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Biomolecules Homework KEY
Honors Biology
1. What properties of carbon make it such an important element in living things?
Carbon can form four covalent bonds; since it can then bond to four different atoms or functional groups,
you get very diverse molecules. Carbon can also form long, stable chains resulting in very large polymers.
These large molecules make up components of cells.
2. Complete the following table:
Description or
Drawing of General
Biomolecule
Structure
A hexagon or pentagon with
Carbomany alcohol groups
hydrates
Monomer
Polymers
A monosaccharide
or simple sugar
1. chitin
2. cellulose
3. starch
4. glycogen
Lipids
Long chain of methyl groups
with a carboxyl group (snakelike)
Cholesterol and steroids are
three joined hexagons and
one pentagon—no alcohol
groups!
Fatty acid
Cholesterol ring
1. Triglyceride
2. Phospholipid
3. Cholesterol
Nucleic Acids
Composed of a 5-carbon
sugar, a nitrogenous base (A,
U, C, G ,T) and a phosphate
group
Nucleotide
1. DNA
2. RNA
Proteins
Amino Acid
Protein
Uses in the Cell for each
polymer
1. Cell wall of fungi and
exoskeleton of arthropods
2. Cell wall of plants
3. Glucose storage in plants
4. Glucose storage in animals
1. Energy storage & insulation in
animals
2. Part of the cell membrane in all
cells
3. A component in animal cell
membranes, and used to build
steroid hormones
1. Long-term, stable information
storage
2. Short-term information
storage, as ribozymes (RNA
catalysts)
There are MANY:
Structural building blocks of the
cell
Enzymes (protein catalysts)
Communication molecules
3. What is a polymer?
A polymer is a long chain of repeating units. The individual units are called monomers.
4. Dehydration synthesis creates polymers. Describe it.
An enzyme or ribozyme aligns two monomers very close together, so that two –OH groups (one on each
monomer) are next to one another. The enzyme (or ribozyme) breaks the covalent bond between an –OH
group and one monomer (freeing the –OH), and between the oxygen and the hydrogen in the other
monomer (freeing an –H). The broken bonds of the two monomers fuse, joining the two pieces into one
bigger molecule. The –OH and the –H that were removed fuse to form water.
5. What is hydrolysis?
The opposite of dehydration synthesis, hydrolysis breaks down large polymers into smaller, individual
monomers. In this instance, water attacks and breaks the bond that formed when the polymer fused,
restoring the –OH group on each molecule.
6. Lipids and some proteins are hydrophobic. What does this mean?
Hydrophobic molecules cannot dissolve in water. They will either form a layer at the top or bottom of the
water column, or clump together to form blobs that will not disperse. An example is oil and water.
Sugar is hydrophilic. What does this mean?
Hydrophilic molecules can easily dissolve and disperse in water.
7. What is the difference between an unsaturated and saturated fat?
Saturated fats are saturated (hold as much as possible) with hydrogen. They do not have double bonds in
the methyl chain. Unsaturated fats have double bonds in the methyl chain, and thus have fewer
hydrogens than an equal-sized saturated fat.
8. Many of the fats in your body are in the form of triglycerides. Describe a triglyceride.
A triglyceride is a polymer of lipids seen mainly in animals. It is composed of three fatty acid chains bound
to a short carbon backbone. It is used for energy storage (you can break down the fatty acids in the
triglyceride and burn them for energy in your mitochondria) and electrical and thermal insulation.
9. The four polymers of glucose fall into two categories. Describe the two categories of
carbohydrate monomers, and the two polymers in each of the categories.
Glucose is the most commonly seen monosaccharide in biology. It is a hexose, a six carbon hexagonal
sugar. There are two structural polymers, used to build parts of cells or organism: chitin, found in the cell
wall of fungi (like mushrooms) and the exoskeletons of the arthropoda (like lobsters and insects); and
storage, used to hold stockpiles of glucose usually to burn for energy in your mitochondria. These are
starch, found in plants, and glycogen, found in animals.
10. What are the differences in use between DNA and RNA?
DNA is a stable, long-term means to store information in the cell. The stored information is actually
instructions to build proteins, and the means to regulate when and where these instructions are actually
accessed in an organism. DNA is also used in reproduction: it is passed on to the offspring cell or creature.
RNA is unstable, and thus breaks down very quickly. Often, sections of DNA are copied into RNA before
proteins can be built. RNA can serve as a special type of catalyst called a ribozyme: a piece of cellular
machinery that can carry out chemical reactions.
11. Complete the following table:
Biomolecule
Carbohydrates
Lipids
Nucleic Acids
Proteins
Functional Groups Present in the Molecule
Mainly alcohol groups, making them hydrophilic
A carboxyl group (making them acidic) and MANY methyl groups (making
them hydrophobic)
The phosphate group (unique to them at this level of biology, making them
easy to identify); alcohols in the sugar, and various groups in the nitrogenous
base
An amino group, a carboxyl group, and whatever is in the R group