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