Biomolecules 6 Flashcards
HOW DOES TEMP AND PH AFFECT ENZYME ACTIVITY
Enzymes generally function in a narrow range of temperature and pH
(Figure 9.7). Each enzyme shows its highest activity at a particular
temperature and pH called the optimum temperature and optimum pH.
Activity declines both below and above the optimum value.
what happens to enzymes at high or low temps
Low
temperature preserves the enzyme in a temporarily inactive state whereas
high temperature destroys enzymatic activity because proteins are
denatured by heat.
how is enzyme affected by concentration of substrate.
With the increase in substrate concentration, the velocity of the enzymatic
reaction rises at first. The reaction ultimately reaches a maximum velocity
(Vmax) which is not exceeded by any further rise in concentration of the
substrate. This is because the enzyme molecules are fewer than the
substrate molecules and after saturation of these molecules, there are no
free enzyme molecules to bind with the additional substrate molecules
The activity of an enzyme is also sensitive to the presence of specific
chemicals that bind to the enzyme.
When 2 substrate molecules of same shape, size and and chemical structure , one of the substrate molecule will blocks the active site of the enzyme hence prveentng catalysis from happening. This is enzyme inhibitor,
what is the competitive inhibition
When the inhibitor closely resembles the substrate in its molecular
structure and inhibits the activity of the enzyme, it is known as
competitive inhibitor. Due to its close structural similarity with the
substrate, the inhibitor competes with the substrate for the substrate-
binding site of the enzyme. Consequently, the substrate cannot bind and
as a result, the enzyme action declines, e.g., inhibition of succinic
dehydrogenase by malonate which closely resembles the substrate
succinate in structure. Such competitive inhibitors are often used in the
control of bacterial pathogens.
types of enzymes
Isomerases: Includes all enzymes catalysing inter-conversion of optical,
geometric or positional isomers.
Ligases: Enzymes catalysing the linking together of 2 compounds, e.g.,
enzymes which catalyse joining of C-O, C-S, C-N, P-O etc. bonds.
oxidoreductase, dehydrogenase : alcohol dehydrogenase
transferase: peptidye transferase
hydrolase: proteases
lyases: histidine ammonia lyase
isomerases: alanine racemase
ligases: dna ligase
what are cofactors
Enzymes are composed of one or several polypeptide chains. However,
there are a number of cases in which non-protein constituents called co-factors are bound to the the enzyme to make the enzyme catalytically active.
what is apoenzyme
enzyme with just protein consitituent and without co factor
what are prosthetic groups
Prosthetic groups are organic compounds and are distinguished from
other cofactors in that they are tightly bound to the apoenzyme. They are permanently present in the active site. They facikitate catalysis of molecules. For example, in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group and it is a part of the active site of the enzyme.
what are co enzymes
Co-enzymes are also organic compounds but their association with
the apoenzyme is only transient, usually occurring during the course of
catalysis. It prepares the site for catalysis. Furthermore, co-enzymes serve as co-factors in a number of
different enzyme catalyzed reactions. The essential chemical components
of many coenzymes are vitamins, e.g., coenzyme nicotinamide adenine
dinucleotide (NAD) and NADP contain the vitamin niacin.
what are metal ions
A number of enzymes require metal ions for their activity which form
coordination bonds with side chains at the active site and at the same
time form one or more cordination bonds with the substrate, e.g., zinc is
a cofactor for the proteolytic enzyme carboxypeptidase.
what will happen to enzymes without cofactor
Catalytic activity is lost when the co-factor is removed from the enzyme
which testifies that they play a crucial role in the catalytic activity of the
enzyme.
