View
87
Download
0
Category
Preview:
Citation preview
BACKGROUND RESEARCH
I. WHAT ARE ENZYMES?
Human cells are subject to biochemical reactions where chemical bonds are
either broken of formed. These reactions are said endergonic if energy is a net
input of energy from an outside source is needed and exergonic if there is energy
released from the reaction, a part of this energy that is given off is heat. All these
reactions need activation energy to perform chemical reactions. They require
energy to force the electron shells of the atoms together despite their natural
electrical repulsion. These endergonic reactions that require an input of energy
would take decades to occur without any help. There are molecules called catalysts
that accelerate the speed of these reactions without being affected or altering their
structure permanently. The catalysts are useful because they reduce the activation
energy needed for a reaction to take place, but it is important to note that they do
not eliminate the need for an input of energy for endergonic reactions (making them
spontaneous).
By lowering the
activation energy, they simply
allow some molecules to reach
the ideal speed so the reaction
happens when the molecules
collide. Our bodies being no
different need our own
Figure 1: Catalysts lowering activation energy. (Audesirk, Byers, p103, 2014)
organic catalysts to speed up the different reactions that take place inside us. Our
cells have their own biological catalysts called enzymes. An enzyme is an efficient
biological molecule responsible for catalyzing biochemical reactions that take place
in the human body and in life in general. They are composed of polymers of amino
acids otherwise known as proteins and a small nonprotein molecule called a
coenzyme. These enzymes have very precise tertiary structures that determine
their function. Enzymes have three very specific characteristics: they are essential
for the cell to maintain homeostasis, the cell often regulates their activity and they
are very specific for a small number of reactants. This forces them only catalyze a
few number of reactions per enzyme, a large majority of the enzymes can only
catalyze one reaction.
II. HOW ENZYMES WORK
The biological molecules have very specific structures that give them their
function; all enzymes have a pocket named the active site. It is in the active site
where one or more substrates can enter. The tertiary or quaternary structure of the
enzyme is responsible for the very clearly defined shape of its active site. Only fixed
molecules have the privilege of entering the active site. The R- groups of the amino
acids that make up the proteins forming the active site have electrical charges that
have to complement those in the enzyme’s substrate in order for them to be
compatible. The process begins when the substrates have the ideal orientation
enter the active site, after which both the active site and substrates will assume new
shapes, which actively encourage the reaction
between the substrates. Temporary bonds
might be created between the amino acids
from the active site and the atoms that make
up the substrates. It is also possible for there to
be electrical interaction between the same
amino acids and the substrates, this may
change the chemical bonds in the substrates.
The shape of the substrates, the acuteness of
the substrates and the tampering of the chemical bonds that make up the substrates
are all factors in the way that an enzyme supports a biochemical reaction. The
enzyme will always return to its original shape before restarting the whole process
once more. The enzymes can catalyze millions of chemical reaction in a second.
III. HOW DO CELLS REGULATE ENZYMES
The rates of these chemical reactions depend on the number of enzymes and
substrates that are present in the reaction. To obtain the ideal rate that will be
beneficial for the organism, cells are needed to regulate enzyme synthesis. Cells
are very complex biological units capable of unparalleled functions. They have
methods to meet their ever-changing needs. When more of an enzyme is needed due
to the presence of its substrate, its production is accelerated. Some enzymes are
even synthesized to be inactive and activated when needed. Another method cells
Figure 2: The cycle of enzyme-substrate interactions. (Audesirk, Byers, p.104, 2014)
use to regulate enzymatic activity is through inhibition. Inhibition is useful since it
forces the cell not to use up all the available substrate and/or forcing it not to
produce more products than the cell can handle. There are two types of inhibition:
competitive inhibition where a molecule is in the active site refusing access to the
substrate and non-competitive inhibition where a molecule attaches on a different
site on the enzyme, changing the conformation of the active site so the substrate no
longer fits. The last way in which cells can regulate enzyme activity is by allosteric
regulation, which is done by allosteric enzymes. These enzymes have two
structural arrangements: an active and inactive one. Some molecules have the
capacity to attach to enzymes in other places than the active site; this site is called
the allosteric site. This causes a change in the shape of the enzyme. Allosteric
activators help the enzyme to stay in its active form; the presence of these
activators is directly proportions to the increase of enzyme activity. On the other
hand, allosteric inhibitors make the enzyme maintain its inactive form, thus
stopping enzyme activity. Feedback inhibition is another important form of
allosteric regulation. It is simply an enzyme that stops producing the product when
the cell has had enough of the product.
IV. WHAT IS CATALASE?
Oxygen is one of the most important and dangerous molecules for living things.
Despite this, we count on oxygen as our main source of energy. It is very reactive
thus sometimes creating danger if it reacts with the wrong molecules or electrons to
create hydrogen peroxide or dangerous superoxides (O2-). These molecules are
dangerous because they attack our genetic material (DNA). Cells, being the chemical
factories they are, create enzymes that inhibit the oxidation of other molecules like
Oxygen gas. One of these molecules is catalase; it is an enzyme that is found in the
microbodies of virtually all aerobic cells. Its function is to protect the cell from the
noxious effect of hydrogen peroxide by decomposing it into Oxygen and Water. The
chemistry behind the mechanism of the catalase catalysis has not been fully solved
yet but its overall reaction is:
2H2O2(aq) --> 2 H2O(l) + O2(g)
Catalase is imperative to life for aerobic living organisms because it is extremely
effective in removing dangerous hydrogen peroxide from our systems. It is
presumed that it functions at rates approaching 200,000 catalytic
events/second/subunit.
V. STRUCTURE OF CATALASE
Catalase like all enzymes have very complicated tertiary structures and in the
case of catalase a complicated quaternary structure. The structure of catalase is
characterized by four identical monomers. Each monomer contains one heme and
one NADP. A heme is a compound that contains an iron; it is precisely the cofactor
that makes up the nonprotein part of hemoglobin.
VI. ENVIRONMENTAL FACTORS THAT AFFECT ENZYMES
Recommended