Biochemistry & Enzymology Practice Test
Honors Biology
1. What is the difference between organic molecules and inorganic molecules?
Organic molecules often contain carbon and hydrogen simultaneously. They are associated with life,
often found in living things or made by living things. Inorganic molecules are all other molecules.
2. Draw the following functional groups:
Alcohol
Carboxyl
Amino
Phosphate
3. Lithium chloride dissociates when placed in water, becoming free lithium ions and free chloride ions.
When sugar is placed in water, the individual sugar molecules move apart, but the molecule itself stays
together. What type of bonds must be present in lithium chloride? What functional group is found on
sugars that make them dissolve in water?
Many ionic attractions disassociate (break apart) in water, like lithium chloride. Covalent molecules do
not break apart, as in the sugar. However, if there are enough hydrophilic functional groups—like the
alcohol groups found in all carbohydrates—than the molecule can dissolve in water.
4. Identify the following organic molecules from their description:
a. A long chain of carbons and hydrogens, this hydrophobic molecule turns blue litmus red. This is a
fatty acid.
b. Long, long, long, double helixes that have lots of phosphate groups. This is DNA, a nucleic acid.
c. Polymer of this type of molecule makes up the exoskeletons of bugs. This is the carbohydrate
chitin, a polymer of the monomer glucose.
d. Enzymes belong to this class of biomolecules. Enzymes are a subset of proteins, polymers of
amino acids.
e. The storage molecule of glucose in animals. Glucose is stored in polymers of glycogen.
5. Of course, you should be able to complete a table like this:
Monomer
Polymer(s)
General
Structure
Uses in the cell or
organism
Fatty Acid
1. Cholesterol
2. steroids (from
cholesterol)
3. phospholipids
4. triglycerides
chains of carbon and
hydrogen
1. Membranes (animals)
2. Hormones
3. Membranes
4. Energy storage (animals)
Nucleic Acids
Nucleotide
1. RNA
2. DNA
1. single strand
2. double helix
Proteins
Amino acids
Protein or Polypeptide
Many shapes
Carbohydrates
Monosaccharide
simple sugars
1. starch
2. glycogen
3. cellulose
4. chitin
hexagonal or
pentagonal shape
Biomolecule
Lipids
or
1. Temporary Information
storage; ribozymes
2. Permanent information
storage
Cell structural components
Enzymes
Messengers
1. Energy storage (plants)
2. Energy storage (animals)
3. Structural- cell wall of
plants
4. Structural- cell wall of
fungi, exoskeleton of
arthopoda
5. Below are three hypothetical molecules. Show what they would look like if they underwent dehydration
synthesis
HO
OH
HO
OH
O
HO
H
HO
OH
O
H
O
H
OH
H
O
How many water molecules would be required to hydrolyse the new molecule back into monomers?
Two water molecules would be required for hydrolysis to occur.
6.
Describe the basic structure of a protein.
Proteins are usually long chains of hundreds or thousands of amino acids. There are 20 different amino
acids used by humans, each with a common backbone (a central carbon bound to a hydrogen, amino
group, and carboxyl group) and a variable (or R) group. Each different R group has a different chemical
profile (unique in shape or chemistry). Therefore, each unique combination of amino acids encodes for a
different protein with its own unique role and abilities.
7. Describe the four levels of protein structure.
Primary (1°) structure is the unique order of the amino acids in the protein chain. It is determined by the
genes in the organism’s DNA. Secondary (2°) structures are regions of the protein that fold into
characteristic shapes, like α-helices (coils) and β-pleated sheets (zigzag folds). Tertiary (3°) structure is
the overall 3-D shape of the protein. Quaternary (4°) structure is not found in all proteins. It is the
overall structure of the complex formed when multiple proteins must work together to accomplish their
task.
8.
Analyze the protein structures below. Identify the two types of secondary structure seen.
9.
In some South American countries, fish fillets are dipped in acid instead of being cooked on a stove.
The end result is pretty much the same. Explain why.
Both changing the heat (exposure to flames on the stove) and changing the pH (exposure to acid)
denature the protein in the fish muscle. The end result is the same…”cooked” fish.
11. Draw a representative reaction curve for an exothermic chemical
reaction (one where the reactants have more energy than the
products.
a. Label the activation energy
b. Redraw the curve showing the effect of an enzyme on the
chemical reaction.
Energy →
10. What do enzymes, ribozymes, and catalysts have in common?
Catalysts lower the activation energy of a chemical reaction, speeding up the bulk reaction while not
being consumed. Enzymes and ribozymes are both types of catalysts, differing only in what they are
made of: proteins for enzymes and ribonucleic acid (RNA) for ribozymes.
Time →
12. Why is it important you get your vitamins?
Vitamins serve as coenzymes, molecules that are required for certain enzymes to catalyze their reactions.
Without their coenzymes, these enzymes cannot function.
13. Describe competitive and noncompetitive inhibition.
You must be able to shut off enzymes that you no longer need.
If you do not, they will continue making their products whether
you need them or not, wasting energy and raw materials.
Competitive inhibition uses a regulator molecule that binds into
the active site of the enzyme, blocking it up. (It is called
competitive inhibition because the regulator molecule
competes with the substrate for entry into the active site.
Noncompetitive inhibition uses a regulator molecule that binds
to a second site in the molecule, and then shuts down the
enzyme by distorting the active site.