Chemistry of life
Basic Chemistry
Matter – anything that takes up space and
has mass.
States of matter
a. Solid
b. Liquid
c. Gas
Elements – basic substances that make up matter; 92 naturally
occurring elements
Four elements that make up >90% of the human
body
1) Carbon (C)
2) Nitrogen (N)
3) Oxygen (O)
4) Hydrogen (H)
Atoms
Smallest unit of an element that has chemical
and physical properties of that element.
Smallest unit to enter into chemical reactions
Structure
Central nucleus containing protons and
neutrons
Outer shells (energy levels) containing
electrons
In the nucleus
Protons – positive charge
Neutrons – no charge
In shells
Electrons – negative charge
Innermost shell (1st energy level) can have 2
electrons
Number of electrons in the outer-most shell
determines the chemical properties of an atom
Atomic number
Number of protons in the nucleus
Determines the identity of the element
Mass number
Number of protons plus the number of neutrons
Isotopes
Isotopes are variations of one type of atom that differ in the
number of neutrons; the number of protons does not change
Radioactive isotopes
a.Unstable isotopes that break down over time
b.Releases detectable energy
c.Low levels of radiation can be used as tracers, X-rays,
mammograms
d.High levels of radiation can be harmful to cells, but can also
be useful, such as for cancer treatment and sterilizing medical
and dental equipment
Hydrogen isotopes
Molecules and compounds
Molecules – form when atoms bond to each other
by covalent bonds
Compounds – form when atoms of different
elements bond
Covalent bonds are formed when atoms share
electrons, usually occurs between same elements of
non-metals.
Atoms can share one or more pairs of electrons
Single bonds – atoms share one pair of
electrons; ex – H2, H-H
Double bonds – atoms share two pairs of
electrons; ex – O2, O=O
Triple bonds – atoms share three pairs of
electrons between them; N2, N≡N
Ionic bonds - Ions are formed when an atom gains or loses
electrons in its outer energy level to become stable
Positive ion (cation) — has lost electrons; indicated by
superscript positive sign, as in Na+ or Ca2+
Negative ion (anion) —has gained electrons; indicated by
superscript negative sign, as in Cl– or O2An ionic bond is formed when positive and negative ions
attract each other; the number of ions used is what is needed
to maintain electrical neutrality
Ionic compounds can dissociate (separate into ions) when
dissolved in water and are then referred to as electrolytes.
When an atom or molecule losses an electron it is said to
be oxidized
When an atom or molecule gains an electron it is said to
be reduced
These reaction is called oxidation-reduction reaction. This
kind of reaction can occur through gain or loss of oxygen
or hydrogen
Water, Acids, and Bases
Water
Most abundant molecule in living organisms; 60-70% of body weight
An inorganic molecule (does not contain carbon atoms), a polar molecule.
Water is a solvent (liquid into which particles are dissolved)
• Facilitates chemical reactions
• Molecules that dissolve in water are said to be hydrophilic (water-loving)
• Molecules that do not dissolve easily in water are said to be hydrophobic
(water fearing)
• Ionic compounds and polar molecules tend to dissolve in water
• Nonpolar molecules do not dissolve in water
Hydrogen bonding between water molecules
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Properties of water
Water molecules are cohesive and adhesive
1) Cohesion - water molecules cling together because of
hydrogen bonding
2) Adhesion - water molecules cling to other substances
due to hydrogen bonds
3) Water flows freely, allowing it to distribute evenly
Acids and Bases
• When water molecules break up, an equal number of
hydrogen ions (H+) and hydroxide ions (OH-) are released
H+ + OH-  H20
• Acids are substances that release hydrogen ions (H+); also
called protons
• Bases are substances that release hydroxide ions (OH-) or
accept hydrogen ions (protons)
• Acids and bases can be strong or weak depending on the
number of H+ or OH• A salt is an electrolyte (ionic compound) formed when an
acid and a base are combined.
HCl + NaOH → NaCl + H2O
sodium chloride is a salt
pH Scale
• Used to indicate the acidity and basicity (alkalinity) of a
solution
• pH 7 is neutral (an equal number of hydrogen ions and
hydroxide ions are released)
• pH above 7 is a base (more hydroxide ions are released
than hydrogen ions)
• pH below 7 is an acid (more hydrogen ions are released
than hydroxide ions)
pH Scale
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pH of body fluids
• Normal pH of blood is 7.4
• Acidosis – blood pH less than 7.35
• Alkalosis – blood pH greater than 7.45
• Blood pH needs to be maintained within a narrow range
Molecules of Life
Four categories of molecules are unique to cells (called
macromolecules or polymers)
1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic acids
Carbohydrates
• Carbohydrates contain carbon, hydrogen, and oxygen
• The ratio of hydrogen (H) atoms to oxygen (O) atoms is
approximately 2:1
• This group is made up of sugars and starches
• Function for quick, short-term cellular energy
• Gives 4 Kcal/gram of energy in the body
• Monosaccharides or simple sugars
a.Glucose – main carbohydrate building block
b.Fructose – found in fruits
c.Galactose – found in milk
• Disaccharides - two monosaccharides joined together
a.Sucrose (table sugar) – glucose + fructose
b.Lactose (milk sugar) – glucose + galactose
c.Maltose (grain sugar) – glucose + glucose
• Starch – storage form of glucose in plants
• Glycogen – storage form of glucose in animals
• Cellulose
• Found in plant cell walls
• Humans are unable to digest cellulose
Starch
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Glycogen
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Lipids
Fats and Oils
• Contain more energy per gram than other biological
molecules – 9Kcal/gram of lipid
• Some function as long-term energy storage in organisms
• Do not dissolve in water
• Consist mostly of carbon and hydrogen atoms; contain few
oxygen atoms
• Also called triglycerides or neutral fats
• Formed when one glycerol molecule reacts with three fatty
acid molecules
• Fats
a.Usually of animal origin
b.Solid at room temperature
c.Used for long-term energy storage, insulation, and
cushioning
• Oils
a.Usually of plant origin
b.Liquid at room temperature
Triglyceride molecule
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Saturated and Unsaturated Fatty Acids
• Saturated fatty acids have only single covalent bonds; lard and butter
are examples
• Unsaturated fatty acids have double bonds between carbon atoms
wherever fewer than two hydrogens are bonded to a carbon atom;
vegetable oils
For fats and oil to be absorbed in the intestine they have to be
emulsified
Emulsifiers are molecules with a polar end and a nonpolar end that
can surround fats so they can mix with water
a.Examples – soaps, detergents, bile
Fatty acids classification according to the number of carbon atoms in its chain
The term essential fatty acids (EFA) refers to those
polyunsaturated fatty acids (PUFA) that must be
provided by foods because these cannot be synthesized
in the body yet are necessary for health.
Phospholipids
• Fatty acid that contain a
phosphate group
• Have a hydrophilic head and
hydrophobic tails
• Form backbone of cellular
membranes
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Steroids
Structure consists of four fused carbon rings with attached
functional groups, derived from cholesterol. They function
as hormones.
Proteins
Proteins are made of amino acid subunits that has
a.Amino group
b.Acid group
c.R (Remainder) group – differentiates the 20 amino acids
Amino acids can be joined together by peptide bonds through the
dehydration reaction
a.Dipeptide – two amino acids joined together
b.Oligopeptide – ten amino acids or less
c.Polypeptide - more than 10 amino acids joined together
Polypeptide
Functions of proteins
• Fibrous structural proteins – collagen and keratin
• Enzymes – globular proteins
• Hormones – chemical messengers; growth hormone,
insulin
• Muscle contraction – actin and myosin
• Transport - hemoglobin
• Protection – antibodies, clotting proteins
• Proteins are generally not use for energy, but as
structullar components and enzymes
Levels of polypeptide structure
1. Primary structure – sequence of amino acids
2. Secondary structure – due to hydrogen bonding that may occur
in a polypeptide; forms coils and folds
3. Tertiary structure results from bonding between R groups;
extensive folding and twists
4. Quaternary structure – arrangement of individual polypeptides
in a protein containing more than one polypeptide
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• The final three-dimensional shape of the protein determines its
function
• If a protein loses its shape, it becomes nonfunctional
• Denaturation – irreversible change in the normal shape of a protein
due to extremes in heat and pH
• Protein can act as enzymes.
• Enzymes – are proteins that catalyzes metabolic reactions at
the body’s normal temperature
a.Named for their substrate or type of reaction
b.Lower the activation energy needed to start a reaction
c.The shape of the active site and its chemical composition
determines specificity of enzyme
d.The reactant the enzyme catalyzes is the substrate
Enzymatic Action
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Nucleic Acids
Nucleic Acids
• Huge macromolecules composed of nucleotides
• Nucleotides composed of 3 subunit molecules:
a.A phosphate
b.A pentose sugar
c.A nitrogen-containing base
• Two classes of nucleic acids
a.DNA
b.RNA
Nucleotide Structure
DNA
• Deoxyribonucleic acid
a.Contain pentose sugar deoxyribose
b.Nitrogen-containing bases
1)Adenine (A)
2)Thymine (T)
3)Guanine (G)
4)Cytosine (C)
• Usually double stranded – double helix
• Makes up the genes that contain hereditary information that
determines the proteins a cell makes
• DNA is like a twisted ladder with alternating sugar – phosphate on the
sides and complementary nitrogenous base pairs as the rungs
• Adenine – thymine
• Cytosine – guanine
• The sequence of groups of three bases codes for an amino acid
DNA structure
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RNA
• Ribonucleic acid
a.Contain pentose sugar ribose
b.The nitrogen-containing base uracil (U) replaces thymine
c.Usually single stranded
• Carries the instructions from DNA for making a protein
Comparison of DNA and RNA
ATP – adenosine triphosphate
• A modified nucleic acid
• Primary energy currency of cells
• Cells break down glucose and fat and convert released
energy into ATP and heat
• Used when cellular reactions require energy
• Breakdown of ATP results in one molecule of ADP (adenosine
diphosphate) and one molecule of inorganic phosphate
• ATP is rebuilt by the addition of inorganic phosphate to ADP
• One glucose molecule can build 36 to 40 ATP molecules
• One fat molecule can build on average 120 ATP molecules
Breakdown and formation of ATP
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Summary of macromolecules and monomer