Organic & Biological molecules
I.
Organic Molecules
a. A cell is mostly water, but the rest is carbon-based molecules
b. Carbon is very diverse, and can form large complex molecules that are necessary
for life; the study of carbon-based molecules is called organic chemistry
c. Why is carbon so important? Remember that carbon has only 4 electrons in its
outer shell, which can hold up to 8 electrons. So, carbon can share electrons by
making up to 4 covalent bonds
d. Carbon acts as an “intersection” for organic molecules to branch off from
e. Hydrocarbons: the simplest organic molecules which contain only carbon and
hydrogen (for example, methane, CH4)
f. Methane is one of the most abundant hydrocarbons in natural gas, and is also
formed by bacteria that live in swamps and the intestines of grazing animals like
cows.
g. Larger hydrocarbons, like octane (eight carbons) are found in gasoline that we use
in cars
h. Biological Molecules
i. Carbohydrates: sugars and starches, are soluble in water, hydrophilic (“waterloving”)
i. Monosaccharides: simple sugars, like glucose and fructose
ii. Both have the same chemical formula C6H12O6, but their atoms are
arranged differently (see fig. 3.9) – they are isomers
iii. Disaccharides: double sugar, which combines two monosaccharides, such
as maltose (combines two glucose molecules together)
iv. Most common disaccharide is sucrose, table sugar, which is glucose and
fructose
v. Polysaccharides: complex carbohydrates, long chains of sugars: polymer
(a large structure composed of smaller units linked together); example is
starch, which is many glucose monomers strung together.
j. Lipids: do not mix with water, are said to be hydrophobic (“water-fearing”)
i. Fats: made of the molecule triglyceride, which is glycerol (a fat) joined
with three molecules called fatty acids
ii. Fats are useful in storing energy for the body, but are slow to burn.
iii. Fat is stored in adipose tissues, which serves as an energy storage as well
as protection for vital organs
iv. Unsaturated fats have less than the maximum number of hydrogen at the
location of the double bond, so one of the fatty-acid “tails” bends
v. Saturated fats have the maximum amount of hydrogens (all three fatty acid
tails are saturated with hydrogens) – no double bonds
vi. Steroids – classified as lipids because they are hydrophobic, but are very
different structurally and functionally from fats
vii. Cholesterol is a steroid, used to make other steroids such as testosterone
and estrogen (sex hormones)
viii. Anabolic steroids: synthetic variants of testosterone (male sex hormone)
ix. Causes a buildup in muscle and bone mass during puberty and maintain
musculature during adult life; used as a performance-enhancing agent
k. Proteins
i. Most elaborate molecule of life
ii. Proteins are long chains (polymers) of amino acids (monomers)
iii. There are tens of thousands of different types of proteins in the body, and
each has a very specific structure and function
iv. Four types of proteins
1. Structural: provide support, i.e., hair, and connective tissue
2. Storage: provide amino acid source, i.e., seeds, eggs
3. Contractile: allow for muscle contraction to occur, i.e., muscles
4. Transport: allow for oxygen to be transported throughout the body,
i.e., hemoglobin found the RBC
l. Monomers: all proteins are constructed from a common set of 20 monomers
called amino acids
m. Each amino acid consists of a central carbon bonded covalently to four other
partners.
n. Three of those partners are common to all amino acids: a carboxyl group (COOH), an amino group (-NH2) and a hydrogen atom.
o. The fourth spot is called the side group and varies between amino acids; the side
group dictates what the amino acid is.
p. Polypeptides: adjacent amino acids will link together via peptide bonds, forming
a polypeptide chain.
q. Typically a polypeptide consists of 100 or more amino acids linked together
r. Protein shape: polypeptides will arrange themselves in various ways to form
protein structures:
i. Primary structure: unique sequence of amino acids in the polypeptide
chain
ii. Secondary structure: primary structure will fold in certain areas and make
a pleated sheet or alpha helix structure
iii. Tertiary structure: continued folding of secondary structure
iv. Quaternary structure: two or more polypeptide chains bonded together.