BIOL 1406 Chapter 05 Flashcards
four classes of large biological molecules
carbohydrates, lipids, proteins, and nucleic acids
Macromolecules
are large molecules composed of thousands of covalently connected atoms
polymer
is a long molecule consisting of many similar building blocks
monomers
small building-block molecules
condensation / dehydration reaction
occurs when two monomers bond together through the loss of a water molecule
enzymes
macromolecules that speed up the dehydration process
hydrolysis
Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction
carbohydrates
include sugars and the polymers of sugars
The simplest carbohydrates are monosaccharides, or single sugars
Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks
monosaccharides
have molecular formulas that are usually multiples of CH2O
Glucose (C6H12O6) is the most common monosaccharide
Monosaccharides are classified by the location of the carbonyl group (as aldose or ketose); the number of carbons in the carbon skeleton
Monosaccharides serve as a major fuel for cells and as raw material for building molecules
disaccharide
is formed when a dehydration reaction joins two monosaccharides. This covalent bond is called a glycosidic linkage.
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 positions of glycosidic linkages.
starch
a storage polysaccharide of plants, consists entirely of glucose monomers
glycogen
is a storage polysaccharide in animals. Humans and other vertebrates store glycogen mainly in liver and muscle cells
cellulose
a polysaccharide, is a major component of the tough wall of plant cells
is a polymer of glucose, but the glycosidic linkages differ
The difference is based on two ring forms for glucose: alpha and beta
chitin
another structural polysaccharide, is found in the exoskeleton of arthropods.
Chitin also provides structural support for the cell walls of many fungi
lipids
are the one class of large biological molecules that do not form polymers.
The unifying feature of lipids is having little or no affinity for water.
Lipids are hydrophobic becausethey consist mostly of hydrocarbons, which form nonpolar covalent bonds.
The most biologically important lipids are fats, phospholipids, and steroids.
saturated fatty acids
have the maximum number of hydrogen atoms possible and no double bonds
unsaturated fatty acids
have one or more double bonds
hydrogenation
is the process of converting unsaturated fats to saturated fats by adding hydrogen
phospholipid
two fatty acids and a phosphate group are attached to glycerol. The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head
steroids
are lipids characterized by a carbon skeleton consisting of four fused rings
cholesterol
an important steroid, is a component in animal cell membranes
enzymatic proteins
function: selective acceleration of chemical reactions
example: digestive enzymes
structural proteins
function: support
example: silk fibers, collagen and elastin in animal connective tissues; keratin in hair, horns, feathers
storage proteins
function: storage of amino acids
example: ovalbumin in egg white; casein, the protein of milk; storage proteins in plant seeds
transport proteins
function: transport of other substances
example: hemoglobin, transport proteins
hormonal proteins
function: coordination of an organism’s activities
example: insulin, a hormone secreted by the pancreas
receptor proteins
function: response of cell to chemical stimuli
example: receptors in nerve cell membranes
contractile and motor proteins
function: movement
example: actin and myosin in muscles, protein in cilia and flagella
defensive proteins
function: protection against disease
example: antibodies combat bacteria and viruses
enzymes
are a type of protein that acts as a catalyst to speed up chemical reactions
polypeptides
are polymers built from the same set of 20 amino acids
protein
consists of one or more polypeptides
amino acids
are organic molecules with carboxyl and amino groups.
Amino acids differ in their properties due to differing side chains, called R groups
linked by peptide bonds
Four Levels of Protein Structure
The primary structure of a protein is its unique sequence of amino acids.
Secondary structure, found in most proteins, consists of coils and folds in the polypeptide chain.
Tertiary structure is determined by interactions among various side chains (R groups).
Quaternary structure results when a protein consists of multiple polypeptide chains.
Primary Structure
the sequence of amino acids in a protein, is like the order of letters in a long word
Primary structure is determined by inherited genetic information
Secondary Structure
The coils and folds of secondary structure result from hydrogen bonds between repeating constituents of the polypeptide backbone
Typical secondary structures are a coil called an helix and a folded structure called a pleated sheet
Tertiary Structure
is determined by interactions between R groups, rather than interactions between backbone constituents
These interactions between R groups include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions
Strong covalent bonds called disulfide bridges may reinforce the protein’s structure
Quaternary Structure
results when two or more polypeptide chains form one macromolecule
Collagen is a fibrous protein consisting of three polypeptides coiled like a rope
Hemoglobin is a globular protein consisting of four polypeptides: two alpha and two beta chains
denaturation
loss of a protein’s native structure
chaperonins
are protein molecules that assist the proper folding of other proteins
x-ray crystallography
to determine a protein’s structure
nuclear magnetic resonance (NMR) spectroscopy
which does not require protein crystallization
bioinformatics
uses computer programs to predict protein structure from amino acid sequences
