Organic Molecules
• Molecules unique to living systems contain carbon and
are referred to as organic molecules
• Carbon, needing 4 more valence electrons, forms
covalent bonds (either polar or non-polar) readily with:
– Carbon
– Hydrogen
– Oxygen
– Nitrogen
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Functional Groups
Small groups of
covalently bonded atoms
arranged in a very
specific manner
Parts of large compounds
(carbohydrates, proteins,
fats and nucleotides)
Determine the chemical
properties of large
compounds (polar vs
nonpolar, acid vs base)
React with functional
groups on other
compounds
Macromolecules
• Most of the anatomy and physiology of the body is
provided by 4 different classes of organic molecules
– Carbohydrates
– Lipids
– Proteins
– Nucleic acids
• Each class consists of small molecular subunits called
monomers (one unit)
– smallest subunits of macromolecules that exhibit
chemical properties of the macromolecule
– able to function individually or in covalently bound
groups
Monomers of Macromolecules
• Monosaccharides
– basic (smallest) unit of carbohydrates (sugars)
• Amino acids
– basic (smallest) unit of proteins
• Fatty acids
– basic (smallest) unit of lipids (fats)
• Nucleotides
– basic (smallest) unit of nucleic acids
Synthesis Reactions of Macromolecules
• Monomers can be covalently bound
to one another to create a molecule
gets progressively larger resulting
in a polymer (many units)
• Two or more small molecules
combine to form a larger one
Dehydration Synthesis
• 2 monomers are covalently bonded together to form a
a new molecule that is larger and structurally more
complex by the removal of a water molecule
(dehydration)
Decomposition Reactions
• Large polymer molecules can be
reduced down to the individual
monomers by breaking the covalent
bond between monomers through a
decomposition reaction
Hydrolysis
• Splitting a polymer by the addition of a water molecule
Carbohydrates
• “hydrated (H2O) carbon”
• Contain carbon, hydrogen, and oxygen
• Carbohydrate names end in the suffix “-ose”
– glucose, maltose, amylose, fructose, sucrose
• The monomer of carbohydrates is the
monosaccharide (one sugar) of which there are a
number of types
– glucose is the most biologically important
• Carbon:Hydrogen:Oxygen in a 1:2:1 atomic ratio
– glucose = C6H12O6
• Because they contain oxygen, they are polar
molecules (hydrophilic or lipophobic)
Monosaccharides
• Simplest molecular form of carbohydrates
• Three major monosaccharides
– obtained by the digestion (hydrolysis) of dietary
polysaccharides
– major function is to supply a source of cellular fuel
for the creation of chemical energy (adenosine
triphosphate ATP)
• Structural isomers (same formula (C6H12O6), different
structure
Disaccharides
• Pairs of monosaccharides covalently bonded together
• Three major disaccharides
– sucrose
• glucose + fructose
– lactose
• glucose + galactose
– maltose
• glucose + glucose
Polysaccharides
• Starch (amylose)
– form of stored carbohydrates produced by plants
– hydrolyzed to glucose molecules during digestion
• Cellulose
– molecule that gives support to cell walls in plants
Polysaccharides
• Glycogen
– form of stored carbohydrates in animal cells
Nucleic Acids
• Largest molecules in the body
• Molecules of instruction and heredity
• Two major classes
– deoxyribonucleic acid (DNA)
– ribonucleic acid (RNA)
• The monomers of nucleic acids are nucleotides
Nucleotides
• A nucleotide has 3 parts
– a nitrogen containing base (arranged in a ring(s))
– a sugar
– a phosphate group
• 5 different nucleotides are used to make nucleic acids
– Each nucleotide is different based on 2 criteria:
• the identity of the nitrogen base
–double ringed bases are called purines
• adenine (A) and guanine (G)
–single ringed bases are called pyrimidines
• cytosine (C), thymine (T) and uracil (U)
• the identity of the sugar (DNA uses deoxyribose
while RNA uses ribose)
• Nucleotides are covalently bound to one another
between the sugar of one nucleotide and the
phosphate of another nucleotide to make long straight
(linear) molecules referred to as nucleic acid strands
DNA
• Double-stranded helical molecule
– looks like a ladder that has been twisted
– each strand is between 100 million to 1 billion
nucleotides in length
– 2 strands are held together by H-bonds between
complimentary nucleotides on opposite strands
• H-bonds can only be made between a purine on
one strand and a pyramidine on the other strand
–A can only bind with T
–G can only bind with C
–U is NOT part of DNA (only found in RNA)
• The sequence of nucleotides in one of the strands
contains the genetic code
• the amino acid sequence of all proteins
Structure of DNA
RNA
• Single-stranded molecule
– made from the nucleotides A, U, G and C
• Three varieties of RNA:
– messenger RNA
– transfer RNA
– ribosomal RNA
Structure of RNA
Adenosine Triphosphate (ATP)
• Source of immediately usable energy for the cell
• Nucleotide derivative bound to 3 phosphate groups
– second and third phosphate groups are attached by
high energy covalent bonds
• phosphate groups are negatively charged and
naturally repel each other
• Enzymes that hydrolyze the high energy bond of ATP
produces releases chemical energy
– ATP → ADP + P + energy
• the body can convert the ADP and P back into
ATP using the energy stored in the covalent
bonds of carbohydrates and lipids as a fuel
ATP
Proteins (Peptides)
• Polymer (chain) of amino acids which are bonded
together through covalent bonds called peptide bonds
• 20 different amino acids are used to create proteins
Amino Acids
• Each of the 20 different amino acids have similar
structural components
– a central carbon atom with an attached:
• an amino (NH2) group
• a carboxyl (COOH) group
• a hydrogen atom
• Each amino acid unique due to the functional group
located at the R position attached to the central
carbon atom
Amino Acids
• The 20 amino acids can also be divided into 2 groups
based on their solubility in water
• The molecular composition of the R group determines
whether an amino acid is
– polar
– nonpolar
• The polarity of amino acids play a crucial role in
determining the overall 3 dimensional structure of
proteins which in turn determines its biological function
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Protein Structure
The 20 different amino acids can be joined by peptide
bonds with an almost infinite number of combinations
Proteins vary greatly in size
– some are as small as 3 amino acids in length
– some are as large as 34350 amino acids in length
4 levels of structural complexity in proteins
Primary structure
– the amino acid sequence of the protein
– glutamic acid – histidine – proline is the amino acid
sequence of thyrotropic releasing hormone
– determined genetically and is required for proper
protein function
• a single amino acid deletion or substitution could
lead to a completely dysfunctional protein
– since each protein has a unique amino acid
sequence, each protein is structurally and
functionally unique
Protein Structure
• Secondary structure
– simple shapes that segments of amino acids make
within the protein
• α helix (coiled), β-pleated sheet (folded) shapes
are held together by intramolecular hydrogen
bonds between nearby amino acids
• Tertiary structure
– the overall 3 dimensional shape of the protein
– determined by polar and nonpolar interactions
between the amino acids of the protein and the
surrounding water
– stabilized by intramolecular hydrogen bonds and
disulfide bridges
• Quaternary structure
– two or more separate polypeptide chains interacting
with one another to create a functional unit
Protein Conformation and Denaturation
• Conformation
– overall 3 dimensional shape (tertiary/quaternary)
that is required for function (activity)
– the function of some proteins requires an ability to
change their conformation
• Denaturation
– drastic conformational change in a protein caused
by the breaking of hydrogen bonds within a protein
• increases in temperature
• increases or decreases in pH
– can be partial or complete
• when a protein is partially denatured, its function
is impaired
• when a protein is completely denatured, its
function is lost
Protein Types and Functions
PROTEINS PERFORM ALL BODY FUNCTIONS
Proteins are categorized into 2 groups
• Globular proteins are water soluble and function in:
– Catalysis
• enzymes speed up biochemical reactions
– Communication
• hormones and neurotransmitters act as signaling
molecules between cells
– Cell Membrane Transport
• channels allow substances to enter/exit cells
• Fibrous proteins are insoluble in water and function in:
– Structural integrity
• collagen and elastin hold body parts together
– Movement
• actin and myosin allow for muscle contraction
Lipids
• Nonpolar organic molecules made mostly of carbon
and hydrogen
• Energy rich molecules that can be used for energy
– typically occurs when there is an absence of usable
carbohydrates in the body
• Major molecule that provides structure to biological
membranes
• Used as signaling molecules for communication
between cells (steroid hormones)
Fatty Acids
• Hydrocarbon chains of 4 to 24 carbon atoms (always
an even number) bound to hydrogen atoms
• Has more energy per molecule than glucose
• 2 different functional groups are at each end
– carboxylic acid group
• provides acidic properties to the molecule
– methyl group
Types of Lipids
• The fatty acids (1, 2 or 3)
may be found in the body
bound to a molecule of
glycerol (glucose derived
molecule)
– monoglyceride
– diglyceride
– triglyceride
Fatty Acids
• 2 different types
– Saturated
• solid at room or body temperature (RT/BT)
– Unsaturated
• some are solid but most are liquid at RT/BT
• Saturated fatty acid
– each carbon in the hydrocarbon chain is saturated
with hydrogen (bonded to 2 hydrogens)
• no double bonds between carbons (C=C)
• Unsaturated fatty acid
– each carbon in the hydrocarbon chain is not
saturated with hydrogen
• contains at least one C=C
• Functions
– energy storage in adipose (fat) tissue
• each fatty acid of a triglyceride contains
approximately 4 times more energy than a single
molecule of a monosaccharide (glucose)
Phospholipids
• Similar in structure to a triglyceride consisting of:
– 1 glycerol
– 2 fatty acids
– 1 phosphate group (PO4-) with attached nitrogencontaining group
• Amphiphilic (both loving) molecule
– has BOTH polar and nonpolar portions
• Hydrophobic “tails” consist of two fatty acids
• Hydrophilic “head” consists of a negatively
charged phosphate and nitrogen-containing
groups
• Found in a liquid state at body temperature
• Predominant molecule in cellular membranes
Phospholipid Structure
Arrangements of Phospholipids in Water
Lipid Related Molecules
• The hydrocarbons in a
molecule of cholesterol
are arranged in a 4
ringed structure
• Cholesterol is used to
make steroid hormones
including:
– cortisol
– aldosterone
– estrogen
– testosterone
• Cholesterol is an
important component in
cellular membranes to
keep them in a fluid state