3 • Key Terms 93
Key Terms
alpha-helix structure (α-helix) type of secondary information from DNA to ribosomes during protein
protein structure formed by folding the polypeptide synthesis
into a helix shape with hydrogen bonds stabilizing monomer smallest unit of larger molecules that are
the structure polymers
amino acid a protein's monomer; has a central monosaccharide single unit or monomer of
carbon or alpha carbon to which an amino group, a carbohydrates
carboxyl group, a hydrogen, and an R group or side nucleic acid biological macromolecule that carries
chain is attached; the R group is different for all 20 the cell's genetic blueprint and carries instructions
common amino acids for the cell's functioning
beta-pleated sheet (β-pleated) secondary structure nucleotide monomer of nucleic acids; contains a
in proteins in which hydrogen bonding forms pentose sugar, one or more phosphate groups, and
“pleats” between atoms on the polypeptide chain's a nitrogenous base
backbone omega fat type of polyunsaturated fat that the body
biological macromolecule large molecule necessary requires; numbering the carbon omega starts from
for life that is built from smaller organic molecules the methyl end or the end that is farthest from the
carbohydrate biological macromolecule in which the carboxylic end
ratio of carbon to hydrogen and to oxygen is 1:2:1; peptide bond bond formed between two amino acids
carbohydrates serve as energy sources and by a dehydration reaction
structural support in cells and form arthropods' phosphodiester linkage covalent chemical bond that
cellular exoskeleton holds together the polynucleotide chains with a
cellulose polysaccharide that comprises the plants' phosphate group linking neighboring nucleotides'
cell wall; provides structural support to the cell two pentose sugars
chaperone (also, chaperonin) protein that helps phospholipid membranes' major constituent;
nascent protein in the folding process comprised of two fatty acids and a phosphate-
chitin type of carbohydrate that forms the outer containing group attached to a glycerol backbone
skeleton of all arthropods that include crustaceans polymer chain of monomer residues that covalent
and insects; it also forms fungi cell walls bonds link; polymerization is the process of polymer
dehydration synthesis (also, condensation) reaction formation from monomers by condensation
that links monomer molecules, releasing a water polynucleotide long chain of nucleotides
molecule for each bond formed polypeptide long chain of amino acids that peptide
denaturation loss of shape in a protein as a result of bonds link
changes in temperature, pH, or chemical exposure polysaccharide long chain of monosaccharides; may
deoxyribonucleic acid (DNA) double-helical be branched or unbranched
molecule that carries the cell's hereditary primary structure linear sequence of amino acids in
information a protein
disaccharide two sugar monomers that a glycosidic protein biological macromolecule comprised of one
bond links or more amino acid chains
enzyme catalyst in a biochemical reaction that is purine type of nitrogenous base in DNA and RNA;
usually a complex or conjugated protein adenine and guanine are purines
glycogen storage carbohydrate in animals pyrimidine type of nitrogenous base in DNA and RNA;
glycosidic bond bond formed by a dehydration cytosine, thymine, and uracil are pyrimidines
reaction between two monosaccharides with quaternary structure association of discrete
eliminating a water molecule polypeptide subunits in a protein
hormone chemical signaling molecule, usually ribonucleic acid (RNA) single-stranded, often
protein or steroid, secreted by endocrine cells that internally base paired, molecule that is involved in
act to control or regulate specific physiological protein synthesis
processes ribosomal RNA (rRNA) RNA that ensures the proper
hydrolysis reaction that causes breakdown of larger alignment of the mRNA and the ribosomes during
molecules into smaller molecules by utilizing water protein synthesis and catalyzes forming the peptide
lipid macromolecule that is nonpolar and insoluble in linkage
water saturated fatty acid long-chain hydrocarbon with
messenger RNA (mRNA) RNA that carries single covalent bonds in the carbon chain; the
, 94 3 • Chapter Summary
number of hydrogen atoms attached to the carbon transcription process through which messenger RNA
skeleton is maximized forms on a template of DNA
secondary structure regular structure that proteins transfer RNA (tRNA) RNA that carries activated
form by intramolecular hydrogen bonding between amino acids to the site of protein synthesis on the
the oxygen atom of one amino acid residue and the ribosome
hydrogen attached to the nitrogen atom of another translation process through which RNA directs the
amino acid residue protein's formation
starch storage carbohydrate in plants triacylglycerol (also, triglyceride) fat molecule;
steroid type of lipid comprised of four fused consists of three fatty acids linked to a glycerol
hydrocarbon rings forming a planar structure molecule
tertiary structure a protein's three-dimensional unsaturated fatty acid long-chain hydrocarbon that
conformation, including interactions between has one or more double bonds in the hydrocarbon
secondary structural elements; formed from chain
interactions between amino acid side chains wax lipid comprised of a long-chain fatty acid that is
trans fat fat formed artificially by hydrogenating oils, esterified to a long-chain alcohol; serves as a
leading to a different arrangement of double bond(s) protective coating on some feathers, aquatic
than those in naturally occurring lipids mammal fur, and leaves
Chapter Summary
3.1 Synthesis of Biological Macromolecules molecule. Monosaccharides are linked by glycosidic
bonds that form as a result of dehydration reactions,
Proteins, carbohydrates, nucleic acids, and lipids are
forming disaccharides and polysaccharides with
the four major classes of biological
eliminating a water molecule for each bond formed.
macromolecules—large molecules necessary for life
Glucose, galactose, and fructose are common
that are built from smaller organic molecules.
monosaccharides; whereas, common disaccharides
Macromolecules are comprised of single units
include lactose, maltose, and sucrose. Starch and
scientists call monomers that are joined by covalent
glycogen, examples of polysaccharides, are the storage
bonds to form larger polymers. The polymer is more
forms of glucose in plants and animals, respectively.
than the sum of its parts: it acquires new
The long polysaccharide chains may be branched or
characteristics, and leads to an osmotic pressure that
unbranched. Cellulose is an example of an unbranched
is much lower than that formed by its ingredients. This
polysaccharide; whereas, amylopectin, a constituent of
is an important advantage in maintaining cellular
starch, is a highly branched molecule. Glucose storage,
osmotic conditions. A monomer joins with another
in the form of polymers like starch of glycogen, makes
monomer with water molecule release, leading to a
it slightly less accessible for metabolism; however, this
covalent bond forming. Scientists call these
prevents it from leaking out of the cell or creating a
dehydration or condensation reactions. When polymers
high osmotic pressure that could cause the cell to
break down into smaller units (monomers), they use a
uptake excessive water.
water molecule for each bond broken by these
reactions. Such reactions are hydrolysis reactions. 3.3 Lipids
Dehydration and hydrolysis reactions are similar for all
Lipids are a class of macromolecules that are nonpolar
macromolecules, but each monomer and polymer
and hydrophobic in nature. Major types include fats
reaction is specific to its class. Dehydration reactions
and oils, waxes, phospholipids, and steroids. Fats are a
typically require an investment of energy for new bond
stored form of energy and are also known as
formation, while hydrolysis reactions typically release
triacylglycerols or triglycerides. Fats are comprised of
energy by breaking bonds.
fatty acids and either glycerol or sphingosine. Fatty
3.2 Carbohydrates acids may be unsaturated or saturated, depending on
the presence or absence of double bonds in the
Carbohydrates are a group of macromolecules that are
hydrocarbon chain. If only single bonds are present,
a vital energy source for the cell and provide structural
they are saturated fatty acids. Unsaturated fatty acids
support to plant cells, fungi, and all of the arthropods
may have one or more double bonds in the
that include lobsters, crabs, shrimp, insects, and
hydrocarbon chain. Phospholipids comprise the
spiders. Scientists classify carbohydrates as
membrane's matrix. They have a glycerol or
monosaccharides, disaccharides, and polysaccharides
sphingosine backbone to which two fatty acid chains
depending on the number of monomers in the
Access for free at openstax.org
Key Terms
alpha-helix structure (α-helix) type of secondary information from DNA to ribosomes during protein
protein structure formed by folding the polypeptide synthesis
into a helix shape with hydrogen bonds stabilizing monomer smallest unit of larger molecules that are
the structure polymers
amino acid a protein's monomer; has a central monosaccharide single unit or monomer of
carbon or alpha carbon to which an amino group, a carbohydrates
carboxyl group, a hydrogen, and an R group or side nucleic acid biological macromolecule that carries
chain is attached; the R group is different for all 20 the cell's genetic blueprint and carries instructions
common amino acids for the cell's functioning
beta-pleated sheet (β-pleated) secondary structure nucleotide monomer of nucleic acids; contains a
in proteins in which hydrogen bonding forms pentose sugar, one or more phosphate groups, and
“pleats” between atoms on the polypeptide chain's a nitrogenous base
backbone omega fat type of polyunsaturated fat that the body
biological macromolecule large molecule necessary requires; numbering the carbon omega starts from
for life that is built from smaller organic molecules the methyl end or the end that is farthest from the
carbohydrate biological macromolecule in which the carboxylic end
ratio of carbon to hydrogen and to oxygen is 1:2:1; peptide bond bond formed between two amino acids
carbohydrates serve as energy sources and by a dehydration reaction
structural support in cells and form arthropods' phosphodiester linkage covalent chemical bond that
cellular exoskeleton holds together the polynucleotide chains with a
cellulose polysaccharide that comprises the plants' phosphate group linking neighboring nucleotides'
cell wall; provides structural support to the cell two pentose sugars
chaperone (also, chaperonin) protein that helps phospholipid membranes' major constituent;
nascent protein in the folding process comprised of two fatty acids and a phosphate-
chitin type of carbohydrate that forms the outer containing group attached to a glycerol backbone
skeleton of all arthropods that include crustaceans polymer chain of monomer residues that covalent
and insects; it also forms fungi cell walls bonds link; polymerization is the process of polymer
dehydration synthesis (also, condensation) reaction formation from monomers by condensation
that links monomer molecules, releasing a water polynucleotide long chain of nucleotides
molecule for each bond formed polypeptide long chain of amino acids that peptide
denaturation loss of shape in a protein as a result of bonds link
changes in temperature, pH, or chemical exposure polysaccharide long chain of monosaccharides; may
deoxyribonucleic acid (DNA) double-helical be branched or unbranched
molecule that carries the cell's hereditary primary structure linear sequence of amino acids in
information a protein
disaccharide two sugar monomers that a glycosidic protein biological macromolecule comprised of one
bond links or more amino acid chains
enzyme catalyst in a biochemical reaction that is purine type of nitrogenous base in DNA and RNA;
usually a complex or conjugated protein adenine and guanine are purines
glycogen storage carbohydrate in animals pyrimidine type of nitrogenous base in DNA and RNA;
glycosidic bond bond formed by a dehydration cytosine, thymine, and uracil are pyrimidines
reaction between two monosaccharides with quaternary structure association of discrete
eliminating a water molecule polypeptide subunits in a protein
hormone chemical signaling molecule, usually ribonucleic acid (RNA) single-stranded, often
protein or steroid, secreted by endocrine cells that internally base paired, molecule that is involved in
act to control or regulate specific physiological protein synthesis
processes ribosomal RNA (rRNA) RNA that ensures the proper
hydrolysis reaction that causes breakdown of larger alignment of the mRNA and the ribosomes during
molecules into smaller molecules by utilizing water protein synthesis and catalyzes forming the peptide
lipid macromolecule that is nonpolar and insoluble in linkage
water saturated fatty acid long-chain hydrocarbon with
messenger RNA (mRNA) RNA that carries single covalent bonds in the carbon chain; the
, 94 3 • Chapter Summary
number of hydrogen atoms attached to the carbon transcription process through which messenger RNA
skeleton is maximized forms on a template of DNA
secondary structure regular structure that proteins transfer RNA (tRNA) RNA that carries activated
form by intramolecular hydrogen bonding between amino acids to the site of protein synthesis on the
the oxygen atom of one amino acid residue and the ribosome
hydrogen attached to the nitrogen atom of another translation process through which RNA directs the
amino acid residue protein's formation
starch storage carbohydrate in plants triacylglycerol (also, triglyceride) fat molecule;
steroid type of lipid comprised of four fused consists of three fatty acids linked to a glycerol
hydrocarbon rings forming a planar structure molecule
tertiary structure a protein's three-dimensional unsaturated fatty acid long-chain hydrocarbon that
conformation, including interactions between has one or more double bonds in the hydrocarbon
secondary structural elements; formed from chain
interactions between amino acid side chains wax lipid comprised of a long-chain fatty acid that is
trans fat fat formed artificially by hydrogenating oils, esterified to a long-chain alcohol; serves as a
leading to a different arrangement of double bond(s) protective coating on some feathers, aquatic
than those in naturally occurring lipids mammal fur, and leaves
Chapter Summary
3.1 Synthesis of Biological Macromolecules molecule. Monosaccharides are linked by glycosidic
bonds that form as a result of dehydration reactions,
Proteins, carbohydrates, nucleic acids, and lipids are
forming disaccharides and polysaccharides with
the four major classes of biological
eliminating a water molecule for each bond formed.
macromolecules—large molecules necessary for life
Glucose, galactose, and fructose are common
that are built from smaller organic molecules.
monosaccharides; whereas, common disaccharides
Macromolecules are comprised of single units
include lactose, maltose, and sucrose. Starch and
scientists call monomers that are joined by covalent
glycogen, examples of polysaccharides, are the storage
bonds to form larger polymers. The polymer is more
forms of glucose in plants and animals, respectively.
than the sum of its parts: it acquires new
The long polysaccharide chains may be branched or
characteristics, and leads to an osmotic pressure that
unbranched. Cellulose is an example of an unbranched
is much lower than that formed by its ingredients. This
polysaccharide; whereas, amylopectin, a constituent of
is an important advantage in maintaining cellular
starch, is a highly branched molecule. Glucose storage,
osmotic conditions. A monomer joins with another
in the form of polymers like starch of glycogen, makes
monomer with water molecule release, leading to a
it slightly less accessible for metabolism; however, this
covalent bond forming. Scientists call these
prevents it from leaking out of the cell or creating a
dehydration or condensation reactions. When polymers
high osmotic pressure that could cause the cell to
break down into smaller units (monomers), they use a
uptake excessive water.
water molecule for each bond broken by these
reactions. Such reactions are hydrolysis reactions. 3.3 Lipids
Dehydration and hydrolysis reactions are similar for all
Lipids are a class of macromolecules that are nonpolar
macromolecules, but each monomer and polymer
and hydrophobic in nature. Major types include fats
reaction is specific to its class. Dehydration reactions
and oils, waxes, phospholipids, and steroids. Fats are a
typically require an investment of energy for new bond
stored form of energy and are also known as
formation, while hydrolysis reactions typically release
triacylglycerols or triglycerides. Fats are comprised of
energy by breaking bonds.
fatty acids and either glycerol or sphingosine. Fatty
3.2 Carbohydrates acids may be unsaturated or saturated, depending on
the presence or absence of double bonds in the
Carbohydrates are a group of macromolecules that are
hydrocarbon chain. If only single bonds are present,
a vital energy source for the cell and provide structural
they are saturated fatty acids. Unsaturated fatty acids
support to plant cells, fungi, and all of the arthropods
may have one or more double bonds in the
that include lobsters, crabs, shrimp, insects, and
hydrocarbon chain. Phospholipids comprise the
spiders. Scientists classify carbohydrates as
membrane's matrix. They have a glycerol or
monosaccharides, disaccharides, and polysaccharides
sphingosine backbone to which two fatty acid chains
depending on the number of monomers in the
Access for free at openstax.org
