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Collegeof Natural andComputational Sciences
Department of Biology
Pre-universityRemedial Programfor the 2014E.C. ESSLCEExaminees
BIOLOGYModule
1

Unit One: The science of biology
1. The methods of science
2. Tools of the biologist
2

3
 Learning Objectives
 After completing this chapter you will be
expected to:
 Define science as a way of knowledge and explain it
 Describe and explain the main steps that scientists
follow when they are investigating something.
 Demonstrate scientific methods
 Plan and conduct an experiment to investigate a
particular observation.
 Write a report for a scientific experiment.
Unit One: The science of biology

Introduction
 Scientists investigate natural events to try to
find out exactly why and how they happen.
 To arrive at an answer, they need conclusive
evidence that a certain factor causes the event.
 Very often, this kind of evidence can only be
obtained by carrying out experiments.
 You will learn how to proceed from identifying
the problem to planning and carrying out an
investigation in such a way that the results will
enable you to conclude that the factor you are
investigating does (or does not) cause the
event to happen.
4

What is the science of biology?
 Biology is the science of life and
living organisms.
 Organism is a living being made
from one cell (bacteria, unicellular
algae) or many cells (animals,
plants and most fungi).
5

Some biologists become astrobiologists.
 These biologists engage in all kinds of research
to try to find evidence of life on other planets in
our Solar System and in galaxies elsewhere in
the Universe.
Other biologists take part in biomedical
research.
 These biologists help in many areas, including
the development of new drugs and vaccines.
 They also study the ways in which diseases
develop to gain a better understanding of them
so that cures can be found. 6

Others still become microbiologists.
These biologists study how micro-
organisms of all kinds function.
Some micro-organisms cause
disease, and understanding how they
work makes a treatment more likely.
Many microbiologists are studying the
HIV to get a better understanding of
how AIDS develops and how it can be
treated.
7

Paleobiology is a fascinating area of
study to many people.
Paleobiologists try to find out more
about the way in which life began on
Earth and how it has evolved from
simple life forms into more complex
ones.
They use evidence from fossils and
from studies of the chemistry of
ancient rocks to make estimates of
when and how new life forms
appeared on the planet. 8

 Besides these biologists, there are others
who are, perhaps, more recognizable.
These include: doctors, dentists, veterinary
surgeons, nurses, physiotherapists, botanists,
zoologists, physiologists, biochemists,
agricultural biologists, ecologists, ethologists,
entomologists, geneticists, oncologists,
neurobiologists, parasitologists … and many,
many others besides.
9

What is science?
 The word science comes from the Latin
word Scientia, which means ‘knowledge’.
 But science isn’t just about having
knowledge: science is a unique system of
acquiring knowledge based on the
scientific method.
 This science is sometimes called
experimental science, because it depends
very heavily on experimentation to obtain
the information.
 This is different from applied science, in
which scientific research is used to meet
certain human needs. However, it is often
difficult to separate the two. 10

 Science is an ongoing effort to find new
information and principles which can
increase human knowledge and
understanding.
 In research, scientists collect evidence
that supports or disproves a particular
suggested explanation of a natural
phenomenon.
 One important idea in science is that any
suggested explanation of a phenomenon
should be capable of being proved wrong.
 If there is no way of proving it wrong, how
can other people accept that it is correct?
 This is what distinguishes science from
religious beliefs. 11

What is the scientific method?
 This is the process by which biologists and
all other scientists approach their work.
 For centuries, people based their
explanations of what they saw going on in
the world around them on observations,
without testing their ideas to see if they
were true.
 One ancient belief was that simple living
organisms could come into being by
spontaneous generation (life from non-
living objects).
 This idea suggests that nonliving objects12

As an example:
Observation: Every year in the spring, the river
Nile flooded areas of Egypt leaving behind mud
containing many nutrients that enabled the
people to grow that year’s crop. However,
along with the muddy soil, large numbers of
frogs appeared that weren’t around in drier
times.
Conclusion: Muddy soil gives rise to frogs!
 life from non-living objects. It took the work
of Louis Pasteur using the proper scientific
method to finally disprove this myth.
13

 Also, before the invention of the refrigerator,
animal carcasses were hung by the heels in
butcher’s shops and people would ask the
butcher to cut off the part they wanted.
 The shop was always full of flies. So people
believed that the meat had turned into flies!
 Because of these and other observations,
many people, including quite eminent
‘scientists’ of the day, produced recipes for
‘creating’ life from non-living objects.
 It took the work of Louis Pasteur using the
proper scientific method to finally disprove
this myth.
14

What are the main steps of the scientific method?
 The scientific method consists of a number of
stages. Biologist would follow the scientific method:
 Ask a question
 Do background research
 Construct hypothesis
 Design and carry out an experiment to test the hypothesis
 Analyze results and draw conclusions
 Accept or reject the hypothesis
 Report results
15

Scientific methods
 The scientific method has five basic steps, plus one feedback
step:
1: Make an observation
2: Ask a question
3: Form a hypothesis
4: Make a prediction
5: Test the prediction
Iterate: use the results to make new hypotheses or
predictions
16

Scientific methods
 Observation: Quantitative and qualitative measurements of
the world
 Inference: Deriving new knowledge based upon old
knowledge Hypotheses: A suggested explanation.
 Rejected Hypothesis: An explanation that has been ruled out
through experimentation.
 Accepted Hypothesis: An explanation that has not been ruled
out through excessive experimentation and makes verifiable
predictions that are true.
17

Scientific methods
 Experiment: A test that is used to rule out a hypothesis or
validate something already known
 Theory: A widely accepted hypothesis that stands the test of
time and Often tested, and usually never rejected
18

Scientific methods
 Summary of the scientific method
 Step 1: Observe behavior or other phenomena
 Step 2: Form a tentative answer or explanation (a hypothesis
(guess a reason)
 Step 3: Use your hypothesis to generate a testable prediction
 Step 4: Make systematic, planned observations (data collection)
 Step 5: Results and Discussion , Use the observations to evaluate
(support, refute, or refine) the original hypothesis
 Step 6: Conclusion
 Step 7: Recommendation
19

How do we study the Natural World?
Question
Hypothesis
Prediction
Observations
Now What???
20

Question
Hypothesis
Prediction
Observations
Experiment
21

After you perform your experiment, you need to analyze
the generated data. Does the data support or not
support your hypothesis?
If your data does not support the hypothesis then……
If your data does support your hypothesis……..
23

What is difference between hypothesis, theory & law?
Hypothesis - “an educated guess”; a tentative
explanation of phenomena. (An educated guess
about what a biologist thinks the explanation of an
observation will be. But it has to be stated in such
a way that it can be tested by an experiment )
Prediction - an educated guess as to how the
biologist thinks his/ her experiment will turn out
Theory - a widely accepted explanation of natural
phenomena; has stood up to thorough & continual
testing.
Law - a statement of what always occurs under
certain conditions.
24

How did the scientific method disprove the
idea of
spontaneous generation?
 What about the belief that rotting meat
produces flies?
 How could you disprove that by using the
scientific method?
 Well, in 1668 an Italian biologist, Francesco
Redi, did just that.
 Many scientists consider this to be the first
true ‘experiment’.
 He used wide-mouth jars containing meat.
 Some jars were left open to the air.
 Others were covered with a piece of gauze.
25

 After several days, maggots and then flies
could be seen in the open jars, but none
appeared in the closed jars.
 Redi hypothesized that only flies could
produce more flies and predicted that, in
his experiment, flies would be found in
the open jars, but not in the covered jars.
He maintained all the jars under the same
conditions and so he controlled many
variables.
26

 By choosing to cover some jars with
gauze rather than an impermeable seal,
he allowed air to enter all the jars –
again he controlled a variable that
could have affected the outcome of the
experiment.
 His results matched his prediction and
when other people tried the
experiment, they too got the same
results.
 Redi was able to conclude that flies
cannot be produced from rotting meat. 27

 He also went on to say that it was
unlikely that any form of spontaneous
generation was possible.
 Most people accepted this for larger
organisms, but, at round about this
time, the microscope had been
invented and the whole world of
microbiology was opened up.
 Many people still believed that micro-
organisms could arise by spontaneous
generation.
28

 Francesco Redi’s 1668 experiment
29

 It took the work of Louis Pasteur to disprove this.
 In 1859, Pasteur carried out experiments to show
that the micro-organisms that caused wine and
broth to go cloudy came from the air and were not
made from the broth itself.
 He used special ‘swan-necked flasks’ like
30

 Pasteur boiled broths in swan-necked
flasks to kill any microorganisms that
might be in them.
 The boiling forced steam and air out of
the flasks.
 When the boiling stopped and the broth
cooled, air was sucked back into the
flasks.
 Some contained a filter to prevent all
solid particles from getting into the
growth medium from the air. 31

 Others had no filter but, in these, the dust
(and the microorganisms) in the air settled
in the lowest part of the neck of the flask.
 All the flasks were kept under the same
conditions in Pasteur’s laboratory.
32

 Pasteur found that the broths stayed
clear for months.
 At the end of this time, he treated the
flasks in one of three ways:
He left some of them as they were.
He broke the necks on some.
He tilted others to allow the dust in
the low part of the neck to mix with
the broths.
33

 The broths in the second two groups of flasks turned cloudy
(due to the presence of micro-organisms) within days.
 The broths in the first group remained clear. After this,
people were forced to admit that spontaneous generation,
even of micro-organisms, could not happen.
 One stage in the scientific method is to ‘do
background research’. Pasteur certainly did that.
 He knew that other scientists had tried to disprove
spontaneous generation before him and he was
able to draw on the results of their experiments and
improve their technique.
34

A summary of Pasteur’s procedure
35

What do we mean by cause and effect?
 Scientific experiments try to establish cause
and effect. This means that they try to prove
that a change in one factor brings about a
change in another factor.
 The factor that the scientist changes, or
manipulates, is called the independent
variable (IV).
 The factor that the scientist measures to see
if it changes when the IV is changed is called
the dependent variable (DV).
36

 Independent variable the variable that
the experimenter changes to see if
this affects
the performance of the dependent
variable. Does the presence or
absence of a drug in a tablet
(independent variable) affect the
recovery of the patient?
 Dependent variable the factor in an
experiment that the scientist
measures to see if it changes when
the independent variable is changed 37

 The scientist will want to find out if changes in
the independent variable produce changes in
the dependent variable.
 In the example the independent variable was the
presence or absence of tomato juice.
 The dependent variable was the number of
tomato seeds germinating.
38

 To prove cause and effect – to prove that it
is changes in the IV (and nothing else) that
are causing changes in the DV – we must
take all the steps we can to ensure that the
experiment is a fair test.
 We must make sure that any other factors
which could affect the results are the same
for the different conditions we set up.
 In the tomato seed example, if one group
of seeds had been at a higher temperature
than the other group, this could have made
them germinate faster.
39

 We wouldn’t have known whether it was
the tomato juice affecting the results or the
temperature.
 Our experiment would not be valid. So we
must keep constant anything other than the
IV that might influence the results. ===
These are controlled variables.
40

 The controlled variables were:
Temperature
lighting conditions
number of seeds per dish, and
volume of liquid added (water or tomato
juice).
41

 Occasionally, there is a variable that might
influence the results that you can’t control. Such
a variable is a confounding variable.
 This is because it ‘confounds’ the interpretation
of the results.
 You couldn’t be certain that it was the IV
producing the changes in the DV because of the
presence of the confounding variable.
 For example, if you measure the carbon dioxide
uptake by wheat plants as the light intensity
changes over the day, you cannot control the
effect of change in temperature. It could be a
confounding variable.
42

 Fair test an experiment in which the only
difference between different repeats of the
experiment is the different values of the
independent variable, all other factors that could
affect the outcome have been kept constant (they
have been controlled)
 Controlled variables factors other than the
independent variable that are kept constant
in order to avoid influencing results
 Confounding variable a factor that can’t be
controlled which may influence the result of the
experiment
43

Accuracy, reliability and validity in
scientific experiments
 People often confuse these ideas,
but they are really quite separate
notions and all are important to
how well an experiment is received
by other scientists.
44

Accuracy
 Accuracy refers to how precisely you measure or
count something.
 For example, you could measure time with a
clock, a wristwatch or a stop-clock accurate to
0.01 seconds.
 The level of accuracy you choose must reflect the
magnitude of what you are measuring.
 You don’t always need the most accurate
measuring instrument.
 For example, if you were timing a reaction that
was likely to last a few minutes at most, the stop-
clock would be the best choice.
45

 But if you were timing something that
lasts several hours, you just don’t
need that level of precision and it
might even be a hindrance – by
measuring the seconds accurately,
you might lose track of the hours!
 To measure volume, you could use:
a syringe
a measuring cylinder
a pipette
a burette
46

 All of these come in various sizes. Look at
the ones shown in the diagrams.
 To measure 3.5 cm3 accurately, the pipette
would be best.
 To measure 200 cm3 you would use the
measuring cylinder.
 This one holds 100 cm3 and so you would
have to fill it twice.
 The burette would be more precise, but
less convenient and would you need the
extra precision on quite a large volume?
47

Reliability
 Reliability is a measure of how
dependable our results are.
 If we were to repeat the investigation,
would we get more or less the same
results?
 There are several things we can do to
increase the reliability of our experiments.
 We can standardize all our procedures, so that
we always do exactly the same thing.
oThis makes it much more likely that we will
be able to repeat our results. 48

 We can repeat it many times ourselves.
This allows us to see, hopefully, a general
pattern.
 It also allows us to:
spot any anomalous results and, if it is
justified, to exclude these
calculate an average result, which is
likely to be more representative than
any individual result
49

Validity
 This is about whether or not our experiment
measures what it says it is measuring.
 In the tomato seed experiment, we said that our
results were due to the presence or absence of
tomato juice.
 For our experiment to be valid, we must be
certain that our results were only due to the
changes in the independent variable and nothing
else.
 So had we not controlled all the other variables,
our experiment would not have been valid.
50

Unit Two: Biochemical / Biological Molecules
Learning Objectives
After completing this unit you will be expected to:
 Define the term biomolecules
Describe list of organic and inorganic molecules
Identify the basic structures of biomolecules
Explain the precursors of each macromolecules
State the physical and chemical nature of water
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Biological Molecules
• Human nutrition is a study of how food affects the
health and survival of the human body.
• Human beings require food to grow, reproduce, and
maintain good health.
• Without food, our bodies could not stay warm, build or
repair tissue, or maintain a heartbeat.
• Eating the right foods can help us to avoid certain
diseases or recover faster when illness occurs.
• These and other important functions are fueled by
chemical substances in our food called biological
molecules and these biological molecules are classified
as carbohydrates, proteins, fats, vitamins, minerals, and
water.
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 Biological Molecules
Carbohydrate
Lipids
Proteins
Nucleic Acids
Vitamins
Water
Minerals
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The organic biomolecules are proteins, carbohydrates, lipids
and nucleic acids
Without any of these four molecules, a cell and organism
would not be able to live
They are important either structurally or functionally for
cells and, in most cases, they are important in both ways
The most commonly known inorganic molecules are water
and minerals, which are still important for the normal
functioning of the cell
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Why study Carbon?
All living things are made of cells
Cells
~72% H2O
~3% salts (Na, Cl, K…)
~25% Carbon compounds
Carbohydrates
Lipids
Proteins
Nucleic acids
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The most common elements in many cells
are:
Hydrogen (H) 59%
Oxygen (O) 24%
Carbon (C) 11%
Nitrogen (N) 4%
Others (such as Phosphorus & Sulphur 2%
combined
(The percentages given are averages for
many different cells.)
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2.1. Carbohydrates
Carbohydrates are loosely defined group of molecules
that contain carbon, hydrogen, and oxygen in the molar
ratio 1:2:1, respectively as structural elements
Their empirical formula is (CH2O)n n (where n refers to
the number of carbons) and bond b/n them is glycosidic
 From the formula you can see that a single carbon is
associated with a molecule of water  hydrated carbon
They are also called ‘saccharides’
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Carbohydrates cont….
 Chemically they contain the elements carbon,
hydrogen and oxygen (Carbohydrates are composed of
C, H, O)
Carbo - hydr - ate
 CH2O
(CH2O)x  C6H12O6
 Function:
Source Energy (energy storage)
 help with communication between cells
(cell-cell recognition)
Raw materials for synthesis of different
chemicals in cell (structural materials)
• Example: sugars & starches….
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Carbohydrates…..
Carbohydrates occur abundantly in nature
Cellulose in wood
Starch in cereals, roots & tubers
Glycogen in animal tissue
Glucose in body fluids
They are aldehydes or ketones:
Example: Glucose is aldehyde and fructose is Ketone.
Carbohydrates are:
Reducing sugar
Non reducing sugar
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Carbohydrates cont….
Properties Reducing Sugars Non-reducing Sugars
Definition Carbohydrates that can act as
reducing agents due to the presence
of free aldehyde groups or free
ketone groups.
Carbohydrates that cannot act
as reducing agents due to the
absence of free aldehyde groups
or free ketone groups.
Reducing Agents Good reducing agents. Not reducing agents.
Chemical
Properties
Have free aldehyde or ketone
groups.
Do not have free aldehyde or
ketone groups.
Fehling’s Test Give a positive reaction towards
the Fehling’s test.
Give a negative reaction
towards the Fehling’s test.
Digestion Do not need digestion Need digestion
Examples Include all monosaccharides and
some disaccharides
Include some disaccharides and
all polysaccharides
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CARBOHYDRATES
SIMPLE
Monosaccharide –
Glucose,
Fructose,
Galactose
Disaccharide –
Maltose,
Sucrose, Lactose
Oligosaccharide –
Raffinose
Stachyose
COMPLEX
Polysaccharide –
Starch,
Glycogen,
Cellulose,
Dextrin
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Carbohydrates….
 Carbohydrates are classified based on the no. of carbon chains
present into three groups:
 Monosaccharides - simple sugars with multiple OH groups (single
sugar molecule containing carbohydrate)
Based on number of carbons (3, 4, 5, 6), a monosaccharide is a
triose, tetrose, pentose or hexose
 Disaccharides - 2 monosaccharides covalently linked (two sugar
molecule containing carbohydrate)
 Polysaccharides - polymers consisting of chains of monosaccharide
or disaccharide (many sugar molecule containing carbohydrate)
 Carbohydrates are polyhydroxy aldehydes or ketones, or substances
that yield these compounds on hydrolysis
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Ex: Glucose is aldehyde and fructose is Ketone
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Figure 5.3b
Pentoses: 5-carbon sugars (C5H10O5)
Ribose Ribulose
Aldose (Aldehyde Sugar) Ketose (Ketone Sugar)
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64

Figure 5.3c
Aldose (Aldehyde Sugar) Ketose (Ketone Sugar)
Hexoses: 6-carbon sugars (C6H12O6)
Glucose Galactose Fructose
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65

Monosaccharide or Simple Sugars
Monosaccharides containing:
The aldehyde group are classified as aldoses, and
Those with a ketone group are classified as ketoses
Compounds with 2-10 carbons per molecule (Diose to
decose)
The important compounds are those have between 3 -
6 carbons (triose, tetrose, pentose & hexoses)
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Monosaccharide or Simple Sugars
Sugars which contain a terminal carbonyl group
(aldehyde functional group) are called Aldoses
With internal carbonyl group (keto functional group) are
called Ketoses
The ring structures of the three hexoses
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Carbonyl
C=O
O double bonded to C
if C=O at end molecule = aldehyde
if C=O in middle of molecule = ketone
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Glucose
It is the most important carbohydrate fuel in human cells.
Its concentration in the blood is about 1 gdm-3
The small size and solubility in water of glucose molecules
allows them to pass through the cell membrane into the cell.
Energy is released when the molecules are metabolized.
Two glucose molecules react to form the disaccharide maltose.
Starch and cellulose are polysaccharides made up of glucose
units.
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Galactose
It looks very similar to glucose molecules.
It can also exist in α and β forms.
It reacts with glucose to make the disaccharide lactose.
However, glucose and galactose cannot be easily converted
into one another.
It cannot play the same part in respiration as glucose.
This comparison of glucose and galactose shows why the
precise arrangement of atoms in a molecule (shown by the
displayed formula) is so important.
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Fructose
Fructose, glucose and galactose are all hexose
However, whereas glucose and galactose are aldoses, where
as fructose is a ketose.
It also has a five-atom ring rather than a six-atom ring.
 Fructose reacts with glucose to make sucrose.
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Ribose and deoxyribose
Ribose and deoxyribose are pentoses
The ribose unit forms part of a nucleotide of RNA
The deoxyribose unit forms part of the nucleotide of DNA.
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Disaccharides
Disaccharides: It is a type of oligosaccharide which are made
up of 2 monosaccharides (Dehydration synthesis)
 Monosaccharides are rare in nature.
Most sugars found in nature are disaccharides
|
Glucose
|
Glucose
|
Maltose
Glycosidic linkage
monosaccharides disaccharide
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Disaccharides…..
During formation disaccharide through dehydration
synthesis
Loss of a hydrogen atom (H) from one of the
monosaccharide & a hydroxyl group (OH) from the
other
The resulting linkage between the sugars is called a
glycosidic bond
The molecular formula of each of these disaccharides is
C12H22O11 = 2 C6H12O6 − H2O
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There are 3 common disaccharides:
•Sucrose, Lactose, & Maltose
Disaccharides : 2 Monosaccharide Units
Crystalline, Water Soluble, Sweet In Taste
Maltose : Malt Sugar , Sucrose : Cane Sugar Lactose : Milk Sugar

Synthesizing Maltose & Sucrose
78
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Dehydration vs. Hydrolysis
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Disaccharides…..
Disaccharides are soluble in water, but they are too
big to pass through the cell membrane by diffusion
Hydrolysis reaction is the reverse of a condensation
reaction and it releases energy
Condensation reaction takes place by releasing
water === This process requires energy
A glycosidic bond forms and holds the two
monosaccharide units together
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Polysaccharides
Polysaccharides are classified into plant and animal
categories.
Monosaccharides can undergo a series of condensation
reactions, adding one unit after another to the chain until
very large molecules (polysaccharides) are formed.
This is called condensation polymerization, and the
building blocks are called monomers.
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The properties of a polysaccharide molecule depend on:
Its length (though they are usually very long)
The extent of any branching (addition of units to the side of
the chain rather than one of its ends)
Any folding which results in a more compact molecule
Whether the chain is 'straight' or 'coiled’
These are the type of carbohydrates which are made up of
many units of monosaccharide
It includes starch, glycogen and cellulose
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Polysaccharides…….
Starches
Carbohydrates provide the bulk of the calories &
starches provide the bulk of that
They are polysaccharides  polymers of glucose
Starches are insoluble in water & thus can serve as
storage depots of glucose.
Plants convert excess glucose into starch for storage
whereas animal as glycogen
Starch is composed of amylose & amylopectin (they
have different polymersation stracture
4/24/2024 83

Polysaccharides
Amylose consists of linear, un-branched chains of several
hundred glucose residues (units)
The glucose residues are linked by a glycosidic bond between
their 1 and 4 carbon atoms and the side chains by 1 and 6
carbons
Amylopectin differs from amylose in being highly branched
4/24/2024

Polysaccharides….
Glycogen
Animals store excess glucose by polymerizing it to form
glycogen
The structure of glycogen is similar to that of amylopectin
Glycogen is broken back down into glucose when energy is
needed (a process called glycogenolysis)
The liver & skeletal muscles are major depots of glycogen
4/24/2024 85

Polysaccharides….
Cellulose
Cellulose is probably the single most abundant organic
molecule in the biosphere.
It is the major structural material of which plants are
made
Cellulose is a polysaccharide with glucose as its monomer
4/24/2024 86

Polysaccharides…
Cellulose differs from starch in its properties:
Because of the orientation of the glycosidic bonds linking
the glucose residues are arranged in a flip-flop manner.
This produces a long, straight, rigid molecule.
There are no sides’ chains in cellulose as there are in
starch.
The absence of side chains allows these linear molecules
to lie close together.
Because of the many -OH groups, as well as the oxygen
atom in the ring, there are many opportunities for
hydrogen bonds to form between adjacent chains.
The result is a series of stiff (not easily bent), elongated
fibrils the perfect material for building the cell walls of
plants.
4/24/2024 87

 A typical structure of cellulose
4/24/2024 88

Polysaccharides ….
Polymers of sugars
Costs little energy to build
Easily reversible = release energy
 Function:
• Energy storage
Starch (plants)
Glycogen (animals)
• Building materials = structure
Cellulose (plants)
Chitin (arthropods)
4/24/2024 89

2.2. Lipids
Lipids are compounds that are insoluble in water but soluble in
non polar solvents like chloroform & Benzene
 Some lipids function in long-term energy storage
 Animal fat has six times more energy per gram than
carbohydrates
It occures widly in plant & animal kingdom
Lipids are also an important component of cell membranes
Lipids include fats, oil, waxes, phospholipids, steroids (like
cholesterol) & releated cpds
Oils are liquids at 20oC but fates are soild at 20oc
4/24/2024 90

Importance of Lipids
As the main component of cell membranes
(phospholipids),
Insulation of heat and water, protection and
cellular communication
In the body, fat serves as an efficient sources
of energy & best reserve
It serves as an insulating material in the
subcutaneous tissues for loss of heat
4/24/2024 91

Importance of Lipids……
The phosphatides of blood platelets are involved in the
production of thromboplastin activity in early stages of
blood clotting
Lipoproteins and glycolipids are essential for maintainig
cellular integrity.
Provides building blocks for different high molecular weigth
substances; like acetic acid synthesis of hormones...
They produce metabolites through oxidation in the tissues
They act as a padding material for protecting internal
organs
4/24/2024 92

Lipids- Classification
Simple Lipids
Fats, oils and wax
Compound
Esters of fatty acids containg groups in addtion to an
alcohol & Fatty acid
Phospholipids, Glycolipids, Aminolipids, Lipoproteins...
Derived
Substances derived from above group by hydrolysis
Steroid/Cholestrol, sterol, lipid soluable vitamins,
hormones....
4/24/2024 93

Lipids- Classification
I. Fats and oil (Simple Lipids)
Fats & oils are made from two kinds of molecules:
Glycerol (a type of alcohol with a hydroxyl
group on each of its three carbons) &
3 fatty acids joined by dehydration synthesis
Since there are 3 fatty acids attached, these are
known as triglycerides
4/24/2024 94

Fats....
Fatty acids have a long
hydrocarbon (carbon &
hydrogen) chain with a
carboxyl (acid-COOH) group
The chains usually contain 16
to 18 carbons
A wax is a simple lipid with
long-chain alcohol & a fatty
acid
Waxes are found in nature as
coatings on leaves & stems
The wax prevents the plant
from losing excessive amounts
of water
4/24/2024

Fatty Acids....
The fatty acids are grouped into two groups based
on the presence of double bond in the C-C:
Saturated and
Unsaturated
4/24/2024 96

Fatty Acids....
Saturated and Unsaturated Fatty Acid:
Saturated fatty acids have no double bonds b/n carbons
Unsaturated have double bonds
The double bonds produce a "bend" in the molecule
Molecules with many of these bends cannot be packed as
closely together as straight molecules, so these fats are less
dense
As a result, triglycerides composed of unsaturated fatty acids
melt at lower temperatures than those with saturated fatty
acids
Example, butter contains more saturated fat than corn oil, &
it is solid at room temperature while corn oil is a liquid
4/24/2024 97

Fatty Acids....
A structure details of saturated & unsaturated fatty acids
4/24/2024 98

Phospholipids (Compound)
Phospholipids have a structure like a
triglyceride, but contain a phosphate
group in place of the third fatty acid
The phosphate group is polar & capable
of interacting with water molecules
Phospholipids form a bilayer in a watery
environment
They arrange themselves so that the
polar heads are oriented toward the
water & the fatty acid tails are oriented
toward the inside of the bilayer
Membranes that surround cells and
surround many of the structures within
cells are primarily phospholipid bilayers
4/24/2024

Steroids (Derived)
The main feature of steroids is the
ring system of three cyclohexanes and
one cyclopentane in a fused ring
system
There are a variety of functional
groups
 The main feature, as in all lipids, is
the large number of carbon-
hydrogens which make steroids non-
polar.
The central core of this molecule, four
fused rings, is shared by all steroids,
including estrogen, progesterone,
aldosterone, testosterone, & Vitamin
D.
4/24/2024

Difference Between Carbohydrates and Lipids
Properties Carbohydrates Lipids
Categorie
s and
Examples
 Monosaccharides:
glucose, fructose,
galactose, xylose
 Disaccharides:
sucrose, lactose,
maltose, trehalose
 Polyols: sorbitol,
mannitol
 Oligosaccharides:
maltodextrins,
raffinose, stachyose,
fructo-oligosaccharides
 Polysaccharides:
amylose, cellulose,
amylopectin, modified
starches, hemicellulose,
pectins, hydrocolloids
 Fatty acids: arachidonic acid,
eicosapentaenoic acid, docosahexaenoic
acid
 Glycerolipids
 Glycerophospholipids:
phosphatidylcholine,
phosphatidylethanolamine, and
phosphatidylserine
 Sphingolipids: sphingomyelins,
cerebrosides, and gangliosides.
 Sterol lipids: testosterone and
androsterone
 Prenol lipids: quinones and
hydroquinones
 Saccharolipids
 Polyketides: erythromycins,
tetracyclines, avermectins
4/24/2024 101

Caloric
Content
 Four calories of energy per
gram of energy is generated
in the human cells when
metabolizing the
carbohydrates.
 Nine calories of energy
per gram of energy is
generated in the human
cells when metabolizing
the lipids == Lipids
provide more than twice
the number of calories
compared to
carbohydrates.
Solubility  Majority of carbohydrates
groups (except
polysaccharides) are soluble
in water, and they are
hydrophilic in nature
 Lipids are not soluble in
water because they are
hydrophobic in nature
4/24/2024 102

Digestion and
Absorption
Digestive enzymes from
saliva, pancreas and small
intestine act directly on
sugars and starches in the
foods and break down
carbohydrates into simple
sugars known as
monosaccharides, which are
absorbed into the
bloodstream for distribution
to organs and tissues. Cells
absorb the simple sugar with
the assistance of the hormone
insulin.
Lipid has a complex
digestive process. The
gallbladder releases the bile
acid into small intestine after
food ingestion and bile
contributes to breaking down
large lipid globules into
microscopic droplets, which
are consequently digested by
enzymes from the pancreas.
Then the lining cells of small
intestine absorb the digested
fat particles and transported
by carrier proteins.
4/24/2024 103

Primary
Functions
in the
Living
Organisms
 Providing energy for body
organs and tissues
 Creating structural components
in animals and plants (e.g.
cellulose in plants and chitin in
arthropods)
 Synthesis of coenzymes (e.g.
ribose in ATP, FAD, and NAD)
and the backbone of the genetic
molecule known as RNA
 Function in immune system,
fertilization, preventing
pathogenesis and blood clotting
 Synthesize of carbohydrates
from carbon dioxide and water
by photosynthesis in plants
 Storing energy in the
cells
 Facilitating the
absorption and
distribution of fat-
soluble vitamins
 Providing structural
stability for cells and
cushioning vital
organs like kidney,
liver,
 Cell signaling
mechanisms
 Synthesis of
reproduction
hormones
4/24/2024 104

Primary
functions in
industry
 The complex carbohydrate
starch used as the main
ingredient in bakery products,
noodles, and pasta production
 Starch is used as a thickening
agent in sauces
 Simple carbohydrates, such
as sugar used in beverages,
candy, jams, and desserts
production
 Used for cosmetic
production
 Wax production
 Used as a lubricant
in many industrial
applications
 Used for emulsion
production
 Cooking oil and
spreads production
4/24/2024 105

Natural Food
Sources
 Wheat, maize, rice,
barley contains starch
(polysaccharides)
 Fruits contain fructose
and dietary fiber
 Milk contains lactose
 Nuts such as peanuts,
cashew nuts,
almonds, walnut
 Fruits such as
avocado
 Seeds such as
sunflower, flax,
rapeseed seeds
 legumes (soy)
 Fish and sea foods
Major Digestive
Enzyme
 The major digestive
enzyme is α-amylase.
 The major digestive
enzyme is Lipase.
4/24/2024 106

2.3. Proteins
Most structurally & functionally diverse group of biomolecules
Function:
involved in almost everything
enzymes
formation of different structure
carriers & transport (membrane channels)
receptors & binding (defence)
signalling (hormones)
storage (bean seed proteins)
4/24/2024 107

Importance or Biochemical functions of Proteins
Proteins are playing key role (the life essence)
Are involved in the structure of the living cell & its function
Enzymes & hormons are proteins
Involved in blood clotting through thrombin and other
proteins
Serve as cementing materials to bind or hold the cell as
tissues
4/24/2024 108

Proteins...
Protein - biological polymer of
a-amino acids
The amino acids are joined
together by peptide linkage
Structure:
Monomer = amino acids
20 different amino acids
Polymer = polypeptide
Protein can be 1 or more
polypeptide chains folded
& bonded together
Large & complex
molecules
4/24/2024

Amino acids
 Structure:
 central carbon
 amino group
 carboxyl group (acid)
 R group (side chain)
variable group
confers unique
chemical properties
of the amino acid
 The "R" group of some amino acids is non polar and
the "R" group of some others is polar.
4/24/2024 110

Nonpolar amino acids
 B/c of difference in R group AA can be grouped as
nonpolar and polar
 Non-polar & hydrophobic
4/24/2024 111

Polar amino acids
 polar or charged & hydrophilic
4/24/2024 112

Building proteins
 Peptide bonds: dehydration synthesis or condensation reaction b/n the
amino group of one amino acid & the carboxyl group of another
 linking NH2 of 1 amino acid to COOH of another
 C–N bond
 The complete product, either one or more chains of amino acids, is
called a protein
Peptide bond
4/24/2024 113

Proteins…
Structure of protein
Based on the variable groups contained in the different amino
acids, proteins can have up to four levels of structure.
Primary: the linear sequence of amino acids forming peptide
bonds
There are 20 different standard α-amino acids used by cells for
protein construction.
4/24/2024 114

 The structures of the 20
amino acids commonly
found in proteins. Each
amino acid has both a
one-letter and three-
letter abbreviation.
 The amino acids differ
in structure by the
substituent on their side
chains.
 These side chains confer
different chemical,
physical, and structural
properties to the final
peptide or protein.
The 20 amino acids
115
4/24/2024

 Secondary structure: After an amino acid chain is formed,
it folds into a unique three-dimensional shape.
 Stretches or strands of proteins or peptides have distinct,
characteristic local structural conformations, or secondary
structure, dependent on hydrogen bonding.
 The two main types of secondary structure are the α-helix
and the ß-sheet.
 the localized organization of parts of a polypeptide
bond (Example: the α helix or β sheet are the two main
types) backbone of hydrogen bonds
116
4/24/2024

i) The α-helix: is a right-handed coiled strand.
The side-chain substituents of the amino acid
groups in an α-helix extend to the outside.
Hydrogen bonds form between the oxygen of
each C=O bond in the strand and the hydrogen
of each N-H group four amino acids below it in
the helix.
The hydrogen bonds make this structure
especially stable. The side-chain substituents of
the amino acids fit in beside the N-H groups.
117
4/24/2024

ii) the ß-sheet: The hydrogen bonding in a ß-sheet is between
strands (inter-strand) rather than within strands (intra-
strand).
The sheet conformation consists of pairs of strands
lying side-by-side.
The carbonyl oxygens in one strand bonds with the
amino hydrogens of the adjacent strand.
The two strands can be either parallel or anti-
parallel depending on whether the strand directions
(N-terminus to C-terminus) are the same or opposite.
The anti-parallel ß-sheet is more stable due to the
more well-aligned hydrogen bonds.
118
4/24/2024

 Tertiary structure : overall folding pattern of the entire
polypeptide.
 Protein molecule bends and twists to form stable state.
Three dimensional arrangements of the polypeptide chain.
Quaternary: is the joining of individual polypeptides into an
active protein.
 Proteins that are just a single monomeric polypeptide have no
quaternary structure.
The association of two or more polypeptides into a multi-subunit
complex
4/24/2024 119

2.4. Nucleic Acids
They are complex macromolecules
They store and transmit genetic information
Nucleic acids are made up of nucleotides
Nucleotides are composed of CNOPH atoms.
Function: store & transmit hereditary information
Two Nucleic Acids:
RNA (ribonucleic acid)
DNA (deoxyribonucleic acid)
Structure: monomers = nucleotides
4/24/2024 121

Nucleic Acids cont…
Nucleotides consist of:
a pentose sugar,
a phosphate group, and
a nitrogen containing base.
There are five different bases in nucleotide
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
Uracil (U)
4/24/2024 122

Fig: 2.4. Basic structure of Nucleotides
124
4/24/2024

Nucleic acids…
 In nucleic acids the sugar of one nucleotide bonds to the
phosphate of another nucleotide
 A nucleotide with three phosphate groups is adenosine
triphosphate (ATP) ==ATP is a storehouse of chemical
energy
 Therefore, a polynucleotide is simply a chain of five-
carbon sugars linked together by phosphodiester bonds
with an organic base protruding from each sugar s
125
4/24/2024

Nucleotides
3 parts
nitrogen base (C-N ring)
pentose sugar (5C)
 ribose in RNA
 deoxyribose in DNA
PO4 group
4/24/2024 126

Types of nucleotides
 Two types of nucleotides
different Nitrogen bases
Purines: are large
 double-ring molecules
 found in both DNA
and RNA
 They include: adenine
(A) and guanine (G).
 Pyrimidines: are small,
 Single-ring molecules
 They include:
 cytosine (C), in both
DNA and RNA
 thymine (T) in DNA &
 uracil (U) in RNA
4/24/2024 127

Building the polymer - nucleotides
4/24/2024 128

Nucleic Acid polymerizations
 Backbone
The “backbone” of DNA and RNA is a
chain of sugars and phosphate groups,
bonded by phosphodiester linkages.
The phosphate groups link carbon 3′ in
one sugar to carbon 5′ in another sugar
to PO4 bond
phosphodiester bond
 new base added to sugar of
previous base
 polymer grows in one direction
N bases hang off the sugar-phosphate
backbone
4/24/2024 129

RNA & DNA
RNA
• single nucleotide chain
DNA
double nucleotide chain
 N bases bond in pairs
across chains
spiraled in a double helix
 double helix 1st proposed as
structure of DNA in 1953 by
James Watson & Francis
Crick
4/24/2024 130

Pairing of nucleotides
Nucleotides bond between
DNA strands
H bonds
purine :: pyrimidine
A :: T
 2 H bonds
G :: C
 3 H bonds
4/24/2024 132

2.5. Vitamins
Vitamins are organic compounds that are needed
in small amounts for metabolic activities
Many vitamins help enzymes function well
Vitamin D is made by cells in your skin
Some vitamins B and vitamin K are produced by
bacteria living in the large intestine
4/24/2024 133

Vitamins …
Sufficient quantities of most vitamins cannot be made by
the body, but a well-balanced diet can provide the
vitamins that are needed
Some vitamins that are fat-soluble can be stored in small
quantities in the liver and fatty tissues of the body
Other vitamins are water-soluble and cannot be stored in
the body
Foods providing an adequate level of these vitamins
should be included in a person's diet on a regular basis
4/24/2024 134

2.6 Water
 Water molecules are formed from 2H & 1(O) atom
 It is tasteless and odorless, existing in 3 states. What are they?
 It is important solvent
 The versatility of water is essential to living organisms
 Water molecules have an unequal distribution of charges
 It is Polar molecule
They have oppositely charged regions.
135
4/24/2024

Water…
Special properties of water
Cohesion & adhesion
surface tension, capillary action
 Good solvent
many molecules dissolve in H2O
hydrophilic vs. hydrophobic
Lower density in a solid state
ice floats!
High specific heat
water stores heat
High heat of vaporization
heats & cools slowly
136
4/24/2024

WATER cont….
Life on earth totally dependent on water
It is very essential for existence of life
All life occurs in water
Water has a unique structure that gives the molecule
extraordinary properties
 H2O H2S (hydrogen sulfide)
Like, Oxygen, sulfur has six outer shell electrons & forms
single bonds with two hydrogen atoms
4/24/2024 137

WATER…
Because sulfur is a larger atom & also less electronegative
than oxygen thus its ability to form hydrogen bonding is
greatly reduced
At room temperature (20oC to 25oC), H2S is a gas, not a
liquids as of H2O
Water is a mother liquor of all forms of life
It is about 72% of the weight of a typical cell, 90% of our
blood & 60-80% of tissues are also water
4/24/2024 138

WATER…
It travels through cells & tissues without damaging to the
delicate membranes
It has high boiling point & exist as a liquid in wide range
of temperature (0oC to 100oC)
B/c strong inter-molecular forces acting between
adjacent molecules of H2O.
It is highly polarized state due to the greater attraction of
the electrons to oxygen hence it becomes electronegative,
leaving the hydrogen electropositive
4/24/2024 139

WATER…
This results in each water
molecule being surrounded by
four other water molecules, with
the negatively charged oxygen
atoms being attached to the
neighboring positively charged
proton
 The oxygen atom forms a
tetrahedron with four hydrogen
atoms, two of its own and one
from each from two neighboring
water molecules
4/24/2024

Chemistry of water
 H2O molecules form H bonds with each other
+ attracted to –creates a sticky molecule
4/24/2024 141

Cohesion of Water
H bonding between H2O creates cohesion
water is “sticky”
surface tension
4/24/2024

2.7. Minerals
They are inorganic compounds used by the body as building
material, and they are involved with metabolic functions
For example, the mineral iron is needed to make hemoglobin
and it binds to hemoglobin in red blood cells and is delivered
to body cells as blood circulates in the body
Calcium, and other minerals, is an important component of
bones and is involved with muscle and nerve functions and
they serve as cofactors for enzymes
Magnesium is an important component of the green pigment,
chlorophyll, involved in photosynthesis
4/24/2024 143

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