Chapter 3 - Nucleic Acids, Proteins, and Enzymes Flashcards
if you were given a diagram of a nucleotide what you expect to find as its components
phosphate, sugar, and a base
how is DNA different than RNA
it contains deoxyribose
the observations that DNA with a higher G + C content is more stable at high temperatures than DNA with a high A+ T content because of what?
because each G and C pair forms three hydrogen bonds between antiparallel strands, whereas each A and T pair forms just two
replication is the synthesis of ____ and transcription is the synthesis of _____
an identical copy of DNA; an RNA template based on the DNA template
Quaternary structure of proteins refers to ____?
the number and kind of protein subunits the protein has
the binding of a substrate to an enzyme
may involve hydrogen bonds and van der waals interactions
in a reaction catalyzed by an enzyme
the enzyme does not affect the equilibrium constant for the reaction
a competitive inhibitor of an enzyme-catalyzed reaction
is usually similar to the substrate
the rate of a reaction catalyzed by an enzyme that has a single polypeptide chain
may be increase or decreased by temperature
enzymes
may be subject to feedback inhibition
what are nucleic acids
palmers that store, transmit, and express hereditary information
two things proteins are essential for
metabolism and structure
pyrimidine
six membered single ring structure
purine
fused double-ring structure
DNA sugar groups
Adenine
Cytosine
Guanine
Thymine
RNA sugar groups
Adenine
Cytosine
Guanine
Uracil
what makes the DNA structure less flexible than that of RNA
lack of a hydroxyl group at the 2’ position of the deoxyribose sugar
complementary base pairing
In DNA A-T C-G In RNA A-U C-G held together primarily by hydrogen bonds
RNA characteristics
single stranded
can fold back on itself to form a double stranded helix
this folding occurs by complementary base pairing
DNA characteristics
double stranded
consists of two polynucleotide strands of the same length
strands are antiparallel: 5’ ends are at opposite ends of the double-stranded molecule
remarkably uniform
sugar-phosphate groups form the sides of the ladder and the bases with their hydrogen bonds form the rungs on the inside
genome
complete set of DNA in a living organism
Enzymes
catalytic molecules that speed up biochemical reactions. most enzymes are proteins (some are RNA molecules)
Defensive proteins
such as antibodies recognize and respond to substances or particles that invade the organism from the environment
peptide bonds
in the “backbone” of a protein are formed as covalent “peptide bonds” between adjacent amino acids.
hormonal and regulatory proteins
such as insulin control physiological processes
receptor proteins
receive and respond to molecular signals from inside and outside the organism
storage proteins
store chemical building blocks– amino acids – for later use.
Structural proteins
such as collagen provide physical stability and enable movement
transport proteins
such as hemoglobin carry substances within the organism
Genetic regulatory proteins
regulate when, how, and to what extent a gene is expressed
functions of proteins
enzymes structure defense signaling receptor membrane transport storage bulk transport gene regulation
what are the building blocks of proteins
amino acids
how can amino acids be classified
on the amino acids they posses
labels amino acids can receive
polar charged (hydrophilic) polar uncharged (hydrophilic) nonpolar (hydrophobic)
what functional groups do amino acids contain?
nitrogen containing amin group and the (acidic) carboxyl group
3 amino acids that are hydrophobic
glycine, proline, and cysteine
primary structure of a protein
is established by covalent bonds
____ of proteins are folded into 3D shapes
the polypeptide chains
secondary structure of a protein
consists of regular, repeated, spatial patterns in different regions of a polypeptide chain.
alpha helix
beta pleated sheet
tertiary structure of a protein
the polypeptide chain is bent at specific sites and then folded back and forth
results in the polypeptides definitive three-dimensional shape
secondary and tertiary structures derive from ___
primary structure
quaternary structure of a protein
results from ways in which these subunits bind together and interact. Hemoglobin is an example of a protein with multiple subunits
catalyst
used to speed up a reaction without itself being permanently altered
proteins that are enzymes speed up biochemical reactions, acting as biological catalysts that are highly specific for their substrates
substrate
name for reactants in a enzyme-catalyzed reaction
an enzymes active site determines its ____
specificity
active site
where the substrate molecule binds to the enzyme
irreversible inhibition
if an inhibitor covalently binds to an amino acid side chain at the active site of an enzyme, the enzyme if permanently inactivated because it cannot interact with its substrate.
EX: DIPF (diisoprpyl phosphorofluoridate)
reversible inhibition
an inhibitor is similar enough to a particular enzyme’s natural substrate that is can bind noncovalently to the active site, yet different enough that no chemical reaction occurs
analogus to a key that inserts into a lock but does not turn it
competitive inhibitor
when a molecule competes with the natural substrate for the active site
noncompetitive inhibitor
binds to an enzyme at a site distance from the active site. this binding causes a change in the shape of the enzyme, altering its activity.
allosteric regulation
occurs when a non-substrate molecule binds or modifies a site other than the active site of an enzyme
the activity of allosteric enzyme complexes results from what
the activity of both positive and negative regulators
what effects enzyme activity
temperature and ph
feedback inhibition
when the end product is present at a high concentration, some of it binds to a site on the commitment step enzyme, thereby causing it to become inactive
