5. Enzymes (Cambridge IGCSE Biology 0610 for exams in 2023, 2024 and 2025) @IGCSEStudyBuddy

Summary

This IGCSE study video covers the role of enzymes in biology. Enzymes are proteins that act as biological catalysts, accelerating metabolic reactions without being consumed. They are specific to their substrates, fitting like a lock and key. Factors like temperature and pH affect enzyme activity, with each enzyme having an optimum level for maximum efficiency. Deviations from this optimum can cause denaturation, rendering enzymes ineffective.

Takeaways

• 🧬 Enzymes are biological catalysts that speed up metabolic reactions in living organisms without being consumed in the process.
• 🔑 The active site of an enzyme is a specific region that fits the substrate like a lock and key, ensuring that enzymes are highly specific to their substrates.
• 🔄 Enzymes remain unchanged after the reaction, allowing them to be used repeatedly in catalyzing reactions.
• 🍽️ Digestive enzymes are crucial for breaking down food molecules efficiently, providing necessary energy and nutrients for survival.
• 🌡️ Temperature affects enzyme activity, with an increase in temperature generally leading to an increase in reaction rate due to greater kinetic energy of molecules.
• 🌡️ Each enzyme has an optimum temperature at which it functions best, and temperatures too high can denature enzymes, altering their active site and inactivating them.
• 📉 Low temperatures can reduce enzyme activity without denaturing them, as molecules have less kinetic energy and fewer successful collisions occur.
• 📊 The rate of enzyme-catalyzed reactions typically increases with temperature up to an optimum point, after which it decreases due to denaturation.
• 🅿️ pH is another critical factor influencing enzyme activity, with each enzyme having an optimum pH level at which it works best.
• 🔄 Deviations in pH from the optimum can cause enzyme denaturation by breaking bonds, altering the active site shape, and reducing enzyme function.

Q & A

What is a catalyst and how does it relate to enzymes?

A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. Enzymes are biological catalysts that are proteins made in living cells, which speed up the rate of metabolic reactions.

Why are enzymes essential for living organisms?

Enzymes are essential because they speed up metabolic reactions that would otherwise occur too slowly to sustain life. They maintain the necessary reaction rates for processes like digestion, which provide energy and nutrients.

What is a substrate in the context of enzymes?

A substrate is the substance upon which an enzyme acts. It is the molecule that the enzyme binds to and transforms during a metabolic reaction.

How does the shape of an enzyme's active site relate to its function?

The shape of an enzyme's active site is crucial as it must fit the substrate exactly for the enzyme to function. This is known as the lock and key mechanism, where the enzyme's active site and the substrate's shape are complementary.

What is meant by the term 'enzyme specificity'?

Enzyme specificity refers to the fact that an enzyme will only act on certain substrates with which it has a complementary shape, ensuring that the enzyme binds only to its specific substrate.

How does temperature affect enzyme activity?

As temperature increases, so does the rate of enzyme-catalyzed reactions due to increased molecular motion and kinetic energy. However, each enzyme has an optimum temperature beyond which it can become denatured and lose its function.

What happens to an enzyme if the temperature becomes too high?

If the temperature is too high, the enzyme's structure can become denatured, causing the bonds in the enzyme to break and altering the shape of the active site, which prevents the enzyme from functioning.

What is the significance of an enzyme's optimum pH?

An enzyme's optimum pH is the pH level at which it works most efficiently. Deviations from this pH can cause the enzyme to denature by breaking the bonds in its structure, changing the active site's shape and reducing its activity.

How do different enzymes have different optimum pH levels?

Different enzymes have evolved to function optimally in different pH environments depending on their location within the body. For example, pepsin in the stomach works best at a low pH, while amylase in saliva functions best at a neutral pH.

Can you provide an example of how pH affects enzyme function?

Yes, pepsin, which is found in the stomach, has an optimum pH of around 2 and will not function effectively at the neutral pH of 7, unlike amylase, which is found in saliva and works best at a pH of 7.

Outlines

00:00

🧬 Enzymes: Biological Catalysts

This paragraph introduces the concept of enzymes as biological catalysts that are proteins made in living cells. It explains that metabolic reactions are essential for life, and enzymes speed up these reactions without being consumed in the process. The active site of an enzyme is described as a specific shape that fits the substrate, allowing the enzyme to act on it. The lock and key mechanism is used to illustrate enzyme specificity, where only the substrate with a complementary shape can bind to the enzyme. The paragraph also discusses the formation of an enzyme-substrate complex and the release of products without altering the enzyme itself.

05:05

🌡️ Temperature and pH: Key Factors in Enzyme Activity

This section delves into how temperature and pH levels affect enzyme activity. It explains that as temperature increases, so does the rate of enzyme-catalyzed reactions due to increased molecular motion and successful collisions. However, each enzyme has an optimum temperature beyond which it becomes denatured, losing its functionality. The paragraph uses a graph to illustrate this relationship, showing a peak in activity at the optimum temperature and a decline as temperatures exceed this point. Similarly, pH levels are crucial, with each enzyme having an optimum pH. Deviations from this optimum can lead to denaturation, altering the enzyme's active site and reducing its ability to bind with the substrate. The paragraph contrasts two enzymes, pepsin and amylase, highlighting their different optimum pH levels and their respective roles in digestion.

10:10

📚 Summary of Enzymes Chapter

The final paragraph serves as a conclusion to the chapter on enzymes, summarizing the key points covered. It emphasizes the importance of understanding enzymes' roles in biological processes and invites viewers to continue their biology revision with more videos from the IGCSE study buddy channel. The paragraph ends with a call to action for viewers to subscribe for further educational content.

Keywords

💡Enzyme

An enzyme is a biological catalyst, which means it is a protein that accelerates the rate of chemical reactions in living organisms without being consumed in the process. In the video, enzymes are described as crucial to life because they speed up metabolic reactions that would otherwise occur too slowly to sustain life. The script uses the example of digestive enzymes, which are necessary for breaking down food molecules into forms that can be used by the body for energy and nutrients.

💡Catalyst

A catalyst is a substance that increases the rate of a chemical reaction without being changed by the reaction itself. The video explains that enzymes are a type of catalyst, which is why they can be used repeatedly. The concept is integral to understanding how enzymes function, as it highlights their role in facilitating reactions without being depleted.

💡Active Site

The active site is the specific region of an enzyme where the substrate binds and the reaction occurs. The video script describes the active site as having a shape that exactly fits the substrate, which is crucial for the enzyme's function. This is illustrated with a diagram showing how the active site's shape complements the substrate, leading to the formation of an enzyme-substrate complex.

💡Substrate

A substrate is the molecule on which an enzyme acts to catalyze a reaction. The video emphasizes that enzymes are specific to their substrates, meaning that an enzyme will only work with a particular substrate whose shape fits the enzyme's active site. This specificity is likened to a lock and key mechanism, where only the correct key (substrate) will fit the lock (active site).

💡Products

Products are the molecules produced after a reaction has taken place. In the context of the video, when an enzyme acts on a substrate, the reaction results in the formation of products. The script explains that the enzyme remains unchanged after the reaction, which is why it can be used repeatedly, while the products are the new molecules created as a result of the enzymatic reaction.

💡Lock and Key Mechanism

The lock and key mechanism is a model that describes the specificity of enzyme action, where the enzyme's active site and the substrate have complementary shapes that fit together perfectly. The video uses this analogy to explain how enzymes are specific to their substrates, ensuring that only the correct substrate can bind to the enzyme and be acted upon.

💡Temperature

Temperature is a factor that affects enzyme activity. The video script explains that as temperature increases, the rate of enzyme-catalyzed reactions also increases due to increased molecular motion and kinetic energy. However, each enzyme has an optimum temperature at which it works best, and temperatures too high can cause the enzyme to denature, or lose its shape and function.

💡Denaturation

Denaturation refers to the loss of an enzyme's native structure and function, often due to extreme temperatures or pH levels. The video describes how high temperatures can cause the bonds within the enzyme to break, altering the shape of the active site and rendering the enzyme nonfunctional. This concept is crucial for understanding how environmental conditions can impact enzyme activity.

💡Optimum Temperature

The optimum temperature is the specific temperature at which an enzyme works most efficiently. The video script notes that different enzymes have different optimum temperatures, and that exceeding this temperature can lead to denaturation. For most enzymes in the human body, the optimum temperature is around 37 degrees Celsius, which is the normal body temperature.

💡pH

pH is a measure of the acidity or alkalinity of a solution and is another factor that affects enzyme activity. The video explains that enzymes have an optimum pH, and deviations from this pH can cause the enzyme to denature. The script provides examples of two enzymes, pepsin and amylase, which have different optimum pH levels, illustrating how pH can influence the function of enzymes in various biological contexts.

💡Enzyme-Substrate Complex

The enzyme-substrate complex is a temporary formation that occurs when an enzyme binds to its substrate. The video script describes this complex as a necessary step in the catalytic process, where the enzyme's active site and the substrate's shape fit together, allowing the reaction to take place. The formation of this complex is a key aspect of how enzymes facilitate chemical reactions.

Highlights

Enzymes are biological catalysts that speed up metabolic reactions in living organisms.

A catalyst increases the rate of a chemical reaction without being changed by the reaction.

Enzymes are proteins made in living cells that catalyze metabolic reactions.

Enzymes are essential for life as they maintain necessary reaction rates for survival.

Without digestive enzymes, animals would not be able to break down food molecules efficiently.

A substrate is the substance on which an enzyme acts, and products are the molecules produced after the reaction.

The active site of an enzyme is the specific region that binds to the substrate.

Enzyme-substrate complexes are formed temporarily during the reaction process.

Enzymes are specific to their substrates due to the complementary shapes of their active sites and substrate molecules.

The lock and key mechanism describes the specific fit between an enzyme's active site and its substrate.

Enzyme specificity means that an enzyme typically acts on only one type of substrate.

The enzyme-substrate complex leads to the formation of an enzyme-product complex, which eventually releases the products.

Enzymes remain unchanged after the reaction, allowing them to be used repeatedly.

Temperature affects enzyme activity, with reaction rates increasing as temperature rises until an optimum is reached.

Each enzyme has an optimum temperature at which it works best, beyond which it can become denatured.

High temperatures can cause enzymes to denature by breaking the bonds in their active sites, altering their shape.

pH also influences enzyme activity, with each enzyme having an optimum pH level for maximum efficiency.

Deviation from the optimum pH can lead to enzyme denaturation by changing the active site's shape.

Different enzymes have different optimum pH levels; for example, pepsin works best at pH 2, while amylase at pH 7.

Understanding enzyme activity is crucial for studying biological processes and their regulation.

Transcripts

hi everyone welcome to IGCSE study buddy

where you can revise biology topics from

the Cambridge IGCSE syllabus

this video summarizes topic 5 enzymes

so what is an enzyme first we must

understand that metabolic reactions are

constantly taking place in organisms in

order to maintain their living state

a catalyst is a substance that increases

the rate of a chemical reaction and is

not changed by the reaction itself so

it's something that makes a reaction

faster but it does not get changed

itself

an enzyme is a biological catalyst that

is they are made in living cells

enzymes are proteins that speed up the

rate of all metabolic reactions

enzymes like catalysts can be used over

and over again because they are not used

up during the reaction

enzymes are crucial to living organisms

as they speed up the metabolic reactions

which would take too long to occur

without them

it maintains the reaction rates of all

metabolic reactions necessary to sustain

life

for example without digestive enzymes

animals would not be able to break down

food molecules quickly enough to provide

the energy and nutrients they need to

survive

a substrate is the substance on which

the enzyme Acts

products are the molecules produced

after the reaction

the enzyme has a shape called the active

site which exactly fits the substances

on which it acts

according to this example the active

site is shown by the red line

an enzyme substrate complex is formed

temporarily when the enzyme combines

with the substrate

here is an illustration of an enzyme

substrate complex

enzymes are specific to their substrate

molecules

the shape of the active site of the

enzyme molecule and the substrate

molecule are complementary

so as demonstrated in the diagram the

yellow substrate has a shape that pairs

perfectly with the shape of the enzyme

ones active site

the enzymes and substrate molecules have

complementary shapes like two pieces of

a jigsaw puzzle so they fit together

this is also known as the lock and key

mechanism

however the yellow substrate will not be

able to perfectly fit into the active

site of enzyme 2 because the shapes of

the substrate and the active site are

not matching so enzyme 2 will not work

in this reaction

therefore enzymes are specific this

means simply that an enzyme which

normally acts on one substance will not

act on a different one

this diagram illustrates how enzymes

work as we know the shape of the

substrate must be complementary or

matching to that of the active site of

the enzyme as the enzyme binds with the

substrate and enzyme substrate complex

is formed

the reaction then occurs on the enzyme

and the enzyme product complex is formed

the products eventually leave the enzyme

the enzyme itself is unchanged at the

end of the reaction

now let's look at the factors that

affect enzyme activity

they are temperature and pH

the rate of an enzyme-catalyzed reaction

increases as the temperature increases

as the temperature is increased the

molecules gain more kinetic energy so

they move faster and there is a greater

chance of successful molecular

collisions happening

therefore the rate of reaction increases

all enzymes have an Optimum temperature

these are certain temperatures in which

a particular enzyme works best in and it

can vary between different enzymes

so different enzymes may work best in

different temperatures

for any enzyme if the temperature gets

too high it will get denatured

this means that the bonds in the enzymes

will break causing the shape of the

enzyme's active site to change

remember the active site has a very

special shape and it fits only one

specific type and shape of substrate

a change in the active site will

therefore cause the enzyme to stop

working

this picture is an example of what will

happen to the active site of an enzyme

if the temperature is too high

as you may notice the shape of the

active site has changed and the

substrate's shape does not match with it

anymore and therefore the enzyme will

not work in this reaction

this graph explains how temperature

affects enzyme activity

so as you may see initially the rate of

the reaction is low when the

temperatures are low

molecules need to collide with one

another and have enough energy for a

reaction to occur

however in low temperatures molecules

are traveling at lower speeds or less

kinetic energy and therefore the rate of

successful collisions are lower

enzyme activity is therefore low in low

temperatures

it is important to note however that low

temperatures do not denature enzymes

then you may notice the rate of the

reaction increases as the temperature

increases and in this graph for this

enzyme the rate of reaction reaches its

highest at an Optimum temperature of 40

degrees Celsius

however Beyond this temperature you may

notice that the rate of reaction

decreases again because the enzyme

becomes denatured and can no longer

function as a biological catalyst

most enzymes have an Optimum temperature

of approximately 37 degrees Celsius in

the human body and start getting

denatured at above 50 degrees Celsius

pH is the other factor that affects

enzyme activity

enzymes also have an optimum pH

this is the pH in which an enzyme works

best and different enzymes may have a

different optimum pH

if the pH deviates too much from their

Optimum it will cause the bonds to break

in the enzymes thereby changing the

shape of their active site resulting in

the enzyme getting denatured

the substrate will not be able to fit

perfectly in the active site

this means the enzyme cannot function

anymore

this graph shows how pH affects the rate

of a reaction with enzymes

the rate of reaction in this graph is

the highest when the pH is 8. that means

that this enzyme's optimum pH is 8.

when the pH stray is too far from the

optimum on either side of the graph the

rate of reaction decreases because the

enzyme gets denatured

examples of two enzymes with a different

Optimum PHR pepsin and amylase

pepsin is an enzyme found in the

stomach's acidic conditions and

therefore made to work best in a pH of

approximately two

amylase on the other hand is found in

saliva and therefore has an optimum pH

of 7.

so although pepsin will work best at a

pH of two it will not function at a pH

of 7. unlike amylase

similarly amylase will speed up the

reaction rate at a ph of 7 but will not

work at a pH of 2 unlike pepsin

so that sums up the main things to be

learned in chapter 5 enzymes hope you

found it useful thank you for watching

and please don't forget to subscribe to

IGCSE study buddy for more biology

revision videos bye