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Principles of Biology
By
Frank H. Osborne, Ph. D.
Chemistry of Life
The Scientific Method
The Scientific Method has several steps:
•A natural phenomenon is observed
•A hypothesis (proposed explanation) is made
•An experiment is performed
•Results are obtained
•The hypothesis is supported or disproved
•Any scientific explanation is called a theory
The Scientific Method
How science works:
•We learn not by proving something but by
disproving something else.
•Inquiry is used to make observations,
formulate hypotheses and test them.
•Science works by asking questions and
answering them.
The Metric System
The Metric System is used for measurement.
•Length is measured in units of the meter.
•Volume is measured in units of the liter.
•Mass is measured in units of kilograms.
•Time is measured in units of seconds.
The Metric System
Prefixes used in the Metric System
Scientific Notation
Numbers are represented as a number
between 1 and 10 x 10 raised to an
appropriate power. Examples:
2800 = 2.8 x 103
.00055 = 5.5 x 10-4
Simple Chemistry
Biology involves understanding some simple
concepts of chemistry.
•Atoms
•pH scale
•Chemical bonding
ATOMS
Atoms are composed of protons,
neutrons and electrons.
•The nucleus is made of protons and neutrons.
•The electrons travel in orbits around the
nucleus.
•Atomic number is the number of protons.
•Atomic mass is the number of protons and
neutrons. Find the number of neutrons by
subtraction.
Atomic Structure
Structure of the
Atom
•Each atom
(element) has its
own symbol.
•Example: Helium
Examples of Atoms
Examples of Atoms
Examples of Atoms
Examples of Atoms
Examples of Atoms
Dot Structures
The outer electrons of the atom are all that
matter in chemical bonding. It is customary to
represent them using dots.
Principal Elements in Protoplasm
Element
Hydrogen
Oxygen
Carbon
Nitrogen
Phosphorus
Sulfur
Water is most
abundant
compound
Symbol
H
O
C
N
P
S
Percentage
63
25.5
9.1
1.4
<1
<1
CHON are most
abundant elements
Molecules
• Molecules are electrically neutral
aggregates of atoms bonded together.
• "Electrically neutral" means that the
number of protons equals the number of
electrons.
Compounds and Molecules
•A compound is a substance with a definite
composition that can be decomposed into two
or more substances (examples are salt (NaCl)
and water H2O)).
•A molecule is the smallest unit of a substance
that has the chemical properties of the
substance.
Bonding
•An ionic bond is formed by complete transfer
of one or more electrons from one atom to
another. Example: NaCl
•A covalent bond is formed by sharing of
electrons between atoms. Example: H2O
Ionic
Bonding
Covalent Bonding
Some Important Compounds
Counting Atoms
The pH Scale
•The pH scale shows the strength of an acid or
a base. It ranges from 0 to 14.
•A pH of 7 is neutral.
•A pH less than 7 is acidic.
•A pH greater than 7 is alkaline (basic).
The pH Scale
ORGANIC CHEMISTRY
Organic chemicals contain
carbon.
The more important ones are:
• carbohydrates
• lipids
• proteins
• nucleic acids
CARBOHYDRATES
Carbohydrates contain carbon (C),
hydrogen (H), and oxygen (O). The ratio
of hydrogen to oxygen is 2:1 in
carbohydrates. This means that
there is twice as much
hydrogen as there is oxygen.
Simple Sugars (Monosaccharides)
Simple sugars
contain from three to
seven carbon atoms.
Some of the larger
ones can form rings.
Glucose Can Form Rings
• Glucose makes a
hexagonal ring form
Condensation Reactions
• A condensation reaction occurs
between two molecules when an enzyme
removes water from them and joins
them together with a single bond. This process
is known as dehydration synthesis.
• The water is always removed in the form of
H from one molecule and OH from the other.
Disaccharides
Disaccharides consist of two monosaccharides
connected by a condensation reaction. An
example is maltose which is formed by
reaction between two glucose molecules.
Formation of Maltose
Polysaccharides
Polysaccharides contain many monosaccharides
linked together by condensation reactions.
These consist of long chains called polymers.
The three polymers of glucose are starch,
cellulose and glycogen.
The Hydrolysis-Synthesis Cycle
The Carbohydrate Pyramid
Many sugars
(many glucose)
Two glucose
(maltose)
One glucose
LIPIDS
• Lipids contain carbon, hydrogen and
oxygen. There is much less oxygen in a
lipid than there is in a carbohydrate.
• The types of lipids are:
• triglycerides
• waxes
• phospholipids
• steroids
Fats and Oils
Fats and oils are examples of triglycerides.
Fat is solid at room temperature, oil is liquid.
The building blocks of triglycerides
are fatty acids and glycerol.
Molecules of triglycerides contain one glycerol
and three fatty acids.
Forming a Triglyceride (1)
Forming a Triglyceride (2)
Saturated/Unsaturated Fats
Saturated fats do not have double bonds
between the carbon atoms.
Unsaturated Fats have double bonds between
the carbon atoms.
Types of Fatty Acids
Waxes
Waxes are formed by condensation reactions
between long-chain fatty acids and long-chain
alcohols. They are found in various places,
such as the surfaces of leaves.
Phospholipids
Phospholipids contain glycerol, two fatty
acids, phosphorus and sometimes nitrogen.
They have polar heads and non-polar tails.
The polar end is hydrophilic.
The non-polar end is hydrophobic.
These molecules are the major component of
all biological membranes
Phospholipids
Diagram of a phospholipid molecule.
Steroids
Steroid molecules have a complicated
structure of interlocking carbon rings. This is
an important type of lipid. It includes the sex
hormones, cortisone, cholesterol, and related
molecules.
PROTEINS
Proteins are long-chain polymers of amino acids
which are linked together by condensation
reactions (dehydration synthesis). They are the
fundamental structural molecules in biology.
The structural properties of proteins
are due to the presence of nitrogen.
Amino Acids
There are 20 different
types of amino acids.
They can
combine in a
variety of ways.
Amino acids are
required for
synthesis of
proteins.
Formation of Proteins
Proteins are formed by condensation
reactions (dehydration synthesis).
When two amino acids are joined together, the
result is a dipeptide (two amino acids) joined
by a peptide bond, and the water molecule
which was removed.
Formation
of Proteins
Peptide
Bond
The Protein Pyramid
Functions of Proteins
Structural proteins. Structural proteins hold
biological structures together or form body
structures. An example is keratin. Keratin is
found in hair, skin, nails, and the corresponding
parts of other animals such as fur, hooves,
claws, as well as fish and reptile scales.
Functions of Proteins
Enzymes. An enzyme is a catalyst that allows
the occurrence of a chemical reaction at body
temperature. All enzymes are proteins.
Condensation reactions are examples of
biological reactions that are catalyzed by
enzymes. There is also an enzyme called
catalase. Catalase is another example of an
enzyme.
NUCLEIC ACIDS
There are two types of nucleic acids.
These are known as:
• Deoxyribonucleic acid (DNA)
• Ribonucleic acid (RNA)
Nucleotides
Nucleotides are the building blocks of nucleic
acids. They have three components: a base, a
sugar and a phosphate. The bases are rings of
carbon and nitrogen atoms and are sometimes
called nitrogenous bases. Phosphate is derived
from phosphoric acid.
The sugar found in DNA is called deoxyribose
while the sugar found in RNA is called ribose.
Formation of Nucleic Acids
The phosphate from one nucleotide becomes
joined to the sugar of another nucleotide by a
condensation reaction. This process builds very
long chains of nucleotides.
The Nucleic Acid Pyramid
Functions of the Nucleic Acids
Deoxyribonucleic acid (DNA). DNA is found in
the chromosomes of the nucleus of the cell. It
directs all aspects of cell function. It is
organized into genes which determine the
properties of the organism.
Functions of the Nucleic Acids
Ribonucleic acid (RNA). There are three types
of RNA. Each is associated in some way with
protein synthesis. The structure of proteins (the
sequence of the amino acids in the protein) is
ultimately determined by the DNA of the cell.
The End
Principles of Biology
Chemistry of Life