Chapter 5
The Structure and Function of Large Biological Molecules
Overview: The Molecules of Life
• All living things are made up of four classes 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
• Molecular structure and function are _________________________________
Concept 5.1: Macromolecules are polymers, built from monomers
• A _________________________________ is a long molecule consisting of many similar building blocks
• 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
• A ___________________________________________________ or more specifically a _________________________________________________ occurs when two monomers bond together through the loss of a water molecule
• Enzymes are macromolecules that _____________________________ the dehydration process
• Polymers are disassembled to monomers by ________________________________, a reaction that is essentially the reverse of the dehydration reaction
The Diversity of Polymers
• Each cell has thousands of different kinds 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
Concept 5.2: Carbohydrates serve as fuel and building material
• _______________________________ include sugars and the polymers of sugars
• The simplest carbohydrates are _______________________________________, or single sugars
• Carbohydrate macromolecules are ________________________________________, polymers composed of many sugar building blocks
Sugars
• Monosaccharides have molecular formulas that are usually multiples of _________________
• Glucose (_________________________________) is the most common monosaccharide
• Monosaccharides are classified by
• _______________________________________________________________________
• _______________________________________________________________________
• Though often drawn as ______________________ skeletons, in aqueous solutions many sugars form ______________
• Monosaccharides serve as a ________________________________________ for cells and as __________________________________________ for building molecules
• A _________________________________ is formed when a dehydration reaction joins two monosaccharides
• This covalent bond is called a ______________________________________________________
Polysaccharides
• ____________________________________, the polymers of sugars, have storage and structural roles
• The structure and function of a polysaccharide are determined by its sugar monomers and the _____________________________ of glycosidic linkages
Storage Polysaccharides
• _________________________________, a storage polysaccharide of plants, consists entirely of glucose monomers
• Plants store surplus starch as granules within _________________________________________
______________________________________________________________________________
• ____________________________________ is a storage polysaccharide in animals
• Humans and other vertebrates store glycogen mainly in _________________________________
______________________________________________________________________________
Structural Polysaccharides
• The polysaccharide _______________________________ is a major component of the tough wall of plant cells
• Like starch, cellulose is a polymer of glucose, but the ___________________________________ differ
• The difference is based on two ring forms for glucose: alpha (a) and beta (b)
• Polymers with a glucose are______________________________
• Polymers with b glucose are ______________________________
• In straight structures, ___________________ on one strand can bond with _______________________ 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 a linkages _________________ hydrolyze b linkages in cellulose
• Cellulose in human food passes through the digestive tract as ____________________________
______________________________________________________________________________
• Some __________________________ use enzymes to digest cellulose
• Many herbivores, from cows to termites, have _____________________________ relationships with these microbes
• ______________________________, another structural polysaccharide, is found in the exoskeleton of _________________________________________
• Chitin also provides __________________________________________________ for the cell walls of many fungi
Concept 5.3: Lipids are a diverse group of hydrophobic molecules
• _________________________ are the one class of large biological molecules that ___________
_____________ form polymers
• The unifying feature of lipids is having little or no ______________________________________
• Lipids are ________________________________ because they consist mostly of hydrocarbons, which form ____________________________ covalent bonds
• The most biologically important lipids are __________________, phospholipids, and steroids
Fats
• Fats are constructed from two types of smaller molecules: ________________________ and ______________________________________
• Glycerol is a ______________________________ alcohol with a ____________________ group attached to each carbon
• A fatty acid consists of a _________________________ group attached to a long carbon skeleton
• Fats separate from water because water molecules form _________________________ with each other and exclude the fats
• In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a ________________________________________, or triglyceride
• Fatty acids vary in _________________ (number of carbons) and in the number and locations of _________________ bonds
• _______________________________ fatty acids have the maximum number of hydrogen atoms possible and __________________ double bonds
• ______________________________ fatty acids have one or more __________________ bonds
• Fats made from saturated fatty acids are called saturated fats, and are ___________________ at room temperature
• Most ____________________ fats are saturated
• Fats made from unsaturated fatty acids are called unsaturated fats or _____________, and are ____________________ at room temperature
• _________________ fats and _____________________ fats are usually unsaturated
• A diet rich in saturated fats may contribute to ____________________________________ disease through _______________________ deposits
• __________________________________________ is the process of converting unsaturated fats to saturated fats by adding hydrogen
• Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds
• These trans fats may contribute more than saturated fats to cardiovascular disease
• The major function of fats is ____________________________________________
• Humans and other mammals store their fat in _________________________________ cells
• Adipose tissue also ___________________________ vital organs and _____________________ the body
Phospholipids
• In a ___________________________, two fatty acids and a phosphate group are attached to glycerol
• The two fatty acid tails are _____________________________, but the phosphate group and its attachments form a _____________________________________ head
• 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 bilayer arrangement found in ___________________
______________________________________________________________________________
• Phospholipids are the major component of all cell membranes
Steroids
• ____________________________ are lipids characterized by a carbon skeleton consisting of four fused rings
• _____________________________, an important steroid, is a component in animal cell membranes
• Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease
Concept 5.4: Proteins have many structures, resulting in a wide range of functions
• Proteins account for more than ___________________ of the dry mass of most cells
• Protein functions include ________________________________________, ________________, _________________________, ____________________________________________________, ____________________________, and ______________________________________________
• _____________________________ are a type of protein that acts as a _____________________ to speed up chemical reactions
• Enzymes can perform their functions repeatedly, functioning as workhorses that carry out the processes of life
Polypeptides
• _________________________________ are polymers built from the same set of 20 amino acids
• A ___________________ consists of one or more polypeptides
Amino Acid Monomers
• Amino acids are _________________________________________________________________
______________________________________________________________________________
• Amino acids differ in their properties due to differing side chains, called ____________________
Amino Acid Polymers
• Amino acids are linked by _______________________________________
• A polypeptide is a polymer of amino acids
• Polypeptides range in _____________________ from a few to more than a thousand monomers
• Each polypeptide has a unique linear ________________________________ of amino acids
Protein Structure and Function
• A functional protein consists of one or more polypeptides __________________, ________________, and __________________ into a unique shape
• The ___________________________________ of amino acids determines a protein’s three-dimensional structure
• A protein’s _____________________________ determines its ___________________________
Four Levels of Protein Structure
• The ____________________ structure of a protein is its _________________ sequence of amino acids
• ____________________________________ structure, found in most proteins, consists of coils and folds in the polypeptide chain
• ____________________________________ structure is determined by interactions among various side chains (R groups)
• ____________________________________ results when a protein consists of multiple polypeptide chains
• Primary structure, the sequence of amino acids in a protein, is like the order of _____________ in a long word
• Primary structure is determined by ___________________________ genetic information
• The coils and folds of secondary structure result from __________________________________ between repeating constituents of the polypeptide backbone
• Typical secondary structures are a coil called an ______________________ and a folded structure called a _____________________________________
• Tertiary structure is determined by interactions between _______________________________, rather than interactions between backbone constituents
• These interactions between R groups include __________________________, _____________________________, ____________________________________________, and __________________________________________ interactions
• Strong covalent bonds called ___________________________________ may reinforce the protein’s structure
• Quaternary structure results when two or more polypeptide chains form one ______________________________________
• __________________________ 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 ____________________ in primary structure can affect a protein’s structure and ability to function
• Sickle-cell disease, an inherited blood disorder, results from a single amino acid _____________________________ in the protein hemoglobin
What Determines Protein Structure?
• In addition to primary structure, _______________________ and _______________________ conditions can affect structure
• Alterations in pH, salt concentration, temperature, or other environmental factors can cause a protein to _________________________
• This loss of a protein’s native structure is called _______________________________________
• A denatured protein is biologically _____________________________
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 ____________________ structure
• _______________________________________ are protein molecules that assist the proper folding of other proteins
• Scientists use _____________________________________________ to determine a protein’s structure
• Another method is __________________________________________________ (NMR) spectroscopy, which does not require protein crystallization
• Bioinformatics uses computer programs to ________________________ 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 ____________________________________
The Roles of Nucleic Acids
• There are two types of nucleic acids:
• ________________________________________________________________________
• ________________________________________________________________________
• DNA provides __________________________________ for its own replication
• DNA directs synthesis of ______________________________________ and, through mRNA, controls protein synthesis
• 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 _________________________________, a ______________________________, and a ______________________________________
• The portion of a nucleotide without the phosphate group is called a nucleoside
Nucleotide Monomers
• Nucleoside = nitrogenous base + sugar
• There are two families of nitrogenous bases:
– _____________________________________(cytosine, thymine, and uracil) have a single six-membered ring
– _________________________________(adenine and guanine) have a six-membered ring fused to a five-membered ring
• In DNA, the sugar is _______________________________; in RNA, the sugar is ______________
• Nucleotide = nucleoside + phosphate group
Nucleotide Polymers
• Nucleotide polymers are linked together to build a polynucleotide
• Adjacent nucleotides are joined by covalent bonds that form between the ___________________________ on the 3¢ carbon of one nucleotide and the ___________________________on the 5¢ carbon on the next
• These links create a backbone of __________________________________________ units with _____________________________________________ as appendages
• The sequence of bases 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 opposite _____________________________ 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: __________________________________________________________________________, and __________________________________________________________________________
DNA and Proteins as Tape Measures of Evolution
• The linear sequences of nucleotides in DNA molecules are passed from _________________ to ___________________________
• Two closely related species are more __________________________ in DNA than are more distantly related species
• Molecular biology can be used to assess ____________________________________ kinship
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