CLOZE-Life and Chemistry:
Large Molecules
Life and Chemistry: Large Molecules
Theories of the Origin of Life
Macromolecules: Giant ___________
Condensation and ________ Reactions
Proteins: Polymers of Amino Acids
Carbohydrates: Sugars and Sugar Polymers
Lipids: Water-________ Molecules
Nucleic Acids: Informational Macromolecules That Can Be Catalytic
All Life from Life
Theories of the Origin of Life
Living things are composed of the same ________ as the inanimate universe.
The ________ of these elements in biological systems is unique.
There are two theories for the origin of life during the 600 million years of
the Hadean:
§ Life from extraterrestrial sources
§ Chemical evolution
Theories of the Origin of Life
Could life have come from outside Earth?
The composition of ________ suggests that some of life's complex molecules
could have come from space.
There is no proof, however, that living things have ever traveled to Earth by
way of a comet or meteorite.
Theories of the Origin of Life
The theory of chemical evolution holds that conditions on the primitive Earth
led to the formation of the large molecules unique to life.
In the 1950s, Stanley Miller and Harold Urey set up an experimental
"primitive" atmosphere and used a ________ to simulate lightning.
Within days, the system contained numerous ________ molecules.
Theories of the Origin of Life
The results of the Miller-Urey experiments have undergone several
interpretative refinements.
The earliest stages of chemical evolution resulted in the emergence of
monomers and ________ that probably have remained generally unchanged for 3.8
billion years.
Macromolecules: Giant Polymers
There are four major types of biological macromolecules:
§ Proteins
§ Carbohydrates
§ Lipids
§ Nucleic acids
Macromolecules: Giant Polymers
These macromolecules are made the same way in all living things, and are
present in all organisms in roughly the same proportions.
An advantage of this biochemical unity is that organisms acquire needed
biochemicals by ________ other organisms.
Macromolecules: Giant Polymers
Macromolecules are giant polymers.
Polymers are formed by ________ linkages of smaller units called monomers.
Molecules with molecular weights greater than 1,000 daltons (atomic mass
units) are usually classified as macromolecules.
Macromolecules: Giant Polymers
The functions of ________ are related to their shape and the chemical
properties of their monomers.
Some of the roles of macromolecules include:
§ Energy storage
§ Structural support
§ Transport
§ Protection and defense
§ Regulation of metabolic activities
§ Means for movement, growth, and development
§ Heredity
Condensation and ________ Reactions
Macromolecules are made from smaller monomers by means of a ________ or
dehydration reaction in which an OH from one monomer is linked to an H from
another monomer.
Energy must be added to make or break a polymer.
The reverse reaction, in which polymers are broken back into monomers, is a
called a ________ reaction.
Proteins: Polymers of ________ Acids
Proteins are polymers of amino acids. They are molecules with diverse
structures and functions.
Each different type of protein has a characteristic amino acid composition and
order.
Proteins range in size from a few amino acids to thousands of them.
________ is crucial to the function of a protein and is influenced largely by
the sequence of amino acids.
Proteins: Polymers of Amino Acids
An amino acid has four groups attached to a ________ carbon atom:
§ A hydrogen atom
§ An amino group (NH3+)
§ The acid is a carboxyl group (COO).
§ Differences in amino acids come from the ________ chains, or the R groups.
Proteins: Polymers of Amino Acids
Amino acids can be classified based on the characteristics of their R groups.
§ Five have charged ________ side chains.
§ Five have polar but ________ side chains.
§ Seven have nonpolar ________ side chains.
§ Cysteine has a terminal disulfide (SS).
§ Glycine has a hydrogen atom as the R group.
§ Proline has a modified amino group that forms a covalent bond with the R
group, forming a ring.
Proteins: Polymers of Amino Acids
Proteins are synthesized by condensation reactions between the ________ group
of one amino acid and the ________ group of another. This forms a peptide
linkage.
Proteins are also called polypeptides. A dipeptide is two amino acids long; a
tripeptide, three. A polypeptide is multiple amino acids long.
Proteins: Polymers of Amino Acids
There are four levels of protein structure: primary, secondary, tertiary, and
quaternary.
The precise sequence of amino acids is called its primary structure.
The peptide backbone consists of ________ units of atoms: NCCNCC.
Enormous numbers of different proteins are possible.
Proteins: Polymers of Amino Acids
A protein's secondary structure consists of regular, ________ patterns in
different regions in the polypeptide chain.
This shape is influenced primarily by ________ bonds arising from the amino
acid sequence (the primary structure).
The two common secondary structures are the ____ helix and the _____ pleated
sheet.
Proteins: Polymers of Amino Acids
The a helix is a right-handed coil.
The peptide backbone takes on a helical shape due to hydrogen bonds.
The R groups point away from the peptide backbone.
Fibrous structural proteins have a-helical secondary structures, such as the
keratins found in hair, feathers, and hooves.
Proteins: Polymers of Amino Acids
b pleated sheets form from peptide regions that lie parallel to each other.
Sometimes the parallel regions are in the same peptide, sometimes the parallel
regions are from different peptide strands.
This sheetlike structure is stabilized by hydrogen bonds between N-H groups on
one chain with the C=O group on the other.
Spider silk is made of b pleated sheets from separate peptides.
Proteins: Polymers of Amino Acids
Tertiary structure is the three-dimensional shape of the completed
polypeptide.
The primary determinant of the tertiary structure is the interaction between R
groups.
Other factors can include the location of ________ bridges, which form between
cysteine residues.
Proteins: Polymers of Amino Acids
Other factors determining tertiary structure:
§ The nature and location of secondary structures
§ Hydrophobic side-chain aggregation and van der Waals forces, which help
stabilize them
§ The ionic interactions between the positive and negative charges deep in the
protein, away from water
Proteins: Polymers of Amino Acids
It is now possible to determine the complete description of a protein's
tertiary structure.
The location of every atom in the molecule is specified in three-dimensional
space.
Proteins: Polymers of Amino Acids
Quaternary structure results from the ways in which multiple polypeptide
subunits bind together and interact.
This level of structure adds to the three-dimensional shape of the finished
protein.
Hemoglobin is an example of such a protein; it has four subunits.
Proteins: Polymers of Amino Acids
Shape is crucial to the functioning of some proteins:
§ Enzymes need certain surface shapes in order to bind substrates correctly.
§ Carrier proteins in the cell surface ________ allow substances to enter the
cell.
§ Chemical signals such as hormones bind to proteins on the cell surface
membrane.
The combination of attractions, repulsions, and interactions determines the
right fit.
Proteins: Polymers of Amino Acids
Changes in temperature, pH, salt concentrations, and oxidation or reduction
conditions can change the shape of proteins.
This loss of a protein's normal three-dimensional structure is called ________
Proteins: Polymers of Amino Acids
Chaperonins are specialized proteins that help keep other proteins from
interacting inappropriately with one another.
When a protein fails to fold correctly, serious complications can occur.
Some chaperonins help folding; some prevent folding until the appropriate
time.
Carbohydrates: Sugars and Sugar Polymers
Carbohydrates are carbon molecules with hydrogen and hydroxyl groups.
They act as energy storage and transport molecules.
They also serve as structural components.
Carbohydrates: Sugars and Sugar Polymers
There are four major categories of carbohydrates:
§ Monosaccharides
§ Disaccharides, which consist of two monosaccharides
§ Oligosaccharides, which consist of between 3 and 20 monosaccharides
§ Polysaccharides, which are composed of hundreds to hundreds of thousands of
monosaccharides
Carbohydrates: Sugars and Sugar Polymers
The general formula for a carbohydrate ________ is multiples of CH2O,
maintaining a ratio of 1 carbon to 2 hydrogens to 1 oxygen.
During the polymerization, which is a condensation reaction, water is removed.
Carbohydrate polymers have ratios of carbon, hydrogen, and oxygen that differ
somewhat from the 1:2:1 ratios of the monomers.
Carbohydrates: Sugars and Sugar Polymers
All living cells contain the monosaccharide glucose (C6H12O6).
Glucose exists as a straight chain and a ring, with the ring form predominant.
The two forms of the ring, a-glucose and b-glucose, exist in equilibrium when
dissolved in water.
Carbohydrates: Sugars and Sugar Polymers
Different monosaccharides have different numbers or different arrangements of
carbons.
Most monosaccharides are ________ isomers.
Hexoses (six-carbon sugars) include the structural isomers glucose, fructose,
mannose, and galactose.
Pentoses are five-carbon sugars.
Carbohydrates: Sugars and Sugar Polymers
Monosaccharides are bonded together covalently by condensation reactions. The
bonds are called glycosidic linkages.
Disaccharides have just one such linkage: sucrose, lactose, maltose,
cellobiose.
Maltose and cellobiose are structural isomers.
Carbohydrates: Sugars and Sugar Polymers
Oligosaccharides contain more than two monosaccharides.
Many proteins found on the outer surface of cells have oligosaccharides
attached to the R group of certain amino acids, or to lipids.
The human ________ blood types owe their specificity to oligosaccharide
chains.
Carbohydrates: Sugars and Sugar Polymers
Polysaccharides are giant polymers of monosaccharides connected by glycosidic
linkages.
Cellulose is a giant polymer of glucose joined by b-1,4 linkages.
Starch is a polysaccharide of glucose with a-1,4 linkages.
Carbohydrates: Sugars and Sugar Polymers
Starches vary by amount of branching.
Some plant starch, such as amylose, is unbranched. Others, such as amylopectin,
are moderately branched.
Animal starch, called ________ is a highly branched polysaccharide.
Carbohydrates: Sugars and Sugar Polymers
Carbohydrates are modified by the addition of functional groups:
§ Glucose can acquire a carboxyl group (COOH), forming glucuronic acid.
§ Phosphate added to one or more hydroxyl (OH) sites creates a sugar phosphate
such as fructose 1,6-bisphosphate.
§ Amino groups can be substituted for OH groups, making amino sugars such as
glucosamine and galactosamine.
Lipids: Water-Insoluble Molecules
Lipids are insoluble in water.
This insolubility results from the many ________ covalent bonds of hydrogen
and carbon in lipids.
Lipids aggregate away from water, which is polar, and are attracted to each
other via weak, but additive, van der Waals forces.
Lipids: Water-Insoluble Molecules
Roles for lipids in organisms include:
§ Energy storage (fats and oils)
§ Cell membranes (phospholipids)
§ Capture of light energy (carotinoids)
§ Hormones and vitamins (steroids and modified fatty acids)
§ Thermal insulation
§ Electrical insulation of nerves
§ Water repellency (waxes and oils)
Lipids: Water-Insoluble Molecules
Fats and oils store energy.
Fats and oils are ________ composed of three fatty acid molecules and one
glycerol molecule.
Glycerol is a three-carbon molecule with three hydroxyl (OH) groups, one for
each carbon.
Fatty acids are long chains of hydrocarbons with a carboxyl group (COOH) at
one end.
Lipids: Water-Insoluble Molecules
Saturated fatty acids have only single carbon-to-carbon bonds and are said to
be saturated with hydrogens.
Saturated fatty acids are rigid and ________ and solid at room temperature.
Animal fats are saturated.
Lipids: Water-Insoluble Molecules
Unsaturated fatty acids have at least one double-bonded carbon in one of the
chains the chain is not completely ________ with hydrogen atoms.
The double bonds cause kinks that prevent easy packing. Unsaturated fatty
acids are liquid at room temperature. Plants commonly have unsaturated fatty
acids.
Lipids: Water-Insoluble Molecules
Phospholipids have two hydrophobic fatty acid tails and one hydrophilic
phosphate group attached to the glycerol.
As a result, phospholipids orient themselves so that the phosphate group faces
water and the tail faces away.
In aqueous environments, these lipids form bilayers, with heads facing
outward, tails facing inward. Cell membranes are structured this way.
Lipids: Water-Insoluble Molecules
Carotenoids are light-absorbing pigments found in plants and animals.
One, b-carotene, is a plant pigment used to trap light in photosynthesis.
In animals, this pigment, when broken into two identical pieces, becomes
vitamin A.
Lipids: Water-Insoluble Molecules
Steroids are ________ molecules.
Steroids are organic compounds with a series of fused rings.
The steroid cholesterol is a common part of ________ cell membranes.
Cholesterol is also is an initial substrate for synthesis of the hormones
testosterone and estrogen.
Lipids: ________ Molecules
Some lipids are vitamins: small organic molecules essential to health.
Vitamin A is important for normal development, maintenance of cells, and night
vision.
Vitamin D is important for absorption of calcium in the intestines.
Vitamin E, an antioxidant, protects membranes.
Vitamin K is a component required for normal blood clotting.
Lipids: Water-Insoluble Molecules
Waxes are highly nonpolar molecules consisting of saturated long fatty acids
bonded to long fatty alcohols via an ester linkage.
A fatty ________ is similar to a fatty acid, except for the last carbon, which
has an OH group instead of a COOH group.
Waxy coatings repel water and prevent water loss from structures such as hair,
feathers, and leaves.
Nucleic Acids: Informational Macromolecules
That Can Be Catalytic
Nucleic acids are ________ that are specialized for storage and transmission
of information.
Two types of nucleic acid are DNA (deoxyribonucleic acid) and RNA (ribonucleic
acid).
DNA encodes ________ information and transfers information to RNA molecules.
The information in RNA is decoded to specify the sequence of amino acids in
proteins.
Nucleic Acids: Informational Macromolecules
That Can Be Catalytic
Nucleic acids are polymers of nucleotides.
A nucleotide consists of a pentose sugar, a phosphate group, and a
nitrogen-containing base.
In DNA, the pentose sugar is deoxyribose; in RNA it is ribose.
Nucleic Acids: Informational Macromolecules
That Can Be Catalytic
DNA typically is double-stranded.
The two separate polymer chains are held together by hydrogen bonding between
their nitrogenous bases.
The base pairing is complementary: At each position where a purine is found on
one strand, a pyrimidine is found on the other.
Purines have a double-ring structure. Pyrimidines have one ring.
Nucleic Acids: Informational Macromolecules
That Can Be Catalytic
The linkages that hold the nucleotides in RNA and DNA are called
phosphodiester linkages.
These linkages are formed between carbon 3 of the sugar and a phosphate group
that is associated with carbon 5 of the sugar.
The ________ consists of alternating sugars and phosphates.
In DNA, the two strands are antiparallel.
The DNA strands form a double helix, a molecule with a right-hand twist.
Nucleic Acids: Informational Macromolecules
That Can Be Catalytic
Most RNA molecules consist of only a single polynucleotide chain.
Instead of the base ________ RNA uses the base uracil.
Hydrogen bonding between ribonucleotides in RNA can result in complex
three-dimensional shapes.
Nucleic Acids: Informational Macromolecules
That Can Be Catalytic
DNA is an information molecule. The information is stored in the order of the
four different bases.
This order is transferred to RNA molecules, which are used to direct the order
of the amino acids in proteins.
Nucleic Acids: Informational Macromolecules
That Can Be Catalytic
Closely related living species have ________ base sequences that are more
similar than distantly related species.
The comparative study of base sequences has confirmed many of the traditional
classifications of organisms.
DNA comparisons confirm that our closest living relatives are chimpanzees: We
share more than 98 percent of our DNA base sequences.
Nucleic Acids: Informational Macromolecules
That Can Be Catalytic
Certain RNA molecules called ________ can act as catalysts.
The discovery of ribozymes provided a solution to the question of whether
proteins or nucleic acids came first when life originated.
Since RNA can be informational and catalytic, it could have acted as a
catalyst for its own replication as well as for the synthesis of proteins.
Nucleic Acids: Informational Macromolecules
That Can Be Catalytic
Nucleotides have other important roles:
§ The ribonucleotide ATP acts as an ________ transducer in many biochemical
reactions.
§ The ribonucleotide GTP powers protein synthesis.
§ cAMP (cyclic AMP) is a special ribonucleotide that is essential for hormone
action and the transfer of information by the nervous system.
All Life from Life
Should we expect to see new life forms arise from the biochemical environment?
During the Renaissance, most people thought that some forms of life arose
directly from inanimate or decaying matter by spontaneous generation.
In 1668, Francisco ________ did an experiment to test this hypothesis.
All Life from Life
The invention of the microscope unveiled a vast new biological world which
some scientists believed arose ________ from their rich chemical environment.
Louis Pasteur completed experiments to disprove this idea.
Environmental and planetary conditions that exist on Earth today prevent life
from arising from nonliving materials, as it might have during the Hadean.
Animation 3.1 Synthesis of Prebiotic Molecules in an Experimental Atmosphere
Animation 3.2 Macromolecules
Animation 3.3 Pasteur's Experiment
Video 3.1 Lysozyme: A three-dimensional model
Video 3.2 Hemoglobin: A three-dimensional model
Video 3.3 Starch: A three-dimensional model
Video 3.4 Cellulose: A three-dimensional model
Video 3.5 Palmitic acid and linoleic acid: A three-dimensional model