The human body is mostly water, with water making up 75% of lean muscle, 83% of blood, and 25% of body fat. Water is a polar molecule with partially charged atoms that allow it to interact strongly with other molecules and surfaces through adhesion and cohesion. This gives water special properties as a solvent and allows it to move through small spaces against gravity. Carbon atoms form the basis of all organic molecules by bonding with itself and other elements. The four main types of organic molecules that make up living things are carbohydrates, lipids, nucleic acids, and proteins. Carbohydrates, lipids, and proteins are polymers made of repeating monomer units, while nucleic acids like DNA and RNA are also polymers that provide

1. Molecules of Life
The stuff we’re made of

2. Water
• The human body is mostly water
– Lean muscle: 75% water
– Blood: 83% water
– Body fat: 25% water
– Bone: 22% water
• All living organisms require water to live

3. Properties of Water
• Water is a polar
molecule
– Each atom has a
partial charge
– Molecule has zero net
charge
• Polar molecules have
special properties
– Good solvents
– Bond with each other
(cohesion)
– Take longer to heat
and cool
O
H H
δ -
δ +
δ +

4. Partial charges on atoms, no net charge overall!

5. Water Trivia
• What occupies more volume – 8 oz of water at
room temperature, or 8 oz of water at -10 F?
Ice Liquid

6. Properties of Water
• Water molecules are
attracted to molecules
of solid surfaces
(adhesion)
• Adhesion allows
water to move
through very small
pores or tubes
against gravity
(capillary action)

7. Carbon
• A carbon atom has 4
outer (valence) electrons
– wants to make 4 bonds
to be stable
• Carbon can bond with
itself and many other
elements
• Because it’s so friendly,
carbon is present in all
life on earth

8. Organic Molecules
• Any molecule containing
carbon is called an
organic molecule
!! Except CO2 !!
• Most organic molecules
are arranged like chains
– Each link is a monomer
– A chain is a polymer
– A large molecule made of
a long chain or chains is a
macro molecule

9. Types of Organic Molecules
• Carbohydrates
• Lipids
• Nucleic acids
• Proteins

10. Carbohydrates
• Molecules used for energy, made of C H O
– Monosaccharide: a simple sugar (glucose, fructose,
galactose)
– Disaccharide: two monosaccharides bound together
(sucrose aka table sugar)
– Polysaccharide: 3 or more monosaccharides (starch is
hundreds of glucose molecules bonded together)

11. Carbohydrates
Glycogen stored in liver cells (red)
Cellulose in plant cell walls (outer blue layer)
Starch compartments in potato cells

12. Lipids
• Fatty compounds made of C H O, don’t
interact with water (hydrophobic)
– Cell membranes are composed two lipid layers,
which keep water from crossing
• Lipids are polymers made up of fatty acid
monomers
– Fatty acids have oily “tails” and polar “heads”
Non polar
(Boo water!)
Polar
(Yay water!)

13. Lipid Layers
• Lipids in water will arrange
themselves to hide their
hydrophobic tails
• Cell membranes are
composed of a phospholipid
bi-layer
• What is a phospholipid?

14. Other Lipids
• Waxes
• Oils
• Steroids

15. Nucleic Acids
• The genetic material in any
cell
– Deoxyribonucleic acid (DNA)
and Ribonucleic acid (RNA)
– Polymer chains composed of a
combination of 5 different
monomers

16. Nucleic Acids
• The monomers are called
nucleotides
– Adenine, Cytosine, Guanine,
Thymine (DNA only), Uracil (RNA
only)
– Bond in specific pairs
– Adenine – Thymine (Uracil)
– Guanine – Cytosine
• Nucleic acid polymers are
millions of monomers long,
wound in a double helix
• Helix unwinds during
replication (copying)

17. DNA Trivia
• The DNA from a single human cell has a
length of ~ 5.9 feet.
• The biggest cells are less than 0.1 inches
across
• How can so much DNA fit in a cell?

18. Proteins
• Structural building blocks of cells in all tissues (not just
muscle!)
• Polymers composed of 300 – 100k+ monomers
• Monomers are called amino acid
• There are 20 amino acids, many of which must come
from your diet

19. Protein Structure
• Primary structure – the
order of amino acids making
up the polymer string
• Secondary structure –
helixes and sheets of the
polymer string folding on
itself

20. Protein Structure
• Tertiary structure – globs of
sheets and helixes folding around
each other
• Quaternary Structure – individual
proteins bound to each other to form a
multi-protein unit with is own unique
function

21. Hemoglobin carries oxygen in the blood

22. Actin fibers in skeletal muscle cells

23. Proteins make up the cell cytoskeleton

24. Enzymes to copy and repair DNA