Download Protein Structure and Function

Chapter 5: The Structure and Function of Large Biological Molecules
 Overview: The Molecules of Life
• All living things are made up of ________________ of large biological molecules:
_______________________________________________
• Within cells, small organic molecules are joined together to form larger molecules
• _____________________ are large molecules composed of thousands of covalently
connected atoms (They include: carbohydrates, proteins and nucleic acids)
• Molecular ______________ and ________________ are inseparable
 Concept 5.1: Macromolecules are polymers, built from monomers
• A ________________ is a long molecule consisting of many
__________________________
• These small building-block molecules are called __________________
• Three of the four classes of life’s organic molecules are polymers:
– ________________________
– ________________________
– ________________________
• The Synthesis and Breakdown of Polymers
– All polymers are built by ______________________________. When this
happens, the two monomers are covalently bonded to each other through the
_________________________________. This is called a condensation
reaction.
• A ____________________________ or more specifically a
____________________________ occurs when two monomers bond
together through the loss of a water molecule
• Each monomer contributes part of the water molecule: one gives the (OH) while the other gives the (-H)
• ______________ are macromolecules that speed up the dehydration
process.
– Polymers are disassembled to monomers by ________________, a reaction
that is essentially the reverse of the dehydration reaction
• Hydrolysis means to _______________________. Bonds of the
monomer are broken by the addition of water. The water molecule
splits.
• One monomer gets the (-OH); the other gets the (-H)
– Digestion is an example of hydrolysis in our body.
– Cells later use dehydration to reassemble new polymers
• The Diversity of Polymers
– Each cell has _____________________________________ of macromolecules
– Macromolecules vary among cells of an organism, vary more within a species,
and vary even more between species
– An immense variety of polymers can be built from a small set of monomers
(there are only 40-50 common monomers)
– The key to diversity is the __________________________________ of the
monomers.
 Concept 5.2: Carbohydrates serve as fuel and building material
• _____________________ include sugars and the polymers of sugars
• The simplest carbohydrates are _____________________, or single sugars
• _____________________ are double sugars
• Carbohydrate macromolecules are _______________________, polymers composed
of many sugar building blocks
• Sugars
– ____________________ have molecular formulas that are usually multiples of
____________
– ______________ (C H O ) is the most common monosaccharide
6 12
6
– Monosaccharides are classified by
• The location of the ___________________ (as ___________ or
_____________)
• The number of carbons in the carbon skeleton (3, 5 and 6 carbons are
most common)
– Though often drawn as _______________________, in aqueous solutions
many sugars ________________
– Monosaccharides serve as a major fuel for cells and as raw material for
building molecules
– A ____________________ is formed when a ______________________ joins
two monosaccharides
– This covalent bond is called a ________________________
• Examples: sucrose (table sugar = glucose + fructose); maltose (brewing
sugar= glucose + glucose); lactose (milk sugar = glucose + galactose)
– Polysaccharides
• _________________, the polymers of sugars, have storage and
structural roles.
• They are macromolecules with a few hundred to a few thousand
monosaccharides joined by glycosidic linkages.
• The structure and function of a polysaccharide are determined by its
sugar monomers and the positions of glycosidic linkages
• Some function for ___________; others for _____________
• Storage Polysaccharides
– ____________, a ________________________________, consists entirely of
__________________________
• Plants store surplus starch as granules within chloroplasts and other
_____________
• Making starch allows a plant to store energy
• The bonds holding the starch together are broken by hydrolysis to
release glucose; the major cellular fuel
– _________________ is a storage polysaccharide in animals
• Humans and other vertebrates store glycogen mainly in __________ and
___________________
• Hydrolysis of glycogen releases glucose when needed
• The stored glycogen is quickly depleted and must be replenished daily (a
draw-back of low carb diets)
• Structural Polysaccharides
– The polysaccharide _______________ is a major component of the
_____________________________
• Like starch, cellulose is a polymer of glucose, but the glycosidic linkages
differ
• The difference is based on two ring forms for glucose: alpha () and
beta ()
• Polymers with  glucose are _______________
• Polymers with  glucose are _______________
– In straight structures, H atoms on one strand can hydrogen-bond with OH
groups on other strands
– Parallel cellulose molecules held together this way are grouped into
________________, which form strong building materials for plants
– Enzymes that digest starch by hydrolyzing  linkages __________ hydrolyze 
linkages in cellulose. This makes cellulose _________________________.
– Cellulose in human food passes through the digestive tract as
_______________________
– Some ___________________ use enzymes to digest cellulose
– Many herbivores, from cows to termites, have symbiotic relationships with
these microbes
– _______________, another structural polysaccharide, is found in the
__________________________. It is similar to cellulose except that it has a
nitrogen-containing appendage.
– Chitin also provides structural support for the __________________
____________
 Concept 5.3: Lipids are a diverse group of hydrophobic molecules
• _________________ are the one class of large biological molecules that
____________________________
• The unifying feature of lipids is having ____________________________
• Lipids are ___________________ because they consist mostly of hydrocarbons,
which form ______________________________
• The most biologically important lipids are ________, _______________, and
________________
• Fats
– _________ are constructed from two types of smaller molecules:
_________________________
• _______________ is a _____________________ with a
______________________ attached to each carbon
• A ______________ consists of a _______________________ attached
to a _____________________________ ( usually 16-18 carbons in
length).
• They are joined as a result of a dehydration reaction.
– To make the fat molecule, three fatty acid molecules each join to glycerol by
an ester linkage (a bond between a hydroxyl group and a carboxyl group)
– The resulting fat is called a _________________ (i.e _____________)
***Note: the fatty acids can all be the same, or they can be two or three different kinds.
– Fats separate from water because water molecules form hydrogen bonds with
each other and exclude the fats
– Fatty acids vary in length (number of carbons) and in the number and locations
of double bonds
– ________________________ have the maximum number of hydrogen atoms
possible and no double bonds
• Saturated fats are solid at room temp. and include most animal fats.
– ________________________ have one or more double bonds
• Unsaturated fats are liquid at room temp. and include oils, plant fats and
fish fats.
– A diet rich in saturated fats may contribute to cardiovascular disease through
plaque deposits
– ________________________ is the process of converting unsaturated fats to
saturated fats by adding hydrogen (Ex: peanut butter and margarine—keeps
the oils from settling out)
– Hydrogenating vegetable oils also creates unsaturated fats with
___________________________
– These _______________ may contribute more than saturated fats to
cardiovascular disease. They are common in baked goods and processed
foods.
– The major function of fats is _____________________
• One gram of fat stores _____________ as much energy as a gram of
starch
– Humans and other mammals store their fat in _________________.
• These cells ___________________ as fat is either deposited or
withdrawn
– Adipose tissue also ________________________________________
(subcutaneous fat)
• Phospholipids
– In a ___________________, two fatty acids and a phosphate group are
attached to glycerol
– The two fatty acid ________________________, but the phosphate group and
its attachments form a _____________________
– When phospholipids are added to water, they self-assemble into a
__________, with the hydrophobic tails pointing toward the interior
– The structure of phospholipids results in a _____________________
__________________________
– Phospholipids are the major component of all cell membranes
• Steroids
– ____________ are lipids characterized by a carbon skeleton consisting of four
fused rings. They include many different types of hormones.
– _________________, an important steroid, is a _________________
________________________. It is synthesized in the liver.
– Although cholesterol is essential in animals, ____________________ may
contribute to cardiovascular disease
 Concept 5.4: Proteins have many structures, resulting in a wide range of functions
• _____________—comes from the Greek word ____________, meaning first place.
They are super important to living organisms.
• Proteins account for more than ______ of the dry mass of most cells
• Protein functions include _______________________________________
____________________________________________________________
• _____________ are a type of protein that acts as a ________________ to speed up
chemical reactions
– Life would not be possible without enzymes. They regulate metabolism.
– Enzymes can perform their functions _______________, functioning as
workhorses that carry out the processes of life
• Polypeptides
– ________________ are polymers built from the same set of
____________________
– A ____________ consists of one or more polypeptides
• Amino Acid Monomers
– _______________ are organic molecules with __________________
____________
– Amino acids ____________ in their properties due to differing side chains,
called ___________________
• At the center of the amino acid is an _____________________ called
the ____________________.
• Its four partners are: an amino group, a carboxyl group, a hydrogen
atom, and an R group.
• Amino Acid Polymers—how are amino acids linked to form polymers?
– Amino acids are linked by _____________________
• These bonds form between the ___________________ of one amino
acid and the ____________________ of the other during a
__________________________. Repeated many times, this results in a
_____________________.
– A polypeptide is a ______________________________. At one end is a free
amino group (N-terminus); at the other is a free carboxyl group (C-terminus)
– Polypeptides range in length from a few to more than a thousand monomers
– Each polypeptide has a unique linear sequence of amino acids
• Protein Structure and Function
– A functional protein is not just a polypeptide chain. It consists of one or more
polypeptides twisted, folded, and coiled into a unique shape
– The sequence of amino acids determines a protein’s three-dimensional
structure
– A protein’s structure determines its function
– Four Levels of Protein Structure
• The ________________________ of a protein is its
____________________________________
• ________________________, found in most proteins, consists of
_________________ in the _______________________
• ______________________ is determined by interactions among various
__________________ (R groups)
• ______________________ results when a protein consists of
_________________________________
– __________________, the sequence of amino acids in a protein, is like the
order of letters in a long word
• Primary structure is determined by ______________________
______________________
– The coils and folds of ________________________ result from
____________________between repeating constituents of the polypeptide
backbone
• Typical secondary structures are a ________ called an _______ and a
_______________ called a ___________________
– ____________________ is determined by interactions between R groups,
rather than interactions between backbone constituents
• These interactions between R groups include ______________
___________________________________________________
___________________________________________________
• Strong covalent bonds called ____________________ may reinforce the
protein’s structure
– ______________________ results when two or more polypeptide chains
form one macromolecule
• _______________ is a fibrous protein consisting of three polypeptides
coiled like a rope
• _______________ is a globular protein consisting of four polypeptides:
two alpha and two beta chains
– Sickle-Cell Disease: A Change in Primary Structure
• A slight change in ___________________ can affect a protein’s structure
and ability to function
– Sickle-cell disease, an inherited blood disorder, results from a
______________________________ in the protein hemoglobin
– What Determines Protein Structure?
• In addition to primary structure, physical and chemical conditions can
affect structure
• Alterations in pH, salt concentration, temperature, or other
environmental factors can cause a _____________________
• This loss of a protein’s native structure is called _____________
• A denatured protein is _________________________
– Protein Folding in the Cell
• It is hard to predict a protein’s structure from its primary structure
• Most proteins probably go through several states on their way to a
stable structure
• ________________ are ___________________ that assist the
_______________________________
• Scientists use _________________________ to determine a protein’s
structure
• Another method is ___________________________ (NMR)
spectroscopy, which does not require protein crystallization
• Bioinformatics uses computer programs to predict protein structure
from amino acid sequences
 Concept 5.5: Nucleic acids store and transmit hereditary information
• The amino acid sequence of a polypeptide is programmed by a unit of inheritance
called a ___________
• Genes are made of DNA, a ______________________
• There are two types of nucleic acids:
– _____________________________
– _____________________________
• DNA provides directions for its own replication
• DNA directs synthesis of ____________________________ and, through mRNA,
______________________________
• Protein synthesis occurs in __________________
• The Structure of Nucleic Acids
– Nucleic acids are polymers called ___________________
– Each polynucleotide is made of monomers called ________________
– Each nucleotide consists of a ________________________________
_____________________________________
– The portion of a nucleotide without the phosphate group is called a
__________________
– Nucleotide Monomers
• Nucleoside = nitrogenous base + sugar
• There are two families of nitrogenous bases:
o ______________________ (cytosine, thymine, and uracil) have a
single six-membered ring
o _________________ (adenine and guanine) have a six-membered
ring fused to a five-membered ring
• In DNA, the sugar is _________________; in RNA, the sugar is
______________
• ___________________ = nucleoside + phosphate group
– Nucleotide Polymers
• Nucleotide polymers are linked together to build a polynucleotide
• Adjacent nucleotides are joined by ___________________ that form
between the ______________________________________
______________________________________________________
• These links create a backbone of sugar-phosphate units with nitrogenous
bases as appendages
• The _____________________ along a DNA or mRNA polymer is
____________ for each gene
– The DNA Double Helix
• A DNA molecule has two polynucleotides spiraling around an imaginary
axis, forming a __________________
• In the DNA double helix, the two backbones run in
__________________________ directions from each other, an
arrangement referred to as ___________________
• One DNA molecule includes many genes
• The nitrogenous bases in DNA pair up and form hydrogen bonds:
______________________________________________________
– DNA and Proteins as Tape Measures of Evolution
• The linear sequences of nucleotides in DNA molecules are
___________________________________________________
• Two closely related species are more similar in DNA than are more distantly
related species
• Molecular biology can be used to assess _____________________
– The Theme of Emergent Properties in the Chemistry of Life: A Review
• Higher levels of organization result in the emergence of new properties
• Organization is the key to the chemistry of life
You should now be able to:
1. List and describe the four major classes of molecules
2. Describe the formation of a glycosidic linkage and distinguish between
monosaccharides, disaccharides, and polysaccharides
3. Distinguish between saturated and unsaturated fats and between cis and trans fat
molecules
4. Describe the four levels of protein structure
• You should now be able to:
5. Distinguish between the following pairs: pyrimidine and purine, nucleotide and
nucleoside, ribose and deoxyribose, the 5 end and 3 end of a nucleotide