Molecular & Cellular Biology
BENCHMARK REVIEW
BENCHMARK SC.912.L.18.1
Describe the basic molecular structures and primary functions of the four major categories of biological macromolecules. (Also
assesses SC.912.L.18.11.) AA
Four principal classes of organic compounds are found in living things: carbohydrates, lipids, proteins, and nucleic acids.
Carbohydrates are organic compounds made of carbon, hydrogen, and oxygen atoms in the proportion of 1:2:1.
Carbohydrates are a key source of energy, and they are found in most foods. The building blocks of carbohydrates are
single sugars, called monosaccharides, such as glucose, C6H12O6, and fructose. Disaccharides are double sugars formed
when two monosaccharides are joined. For example, sucrose, or common table sugar, consists of both glucose and
fructose. Polysaccharides such as starch are chains of three or more monosaccharides. Starch and cellulose, which are
found in plants, and glycogen, which is made by animals, are examples of polysaccharides.
Lipids are nonpolar molecules that are not soluble or mostly insoluble in water. They include fats, phospholipids,
steroids, and waxes. Phospholipids make up the lipid bilayer of cell membranes. Steroids include cholesterol, which is
found in animal cell membranes.
Other lipids include some light-absorbing compounds, such as the plant pigment chlorophyll.
Fats are lipids that store energy.
Proteins are usually large molecules formed by linked smaller molecules called amino acids.
Amino acids are the building blocks of proteins. Twenty different amino acids are found in proteins. Some amino acids
are polar, and others are nonpolar. Some amino acids are electrically charged, and others are not charged. Proteins fold
into compact shapes, determined in part by how the protein’s amino acids interact with water and one another.
Some proteins are enzymes and promote chemical reactions. Other proteins have important structural functions. Other
proteins called antibodies help your body defend against infection. Specialized proteins in muscles enable your muscles
to contract. In your blood, a protein called hemoglobin carries oxygen from your lungs to body tissues.
Nucleic acids are long chains of smaller molecules called nucleotides. A nucleotide has three parts: a sugar, a base, and a
phosphate group, which contains phosphorus and oxygen atoms. There are two types of nucleic acids—DNA and RNA—
and each type contains four kinds of nucleotides. DNA, or deoxyribonucleic acid, consists of two strands of nucleotides
that spiral around each other. Chromosomes contain long strands of DNA, which stores hereditary information. RNA, or
ribonucleic acid, may consist of a single strand of nucleotides or of based-paired nucleotides. RNA plays many key roles
in the manufacture of proteins.
Benchmark Practice
1. A carbohydrate is an organic compound that is
composed of carbon, hydrogen, and oxygen. The
unique structure of carbohydrates makes them
useful material for building cell walls in plants.
Which of the following is a function of
carbohydrates in animals?
A.
B.
C.
D.
digesting food
fighting disease
storing short-term energy
transmitting nerve impulses
2. A scientist analyzing an unknown substance has
determined that it consists of carbon, hydrogen and
oxygen. During experimentation, she determines
that the substance is soluble in oil but not in water.
Which of the following macromolecules is the
unknown substance most likely to be?
A.
B.
C.
D.
Carbohydrate
Lipid
Nucleic Acid
Protein
3. Animals breathe in oxygen (O2). This O2 is used in
their bodies in the breakdown of the glucose and
fatty acids. The main function of the breakdown of
glucose and fatty acids is to provide energy for
chemical reactions by producing which of the
following?
A.
B.
C.
D.
enzymes
deoxyribonucleic acid
adenosine triphosphate
proteins
4. Enzymes are a special type of protein that speeds
up biological reactions. How do they accomplish
this task?
A. They are able to operate at any pH value.
B. They lower the activation energy of
reactions.
C. They form peptide bonds between amino
acids.
D. They decrease the number of collisions in
the reacting substances.
5. Hormones are proteins that regulate many
functions in the body, such as growth and cell
differentiation. Which of the following does NOT
describe a function of proteins in living organisms?
A. They catalyze biochemical reactions.
B. They provide support for connective
tissues.
C. They serve as a short-term energy source
for the body.
D. They carry molecules from one place to
another in the body.
Test Practice SC.912.L.18.1
1. Two of the four principle classes of organic
compounds are proteins and nucleic acids. What is
the relationship between proteins and nucleic
acids?
A.
B.
C.
D.
Nucleic acids use proteins for energy.
Nucleic acids are a subset of proteins.
Proteins are long polymers of nucleic acids.
Nucleic acids contain the information to make
proteins.
2. Proteins are used to enable movement, provide
structure and support, and carry out important
chemical reactions inside the body. What is needed
in order for the human body to synthesize proteins?
A.
B.
C.
D.
a diet rich in amino acids
sufficient sunlight and water
1,200 calories of nutrients per day
minerals and fats in sufficient amounts
3. 3 The diagram below illustrates the structure of
glucose.
Which of the following describes how the body uses
molecules like the one illustrated above?
A. Sugars form carbohydrates, which are linked
together to form fats that store energy.
B. Carbohydrates are broken down into glucose,
which is stored inside the body’s cells.
C. Sugars are broken down into proteins that
become the building blocks of the body’s
tissues.
D. Carbohydrates, such as glucose, are broken
down to release chemical energy that is used by
the body’s cells.
4. Phospholipids are linear molecules with one polar
end and one nonpolar end. How does this structure
relate to their function in cell membranes?
A. The polar tails of phospholipids form the
outside of the cell membrane.
B. The nonpolar heads of phospholipids form the
outside of the cell membrane.
C. The polar heads of phospholipids combine to
form the middle of the cell membrane, with the
tails on the outside.
D. The nonpolar tails of phospholipids combine to
form the middle of the cell membrane, with the
heads on the outside.
5. The most important macromolecules in organisms
are made up of smaller units. Which is the correct
pairing of a macromolecule and its smaller
monomer?
A.
B.
C.
D.
Nucleic acid – fatty acid
Protein - amino acid
Carbohydrate - nucleotide
Lipid – monosaccharide