Chemical Basis of Life
Chapter 2: Section 3
Organic vs. Inorganic Chemicals
in the Human Body
• Organic: chemicals that contain carbon and
hydrogen atoms
▫ Compounds dissolve in organic liquids, such as
ether or alcohol.
▫ Can dissolve in water but do not release ions and
are called nonelectrolytes.
• Inorganic: chemical substances that lack
carbon and hydrogen atoms.
▫ Dissolve/react with water to release ions;
electrolytes
Inorganic Substances
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Water
Oxygen
Carbon Dioxide
Salts
Inorganic Substances: Water
• Most abundant compound in living material and
accounts for 2/3 of the weight of an adult human.
• Important solvent because substances dissolve in it
▫ Solute: substance dissolved in water and broken down
into smaller and smaller pieces.
• Moves chemicals within the body
▫ Aqueous portions of blood carry substances such as
oxygen, sugars, salts, and vitamins, from digestive
organs to respiratory organs.
• Can absorb and transport heat
▫ Blood carries heat released from muscle cells during
exercise from deeper parts to the surface.
Inorganic Substances: Oxygen
• Oxygen enters through respiratory organs and
transported by blood
• RBCs bind and carry oxygen
• Cellular organelles use oxygen to release energy
from sugar glucose and other nutrients.
• Released energy drives the cell’s metabolic
activities
Inorganic Substances: Carbon Dioxide
• Simple, carbon-containing compound
• Produced as a waste-product when certain
metabolic processes release energy, and it is
exhausted by the lungs
Inorganic Substances: Salts
• Salt is a compound composed of oppositelycharged ions
• Abundant in tissues and fluids
• Provide necessary compounds such as:
▫ Refer to handout 
• Important in metabolic processes:
▫ Transport of substances into and out of cells
▫ Muscle contraction
▫ Nerve impulse conduction
Organic Substances
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Carbohydrates
Lipids
Proteins
Nucleic Acids
Organic Substances: Carbohydrates
• Carbohydrates: provide much of the energy
cells require
• Supply materials to build certain cell structures
and often are stored as reserve energy supplies
• Consist of carbon, hydrogen, and oxygen
▫ Contain twice as many hydrogen as water; think of
H2O, C6H12O6, and C12H22O11.
Organic Substances: Carbohydrates
• Carbon atoms of carbohydrate molecules join in
chains whose lengths vary with the type of
carbohydrate
• Shorter chains = sugars
• Sugars w/6-carbon atoms= simple sugars or
monosaccharides, and are the building blocks
of complex carbohydrates
▫ Examples of simple sugars: glucose, fructose,
galactose
Organic Substances: Carbohydrates
• Complex carbohydrates: number of simple
sugar molecules link to form molecules of
varying sizes.
• Disaccharides: (double sugars) molecules
contain two simple sugar building blocks
▫ Examples: sucrose and lactose
• Polysaccharides: made up of many simple
sugar units joined together
▫ Example: plant starch; and animals (humans)
synthesize glycogen
Organic Substances: Lipids
• Lipids: insoluble in water but soluble in certain
organic solvents, such as ether or chloroform.
• Include a variety of compounds that are vital to
cell functions:
▫ Fats (most common)
▫ Phospholipids
▫ Steroids
Organic Substances: Lipids
• Fats: primarily to store energy for cellular
activities
• Store more energy, gram for gram, than
carbohydrate molecules.
• Composed of carbon, hydrogen, and oxygen
atoms.
▫ Unlike carbohydrates, fats have a much smaller
portion of oxygen atoms.
Organic Substances: Lipids
• Building blocks of fat molecules are:
▫ Fatty Acids
▫ Glycerol
• Each glycerol binds with 3 fatty acid molecules
to produce a single fat, or triglyceride, molecule.
• Glycerol portions are identical but fatty acid
portions are different because there are many
kinds of fatty acids.
▫ Variations in fatty acid chains create different
kinds of fatty acids.
Organic Substances: Lipids
• Saturated
▫ Each carbon atom is bound to as many hydrogen
atoms as possible and is thus saturated with
hydrogen atoms
• Unsaturated
▫ Fatty acids with double bonds
• Polysaturated
▫ Fatty acids with MANY double bonds
Organic Substances: Lipids
• Like fatty acids, there are different kinds of fat
molecules.
• Saturated fats
▫ Made of saturated fatty acids
• Unsaturated fats
▫ Made of unsaturated fatty acids
Organic Substances: Lipids
• Phospholipids: contains a glycerol portion and
a fatty acid portion, but it only has a two fatty
acid chains.
• Place for third chain is replaced by a phosphate
group
• Hydrophilic head- water-loving
• Hydrophobic tails- water-hating
• Important in cellular structure
Organic Substances: Lipids
• Steroid: complex structures that contain 4
connected rings of carbon atoms
• Cholesterol is a very important steroid for
body cells and is used to synthesize other
steroids
• Other steroids include:
▫ Sex hormones (estrogen, progesterone,
testosterone)
▫ Several hormones from adrenal gland
Organic Substances: Proteins
• Protein: wide variety of functions; structural
materials, energy sources, hormones.
• Glycoproteins: proteins and carbohydrates
that serve as a receptor on a cell’s surface and
bond to specific molecules.
• Antibodies detect and destroy foreign
substances in the body.
• Enzymes make metabolism occur faster and
are EXTREMELY important.
Organic Substances: Proteins
• Proteins composed of carbon, hydrogen, and
oxygen, plus nitrogen and sometimes sulfur
atoms.
• Building blocks of proteins are called amino
acids.
▫ There are 20 different kinds of amino acids that
occur commonly in living organisms.
Organic Substances: Proteins
• Protein structure:
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Primary
Secondary
Tertiary
Quaternary
• Each level of structure increases complexity
• Protein 3D shape = conformation
• When hydrogen bonds holding protein shape
break because of heat, radiation, electricity, pH,
or chemicals, the protein denatures.
Organic Substances: Nucleic Acids
• Nucleic Acids: form genes and take part in
protein synthesis
• Usually large and complex molecules
• Contain carbon, hydrogen, oxygen, nitrogen, and
phosphorus, which form the building blocks of
nucleotides.
▫ 5-carbon sugar, phosphate group, and one of
several nitrogenous bases
Organic Substances: Nucleic Acids
• Two kinds of Nucleic Acids
▫ RNA (ribonucleic acid)
 Nucleotides contain ribose
 Single chain but can fold into various shapes to
control when genes are accessed
▫ DNA (deoxyribonucleic acid)
 Nucleotides contain deoxyribose
 Double chain that is held together by hydrogen
bonds