Molecules of Life

The stuff we’re made of

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

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 +

O

H H

δ -

δ +δ +

O

H H

δ -

δ +δ +

Partial charges on atoms, no net charge overall!

Water Trivia

• What occupies more volume – 8 oz of water at room temperature, or 8 oz of water at -10 F?

Ice Liquid

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)

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

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

Types of Organic Molecules

• Carbohydrates

• Lipids

• Nucleic acids

• Proteins

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)

Carbohydrates

Glycogen stored in liver cells (red)

Cellulose in plant cell walls (outer blue layer)

Starch compartments in potato cells

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!)

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?

Other Lipids

• Waxes• Oils • Steroids

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

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)

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?

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

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

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

Hemoglobin carries oxygen in the blood

Actin fibers in skeletal muscle cells

Proteins make up the cell cytoskeleton

Enzymes to copy and repair DNA