units of moles per liter
solution. The term "pH" comes from the
German word "potenz," which means
"power," combined with H, the element
symbol for hydrogen, so pH is an
abbreviation for "power of hydrogen."
Note About Safety
Chemicals that have very low or very
high pH are often corrosive and can
produce chemical burns. It's fine to
dilute these chemicals in pure water to
test their pH. The value won't be
changed, but the risk will be reduced.
There are a number of applications in
chemistry and biology where changes in
pH can have a major negative effect.
One example of this exists in the human
body; changes to blood pH could have a
devastating effect, so a mechanism
within the body known as the
bicarbonate buffering system keeps
your blood's pH in check. In laboratory
settings, a buffer solution is used to
achieve similar results. The buffer
solution maintains a balance in the pH
of whatever is being worked with,
preventing outside influences from
shifting the pH and potentially ruining
everything.
Buffer Solutions
A buffer solution is made up of a weak
acid and its conjugate base or a weak
base and its conjugate acid. The two
components maintain a pH balance that
resists change when strong acids or
bases are added to it.
Buffer Preparation
The solution is made by taking a weak
acid and adding its conjugate base
(which is formed by removing a proton
from the same type of acid) or by
combining a weak base with its
conjugate acid. The use of conjugates is
what gives a buffer solution its
resistance to pH changes; it creates an
equilibrium between the acid and the
base which is difficult for other acids or
bases to overcome. Even when strong
acids or bases are added, the
equilibrium between the weak acid/base
and its conjugate reduces the impact of
the addition on overall solution pH.
Examples of Buffers:
blood - contains a bicarbonate buffer
system
TRIS buffer
phosphate buffer
As stated, buffers are useful over
specific pH ranges. For example, here is
the pH range of common buffering
agents:
Buffer
pKa
citric acid
3.13., 4.76,
6.40
pH range
(NaOH), is added to raise the pH of
alkaline buffers.
Buffering pH
Buffer solutions have a wide range of
applications, both in the real world and
in the lab. A buffered pH is required for
most enzymes to function correctly, and
buffering is used to ensure proper color
concentration when using dyes. Buffer
solutions are also used to calibrate
equipment, especially pH meters that
might be miscalibrated if a buffer is not
present. It's worth noting that buffer
solutions do not necessarily have a
neutral pH, just a balanced one; buffer
solutions made from citric acid,
ammonia, acetic acid (which is found in
vinegar in low concentrations) and other
compounds can have pH values as low
as 2 or higher than 10. This allows the
use of buffer solutions in work with very
strong acids or bases.
Buffer Capacity
2.1 to 7.4
acetic acid 4.8
3.8 to 5.8
KH2PO4
7.2
6.2 to 8.2
borate
9.24
8.25 to
10.25
CHES
9.3
8.3 to 10.3
When a buffer solution is prepared, the
pH of the solution is adjusted to get it
within the correct effective range.
Typically a strong acid, such as
hydrochloric acid (HCl) is added to lower
the pH of acidic buffers. A strong base,
such as sodium hydroxide solution
While buffer solutions are resistant to
changes in pH, this doesn't mean that
the pH of a buffer solution can't change
if enough strong acid or strong base is
added. The amount of a strong acid or
base that a buffer solution can take
before significant pH changes occur is
known as the buffer capacity. The
capacity differs depending on the core
components of the buffer solution and
how much of the strong acid or base is
added to the solution. If adding a strong
acid to the buffer solution, the capacity
is equal to the amount of the base in the
solution. If adding a strong base, the
capacity is equal to the amount of the
acid in the solution.
MODULE II. Buffer Effects on
Solution
the K equation because of its constant
value.
M2 Lesson 2- Effects of Temperature
on Buffer Solutions
A- + H2O
The pH of solutions is also affected by
changes in temperatures. Chemical
equilibrium exists in all buffer systems
that are usually affected by temperature,
concentration, and pressure as learned
from Le Chatelier’s Principle.
This K equation is the key to the
buffering effect such that if [OH-]
increases, then [HA] and [A-] must
change. Some of the HA molecules
react with the added OH-, making the
solution less basic than without the
conjugate base(A-). Thus the buffering
effect can be stated as: if K is small, the
buffering effect is small because there’s
not much HA in the solution. If the value
of K increases with temperature, then
the buffering effect is stronger at a
higher temperature. If K decreases, then
the buffering effect is weaker when it's
warmer.
Thus the pH of any solution is
temperature dependent due to this
dynamic equilibrium where pK changes
with temperature, it follows that pH must
also change.
In a buffered solution consisting of a
mixture of a weak acid and its conjugate
base that provides the buffering
capacity, its pH changes very little as a
small amount of strong acid or base is
added into it. The dissociation constant
for the weak acid changes with
temperature resulting in a small change
in pH so that the pK at a particular
temperature remains constant.
In an unbuffered solution, there is no
buffering capacity so that the pH
changes significantly as a small amount
of strong acid or base is added into it.
Effect of increasing the temperature on
Buffer Capacity
In a buffer solution, as long as
dissociation constant changes with
temperature, then the concentration of
the ions also changes. Consider the
following equilibrium reactions: The
brackets in the equation means “the
concentration of”. H2O is not included in
HA + OH-
K = [HA] [OH-] / [A-]
M2 Lesson 3- Computation of pH of
Unbuffered Solutions and Buffered
Solutions
The pH of solutions is directly measured
using pH paper and pH meter. However,
this can also be determined by
computation using appropriate
mathematical formulas and equations
such as the Henderson-Hasselbalch
Equation.
Buffers are chosen with an appropriate
pH range for control. This pH range is
measured by the HendersonHasselbalch equation derived as
follows: we will imagine a buffer
composed of acid, HA, and its conjugate
base, A-. We know that the acid
dissociation constant pKa of the acid is
given by this expression:
Ka = [H+] [A-] / [HA]
The equation can be rearranged as
follows:
MODULE III. The Cell
Introduction
[H+] = Ka [HA] / [A-]
pH = pKa + log ( [A-] /
[HA]) Henderson-Hasselbalch equation
Where pH refers to the concentration of
H+, pKa is the acid dissociation
constant, [A-] is the concentration of the
conjugate base, and [HA] is the
concentration of the starting acid.
From the equilibrium constant K and the
initial concentration of the acid, the pH
of a buffer solution can be calculated.
The equilibrium constant reveals the
strength of the weak acid or the buffer.
The concentration of [H+] can also be
solved using the Ka and the equilibrium
equation. pH of the solution can also be
calculated from the concentration of [H+]
as follows: pH = - log ([H+])
Buffer Effectiveness
An effective buffer should be made of an
acid and its conjugate base or a base
and its conjugate acid where the Ka
value is very similar to the desired pH.
The exact ratio of the conjugate base to
the acid is determined from the Ka value
and the Henderson-Hasselbalch
equation for the desired pH. The buffer
is most effective when the amounts of
acid and its conjugate base are
approximately equal.
LAB Expt 1, 2 - pH &
Buffers.pdf
Cells are the structural and functional
units of all living organisms. The human
body is composed of trillions of cells that
provide structure for the body, take in
nutrients from food, convert nutrients
into energy, and carry out specialized
functions.
Cells share many common features, yet
they can look very different. They have
adapted over billions of years to a wide
array of environments and functional
roles. However, all cells rely on the
same basic strategies in order to
survive: allow necessary substances in
and permit others out, maintain their
health, and replicate themselves.
Cells are the smallest common
denominator of life. Some cells are
organisms unto themselves; others are
part of multicellular organisms. All cells
are made from the same major classes
of organic molecules: nucleic acids,
proteins, carbohydrates, and
lipids. Though they are small, together
they form tissues that themselves form
organs, and eventually entire
organisms.
Parts of a Eukaryotic Cell
M3 Lesson 1 - Types of Cells
Types of Cell
1. Cell membrane – It controls what
gets in and out of the cell
1. Prokaryotic Cell
These are unicellular organisms that do
not develop or differentiate into
multicellular forms. They are identical
and capable of independent existence.
2. Cytoplasm – It is the living substance
of the cell
Cytosol - It is the fluid portion of the
cell.
They lack a nucleus and membranous
organelles.
Organelles – small, membrane-bound
compartments.
Include all bacteria and archaea
(archaebacteria).
Mitochondrion – It is the powerhouse of
the cell
Endoplasmic Reticulum – Responsible
for intracellular transport
2. Eukaryotic Cell
These cells contain a nucleus and
membrane-bound compartments, called
organelles, in which specific metabolic
activities take place.
Include fungi, animals, and plants as
well as some unicellular organisms.
Golgi body – Modifies, packages and
transports proteins
Lysosome – Suicide bag of the cell
Peroxisome – Detoxifies the cell
3. Nucleus - A rounded structure at the
center of the cell that controls the
metabolic activities. It contains the
DNA.
Animal Cell
Structurally, plant and animal cells are
very similar because they are both
eukaryotic cells. However, plant cells
are usually larger than animal
cells. They also contain structures that
are absent in a typical animal cell, such
as chloroplasts, plastids cell wall and
large vacuoles. On the other hand,
there are organelles found in an animal
cell that are absent in plant cells. These
incudes centrioles, lysosomes (rarely
seen in plant cells), microvilli, cilia, and
filaments.
as part of the same organism or
foreign. Some proteins work like
fasteners, binding cells together so they
can function as a unit. Other membrane
proteins serve as communicators,
sending and receiving signals from other
cells.
Parts of the Cell Membrane:
Parts of the
Cell_08102020-1.pdf
M3 Lesson 2 - The Cell Membrane
The Cell Membrane
1. Phosphate head
Polar
Hydrophilic
2. Fatty Acid Tail
Non-polar
The cell membrane serves as a clear
boundary between the cell’s internal and
external environment. It is also called
plasma membrane or plasmalemma. It
is semi-permeable with a framework of
fat-based molecules called
phospholipids, which prevent hydrophilic
substances from entering or escaping
the cell.
All membranes are phospholipid
bilayers with embedded proteins. Some
of these proteins act as gatekeepers,
determining what substances can and
cannot cross the membrane. Others
function as markers, identifying the cell
Hydrophobic
3. Proteins
a) Transmembrane Proteins
b) Integral Proteins
c) Peripheral Proteins
Parts of the Cell
Membrane_08072020-1.pdf
MODULE IV. Biochemical Processes
Introduction
M4 Lesson 1 - Processes in
Biochemical Systems
All molecules in a living cell are lifeless.
Molecules move in seemingly random
chance or by mere coincidence.
Interacting with one another to form
complex products that result in wonders
each of us can observe. Despite the
contradiction, however, this puts up the
notion that life has a molecular basis
and the cell is considered to be the
basic functional unit of life. This tells us
that in order to understand the secrets
to how living things came as to what it is
now, is to fully understand how each of
these molecules is vital in fulfilling their
roles to perform the mechanism to make
the non-living alive!
All living organism needs energy to fully
function. Energy is what drives
biochemical processes. Metabolism is
the collective term used as the sum of
all of these chemical reactions and it is
divided into two types; Anabolism
(Building up) and Catabolism (Breaking
down). Both processes involve the
expense or release of energy,
respectively.
Processes in Biochemical Systems
When we say biochemical systems, this
includes all the metabolic processes that
the cell undergoes. For students to
understand the gist of this topic, they
should be familiar with the cell’s
organelles and their functions. Take
note on each organelle's role in the cell
as mentioned.
In every biochemical systems, energy is
involved, each can be either be through
physical or chemical means. These
reactions may or may not require energy
in the form of ATP. Watch the Video
below to have further understanding
about this collective biochemical
processes.
M4 Lesson 2 - Transport Processes
Transport Processes
A. Active and Passive Transport
Passive Transport - From High
Concentration to Low Concentration or
Along with a Gradient Concentration.
Also known as “Downhill transport”. No
energy required.
Examples: Hemolysis, Diffusion of
dissolved sugar in water, and Entry of
fructose inside the cell.
Active Transport - From Low
Concentration to High Concentration or
Against a Gradient Concentration.
Utilized by Pumps/Carrier Proteins. Also
knows as Uphill Transport. Energy
requiring.
D. Osmosis
Basically a diffusion of water molecules
from high H2O concentration to low H2O
concentration across a semipermeable
membrane.
Ex: Endocytosis, Exocytosis, and
Sodium-Potassium pump
B. Dialysis
A process of separating molecules in
solution by the difference in their rates
of diffusion through a semipermeable
membrane, such as dialysis tubing,
cellophane, and longganisa membrane.
You may try the video link below at your
own home by using diluted betadine as
your iodine source.
C. Diffusion
It is the movement of a substance from
an area of high concentration to an area
of low concentration. Diffusion happens
in liquids and gases because their
particles move randomly from place to
place. Diffusion is an important process
for living things; it is how substances
move in and out of cells.
E. Lowering of Surface Tension
Lowering Surface Tension is done by
surfactants. Surfactants can be further
classified into 3: Emulsifiers, Soaps, and
Detergents. Surfactants are compounds
that lower the surface tension (or
interfacial tension) between two liquids,
between a gas and a liquid, or between
a liquid and a solid. Besides salt. One
known biological substance that lowers
surface tension is called Bile. Bile can
be found from our gallbladder and is
used in absorption by emulsifying fats.
M4 Biochemical
Processes lesson1 ONLINE.pdf
MODULE V. Properties of
Carbohydrates
Introduction
Carbohydrates are vital sources of
energy for both plants and animals.
They also serve as the skeletal structure
for plants and as storage for the
chemical energy of both plants and
animals. In terms of chemical structure,
carbohydrates are derivatives of
aldehydes and ketones. Their
interesting chemical reactions are due to
such functional groups.
Any material containing carbohydrates
yields positive results in the Molisch
Test. This test is based on the
dehydration of monosaccharides by
concentrated sulfuric acid to form
furfural derivatives and the subsequent
reaction with α-naphthol to form colored
complexes.
Carbohydrates with a free aldehyde or
ketone groups have reducing properties.
They are oxidized by alkaline solutions
of cupric sulfate (Fehling’s and
Benedict's reagents) producing a
reddish-brown precipitate because of
the reduction of cupric to cuprous ions.
Nylander's reagent, an alkaline solution
of bismuth sub-nitrate when added to
reducing sugars, produces a black
precipitate due to the formations of
metallic bismuth. Barfoed's reagent, a
solution of cupric acetate in a weak
acetic acid, serves as another test as it
is acted upon by reducing
monosaccharides but not by reducing
disaccharides.
The simplest carbohydrates called
monosaccharides consist only of one
saccharide unit and thus cannot be
hydrolyzed. The most abundant in the
group is glucose. Other common
monosaccharides are fructose,
galactose, ribose, and deoxyribose.
Disaccharides consist of
monosaccharide units joined by a
glycosidic linkage. Common
disaccharides include sucrose, lactose,
and maltose. Polysaccharides, the most
complex of all carbohydrates, composed
of many saccharide units, can be
hydrolyzed by enzymes or by heating
with dilute acids.
M2 Lesson 1
M2 Lesson 2
Definition of Carbohydrates.pdf
Classifications of Carbohydrates.pdf
M5 Lesson 1 - Reactions of
Carbohydrates
A. Reaction with Acids
Molisch’s test is a general for the
presence of carbohydrates in a given
analyte. This test is named after CzechAustrian botanist Hans Molisch, who is
credited with its discovery. Molisch’s test
involves the addition of Molisch’s
reagent (a solution of ∝-naphthol in
ethanol) to the analyte and the
subsequent addition of a few drops of
concentrated H2SO4 (sulfuric acid) to
the mixture.
thymol), resulting in the formation of a
purple or reddish-purple colored
complex.
The formation of a purple or a purplishred ring at the point of contact between
the H2SO4 and the analyte + Molisch’s
reagent mixture confirms the presence
of carbohydrates in the analyte. An
image detailing a positive result for
Molisch’s test is provided below.
Moore’s Test is a test for the presence
of reducing sugar. When a solution of
reducing sugar is heated with an alkali
(NaOH), it turns yellow to dark brown
solution liberating the odor of caramel.
This is due to the liberation of aldehyde
which subsequently polymerizes to form
a resinous substance. “Caramel”
B. Reaction with Alkali
C. Reducing Property- only the
reducing sugars ( monosaccharides
& disaccharides except for sucrose)
do respond to this test.
The formation of a purple ring at
the junction of two liquids
shows the visual evidence of Molisch's
test with all carbohydrates
A positive reaction for Molisch’s test is
given by almost all carbohydrates
(exceptions include tetroses & trioses).
It can be noted that even some
glycoproteins and nucleic acids give
positive results for this test (since they
tend to undergo hydrolysis when
exposed to strong mineral acids and
form monosaccharides).
In Molisch’s test, the carbohydrate (if
present) undergoes dehydration upon
the introduction of concentrated
hydrochloric or sulfuric acid, resulting in
the formation of an aldehyde. This
aldehyde undergoes condensation
along with two phenol-type molecules
(such as ∝-naphthol, resorcinol, and
1. Fehling’s solution is a complex
compound of Cu2+. When aldehyde
compound is treated with Fehling’s
solution Cu2+ is reduced to Cu+ and the
aldehyde is reduced to acids. During the
reaction, a red precipitate is formed.
Aromatic aldehydes do not respond to
Fehling’s test. An aqueous solution of
the compound may be used instead of
an alcoholic solution. Formic acid also
gives this test.
General equation for:
RCHO
+ CuSO4
→ R-COOH + Cu2O + H2O
Note: The appearance of red precipitate
confirms the presence of an aldehydic
group.
Note: The appearance of shiny silver
mirror confirms the presence of reducing
sugar
The above image shows Fehling’s test
with a sucrose solution (-) that remains
blue or no reaction with non-reducing
sugar while glucose solution (+) gives
a brick-red precipitate. Glucose is an
example of a reducing sugar while
sucrose is
a nonreducing sugar.
2. Tollen’s Test: (Silver Mirror Test).
Tollen's reagent consists of silver
ammonia complex in ammonia solution.
Aldehydes react with Tollen's reagent
gives a grey-black precipitate or a silver
mirror. Always a freshly prepared
Tollen’s reagent should be used.
Aldehydes are oxidized to the
corresponding acid and silver in Tollen's
reagent is reduced from the +1 oxidation
state to its elemental form.
General equation for Tollen's
Test:
RCHO + AgNO3 + NH4OH →
R-COOH + 3NH3 + H2O + 2Ag↓(silver
mirror)
3. Nylander’s Test - is a medical test
for glucose in the urine, making use of a
solution that contains bismuth
subnitrate. The solution forms a black
precipitate in a positive reaction.
To prepare the reagent for the test,
dissolve four grams of sodium tartrate in
100 cubic centimeters of a ten percent
caustic soda solution. Then add two
grams of bismuth subnitrate. Heat the
mixture to 50 degrees Celsius and filter
after cooling. Preserving the reagent,
even for months, leaves it unaltered.
The test works on the principle that
when a subnitrate of bismuth comes in
contact with grape sugar in a boiling
alkaline solution, it reduces to black
metallic bismuth.
The conclusion of the test is that when
reducing sugar is present, there is a
brown to the black coloration of the
solution where the metallic bismuth
settles down.
Nonreducing sugars such as sucrose
do not react with Fehling’s, Tollen’s,
Nylander’s, and Benedict’s reagent. It
can produce a positive result with the
reagent only if it is heated with dilute
hydrochloric acid before the test. Once
sucrose has been broken down using
this method, it produces glucose and
fructose, which can be detected by
Benedict’s reagent.
The 2nd test tube shows a positive
result of reducing sugar with Nylander's
test,
4. Benedict's Test- A Benedict’s test is
used to determine the presence of
reducing sugars such as fructose,
glucose, maltose, and lactose. It is also
used to test for the presence of glucose
in urine.
In Benedict’s test, a chemical reagent
known as Benedict’s reagent or solution
is used. This reagent is prepared from
sodium carbonate, sodium citrate, and
copper (II) sulfate.
A positive test with Benedict’s reagent is
indicated by a change in color, often
from blue to a brick-red precipitate.
When testing for the presence of
reducing sugars in food, a food sample
is dissolved in water and a minimal
amount of Benedict’s reagent is added.
The mixture is then heated in a water
bath. A positive result for the presence
of reducing sugars in the food is
indicated by the formation of a
precipitate and a change in color.
Benedict’s reagent contains blue copper
(II) ions, which are reduced to copper
(I). These are precipitated as red copper
(I) oxide, which is not soluble in water.
M5 Lesson 2 - Hydrolysis of
Carbohydrates
Polymers are broken down by
hydrolysis, which is essentially the
reverse of condensation; The -OH group
from water attaches to one monomer
and an H attaches to the other. This is a
hydrolysis reaction because water
(hydro) is used to break (lyse) a bond.
When a bond is broken energy is
released. Polysaccharides such as
starch, glycogen, and dextrin give
positive results with iodine test.
Starch would not give a positive
Fehling's test because starch is a nonreducing polysaccharide and Fehling's is
a test for reducing sugar. However,
after hydrolysis into monosaccharide by
the actions of strong acids, its
components (glucose molecules) gives
a positive result with Fehling's reagent.
Fehling's test is considered positive
when the solution turns from blue to
orange. To test the presence of starch
chemically, an iodine solution is used. If
it turns from red to black or blue, the test
is positive.
M5 Lesson 3 - Specific Reactions of
Carbohydrates
Specific reactions characterize different
carbohydrates. Groups of carbohydrates
may be differentiated by their particular
reactions with the same reagent. Some
examples are: Hexoses which are
monosaccharides with six carbon atoms
and pentoses which have five carbon
atoms are differentiated by the Bial's
Orcinol test. The furfural formed from
the dehydration of a pentose with orcinol
forms a blue-green color solution while
that from hexose is a muddy brown
solution.
Ketoses (carbohydrates with ketone
functional group) give cherry red
solution within two minutes with
Seliwanoff's test, while aldoses are
carbohydrates with aldehyde functional
group require a longer time. This
test involves the reaction of resorcinol
and acid on the sugar,
forming hydroxymethylfurfural as a
result of dehydration. Reducing sugars
from osazone crystals when heated with
an excess of phenylhydrazine HCl. This
reaction serves to identify the sugars by
the structure of the crystals and the
time required to form them.
glycogen, a highly branched complex
polysaccharide, gives a pale reddishbrown solution. The difference in the
color of the complexes is due to the
structure of these polysaccharides.
Starch is made up of linear chains of
glucose units of amylose which
undergo helical formation. A helix
containing 6 glucose units is enough to
accommodate large molecules like
Iodine. Thus, branched polysaccharides
like glycogen, give a less intense color
of the solution because of interruptions
in the helices.
Learning Activity 1.
A. Bial's Orcinol test
Hexoses which are monosaccharides
with six carbon atoms and pentoses
which have five carbon atoms are
differentiated by the Bial's Orcinol test.
The furfural formed from the dehydration
of a pentose with orcinol forms a bluegreen solution while that from hexose is
a muddy brown solution. Watch the
youtube presentation and take note of
your observation.
B. Test for Reducing Sugars
Similarly, upon oxidation with nitric acid,
hexoses produce crystals that are
soluble in dilute acid and water.
Galactose in particular produces mucic
acid, a dicarboxylic acid, and an
isomer of saccharic acid which is
identified by its insolubility in acid and
water.
Reducing sugars form osazone crystals
when heated with an excess of
phenylhydrazine HCl. This reaction
serves to identify the sugars by the
structure of the crystals and the time
required to form them.
Polysaccharides from characteristic
colored complexes with Iodine. Starch
gives a blue color with Iodine solution.
Dextrin a product of partial hydrolysis of
starch gives a color red solution and
Similarly, upon oxidation with nitric acid,
hexoses produce crystals that are
soluble in dilute acid and water.
Galactose in particular produces mucic
acid, a dicarboxylic acid, and an isomer
C. Mucic Acid Test
of saccharic acid which is identified by
its insolubility in acid and water. This is
a specific test for galactose and is given
by galactose as well as lactose, which is
made up of galactose and glucose.
Oxidation of most monosaccharides by
nitric acid yields soluble dicarboxylic
acids. However, oxidation of galactose
yields an insoluble mucic acid. Lactose
will also yield a mucic acid, due to the
hydrolysis of the glycosidic linkage
between its glucose and galactose
subunits. Being insoluble,
galactosaccharic acid crystals separate
out.
which undergo helical formation. A helix
containing 6 glucose units is enough to
accommodate large molecules like
Iodine. Thus, branched polysaccharide
like glycogen, give a less intense color
of the solution because of interruptions
in the helices.
M6 EXPERIMENT 6
M5 Expt. 5
GENERAL Reactions of Carbohydrates
SPECIFIC Reactions
of Carbohydrates ONLINE.p
ONLINE.pdf
MODULE VI. Properties of Lipids
Introduction
D. Test for keto sugar (Seliwanoff's
test)
Ketoses (carbohydrates with ketone
functional group) give cherry red
solution within two minutes with
Seliwanoff's test, while aldoses are
carbohydrates with aldehyde functional
group require a longer time. This test
involves the reaction of resorcinol and
acid on the sugar, forming
hydroxymethyl furfural as a result of
dehydration.
E. Test for polysaccharides
Polysaccharide forms characteristic
colored complexes with Iodine. Starch
gives a blue color with an Iodine
solution. Dextrin a product of partial
hydrolysis of starch gives a color red
solution and glycogen, a highly
branched complex polysaccharide,
gives a pale reddish-brown solution. The
difference in the color of the complexes
is due to the structure of these
polysaccharides. Starch is made up of
linear chains of glucose units of amylose
What Are Lipids?
Lipids are a group
of macromolecules that have a wide
variety of functions in living cells.
Examples include storing energy,
signaling between cells, and forming
the cell membrane. They are made
from monomers (building blocks)
called fatty acids. The functional group
attached to each monomer determines
the specific type of lipid it will be.
Lipids are insoluble in water, making
them especially important in cell
functions. Unlike water, they are nonpolar. Because of this, they will not mix
with water.
In fact, they are referred to
as hydrophobic, which literally means
"water-fearing". If you have ever tried to
mix oil and water, you've probably
noticed that they remain separate. This
is because oil is a lipid and non-polar.
Saturated fats have
straight carbon chains because they
only contain single carbon-carbon bonds
(alkane). Saturated fats pack together
closely and are solid at room
temperature. Saturated fats are typically
found in animal products. Butter is a
good example.
Unsaturated fats have a kink in their
chain caused by a double bond or even
a triple bond between carbons (alkenes,
alkynes). Because of these kinks,
unsaturated fats can't pack together
very closely, making them liquid at room
temperature. They are typically found in
plant products. Vegetable oil is a good
example.
The hydrocarbon chains of both
saturated and unsaturated fats are
attached to a carboxylic acid functional
group. This is what makes them
fatty acids.
Triglycerides
Lipids that store energy is called
triglycerides. These molecules have
three long chains of fatty acids attached
to a glycerol backbone. In
many organisms,
extra carbohydrates are often stored as
triglycerides in fat tissue.
Triglycerides are excellent long-term
energy storage molecules because they
will not mix with water and break down.
We can also eat triglycerides (in
delicious fried foods, often) and break
them down to get energy.
M6 Lesson 1- Lipids
A lipid is a fat-soluble molecule. To put
it another way, lipids are insoluble in
water but soluble in at least one organic
solvent. The other major classes of
organic compounds (nucleic
acids (Links to an external site.),
proteins, and carbohydrates) are much
more soluble in water than in an organic
solvent. Lipids are hydrocarbons
(molecules consisting of hydrogen and
oxygen), but they do not share a
common molecule structure.
Lipids that contain an ester functional
group may be hydrolyzed in water.
Waxes, glycolipids, phospholipids, and
neutral waxes are hydrolyzable lipids.
Lipids that lack this functional group are
considered nonhydrolyzable. The
nonhydrolyzable lipids include steroids
and fat-soluble vitamins A, D, E, and K.
M6 Lesson 2-Physical and Chemical
Properties of Lipids
Lipids are very diverse in both their
respective structures and functions.
These diverse compounds that make up
the lipid family are so grouped because
they are insoluble in water. They are
also soluble in other organic solvents
such as ether, acetone, and other lipids.
Lipids serve a variety of important
functions in living organisms. They act
as chemical messengers, serve as
valuable energy sources, provide
insulation, and are the main
components of membranes. Major lipid
groups
include fats, phospholipids, steroids,
and waxes.
Module 7 LAB
LIPIDS ONLINE.pdf
MODULE VII. Proteins and Amino
Acids
M7 Lesson 1 - Formation of
Polypeptides
Peptides and proteins are formed when
amino acids are joined together by
amide bonds. The amide bond is called
a peptide bond. A dipeptide has two
amino acids joined together by one
peptide bond. Polypeptides have many
amino acids, while proteins have more
than 40 amino acids.
Introduction
Peptide bonds are formed by a
condensation reaction. Amino acids are
joined together and water is released.
Amino acids are organic compounds
containing an amino group and a
carboxyl group. Amino acids are a set
of 20 different molecules used to build
proteins. Proteins consist of one or
more chains of amino acids
called polypeptides. The sequence of
the amino acid chain causes the
polypeptide to fold into a shape that is
biologically active. The amino acid
sequences of proteins are encoded in
the genes.
The 20 common amino acids make up
proteins in the body are mostly α-amino
acids. All the amino acids in the body
are L-isomers. alpha (α) carbon, which
is covalently linked to both the amino
group and the carboxyl group. Also
bonded to this carbon are hydrogen and
a variable side chain (R group). R
group gives each amino acid its identity.
Formation of Polypeptides:
1. Remove oxygen from the precedent
amino acid and two hydrogens from the
subsequent amino acid
2. Place the two groups next to each
other.
M7 Lesson 2 - Tests for Proteins
Xanthoproteic test
Biuret test
•
•
•
It is the general test for the
identification of proteins
In the presence of an alkaline
solution, Cu2+ ion forms as a
complex with the peptide bonds
due to the unshared electron
pairs in nitrogen, and the oxygen
in the water.
Once the complex has been
formed, the solution turns from
blue to purple.
•
•
It is the test for the presence of
aromatic amino acids
Amino acids containing an
aromatic nucleus react with
concentrated HNO3 to form a
yellow-colored complex on
heating, it changes to orange-red
color when excess NaOH is
added
Millon’s test
•
Ninhydrin test
•
•
•
It is the test for the presence of αamino acid in proteins
Ninhydrin causes oxidative
decarboxylation and deamination
of α-amino acids producing an
aldehyde, carbon dioxide, and
ammonia
Nnhydrin is reduced to
hydrindantin which reacts with
the liberated ammonia and
another molecule of ninhydrin
•
•
It is the test for phenolic
compounds
It is also used to detect the
presence of tyrosine – the only
amino acid containing a phenol
group
Tyrosine is first nitrated by nitric
acid in the test solution, then the
nitrated tyrosine complexes
mercury (I) and mercury (II) in the
solution to form either a red
precipitate or a red solution
Hopkins-Cole test
•
•
It is a test for the presence of
tryptophan – the only amino
acid containing an indole
group
The indole reacts with
glyoxylic acid in the presence
of a strong acid to form a
violet cyclic product
Lead Sulfide test
•
•
•
It is a test for the presence
of cysteine or cystine
The organic sulfur in
cysteine or cystine is
released as inorganic S8 ions which form lead
sulfide
The positive result is the
formation of black or
brown precipitate