5. Enzymes (Cambridge IGCSE Biology 0610 for exams in 2023, 2024 and 2025) @IGCSEStudyBuddy
Summary
TLDRThis 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
🧬 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.
🌡️ 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.
📚 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.
Mindmap
Keywords
💡Enzyme
💡Catalyst
💡Active Site
💡Substrate
💡Products
💡Lock and Key Mechanism
💡Temperature
💡Denaturation
💡Optimum Temperature
💡pH
💡Enzyme-Substrate Complex
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
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