2.5 & 8.1 Enzymes
TOPIC 2, 7 & 8 BIOCHEMISTRY
• Challenge: by changing one letter at a time, get
from ‘TREAD’ to ‘BLINK’. All intermediates must be
real English words.
Read & Consider Understandings
2.5.1-2.5.2 & 8.1.1-8.1.2
1 - ENZYMES
METABOLISM
Consists of linear sequences of enzyme-catalyzed
reactions that may be categorized into one of
two groups:
 Anabolic reactions –
 Catabolic reactions –
ENZYMES
Enzymes are biological catalysts made of protein.
 Enzymes are effective in very small amounts
 Remain unchanged at the end of a reaction
ACTIVATION ENERGY

All reactions require an initial input of energy to “get the
ball rolling.” In the process of reaction all molecules
momentarily exist in an unstable, high energy,
intermediate stage. Enzymes decrease the energy needed
to get started.
ACTIVE SITE
In a reaction catalyzed
by an enzyme the
starting substance is
called a substrate and
will be converted to the
product.
 Enzymes have
specifically formed
pockets that match the
enzyme to the
substrate, active site.

ENZYME SUBSTRATE SPECIFICITY

Enzymes only catalyze one type of reaction or
only a very small group of highly similar
reactions.
Lock and Key Hypothesis
INDUCED-FIT MODEL

Following the formation
of the enzyme-substrate
complex, there is a
temporary change in
shape for the enzyme –
induced fit.
LINEAR PATHWAY

Chemical changes within living
things occur with a number of
intermediate stages. Each stage
has its own enzymes.
 Linear
chain pathways: the product
of one reaction will be the substrate
of the next until the end product is
achieved.
CYCLIC PATHWAYS
The initial substrate enters the cycle
Enzyme (1) combines the regenerated 'intermediate
4' with the initial substrate to catalyses the
production of intermediate 1.
Enzyme (3) is specific to intermediate 2 and catalyses
it conversion to product and intermediate 3
COLLISIONS
Radom movement of enzyme and substrate within
aqueous solution brings enzyme and substrate together.
BIOINFORMATICS
Used to test 300,000
new chemicals that could
act in the fight against
malaria.
 19 chemicals were
identified as useful
enzyme inhibitors.
 15 chemicals were
identified that will “tag”
P. falciparum to locate
the protozoan.

• Do you denature proteins? When?
Read & Consider Understandings
2.5.3-2.5.5
2 – ALTERED ENZYMES
DENATURATION

Denaturation is a structural change in a protein
that results in the loss (usually permanent) of
its biological properties.
 Temperature
 pH
TEMPERATURE

X is the optimal temperature for enzyme
catalysis.
PH
The two enzyme shown in the image illustrate the
fact that different enzymes can have very
different optimal pHs.
e.g. Blue curve = pepsin (a)= pH3, Red curve =salivary amylase
(b)= pH 7.2
SUBSTRATE CONCENTRATION

As the substrate concentration is increased the
rate of reaction increases. There are more
collisions between the substrate and the enzyme.
ENZYMES IN INDUSTRY
ENZYME VS. CATALYST
The advantaged of using enzymes over chemical
catalysts include:
 They
are specific, typically catalyzing one particular
compound or one type of bond only.
 They are efficient, requiring only a small quantity of
the enzyme to catalyze the production of a huge
quantity of product.
 They are able to work at normal temperature and
pressure, and so require much less energy input.
LACTOSE FREE MILK
•Efficient conversion of lactose to
glucose and galactose.
•High % lactose conversion is
achieved.
•All these factors reduce cost
particularly on the
downstream processing and
purification.
• Define enzymes, substrate, and active site.
Read & Consider Understandings
8.1.3-8.1.4
3 – ENZYME INHIBITION
ENZYME INHIBITION

Inhibitors are substances that reduce or
completely stop the action of an enzyme.
Studies of inhibitors have increased our
understanding of:
 The
chemistry of the active sites of enzymes;
 The natural regulation of metabolism and which
pathways operate;
 The ways certain commercial pesticides and some
drugs work, namely by inhibiting specific enzymes
and preventing particular reactions.
COMPETITIVE INHIBITION:
The substrate and inhibitor are chemically very
similar in molecular shape.
 The inhibitor will bind to the active site, blocking
the substrate.

NON-COMPETITIVE INHIBITION:
The inhibitor can bind to another region of the
enzyme molecule.
 The bonding of the inhibitor with the enzyme
causes structural changes in the enzyme
molecule.

END-PRODUCT INHIBITION


Allosteric enzymes have
two sites, the active site
and an additional site
where another molecule
could lock in (non-competitive)
End-product inhibition: In
this situation the final
product acts as the
allosteric molecule of
inhibitor for the enzyme
of the first step (most are
allosteric/non-competitive)
WORKS CITED
"Frequently Asked Questions." FAQ. Mosquito.Org,
n.d. Web. 01 July 2015.
 Haegens, Noel. "Bakery Technology - Enzymes."
Class of Foods. N.p., n.d. Web. 29 June 2015.
 Lee, Calvin. "Lemon Water and Vitamin C."
Continuing Medical Education for Calvin Lee, MD,
Modesto Surgeon. N.p., n.d. Web. 29 June
2015.Valaparla, Sneha. "What Are Enzymes?"
Read & Digest. N.p., n.d. Web. 29 June 2015.
 Walpole, Brenda. Biology for the IB Diploma. 2nd
ed. Cambridge, UK: Cambridge UP, 2014. Print.
