Chapter 2: Life, Chemistry, Energy
Key Terms:
adhesion: atraction of one substance to another
amphiatic: having both hyrophilic and hydrophobic parts
anabolic rx: metabolic rx where energy is stored in chemical bonds following the law of
conservation of matter
anions: negative ion that has gained electrons
atomic number: number of protons in an element; sorting factor on the periodic table
atoms: building blocks of all matter; rx determined by electrons
bilayer: made of lipids and composition of all biological membranes
bohr model: diagram of how bonds connect by showing the electrons in the elecron shells
carbohydrates: general formula of Cn(H20)n; function to store energy, transport stored
energy, structural molecules and recognition or signaling molecules
catabolic rx: metabolic rx where energy is released from chemical bonds; follows law of
conservation of matter
cations: positive ion that has lost electrons
chemical bond: three types; ionic, covalent, and hydrogen bonds (in order of
chemical rx: requires ENERGY
cohesion: attraction between molecules of the same substance
condensation rx: combining of two molecules with the byproduct of H20
covalent bond: consist of shared pairs of electrons between 2 atoms; not always equal
(polaar covalent bonds)
disaccharide: two monosaccharides (simple sugars) connected in a dehydration rx
electron shells: the "rings" around the nucleus in an atom
electronegativity: tendency of an atom or radical to attract electrons to form an ionic bond
electrons: one of three main subatomic particles inside an atom; the protons and neutrons
reside in the nucleus and the electrons reside in the elecron shells around the nucleus
Questions:
1. The search for water is important to life because all life on earth requires water. If there is
water on a planet, then there is probably life there too.
2. The electrons that are shared form covalent bonds. When an electron is given of to
complete an electron shell in another atom is an ionic bond. When hydrogen (+) is attracted
to a negative side of another electronegative molecule then they form a hydrogen bond.
3. The octet rules say that a full electron shell (except the one closest to the nucleus which
has 2 elecrons) will have 8 electrons to be satisfied. If the atom doesn't have the 8 electrons
then it will constantly be looking to take another electrons.
4. Ionic bonds form by electrical attraction between a cation and an anion. Covalent bonds
consist of sharing pairs of electrons in order to fill the outer valence. Hydrogen bonds are
very weak because they form within or between molecules with polar covalent bonds. They
are very important in determining the properties of water and the structure fo large
macromolecules, like DNA.
5. Water is a polar molecule because the oxygen molecule forms two polar covalent bonds
with the two hydrogen molecules. The electonegativity of oxygen is much greater than the
positive charges of the two hydrogens combined so the hydrogen molecules are forced
together to form an "L" shape. Water's cohesive property comes from strong H-bonds
between water molecules. Water's adhesive property comes from its ability to make hbonds with other molecules (not H2O). Water has a high specific heat and high heat of
vaporization because the molecules resist change and want to stay at the same
temperature.
6. Hydrophobic means "water-fearing" or water-repelling. Hydrophobic molecules (nonpolar)
are not attracted to the polar water molecules. Hydrophilic means "water-loving."
Hydrophilic molecules are polar and are attracted to water.
7. Dehydration synthesis is when two momomers/poymers are combined and give off H2O
as a byproduct.
8. Sugars are like legos because they have monosaccharides, or the basic building blocks
of carbs, which allow two monosaccharides to be combined to a disaccharide.
9. Cellose is found in numerous rows of parallel molecules that form hydrogen bonds with
other rows to form sheets (thin fibrils). Starched branch off at odd angles making starch less
compact than cellulose. And glycogen has many many branches whose offshoots are more
compacted that starch branching. Glycogen is easily digested by humans because the
numerous branches provide for many spots for the enzymes to latch on and begin eating
away at the molecules. With starch, this process is slightly slower because there are less
offshoots on the branches. And with cellulose this process is too slow. The enzymes have
difficulty penetrating the structure of the cellulose sheets so they can't digest cellulose.
10. A saturated fatty acid has only single bonds on the three fatty acid tails of a triglyceride.
A nonsaturated fatty acid has single and double bonded carbons on the fatty acid tails.
Nonsaturated fatty acids are much easier to break down because of the kink in their
structure at each double bond. Becuase of this they also take up more space.
11. The first law of thermodynamics says that the total amount of energy before a rx is
equal to the total amount of energy after a rx. In a metabolic rx no energy is created or
destroyed. It all must come from somewhere. The second law says that after a rx, the
amount of energy available to do work is always less than the original amount (some is
unusable). With metabolism, energy that is stored in chemical bonds is called anabolism,
and energy that is released from chemical bonds is catablolism. The energy supply must
constantly be replenished for an organism to have a steady supply of energy to undergo
necessary daily functions. 40 % of the energy that is lost in a rx is given off as heat.