Enzymes - Catalysts

Summary

This educational video script delves into enzymes, highlighting their role as protein-based catalysts that accelerate chemical reactions by reducing activation energy. It introduces the concepts of the lock and key model and the induced fit model, explaining how enzymes interact with substrates. The script also covers factors affecting enzyme activity, such as pH, temperature, substrate concentration, and the presence of inhibitors and activators. Additionally, it touches on enzymes like protease, lipase, and kinase, emphasizing their specific functions in biochemical processes.

Takeaways

• 🔬 Enzymes are primarily protein-based catalysts that accelerate chemical reactions by lowering activation energy.
• 📉 Enzymes reduce the activation energy needed for reactions without changing the energy of reactants or products.
• 💡 Ribozymes are RNA-based enzymes, proving that not all enzymes are proteins.
• 🔑 Enzymes have a specific active site for substrates, and there are two models: the lock-and-key model and the induced fit model.
• 🔄 Enzymes form an enzyme-substrate complex during reactions and are not consumed, allowing them to be reused.
• ⚖️ Factors affecting enzyme activity include pH, temperature, substrate concentration, and the presence of inhibitors or activators.
• 🔥 Enzymes have an optimal pH and temperature for activity. Deviations can reduce effectiveness, with high temperatures leading to denaturation.
• 🛑 Inhibitors can be competitive, binding at the active site, or non-competitive, altering enzyme shape by binding elsewhere.
• ⚙️ Activators enhance enzyme activity, and some enzymes require cofactors (metal ions) or coenzymes (organic molecules) to function.
• 🧪 Enzymes have specific functions, such as protease for proteins, lipase for fats, and kinase for phosphate group transfer.

Q & A

What are enzymes and their primary function?

Enzymes are protein-based catalysts that speed up chemical reactions by lowering the activation energy required for the reaction.

How do enzymes lower the activation energy of a reaction?

Enzymes lower the activation energy by providing an alternative pathway for the reaction, where the energy needed for the transition state is reduced, making the reaction occur faster.

What is the difference between catalyzed and uncatalyzed reactions in an energy diagram?

In an uncatalyzed reaction, the energy required for the transition state (activation energy) is higher. In a catalyzed reaction, the transition state energy is lower, making the activation energy smaller and speeding up the reaction.

What are ribozymes and how do they differ from most enzymes?

Ribozymes are RNA-based catalysts, unlike most enzymes, which are protein-based. Ribozymes also facilitate chemical reactions, similar to protein enzymes.

How can you identify an enzyme from its name?

Enzymes usually have the suffix '-ase.' For example, sucrase is an enzyme that breaks down sucrose into glucose and fructose.

What is the lock-and-key model of enzyme action?

The lock-and-key model describes how the substrate fits exactly into the enzyme’s active site, just like a key fits into a lock, triggering the reaction.

How does the induced fit model differ from the lock-and-key model?

In the induced fit model, the enzyme slightly changes its shape as the substrate enters the active site, making the enzyme-substrate interaction more complementary.

What factors affect enzyme activity?

Enzyme activity is affected by factors such as pH, temperature, substrate concentration, inhibitors, and activators. Each enzyme has optimal conditions where it works best.

What is the difference between competitive and non-competitive inhibitors?

Competitive inhibitors bind to the enzyme’s active site, preventing the substrate from binding. Non-competitive inhibitors bind to an allosteric site, changing the enzyme’s shape and reducing its ability to bind to the substrate.

What are cofactors and coenzymes, and why are they important?

Cofactors are inorganic ions (e.g., zinc), while coenzymes are organic molecules (e.g., vitamins). Both are required by some enzymes to function properly and assist in catalyzing reactions.

Outlines

00:00

🔬 Introduction to Enzymes and Their Role in Chemical Reactions

The video begins by explaining enzymes as protein-based catalysts that accelerate chemical reactions by reducing activation energy. Using an energy diagram, it contrasts catalyzed and uncatalyzed reactions, highlighting how enzymes lower the activation energy. The video also introduces RNA-based catalysts called ribozymes and explains how enzyme names often end with 'ase,' such as sucrase, which breaks down sucrose into glucose and fructose. Enzymes possess a unique three-dimensional active site designed to bind with specific substrates, such as sucrose in this case.

05:00

🧩 Lock and Key vs. Induced Fit Models of Enzyme Function

This section explains the two primary models for enzyme-substrate interactions. The 'lock and key' model depicts a perfect fit between the enzyme and substrate, while the 'induced fit' model describes a scenario where the enzyme slightly alters its shape to bind more effectively to the substrate. The video uses sucrase and sucrose as examples to illustrate these interactions, highlighting how the enzyme returns to its original form after catalyzing the reaction.

10:10

⚡ Enzyme Activity and Reusability in Reactions

This part discusses how enzymes are not consumed in reactions, allowing them to be reused. It describes the formation of an enzyme-substrate complex (ES), which transitions to the enzyme (E) and products (P). The enzyme starts and ends the reaction unchanged, enabling continuous catalysis of similar reactions. The key takeaway is that enzymes increase reaction rates without being depleted.

15:13

🌡️ Factors Influencing Enzyme Activity: pH and Temperature

This segment explores two factors that affect enzyme activity: pH and temperature. Enzymes typically have an optimal pH range (6-8), with exceptions like pepsin, which operates best in acidic environments (pH 2-3). Similarly, enzymes have optimal temperature ranges, and extreme temperatures can denature them, reducing their function. Graphs illustrate how both pH and temperature influence the rate of enzyme activity.

📈 Enzyme Concentration and Saturation

The video explains how enzyme and substrate concentrations affect reaction rates. Initially, increasing the concentration boosts the reaction rate, but this effect diminishes once saturation is reached, where additional substrate or enzyme has little impact. A graph illustrates this relationship, emphasizing that enzymes have a maximum efficiency limit.

⛔ Inhibitors and Activators of Enzyme Activity

This section introduces competitive and non-competitive inhibitors. Competitive inhibitors bind to the enzyme's active site, blocking the substrate, while non-competitive inhibitors attach to an allosteric site, altering the enzyme's shape and preventing substrate binding. In contrast, activators enhance enzyme activity by facilitating substrate binding. The video emphasizes how these molecules regulate enzyme functionality.

🧪 Cofactors, Coenzymes, and Their Role in Enzyme Function

This part covers cofactors and coenzymes, which are essential for some enzymes to function. Cofactors are typically inorganic ions (e.g., zinc), while coenzymes are organic molecules (e.g., vitamins). These components assist enzymes in catalyzing complex reactions, further illustrating the diverse factors involved in enzyme activity.

🔧 Types of Enzymes and Their Functions

The video lists various enzymes, each specializing in different functions. Examples include protease (breaks down proteins), lipase (digests fats), isomerase (rearranges molecules), transferase (transfers functional groups), kinase (transfers phosphate groups), and dehydrogenase (removes hydrogen atoms). The video also explains amylase (breaks down starch) and oxidoreductase (catalyzes electron transfer in redox reactions). These enzymes demonstrate the diversity of biological processes they support.

🌊 Hydrolase and Redox Reactions

In the final segment, hydrolase is introduced as an enzyme that catalyzes hydrolysis, breaking large molecules into smaller ones using water. The video also revisits oxidoreductase, further explaining its role in facilitating oxidation-reduction (redox) reactions, crucial for electron transfer between molecules. These enzyme types are fundamental in various biochemical processes.

Keywords

💡Enzyme

Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy required for the reaction. In the video, enzymes are explained as mostly protein-based, though some, like ribozymes, are made of RNA. The main function of enzymes is demonstrated with examples like sucrase breaking down sucrose into glucose and fructose.

💡Activation Energy

Activation energy is the energy required to start a chemical reaction. Enzymes work by lowering this activation energy, making reactions occur more easily. In the video, an energy diagram shows how the activation energy is lower in a catalyzed reaction compared to an uncatalyzed one.

💡Active Site

The active site is the specific region of an enzyme where the substrate binds, and the reaction takes place. It has a unique three-dimensional shape that is complementary to the substrate. The video explains the importance of this shape in the lock and key and induced fit models of enzyme activity.

💡Substrate

A substrate is the molecule upon which an enzyme acts. In the example provided in the video, sucrose is the substrate that binds to the enzyme sucrase, which then catalyzes its breakdown into glucose and fructose. The interaction between the enzyme and substrate forms the enzyme-substrate complex.

💡Lock and Key Model

The lock and key model is a theory that describes how enzymes and substrates interact. It suggests that the substrate fits exactly into the active site of the enzyme, like a key fitting into a lock. The video contrasts this model with the induced fit model, where the enzyme changes shape to better fit the substrate.

💡Induced Fit Model

The induced fit model is an updated version of the lock and key model. It states that when a substrate enters the active site of an enzyme, the enzyme slightly changes shape to make the fit more precise. This model is discussed in the video to show how enzyme-substrate interactions can adapt for better efficiency.

💡Competitive Inhibitor

A competitive inhibitor is a molecule that competes with the substrate for the active site of an enzyme. When a competitive inhibitor binds to the active site, it blocks the substrate, preventing the enzyme from catalyzing the reaction. The video demonstrates this concept with a diagram showing the inhibitor and substrate vying for the same site.

💡Non-Competitive Inhibitor

A non-competitive inhibitor binds to a different site on the enzyme, known as the allosteric site, causing the enzyme to change shape. This change prevents the substrate from binding to the active site, thus inhibiting enzyme activity. The video uses this concept to explain how enzymes can be regulated without competing for the same site.

💡Optimal pH

Optimal pH refers to the specific pH level at which an enzyme functions most efficiently. Most enzymes in the human body have an optimal pH between 6 and 8. The video uses the example of pepsin, an enzyme in the stomach, which works best at a pH of 2-3 due to the acidic environment.

💡Cofactors and Coenzymes

Cofactors are inorganic ions, such as zinc, that assist enzyme activity, while coenzymes are organic molecules like vitamins. These molecules are necessary for some enzymes to function properly. The video briefly mentions their role in ensuring that enzymes can catalyze reactions efficiently.

Highlights

Enzymes are protein-based catalysts that speed up chemical reactions by lowering activation energy.

Activation energy is reduced when a catalyst is present, resulting in faster reactions.

Some enzymes are not made of proteins, such as RNA catalysts known as ribozymes.

Enzymes typically have the suffix 'ase,' like sucrase, which breaks down sucrose into glucose and fructose.

The active site of an enzyme has a unique three-dimensional shape, specific to the substrate it binds with.

Lock and Key Model: The substrate fits exactly into the enzyme’s active site, similar to a key fitting into a lock.

Induced Fit Model: The enzyme changes its shape slightly to fit even better with the substrate, enhancing its function.

Enzymes are not consumed in the reaction, as they appear unchanged at the end and can be reused for subsequent reactions.

Enzyme activity is affected by factors such as pH, temperature, substrate concentration, and inhibitors.

Most enzymes have an optimal pH between 6 and 8, but some, like pepsin, work best at a pH between 2 and 3.

Enzymes can denature at high temperatures, losing their shape and, consequently, their ability to function.

Competitive inhibitors bind to the enzyme’s active site, blocking the substrate from binding.

Non-competitive inhibitors bind to an allosteric site, changing the enzyme’s shape, making it nonfunctional for the substrate.

Enzymes may require cofactors (e.g., metal ions) or coenzymes (e.g., vitamins) for optimal activity.

Different enzymes specialize in specific functions, such as proteases breaking down proteins, and lipases breaking down fats.

Transcripts

in this video we're going to talk about

enzymes

so what are enzymes

enzymes at least most of them are

protein-based catalysts that speed up

chemical reactions

and the way they speed up chemical

reactions is by lowering the activation

energy

so let's draw an energy diagram

we have energy on the y-axis the

reaction coordinate on the x-axis

in blue this would be the uncatalyzed

reaction

so this is the energy of the reactants

the products

and the difference between the energy of

the transition state and the reactants

is the activation energy now in red i'm

going to show the energy diagram with

the use of a catalyst

so the energy of the reactants and

products will be the same

but notice that the energy of the

transition state is a lot less

so as you can see with the catalyzed

reaction in red the activation energy

has been decreased and that's how

enzymes speed up chemical reactions

now most enzymes are protein-based

catalysts but there are some enzymes

that are not made up of proteins

and these are rna catalysts known as

ribozymes

now let's get rid of this picture

it's very easy to identify an enzyme if

you're given its name

enzymes

they have the suffix ace

for instance sucrase

is an enzyme

that breaks down sucrose

into

fructose

and glucose

so here's the overall reaction this is

sucrose

and then with the enzyme sucrase

this will speed up the chemical

breakdown of sucrose into

glucose

and fructose

now enzymes have an active site with a

unique three-dimensional shape that is

specific

for the substrate that it binds with

so let's use this reaction as an example

so this will be

the enzyme

and this is going to be the substrate

which is sucrose sucrose is a

disaccharide

it's made up of

two

sugar units glucose and fructose

so i'm going to write e for enzyme s for

substrate as you can see

the active site of the enzyme which is

right here

it has a unique shape

that is complementary to the substrate

now there's two types of models that you

need to be familiar with the lock and

key model and the induced fit model

the basic idea of the lock and key model

is that the substrate fits exactly

with the active side of the enzyme just

as a key fits exactly into the lock

activating the door so that it opens

but the induced fit model

there's a little bit more to it with the

induced fit model as the substrate

enters the active site

the shape of the enzyme

changes slightly so that it fits even

better with the substrate

so it changes slightly such that it

becomes even more complementary

to the shape of the the substrate so

that's the idea of the induced fit model

the enzyme

enhances its shape so that it fits

better with the substrate

now let's get rid of this

i'm always running out of space here

so once the enzyme combines with the

substrate

we're going to get something called

an enzyme substrate complex

abbreviated es

so this is when the enzyme is catalyzed

in the reaction in this case the

breakdown of sucrose

and then once it finishes

doing its job it's going to return back

to its original shape

and then the products will be released

so we have g for glucose

f for fructose

so we have the original enzyme and these

are the products

so as you can see

the enzyme

is a catalyst that is not used up in a

reaction

so if we were to write the overall

reaction of this

so it's going to be s

plus e

and then that's going to turn into

es the enzyme substrate complex

that's the intermediate for this

reaction

and then it's going to be e

plus p where p is the products so notice

that the enzyme appears in the beginning

of the reaction

and at the end of the reaction

so the enzyme is not used up in the

chemical reaction it can be reused to

react with another sucrose molecule

converting that into glucose and

fructose

so make sure you understand that enzymes

they speed up chemical reactions but

they're not consumed in the reaction

now let's move on to the next point the

factors that affect

enzyme activity

so the first one is the ph

enzymes have an optimal ph

upon which they work

most enzymes

their optimal ph is somewhere between

six and eight

because

your body has a ph between six and eight

the optimal ph

will be the x value that occurs at this

point

so in this example that would be

somewhere around seven

on the y-axis

we have the rate so at this point the

enzyme it's working at its best at its

highest rate

now some

enzymes

they have an optimal ph that is not

around seven

for instance the enzyme pepsin

has an optimal ph somewhere between two

and three because it exists in your

stomach under acidic conditions

another factor that affects enzyme

activity is temperature

and like ph there's a graph that

corresponds to that so we have

temperature on the x-axis

and the rate of the reaction on the

y-axis

now the graph will look something like

this

so there is an optimal temperature

at which the rate is at its maximum

so below that increasing the temperature

will increase

the rate of

the enzyme activity

that is the left side

because as you increase the temperature

along the x-axis you can see the rate is

going up

now once you go past that

optimal

spot or that optimal temperature as you

can see

the rate of the reaction quickly

decreases

at certain temperatures or rather at

certain high temperatures

proteins can be denatured they can lose

their shape and thus they can lose

their ability to function

and so if the temperature is too high

the enzyme is not going to work as well

as it should

because of denaturation so that's

something to keep in mind

so proteins their shape is dependent on

the temperature

and the ph

another factor that affects

the enzyme activity is the concentration

as you increase the concentration of the

substrate or the enzyme

the rate of the reaction will increase

as well

up to a limit

if the concentration is too high

once you reach that optimal rate of

reaction increase in the concentration

won't work anymore so let me give you a

graph to help you visualize this

so we're going to have the rate of the

reaction on the y-axis

and the concentration on the x-axis

let's use c as to say to represent the

concentration of the substrate

so initially

as you increase the concentration of the

substrate by moving to the right

the rate of the reaction will increase

now eventually it's going to level off

so at this point this is true increasing

the concentration of the substrate or

the enzyme the rate is going up

now once you reach that

optimal rate of the reaction

which is probably going to be somewhere

just above that red line

once you get close to it

increasing the concentration

has

negligible effect on the rate of the

reaction as you can see the rate is not

changing much

so this is true up to a certain limit

now another factor that affects

enzyme activity

are the presence of inhibitors and

activators

inhibitors are substances that

inhibit

the activity of an enzyme so it slows it

down

so let me draw an enzyme

so

there goes my enzyme and let's draw a

similar substrate that we had before

now there's two types of inhibitors that

you need to be familiar with

competitive inhibitors which i'm going

to draw in green

so this would be the competitive

inhibitor

this inhibitor

wants to bind at the active site of the

substrate

so if it gets there it's going to

block the substrate from entering that

site so let's put that there

so that will be an example of a

competitive inhibitor if it bonds to the

active site the substrate can't get in

and so it prevents the substrate from

interacting with the enzyme

so that's why they're competitive

inhibitors

the inhibitor competes with the

substrate for the same active site

now another type of inhibitor is a

non-competitive inhibitor

which i'm going to put in green

so this non-competitive inhibitor which

is also like an allosteric inhibitor

it binds to the allosteric site

of the enzyme

so the allosteric site is somewhere

away from

the active site which is here i'm going

to write a s for active

site so once that

non-competitive inhibitor or allosteric

inhibitor bonds to that site

the enzyme changes shape such that it no

longer fits with the substrate

so let me go back to my terrible drawing

skills

so now the substrate can't bond with

this enzyme

because it no longer fits with the

enzyme

so that's how a non-competitive

inhibitor could

decrease enzyme activity with this

substrate

an activator is basically the opposite

of an inhibitor an activator would be

something that would activate the enzyme

towards the substrate

so those are some factors that affect

enzyme activity

in addition some enzymes require

cofactors and coenzymes to function

cofactors include inorganic metal ions

such as the zinc 2 plus cation

and coenzymes include organic molecules

such as

vitamins

as you continue to study biology or even

biochemistry you're going to encounter

some complicated chemical reactions

and if you could understand the name of

the enzyme

that catalyzed that reaction

then you can understand what's happening

in the reaction

the first enzyme that we're going to

talk about

is protease

so this is an enzyme that breaks down

proteins and polypeptides

into amino

acids the second one that we're going to

briefly review is lipase

so ace tells you that it's an enzyme

the root word lipe or lipid tells you

dealing with lipids and fats

lipase is an enzyme that breaks down

fats such as triglycerides

into glycerol

and fatty acids

another example is

isomerase

so the root word isomer this is an

enzyme that catalyzes rearrangement

reactions

it can convert a compound

into its isomer

number four

transferase

so this is an enzyme that is going to

transfer something

it transfers a functional group from one

molecule to another

the next one is kinase

so this enzyme

transfers a phosphate group

particularly from atp to another

molecule

number six

dehydrogenase

so let's think about this word

hydrogen

and the word d

so this is an enzyme that removes

hydrogen atoms from a molecule

next

amylase

think of

starches such as amylosin amylopectin

well starch plant starch is composed of

for the most part 20 amylose and 80

amylopectin if i remember it correctly

but amylase is an enzyme that breaks

down starch into simple sugars like

glucose

number eight

oxido reductase

so think of the word oxidation and

reduction so we're dealing with redox

reactions

in a redox reaction there's a transfer

of electrons

in an oxidation reaction

electrons are lost

but in a reduction reaction a substance

picks up or gains electrons

so oxidoreductase

is an enzyme that catalyzes

the transfer of electrons from one

molecule to another

number nine is hydrolase

so think of the word hydrolysis

used in water to split a big molecule

into two smaller components

so hydro excuse me hydrolase

is an enzyme that catalyzes

hydrolysis reactions

so those are some enzymes that you may

want to familiarize yourself with