BI 108: Lecture 2 01/24/2014
A. Types of Biomolecules that exist in the 70% water of the cell.
a. Proteins (polypeptides, “polyamino acids”)
b. Nucleic acids (RNA & DNA; composed of many units of nucleotides)
c. Carbohydrates (polysaccharides)
d. Lipids (NOT water soluble)
B. What are the chemical properties of biomolecules?
a. All biomole. contain C
b. Nonpolar IS THIS TRUE?
c. Electrons shared in bonds ofwater are shared unequally b/c they’re more attracted to the
nucleus of the O2 atom than to those of the H2 atoms
i. The consequence of unequal electron sharing is polarity
C. What are the properties of C
D. What does it mean to be polar? (solubility, etc.)
E. Chemical bonds can be covalent or noncovalent (hydrogen bonds, hydrophobic interactions and Van
A. BI 108 Lecture 3 01/24/2014
A. In cells, the order of these molecules in decreasing amounts is Proteins, nucleic acids, carbohydrates
B. Water solubility, charge, size, shape are important characteristics of biomolecules
C. Solubility: Add polar groups to hydrophobic molecules (Carbonbased molecules can be made
water soluble in this way)
• Adding Oxygen in one form or another can make it more water soluble
• Polar groups often referred to as “functional groups” N=7 biologically important functional
groups in biomolecules
o Adding oxygen in the form of hydroxyl, aldehyde, carbonyl (at the end of a carbon
chain) will make it more H20 soluble. carbonyl group becomes a Keto group when it’s
placed between the carbons in a molecule
• COOH (Carbonyl +alcohol = carboxyl group) can act as weak acids; proton donor. Acidic
• Amines have an amino group.
o Amino groups have a NH2 component to it and accepts H+ in living tissues to form
o Q: What determines whether the acidic and basic groups ionize? ANSWER:
environmental pH (ex: if there are more H atoms floating around in the environment,
the molecule is more able to accept the H)
o Q: Under what pH conditions do acid groups exhibit charge (ionization)? ANSWER:
when the H+ ion concentration is low (neutral, physiological, or alkaline conditions)
o Q: Under what pH conditions do basic groups exhibit charge (ionization)? ANSWER: at
high H+ (acidic) conditions
• When a phosphate group covalently links to a carbon, you’re left with two negative charges.
Adds a lot of polarity/water solubility. Becoming more electronegative in the molecule (because
of 2 negative charges) which makes the biggest changes in the behavior of the molecule.
• Sulfhydryl groups added to an organic compound are referred to as thiols. Some amino acids
(cysteine) contain sulfhydryl groups; the hydrogens can be oxidized and the two sulfurs join in
a disulfide (covalent) bond. Changes behavior of the molecule.
• KNOW THE FORMULAS FOR THESE GROUPS
D. Macromolecules: macromolecules are formed by joining monomers in
condensations/dehydrations reactions; most biomolecules are large and called macromolecules.
• Polymerization= joining monomers to derive polymers. BI 108 Lecture 3 01/24/2014
• Lipids don’t form true polymers; function mostly as monomers or dimers. Lipids mostly provide
• (dehydration/condensation reactions involve removing water) In order to undergo a
condensation reaction, the two monomers/functional groups must have the means to produce a
o Dimer+another monomer with water attached can produce another covalent bond
• Polymers are broken down into monomers in hydrolysis reactions. REQUIRES WATER.
Because of the HUGE percentage of water in the cellular environment, the availability of water
is never an issue.
o It requires two water molecules to break a trimer into 3 separate molecules through
A. Carbohydrates: hydrates of carbon. Threecarbon sugars the simplest commonly found (ose
• 5carbon sugars form a pentose, closed ring. 4carbons and 1 oxygen form the ring, but the
last carbon is protruding from the ring and interacts with the environment. The oxygen comes
from an altered hydroxyl group.
o Numbering starts with the unlike atom and begins clockwise. Ribose sugar has the
completed OH on the 2 carbon and is the pentose sugar in RNA. Deoxyribose does
NOT have the oxygen on the 2 carbon and is the pentose sugar in DNA.
Straight chain sugars do NOT stay straight for long; tend to curve and bond with other
functional groups if thermodynamically favorably (ex: straight glucose. Which can also
be called aldose sugar because of the aldehyde on the final carbon) BI 108 Lecture 3 01/24/2014
Alpha glucose has its hydroxyl group projecting downwards (on carbon 1);
monomer for starch in plants (storage)
Beta glucose has its hydroxyl group projecting upwards (on carbon 1); storage
for cellulose for making cell walls in plants. BI 108: Lecture 4 01/24/2014
D. Note : Active learning folder on blackboard has a thing so that you can alter the structure of a molecule
and see how it affects it (study tool)
E. Learn common functional groups!!
It would take 99 water molecules to hydrolyze a polymer containing 100 individual monomers (n1; where
n= the number of monomers)
B. Hexose structural isomers of glucose include alphaMannose, alphaGalactose, fructose (this one has
carbons 1 and 6 projecting out of a pentose ring; these two carbons can interact with the environment).
C. Functional groups 1 and 5 participate in the formation of glucose ring structure
D. Isomers= structural and stereo types.
E. Only way to discern between asymmetrical molecules is through optical means: how does it behave
when polarized light is exposed to it. They will reflect light in opposite directions.
F. Stereoisomers of bio relevant monosaccharides are predominantly in the Dform.
• Disaccharides are made from the covalent linkage of two monosacchardies through an alpha
1>4 glycoside bond. Carbon1 is from the first monomer and Carbon4 is from the second
• Maltose is an example of a heterodimer because the two glucose molecules that form it are
different (alpha and beta; though the linkage is still the same where Carbon1 of the alpha links
to the Carbon4 of the beta)
• Beta(1>4) Glycoside bonds involve cellbiose dimers/cellulose polymers.
o Alternating position of the hydroxyl groups in the cellulose polymer structure means
that it is more stable (than starch, for example).
G. VERSUS BI 108: Lecture 4 01/24/2014
1. Sometimes in the branching of starch and glycogen, an alpha (1>6) glycoside bond will form.
2. Muscles and liver store glycogen in animals (for glucose storage)
3. Carbohydrates also work as cell coating and as a means for cell recognition with other cells @ the
4. Chemically modified sugars: chitin (has a similar linkage structure to cellulose which aids in its
stability); Bacterial cell walls are made of chemically modified sugars in complex with proteins and
called “peptiglycogen.” BI 108: Lecture 4 01/24/2014
A. Lipids: nonpolar hydrocarbons (ex: fats and oils for energy storage, phospholipids for cell
membranes, carotenoids, steroids)
• Carotenoids (pigmnts, some vitamins) and steroids (hormones, cholesterol) also included
o Beta carotene does not have oxygen in it, therefore it is hydrophobic. Retinol/vitamin A
is essentially beta carotene split in half with the ends replaced by hydroxyl groups.
Therefore they mix with water a little bit.
o Steroid: cholesterol is a constituent of membranes and is the source of steroid
hormones. Largely hydrophobic (there’s just a single hydroxyl group to interact with
water). Steroid ring structure is 3 5ringed structure. Vitamin D2 has extra CH3 tails,
cortisol has fewer branches, testosterone has no extra branches.
Are more hydrophobic than hydrophobic so they can