BIOEXCEL 190 - Biomolecules KEY


____.) Name the four main groups of biomolecules.
1. carbohydrate
2. protein
3. lipid
4. nucleic acid

____.) Regardless of the type of biomolecule, the formation and breakdown of a polymer can be described by the following equation:

Write the name of the chemical mechanism described by the equation above.
a = hydrolysis reaction
b = dehydration synthesis (condensation synthesis)

____.) What is the building block or subunit for carbohydrate formation?

____.) What functional groups are found in carbohydrates? Why are these functional groups important to the function of carbohydrates?
There are many hydroxyl groups in a carbohydrate, which allows it to be readily soluble in an aqueous solution.

____.)What is the general formula for a monosaccharide?

____.) Circle all of the following compounds that are carbohydrates.

____.) How could you make C60H102O51 ?
Link together 10 glucose molecules through dehydration synthesis. Notice that you will lose one water molecule each time you link another glucose molecule to the polymer.

____.) What is a structural isomer? What is geometric isomer?
Structural Isomer = compounds that have the same molecular formula but differ in their covalent arrangements of their atoms
Geometric Isomer= compounds that have the same molecular formula but differ only in their spatial arrangements

____.) From the following compounds, circle the structural isomers and put a box around the geometrical isomers.

a. When the linear form of glucose closes to form a ring, the hydroxyl group at the point of closure can be trapped in either one of two possible positions (alpha or beta). Label the compounds shown below (A F) as either alpha or beta.

b. In molecules A and B, number the carbon atoms corresponding to the numbered carbons in the linear structure.
c. Name molecule E and F.

____.) Can humans digest cellulose? Starch? Why or why not?
Humans cannot digest cellulose because they do not have the required enzyme to break the 1-4 beta linkages of glucose. Human can digest starch because they do have the enzyme which breaks the 1-4 alpha linkages of glucose.

____.) Can cows digest cellulose? If not, how are they able to obtain nutrients from grasses and grains?
Just like all mammals, cows cannot digest cellulose. However, cows have bacteria in their rumen which have the required enzyme to break down the 1-4 beat linkages of glucose. Thus, cows are able to get nutrient value of intestinal grains and grasses which are loaded with cellulose.

a. Table sugar is also know as what?
b. In regards to the answer to part a, is it a disaccharide or a polysaccharide?
c. How is table sugar made?
Sucrose is made by linking together glucose and fructose.

____.) Circle all of the following that are structural polysaccharides. chitin, cellulose
a. glucose
b. chitin
c. cellulose
d. glycogen
e. maltose
f. amylose

____.) Of the structures below, circle only the lipids and write the name of the family to which it belongs.

____.) Lipids are made of what two basic compounds?
glycerol and fatty acids

____.) What functional group(s) is/are found in lipids? Are these functional groups polar or nonpolar?
Many lipids have methyl groups that are nonpolar and carbonyl groups, which in most biomolecules act in a nonpolar manner. Phospholipids also have phosphate groups that are polar in nature.

____.) What is the difference between saturated and unsaturated fats? Which, saturated or unsaturated fats, are better for you? Why?
These terms are derived from the structure of the fatty acid. If the fatty acid has double bonds, it is said to be unsaturated. If the fatty acid has no double bonds saturated. Saturated fats are the kind that lead to cardiovascular problems such as plaques in the arteries.

a. Draw the two structures formed by phospholipids when they are placed in an aqueous environment.

b. Why do these structures form?
Micelles and phospholipid bilayers form when lipids are placed in an aqueous environment. These structures form because water with its polar properties is trying to exclude the hydrophobic fatty acid tails of the lipid molecules.

____.) Shown below are the structures of 8 of the 20 amino acids. On each of the amino acids:
a. draw a box around the asymmetric carbon.
b. circle the R group.
c. label each as polar or nonpolar.

Below is a sketch that represents an example of a protein embedded into a phospholipid bilayer.

d. The linear sequence of amino acids that make up this protein represents what level of protein structure?
primary structure - the sequence of amino acids linked together via peptide bonds
e. Draw the two most common secondary structures of a protein. What interactions maintain the secondary structure of a protein?
Helices and pleated sheets are the two most common secondary structures of proteins. Hydrogen bonding between the hydrogen and oxygen in the backbone of the protein holds the secondary structure together.
f. The protein above contains the 8 amino acids from parts a c. Predict whether each of these amino acids would be found most likely in the phospholipid bilayer or in the aqueous environment.
The nonpolar amino acids (Gly, Phe, Met) will be more likely to be found in the phospholipid bilayer while polar and charged amino acids (Ser, Cys, Tyr, Asp, Arg) will be more likely confined to the aqueous environment.

____.) Show how the following two amino acids are linked together.

____.) Name the biomolecule that is formed by the following basic molecular units.

____.) Label the 3 major components of the following nucleotide.

____.) How are the components joined to form a nucleic acid?
Nucleotides are joined by covalent bonds called phosphodiester linkages between the phosphate of one nucleotide and the sugar of the next monomer.

____.) Fill in the following chart.

____.) Match the molecule with its class of macromolecules.
A. Carbohydrate
B. Lipid
C. Protein
D. Nucleic Acid

1. Glycogen = A
2. Cholesterol = B
3. RNA = D
4. Collagen = C
5. Hemoglobin = C
6. A gene = D
7. Triacylglycerol = B
8. Pepsin = C
9. Cellulose = A
10. Chitin = A

____.) For the following molecules, list all the different types of functional groups that are present as well as how many of each type there are.

2002-2003 Kevin Hong