1 Flashcards
Hydrolase
Hydrolysis (catabolic)
Acetyl-CoA synthetase—combines acetate and coenzyme
A to form acetyl-CoA for the Krebs cycle
Ligase or Polymerase
Lipase—breaks down lipid molecules
Hydrolase
Phosphoglucoisomerase—converts glucose 6-phosphate
into fructose 6-phosphate during glycolysis
Isomerase
Joining two or more chemicals together (anabolic)
Ligase or Polymerase
Rearrangement of atoms within a molecule (neither catabolic
nor anabolic)
Isomerase
Splitting a chemical into smaller parts without using
water (catabolic)
Lyase
Fructose-1,6-bisphosphate aldolase—splits fructose
1,6-bisphosphate into G3P and DHAP
Lyase
Lactic acid dehydrogenase—oxidizes lactic acid to form
pyruvic acid during fermentation
Oxidoreductase
Transfer of electrons or hydrogen atoms from one molecule
to another
Oxidoreductase
Moving a functional group from one molecule to another
(may be anabolic)
Transferase
Hexokinase—transfers phosphate from ATP to glucose in
the first step of glycolysis
Transferase
Type of Reaction Catalyzed
Moving a functional group from one molecule to another
(may be anabolic)
breaks down lipid molecules
Lipase
converts glucose 6-phosphate
into fructose 6-phosphate during glycolysis
Phosphoglucoisomerase
combines acetate and coenzyme
A to form acetyl-CoA for the Krebs cycle
Acetyl-CoA synthetase—
transfers phosphate from ATP to glucose in
the first step of glycolysis
Hexokinase
splits fructose
1,6-bisphosphate into G3P and DHAP
Fructose-1,6-bisphosphate aldolase
—oxidizes lactic acid to form
pyruvic acid during fermentation
Lactic acid dehydrogenase
The shape of an enzyme’s functional site, called its _______ is complementary to the shape of the enzyme’s substrate
active site
shapes and locations of only a few amino acids in a protein enzyme or nucleotides in a ribozyme determine the
shape of that enzyme’s active site.
critical to enzyme
activity, has been likened to the fit between a lock and key
Enzyme-substrate specificity,
almost as if a lock could grasp its key once it had been inserted. This
latter description of enhanced enzyme-substrate specificity is
called the_________
induced-fit model
In some cases, several different enzymes possess active sites that are complementary to various portions of a single substrate molecule.
In some cases, several different enzymes possess active sites that are complementary to various portions of a single substrate molecule.
For example, an important precursor
metabolite called ______________
phosphoenolpyruvic acid (PEP)
In one catabolic pathway, PEP is converted to
pyruvic acid
The enzyme and its substrate bind to form a temporary
intermediate compound called an
n enzyme-substrate complex
Bonds within the substrate are broken, forming_______ in catabolic reactions.
two or
more products
The binding of the substrate induces the enzyme
to fit the shape of the substrate even more closely—the
________
induced-fit model.
Many factors influence the rate of enzymatic reactions, including _____, _____, ______, _____, _____, ______
temperature, pH, enzyme and substrate concentrations, and
the presence of inhibitors.
The optimum temperature for the enzymes
in the human body is ____, which is normal body temperature.
37°C
The enzymes of some other
microorganisms, however, function best at different temperatures; this is the case for ______, organisms that grow
best at temperatures above 80°C.
hyperthermophiles
If temperature rises beyond a certain critical point, the
noncovalent bonds within an enzyme (such as the hydrogen
bonds between amino acids) will break, and the enzyme will
_____
denature
Denaturation is said to be _____when
an enzyme cannot regain its original structure once conditions
return to normal
permanent
In other cases, denaturation is _______ the denatured enzyme’s
noncovalent bonds re-form on the return of normal conditions
reversible
Rising temperature enhances
enzymatic activity to a point, but above some optimal temperature an
enzyme denatures and loses function
) At lower substrate concentrations, enzyme activity increases as
the substrate concentration increases and as more and more active
sites are utilized.
At the substrate concentration at which all active sites are utilized, termed the _______ enzymatic activity reaches a
maximum, and any additional increase in substrate concentration has no
effect on enzyme activity
saturation point,
Enzymes typically have some
optimal pH, at which point enzymatic activity reaches a maximum.
______ provides a way to control the growth of unwanted microorganisms by denaturing their proteins
Changing the pH
. Eventually, when all enzyme active sites have bound substrate, the enzymes
have reached their_______, and the addition of more substrate _______ the rate of enzymatic activity
saturation point
will not increase
eukaryotic cells control some enzymatic activities by compartmentalizing enzymes inside membranes so that certain metabolic reactions proceed physically separated from the
rest of the cell.
An enzyme can be activated by the binding of a cofactor
to the enzyme at a site located away from the active site a
site called an_______
allosteric site
the binding of an activator, such as a heavy-metal ion or other
cofactor, to an allosteric site causes the enzyme’s active site to
CHANGE THE SHAPE which activates the enzyme
Substances that block enzyme activity are called_____
inhibitors
______ are shaped such that they fit into
an enzyme’s active site and thus prevent the normal substrate
from binding
Competitive inhibitors
Competitive inhibitors
Such inhibitors do not undergo
a chemical reaction to form products. Competitive inhibitors can
bind permanently or reversibly to an active site
reversible competition can be overcome by an increase in the_________, increasing the likelihood that active sites
will be filled with substrate instead of inhibitor
concentration
of substrate molecules
________ can fill
the active site of an enzyme required
for the conversion of PABA into folic
acid
Sulfanilamide
do not attach to the active site
but instead bind to an allosteric site on the enzyme
Noncompetitive inhibitors
Cells often control the action of enzymes through feedback
inhibition
feedback
inhibition
Electrons are transferred from an electron donor (a molecule that donates an electron) to an electron acceptor (a
molecule that accepts an electron). Such electron transfers
are called _______
oxidation-reduction reactions, or redox reactions
oxidation
involves______; reduction involves____
loss, gain
In contrast, a molecule may be oxidized in one of three
ways:
by losing a simple electron, by losing a hydrogen atom, or
by gaining an oxygen atom.
r. Three important electron carrier
molecules are _____, ______,_____These molecules are
derived from vitamins
nicotinamide adenine dinucleotide (NAD+),
nicotinamide adenine dinucleotide phosphate (NADP+),
and flavin adenine dinucleotide (FAD).
. This happens by a general process called _______, in which inorganic phosphate is added to a substrate
phosphorylation
Why is ATP well
suited to serve as the primary short-term energy carrier in
metabolic pathways?
First, it is multifunctional as a ribonucleotide for use in synthesizing RNA.
Second, it is highly water
soluble and can accumulate to high concentrations in cells
with no ill effects.
Third, it has two different levels of energy
which
involves the transfer of phosphate to ADP from another
phosphorylated organic compound
- Substrate-level phosphorylation
in which
energy from redox reactions of respiration (described
shortly) is used to attach inorganic phosphate to ADP
Oxidative phosphorylation
______ which
are chemicals that increase the likelihood of a reaction but are
not permanently changed in the process
catalysts,
in which light energy
is used to phosphorylate ADP with inorganic phosphate
- Photophosphorylation
Organic catalysts are
known as ______
enzymes.
______are inactive if they are not bound to one
or more of the nonprotein substances called _____
Apoenzymes
cofactors
