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Chapter 3: ​Enzymes 
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Enzyme: An enzyme is a biological catalyst that accelerates
metabolic reactions
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The substrate is held in place by the temp
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However,
the enzyme molecules are more flexible and can change shape slightly as the substrate
enters the enzyme
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​( induced fit hypothesis)

Enzymes reduce activation energy:

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Enzymes speed up the rate of a reaction by lowering the activation energy of a
reaction
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Given some extra energy , [​ACTIVATION ENERGY​]
Mammals optimum temp
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By measuring the amount of product accumulated over a period of time
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By measuring the ​rate at which the reactants disappear from the reaction
mixture​, the effect of the enzyme on the rate of reaction can be determined
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measuring the rate at which starch disappears when the enzyme amylase is added
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At any moment, almost every enzyme molecule has a substrate molecule in its
activation site
The rate at which the reaction occurs depends only on how many enzyme molecules
there are and the ​speed at which the enzymes can convert the substrate into a
product, release it and bind to another substrate molecule

Factors that affect enzyme concentration:
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As the concentration of enzymes is increased, there are more available active sites
for substrates to fit into
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The​ limiting factor is the
enzyme concentration​
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At this point,the ​limiting factor is the substrate concentration
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The effect of substrate concentration:
- As the concentration of the substrates increases, there are greater chances of collision with
enzyme
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The​ limiting factor is the substrate concentration​
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At this point, the ​limiting factor is the
enzyme concentration
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and enzyme activity:
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The protein nature of the enzymes makes them extremely ​sensitive to thermal

changes​
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As you have seen, each enzyme has a certain
temperature at which it is more active
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The enzyme ​activity gradually lowers as the temperature rises ​more than the
optimal temperature until it reaches a certain temperature at which the enzyme
activity ​stops completely due to the change of its natural composition
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The enzyme ​activity stops completely at 0C°​, but if
the​ temperature rises again, then the enzyme gets reactivated once more
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It also determines whether the
liquid is acidic, basic or neutral
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​Liquids with
pH 7 are neutral and equal the acidity of
pure water at 25 C°​
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Enzymes are protein substances that ​contain acidic carboxylic groups
(COOH–) and basic amino groups (NH2​)
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Each enzyme has a pH value that it works at with maximum efficiency called
the optimal pH
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For example, pepsin works at a low
pH, i
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e, it is basic
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4

Competitive, reversible inhibition:

Inhibitor: a
​ substance which slows down or prevents a particular chemical reaction or other
process or which reduces the activity of a particular reactant, catalyst, or enzyme
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The inhibitor competes for the same
active site as the substrate molecule
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The inhibitor is ‘stuck’ on the enzyme and ​prevents
any substrate molecules from reacting with the enzyme​
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Therefore, the​ amount of enzyme inhibition depends upon the inhibitor
concentration, substrate concentration, and the relative affinities of the inhibitor and
substrate for the active site
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​ The noncompetitive inhibitor ​reacts either remotely from or very
close to the active site​
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​Noncompetitive inhibitors are usually
reversible but are not influenced by concentrations of the substrate as is the
case for a reversible competitive inhibitor
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As the
enzyme converts substrate to product, it is slowed down because the end product
binds to another part of the enzyme and prevents more substrate binding
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Maximum rate velocity:
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The reaction rate is measured at different substrate concentrations while keeping the
enzyme concentration constant
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Michaelis-menten constant :
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​ ubstrate concentration at which an enzyme works at half its maximum rate (1/2 Vmax)​
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​Inverse measure​; a ​higher Km means that more substrates need
to be present for enzymes to be saturated​ (binded with a substrate), which means l​ ow affinity​
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So the ​lower the Km, the faster the reaction will proceed to its
maximum rate​
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However, since 1/infinity = 0, which can be plotted, Vmax can be found by plotting 1/[S]
(inverse substrate concentration) on the x-axis and 1/velocity (inverse rate)
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To find Vmax, you
can calculate it like this (let's pretend that 1/Vmax is ​20​ in this example):
1/Vmax = 20

1= 20 x Vmax
Vmax = 1/20
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Vmax = ​0
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To find the Km, you
can calculate it like this (let's pretend -1/Km is ​-10​ in this example):
-1/Km = -10

-1= -10 x Km
Km = -1/-10
Km = 1/10
Km= ​0
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Little droplets of this mixture are then added to a solution of calcium chloride
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The jelly bead contains the enzyme
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More tolerant to PH changes as the enzyme molecules are held firmly in shape by
the alginate beads, thus don’t denature easily
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Active site may be distorted by immobilizing
Substrate passes through matrix when immobilized
Some product is retained within matrix



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