Enzymes Explained: Catalase, Activation, Inhibition, and Lab Measurement

Name: Enzymes
Uploaded: 2026-01-26T03:45:31.874820+00:00
Channel: Bozeman Science
Description: Summary and key takeaways on Enzymes Explained: Catalase, Activation, Inhibition, and Lab Measurement, covering What Are Enzymes? Enzymes are biological

Bozeman Science

Jan 26, 2026

•

3 min read

YouTube video ID: ok9esggzN18

Source: YouTube video by Bozeman Science — Watch original video

PDF

What Are Enzymes?

Enzymes are biological catalysts that speed up chemical reactions without being consumed.
They are essential for every metabolic pathway (photosynthesis, glycolysis, citric‑acid cycle, etc.).

Catalase and Hydrogen Peroxide

Catalase is a ubiquitous enzyme found in almost all eukaryotic cells.
Its specific reaction: 2 H₂O₂ → 2 H₂O + O₂ (balanced equation).
The enzyme can decompose about 40 million hydrogen‑peroxide molecules each second, turning a potentially toxic compound into harmless water and oxygen.

Enzyme Structure and the Active Site

Enzymes are large proteins with a specially shaped pocket called the active site.
The substrate (e.g., H₂O₂ for catalase) fits into this pocket like a key into a lock.
Binding lowers the activation energy, allowing the reaction to proceed rapidly.

Turning Enzymes On: Activation

Gene regulation: the cell may not produce the enzyme until it is needed.
Cofactors (inorganic) – small non‑carbon molecules or ions (e.g., heme‑iron) that must bind to the enzyme.
Coenzymes (organic) – vitamin‑derived molecules such as thiamine (vitamin B1) that assist enzyme function.
Without the required cofactors or coenzymes, the enzyme becomes inactive.

Turning Enzymes Off: Inhibition

Competitive inhibition – a molecule resembling the substrate occupies the active site, preventing the real substrate from binding.
Allosteric (non‑competitive) inhibition – an inhibitor binds to a separate site, causing a conformational change that either blocks the active site or reshapes it so the substrate no longer fits.
These mechanisms allow cells to fine‑tune metabolic flux and maintain homeostasis.

Measuring Enzyme Activity in the Lab (Catalase Experiment)

Setup: Fill a beaker with hydrogen peroxide, place filter‑paper disks soaked in varying concentrations of catalase.
Independent variable: Enzyme concentration.
Dependent variable: Time for disks to rise (or number of floats per second), reflecting oxygen production.
Observations: Reaction rate increases with enzyme concentration until it plateaus.
Alternative measurements: Track product formation (oxygen) or substrate consumption; also vary temperature, pH, etc.

Factors Influencing Enzyme Rate

Temperature: Rate rises with temperature until the enzyme denatures; most human enzymes peak near 37 °C.
pH: Each enzyme has an optimal pH; deviation reduces activity.
Substrate concentration: Higher concentrations increase rate up to a saturation point.
Presence of inhibitors or activators: As described above.

Why Enzymes Matter

They protect cells from harmful by‑products (e.g., hydrogen peroxide).
They enable metabolic pathways to occur at biologically relevant speeds.
Understanding their regulation is crucial for fields ranging from medicine to biotechnology.

Bottom Line

Enzymes like catalase illustrate how proteins accelerate reactions, how they are switched on by cofactors/coenzymes, and how they are switched off by competitive or allosteric inhibitors. Laboratory experiments measuring reaction rates reinforce these concepts and highlight the delicate balance cells maintain to stay alive.

Enzymes are the molecular engines of life—catalyzing essential reactions, being tightly regulated by activation and inhibition, and measurable through simple lab assays—so mastering their behavior is key to understanding biology and applying it in health, research, and industry.

Frequently Asked Questions

Who is Bozeman Science on YouTube?

Bozeman Science is a YouTube channel that publishes videos on a range of topics. Browse more summaries from this channel below.

Does this page include the full transcript of the video?

Yes, the full transcript for this video is available on this page. Click 'Show transcript' in the sidebar to read it.

What Are Enzymes?

- Enzymes are biological catalysts that speed up chemical reactions without being consumed. - They are essential for every metabolic pathway (photosynthesis, glycolysis, citric‑acid cycle, etc.).

Why Enzymes Matter

- They protect cells from harmful by‑products (e.g., hydrogen peroxide). - They enable metabolic pathways to occur at biologically relevant speeds. - Understanding their regulation is crucial for fields ranging from medicine to biotechnology.

Helpful resources related to this video

If you want to practice or explore the concepts discussed in the video, these commonly used tools may help.

Catalase Enzyme Assay Kit Recommended

Provides a hands‑on way to measure catalase activity in classroom or home labs, perfect for students learning enzyme kinetics now

Amazon →

Biochemistry Lab Manual For High School

Guides students through enzyme experiments and data analysis, supporting current AP Biology curricula

Amazon →

Biology Textbook Ap Biology 2024 Edition

Covers enzymes, catalase, and metabolic regulation in depth, essential for exam preparation today

Amazon →

Links may be affiliate links. We only include resources that are genuinely relevant to the topic.

Summarize another video

Full Transcript YouTube

Hi. It's Mr. Andersen and welcome
to Biology Essentials video 48. This podcast
is on enzymes. Enzymes remember are chemicals
that aren't consumed in a reaction but can
speed up a reaction. One of the major ones
we'll talk about this year in AP bio is called
catalase. Catalase is an enzyme that's found
in almost all living cells, especially eukaryotic
cells. But what it does is it breaks down
hydrogen peroxide. Hydrogen peroxide you probably
knew growing up, you'd put it on a cut maybe
and it would bubble or you could use it to
bleach your hair. That's pretty dilute hydrogen
peroxide. Actually concentrated hydrogen peroxide,
this is somebody who's touch 30% hydrogen
peroxide, it damages and kills cells. And
so hydrogen peroxide is just produced naturally
in chemical reactions but your cell has to
get rid of it before it builds up an appreciable
amounts. And it uses catalase to do that.
And so if we were to look at the equation,
so we've got hydrogen peroxide or H2O2 is
going to breakdown into two things. One is
water and the other one is O2, oxygen. And
so this is not a balanced reaction. So if
I put a 2 there and I put a 2 here, so hydrogens
I've got 4, 4. Oxygens I've got 4, so perfect.
So this is a balanced equation. So you've
got 2 hydrogen peroxide breaking down into
2 water molecules and 1 oxygen molecule. But
it does that using an enzyme. And so in other
words, hydrogen peroxide, let me get my arrows
to fit in here is going to feed into catalase
and it's going to break that down into these
2 products, water and oxygen. And it does
that at an incredible rate. I was reading
that 40 million hydrogen peroxides will go
into a catalase and be broken down into water
and oxygen, 40 million every second. And so
it's incredibly fast at breaking down that
hydrogen peroxide into something that it can
use. And so how does it do that? Well that's
what I'm going to talk about. And so basically
an enzyme, let me try and draw an enzyme,
so if an enzyme looks like this. It's a giant
protein, so if we say it looks like that,
it's going to have an area inside it called
the active site. And so the active site, let's
see how I could do this, good, so the active
site is basically going to be a part on the
enzyme where there's a hole in it. So this
is this giant protein, it's got an active
site, and the substrate is going to fit into
to it. And so going back to how do enzymes
work, well the active site is going to be
an area within the enzyme, so this would be
the enzyme here, and basically the substrate
fits into it. And so what was the example
we were just talking about? The enzyme was
catalase. What was the substrate? Substrate
is H2O2 or hydrogen peroxide. So that's how
enzymes work. It basically tugs on the substrate
and breaks it down. It's very important in
chemical reactions. And sometimes we want
to turn on enzymes and sometimes we want to
turn off enzymes. And so in every step of
photosynthesis, in every step of cellular
respiration, glycolysis, citric acid cycle,
all of those chemical reactions remember have
to have an enzyme that's associated with them
that can speed up that reaction. And so it's
really important that we sometimes activate
or turn on those enzymes. It's also just as
important that sometimes we turn them off.
And so there are two types of inhibition.
Inhibition can either be competitive, that's
where a chemical is blocking the active site
or allosteric when we're actually changing
the shape or giving it another shape. Chemical
reactions, another important thing that we
want to measure with them is the rate of a
chemical reaction. We can do that by either
measuring the reactants or the products. So
let me stop talking about what I'm going to
talk about and actually talk about it. And
so here is our enzyme. Our enzyme that we
talked about is called catalase. So catalase
is going to be a protein. It has a specific
shape and so if we go down here to the enzyme,
this would be the enzyme right here, it's
going to have an active site. An active site
is the area when the substrate can fit in.
And so the substrate is going to be this green
thing in this picture. It'll fit right in
here. It fits almost like a key fits a lock.
And so it's going to be a perfect fit between
the two. Every chemical reaction is going
to have a different enzyme that breaks that.
And so the important part is right here. So
now once we have the enzyme inside the active
site, there's going to be a chemical tug.
In other words it's going to pull on that
chemical. It's going to lower it's activation
energy so it can actually break apart into
its products. And so if this is our H2O2 right
here, there's going to be a tug on those chemicals.
Sometimes it will actually change the pH,
sometimes it'll put a mechanical tug on it,
but basically what it's going to do is it's
going to make it easier for those chemicals
to spontaneously break apart. Now hydrogen
peroxide by itself, H2O2, if you leave it
in a bottle for millions and millions of years,
if you come back it's spontaneously going
to break down into water and oxygen but that's
going to take years and years and years to
do that. And with an enzyme it can happen
in seconds. It's like I said, 40 million hydrogen
peroxides can feed through this, create all
of this water and can do that really really
quickly. And so enzymes are ready to go and
so we want to control which enzymes are firing
at which time and which ones are being released.
And so there's basically a turn on and then
there's a turn off. And so how do we turn
enzymes on? Well there's two ways that we
can do that. Number 1, we could just not produce
them until they're needed. And so lots of
times we won't produce a protein until it's
required and so we do what's called gene regulation,
where we don't even code those proteins until
we're ready to use them. But also we can activate
them. And so activation is adding something
to an enzyme to actually make it work. And
so you don't have to remember the names of
these, but this is succinate dehydrogenase
and it's a cool enzyme that's used both in
the citric acid cycle and the electron transport
chain. So this is going to be on, it's going
to be embedded in that inner mitochondrial
membrane and so it's going to run two specific
reactions. So it's going to convert certain
reactants into products. But if you just build
succinate dehydrogenase by itself, it doesn't
do anything. It's not going to work. It has
to be activated. And so there are two type
of activators. Those that are called cofactors
and those that are called coenzymes. And so
if you were to look in here there's going
to be things that have to be added to that
enzyme before it can actually function. And
so the two types are cofactors, coenzymes.
I came up with some that you might know. Cofactors
are basically going to be small chemicals
that are inorganic. What that means is they're
not made up of carbon. And so heme is an example
of a co-factor. Heme is also what's found
in blood. It has an iron atom in the middle
and so that's why we call it hemoglobin. And
so what it does is it's creating that hemoglobin
protein and activating it. And so cofactors
are going to be inorganic. And so in other
words they are not containing carbon. And
then we're going to have coenzymes and those
are going to be organic. And so they're helping
that enzyme to work. An example of a coenzyme
would be thiamine. And so thiamine, another
name for that is vitamin B1. And so vitamins
are a required organics that we need inside
our diet and they help enzymes function. And
if you don't get enough vitamin B1 in your
body then you die as a result of the neurological
issue. And same thing with cofactors. So these
are required for life. But basically what
happens is once we have the cofactors and
the coenzymes now we have an enzyme that can
actually function. And now it can do what
it's meant to do. But if we remove those cofactors,
if we remove those inorganics and those organics
then it will actually come to a stop or it
won't function anymore. So that's activation.
That's how we turn enzymes on. But sometimes
we want to turn them off. And so let me kind
of get you situated. We've got our enzyme
here, we've got our substrate that's going
to fit here so if you think about it as an
engineer for a second, how could we stop that
substrate, again 40 million of them coming
through the active site in catalase? How do
we slow it down? Well there are two types
of inhibition. First on is called competitive
inhibition. Competitive inhibition is when
you use an inhibitor, which is another chemical
and you just get that to bond into the active
site. So if you have that bonding in the active
site then that substrate can't fit in and
so we're going to stop the reaction. So if
we make an inhibitor that bonds to the active
site we call that competitive inhibition because
it's competing for the space with the substrate.
Now we can also do that non-competitive inhibition
and we usually call that allosteric. Allosteric
reaction works the same way. Here we are.
We've got our enzyme. Here's our substrate.
It's trying to fit into the active site. We
also have what's called an allosteric site,
which is going to be another site on the enzyme
itself. And so one type of allosteric or changing
the shape inhibition that we can do is we
can have an inhibitor now that's just going
to bond to that allosteric site. When it bonds
to the allosteric site it's covering up the
active site and so now there's going to be
no way that that substrate can fit in. But
since it's not actually bonding to the active
site we call that allosteric. Allosteric means
different shape or different shape of the
enzyme. So that's a type of non-competitive
inhibition. Or we can do it this way. So this
would be another type of allosteric inhibition.
We can have an inhibitor bond to an allosteric
site, but if you look at the active site in
this picture, here's the active site, once
this inhibitor bonds with the allosteric site
it now changes the shape of the active site.
Once you've changed the shape of the active
site, remember the substrate only fits if
it's like a lock and a key, now it's not going
to fit anymore. And so this is another type
of allosteric inhibition. And so we use feedback
loops and we use inhibitors and cofactors
and coenzymes to regulate what enzymes are
going off at what time. Now when we do the
enzyme lab we are using catalase. And so when
we do it in class we're using catalase. It's
an enzyme we use, an enzyme that's found in
yeast. We then fill up a beaker with hydrogen
peroxide. We put our little disks of filter
paper or chads at the bottom. We dip them
in varying concentrations of the enzyme and
we then see how long it takes for them to
float up. And so what we're varying or the
independent variable is going to be, the independent
variable is going to be the amount of the
enzyme. And the dependent variable is going
to be how long it takes for them to float
or the number of floats per second. And so
you can imagine, let me get a better color,
if I increase the concentration of the enzyme,
we're going to increase the rate of the reaction.
But eventually you can see how it starts to
level off here. Eventually if you have enough
of those, let me change to a different color,
eventually it's going to level off. And so
when we're measuring reaction rate we could
measure two things. We could measure the products
that are created or we could measure the amount
of reactants that are being consumed. In the
enzyme lab we're measuring the amount of oxygen
so we're measuring the amount of products
that are created. But there's other things
we could measure in this. Not only the concentration
of the enzyme, we could measure the temperature,
we could measure the pH. We could measure
a lot of different things and remember organisms,
if we were to measure temperature for example
the reaction rate's going to increase and
eventually the enzyme is going to denature
and so there's going to be an optimum set
point. And since you have an internal temperature
of 37 degrees celsius, most of the enzymes
inside your body are prime to work at that
specific rate. And so that's enzymes and they
are used to maintain that internal balance
and I hope that's helpful.