Chapter 5-Lecture Flashcards
All living things are made up of four classes
of large biological molecules:
carbohydrates, lipids, proteins, and nucleic acids
_________________: are large molecules and are complex
Macromolecules
Large biological molecules have unique properties that arise from
the orderly arrangement of their atoms
Macromolecules are polymers, built from _________
monomers
Three of the four classes of life’s organic molecules are _____________
____________ ______________ _______________
polymers
Carbohydrates
Proteins
Nucleic acids
_____________________ are specialized macromolecules that speed up chemical reactions such as those that make or break down polymers
Enzymes
________________________ occurs when two monomers bond together through the loss of a water molecule
A dehydration reaction
Polymers are disassembled to monomers by ____________________ , a reaction that is essentially the reverse of the dehydration reaction
hydrolysis
The Diversity of Polymers
Each cell has thousands of different ____________________
Macromolecules
these vary among cells of an organism, vary more within a species, and vary even more between species
Carbohydrates include
sugars and the polymers of sugars
The simplest carbohydrates are _________________, or simple sugars
monosaccharides
Carbohydrate macromolecules are ________________________ polymers composed of many sugar building blocks
Sugars
polysaccharides,
______________________ have molecular formulas that are usually multiples of CH2O
Glucose (C6H12O6) is the most common monosaccharide
Monosaccharides
Monosaccharides are classified by
The location of the carbonyl group (as aldose
or ketose)
The number of carbons in the carbon skeleton
Though often drawn as linear skeletons, in aqueous solutions many sugars form ___________________
Monosaccharides serve as a_____________________ _______________________________________________
rings
major fuel for cells and as raw material for building molecules
________________: is formed when a dehydration reaction joins two monosaccharides via a covalent _____________ bond
A disaccharide
This covalent bond is called a glycosidic linkage
the polymers of sugars, have storage and structural roles
Polysaccharides,
The architecture and function of a polysaccharide are
determined by its sugar monomers and the positions of its glycosidic linkages
Starch is to plants __________________ is to animals
glycogen
___________________: a storage polysaccharide of plants, consists entirely of glucose monomers
Plants store surplus starch as granules within chloroplasts and other plastids
Starch
The simplest form of starch is amylose
________________ is a storage polysaccharide in animals
Glycogen
Glycogen is stored mainly in liver and muscle cells
Hydrolysis of glycogen in these cells releases
glucose when the demand for sugar increases
The polysaccharide ____________________ is a major component of the tough wall of plant cells
cellulose
Like starch, cellulose is a polymer of glucose, but
the glycosidic linkages differ
_______________: another structural polysaccharide, is found in the exoskeleton of arthropods
_______________: also provides structural support for the cell walls of many fungi
Chitin
______________: are a diverse group of hydrophobic molecules. They are the one class of large biological molecules that does not include true polymers
Lipids
The unifying feature of lipids is that they mix poorly, if at all, with water
Lipids are hydrophobic because
they consist mostly of hydrocarbons, which form nonpolar covalent bonds
The most biologically important lipids are
fats, phospholipids, and steroids
Fats are constructed from
two types of smaller molecules: glycerol and fatty acids
Glycerol is
a three-carbon alcohol with a hydroxyl group attached to each carbon
A fatty acid consists
of a carboxyl group attached to a long carbon skeleton
Fats separate from water because
water molecules hydrogen-bond to each other and exclude the fats
In a fat, three fatty acids are joined to glycerol
by an ester linkage,
creating a triacylglycerol,
or triglyceride
The fatty acids in a fat can be all the same or of
two or three different kinds. Fatty acids vary in length (number of carbons) and in the number and locations of double bonds
_______________: fatty acids have the maximum number of hydrogen atoms possible and no double bonds
Saturated
_______________: fatty acids have one or more double bonds
Unsaturated
Fats made from saturated fatty acids are
called saturated fats and are solid at room temperature
Most animal fats are saturated
Fats made from unsaturated fatty acids are
called unsaturated fats or oils and are liquid at room temperature Plant fats and fish fats are usually unsaturated
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
Hydrogenation
Hydrogenating vegetable oils also creates unsaturated fats with _____________________
These trans fats may contribute more than saturated fats to cardiovascular disease
trans double bonds
The major function of fats is ____________
energy storage
Humans and other mammals store their long-term food reserves in
adipose cells
Adipose tissue also cushions vital organs and insulates the body
, two fatty acids and a phosphate group are attached to glycerol
phospholipid
The two fatty acid tails are______________, but the phosphate group and its attachments form a ____________ head
hydrophobic
hydrophilic
When phospholipids are added to water, they
self-assemble into double-layered structures
called
phospholipid bilayers
At the surface of a cell, phospholipids are also arranged in a bilayer, with the hydrophobic tails pointing toward the interior
_______________: are lipids characterized by a carbon skeleton consisting of four fused rings
Steroids
________________: a type of steroid, is a component in animal cell membranes and a precursor from which other steroids are synthesized. A high level of cholesterol in the blood may contribute to cardiovascular disease
Cholesterol,
_____________: include a diversity
of structures, resulting in a wide range
of functions
Proteins
Proteins account for more than 50% of the dry mass of most cells
Some proteins speed up chemical reactions
Other protein functions include defense, storage, transport, cellular communication, movement, or structural support
Enzymes are proteins that act as _____________ to speed up chemical reactions
catalysts
Enzymes can perform their functions repeatedly, functioning as
workhorses that carry out the processes of life
__________________ are unbranched polymers built from these amino acids
Polypeptides
A protein is a biologically functional molecule that consists of one or more ______________________
polypeptides
____________: are organic molecules with amino and carboxyl groups
Amino acids
Amino acids differ in their properties due to
differing side chains, called R groups
Amino acids are linked by covalent bonds called __________________________________
peptide bonds
_________________: is a polymer of amino acids
A polypeptide
Each polypeptide has a unique linear sequence of amino acids, with a _________ end and ________ end
carboxyl end (C-terminus) and an amino end (N-terminus)
The specific activities of proteins result from their intricate three-dimensional architecture
A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape
The sequence of amino acids determines a protein’s three-dimensional structures
A protein’s structure determines how it works
_______________________: of a protein is its sequence of amino acids
The primary structure
Primary structure is like the order of letters in a long word
Primary structure is determined by inherited genetic information
The coils and folds of _______________ result from hydrogen bonds between repeating constituents of the polypeptide backbone
secondary structure
Typical secondary structures are a coil called an helix and a folded structure called a pleated sheet
_________________: the overall shape of a polypeptide, results from interactions between
R groups, rather than interactions between backbone constituents
Tertiary structure,
These interactions include hydrogen bonds,
ionic bonds, hydrophobic interactions, and _________________________________
van der Waals interactions
Strong covalent bonds called ______________ may reinforce the protein’s structure
disulfide bridges
_______________: results when two or more polypeptide chains form one macromolecule
Quaternary structure
__________________: is a fibrous protein consisting of three polypeptides coiled like a rope
Collagen
__________________: is a globular protein consisting of
four polypeptides: two alpha and two beta chains
Hemoglobin
What Determines Protein Structure?
In addition to primary structure, physical and chemical conditions can affect structure
This loss of a protein’s native structure is
called
denaturation
Alterations in pH, salt concentration,
temperature, or other environmental factors
can cause a protein to unravel
A denatured protein is biologically inactive
It is hard to predict a protein’s structure from its _________________________
primary structure
Most proteins probably go through several stages on their way to a stable structure
____________________ are protein molecules that assist
the proper folding of other proteins
Chaperonins
With out chaperonins proteins may miss fold and result in
Diseases such as Alzheimer’s, Parkinson’s,
and mad cow disease are associated with misfolded proteins
______________________ store, transmit, and help express hereditary information
Nucleic acids
The amino acid sequence of a polypeptide is programmed by a unit of inheritance called _____________
a gene
Genes consist of DNA, a _____________ made of monomers called ___________________
nucleic acid
nucleotides
There are two types of nucleic acids
Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA)
DNA provides directions for its own replication
DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis
This process is called
gene expression
Each gene along a DNA molecule directs synthesis of a messenger RNA (mRNA)
The mRNA molecule interacts with the cell’s protein-synthesizing machinery to direct production of a polypeptide
The flow of genetic information can be summarized as DNA → RNA → protein
Nucleic acids are polymers called
polynucleotides
Each polynucleotide is made of monomers called
nucleotides
Each nucleotide consists of a
nitrogenous base, a pentose sugar, and one or more phosphate groups
The portion of a nucleotide without the phosphate group is called a
nucleoside
Nucleoside = nitrogenous base + sugar
Nucleotide = nucleoside + phosphate group
There are two families of nitrogenous bases
Pyrimidines and Purines
____________
have a single six-membered ring
Pyrimidines (cytosine, thymine, and uracil)
___________________ have a six-membered ring fused to a five-membered ring
In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose
Purines (adenine and guanine)
Nucleotides are linked together to build a
polynucleotide
DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a _____________
The backbones run in opposite 5 → 3 directions from each other, an arrangement referred to as ____________
One DNA molecule includes many genes
double helix
antiparallel
Only certain bases in DNA pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C)
This is called complementary base pairing
RNA, in contrast to DNA,
is single stranded
Complementary pairing can also occur between two RNA molecules or between parts of the
same molecule
In RNA, thymine is replaced by____________ so
A and U pair
uracil (U)
