Biology 120 Notes (Part 3) Water

Water - Essential to Life

• Water makes up 60-70% of the human body.
• ==Water== is the most critical molecule for life on Earth.

Why?

• The first reason is because water is a polar molecule.
• The second reason is because it can form hydrogen bonds.

Properties of Water

• Water has a high heat capacity.
• Water has a high heat of vaporization.
• Water is a good solvent.
• Molecules can be hydrophobic or hydrophilic.
• Water molecules are cohesive and adhesive.
• Water has surface tension and capillary action.
• Ice is less dense than liquid water.
• Water expands as reaches 0 degrees Celsius.

The Importance of Organic Molecules

==Organic compounds== are molecules that contain carbon bonded to hydrogen and other elements.

Why Carbon?

• Carbon is the most versatile atom on Earth.
• The number of valence electrons.
• Carbon is able to form many bonds.

Comparing Inorganic vs. Organic Molecules

• ==Inorganic molecules== are made up of various elements, usually have ionic bonds, are small molecules, and are associated with non-living things.
• ==Organic molecules== are always composed of carbon and hydrogen, always have covalent bonds, are larger molecules, and are associated with living things.

The Carbon Skeleton and Functional Groups

• The ==carbon chain== is the equivalent to a skeleton or backbone.
• ==Functional groups== are attached to the carbon skeleton.

Functional Groups

• H-, N-, O-, P-, and S- contain functional groups found in organic compounds.
• ==Amino groups== act as bases (N.)
• ==Carboxyl groups== act as acids (COO or COOH) which have two oxygens.
• ==Carbonyl groups== have sites that link molecules into more complex compounds (CO or COH) which have one oxygen.
• ==Hydroxyl groups== act as weak acids (OH.)
• ==Phosphate groups== have two negative charges (P.)
• ==Sulfhydryl groups== link together via disulfide bonds (S.)
• An important thing to remember is how ==“R” equals the carbon skeleton==.
• ==Hydrogen bonds== between functional groups help stabilize biological molecules and allows them to perform their biological function.
• ==Hydrogen bonds== connect two strands of DNA together to create the double helix.
• ==Isomers== are organic molecules that have identical molecular formulas but a different arrangement of atoms.