Enzymes
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Questions and Answers

What does a blue-black color change indicate when iodine is added to the solution?

  • Presence of amylase
  • Completion of the reaction
  • Increase in temperature
  • Presence of starch (correct)

The reaction time of the enzyme activity decreases as the temperature increases.

True (A)

What is the role of amylase in the investigation?

To break down starch into simpler sugars.

The iodine solution is used to test for the presence of __________ in the reaction.

<p>starch</p> Signup and view all the answers

Match the following components of the experiment with their purposes:

<p>Iodine = Detect starch presence Amylase = Catalyze starch breakdown Heating = Set reaction temperature Droplets = Monitor reaction progress</p> Signup and view all the answers

What is the optimum pH for most enzymes?

<p>7 (D)</p> Signup and view all the answers

Enzymes produced in the stomach have an optimum pH of 9.

<p>False (B)</p> Signup and view all the answers

What happens to an enzyme if the pH is moved too far from its optimum?

<p>The enzyme will denature and activity will stop.</p> Signup and view all the answers

The optimum pH for enzymes produced in the duodenum is around _______.

<p>8 or 9</p> Signup and view all the answers

Match the following enzymes to their corresponding optimum pH:

<p>Stomach Enzymes = 2 Duodenum Enzymes = 8 or 9 Most Enzymes = 7</p> Signup and view all the answers

What are enzymes primarily classified as?

<p>Proteins (B)</p> Signup and view all the answers

Enzymes are permanently changed after they catalyze a chemical reaction.

<p>False (B)</p> Signup and view all the answers

What is the function of enzymes in living organisms?

<p>To speed up the rate of metabolic reactions.</p> Signup and view all the answers

Enzymes are biological catalysts made in __________.

<p>living cells</p> Signup and view all the answers

Match the following enzyme terms with their definitions:

<p>Catalyst = Substance that speeds up a chemical reaction Substrate = Molecule that is broken down or joined in a reaction Active Site = Region of the enzyme where the substrate binds Product = Resulting molecule from an enzyme-catalyzed reaction</p> Signup and view all the answers

Which of the following statements best describes enzyme specificity?

<p>Each enzyme is specific to one particular substrate. (B)</p> Signup and view all the answers

How long would it take to digest a meal without digestive enzymes?

<p>2 - 3 weeks</p> Signup and view all the answers

The lock and key model illustrates how enzymes interact with their substrates.

<p>True (A)</p> Signup and view all the answers

Which hypothesis explains the specificity of enzymes to their substrates?

<p>Lock and key hypothesis (A)</p> Signup and view all the answers

Enzymes are consumed in the reaction and cannot catalyze further reactions.

<p>False (B)</p> Signup and view all the answers

What forms when a substrate fits into the active site of an enzyme?

<p>Enzyme-substrate complex</p> Signup and view all the answers

The shape of an enzyme is important because it allows the formation of the _____ complex.

<p>enzyme-substrate</p> Signup and view all the answers

Match the following enzyme characteristics with their descriptions:

<p>Specificity = Enzymes work on particular substrates only Active Site = Region where substrates bind to the enzyme Catalysis = Process of increasing the rate of a reaction Product = Substance formed from a chemical reaction</p> Signup and view all the answers

What is the first step in enzyme action?

<p>Enzyme and substrate collide (C)</p> Signup and view all the answers

After products are formed, they fit perfectly back into the enzyme's active site.

<p>False (B)</p> Signup and view all the answers

What happens to an enzyme after it catalyzes a reaction?

<p>It remains unchanged.</p> Signup and view all the answers

What is the optimum temperature for enzyme activity in the human body?

<p>37⁰C (B)</p> Signup and view all the answers

Denaturation of enzymes is a reversible process.

<p>False (B)</p> Signup and view all the answers

What happens to enzyme activity when the temperature is increased from 0⁰C to the optimum temperature?

<p>Enzyme activity increases.</p> Signup and view all the answers

Enzymes are ____, which have a specific shape critical for their function.

<p>proteins</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Optimum temperature = The temperature at which enzyme activity is highest Denaturation = Loss of the enzyme's shape and function due to high temperature Active site = Region on the enzyme where substrates bind Substrate = The molecule upon which an enzyme acts</p> Signup and view all the answers

What happens to an enzyme when it is heated beyond its optimum temperature?

<p>It becomes denatured (D)</p> Signup and view all the answers

Low temperatures cause enzymes to become denatured.

<p>False (B)</p> Signup and view all the answers

What effect does increasing the temperature have on enzyme activity before reaching the optimum temperature?

<p>It increases the activity of enzymes.</p> Signup and view all the answers

What indicates that starch has been digested in the experiment?

<p>Iodine solution remains orange-brown (B)</p> Signup and view all the answers

The enzyme amylase works best in high pH environments.

<p>False (B)</p> Signup and view all the answers

What role does the buffer solution play in the experiment?

<p>It maintains a stable pH during the reaction.</p> Signup and view all the answers

The enzyme _________ is used in the experiment to digest starch.

<p>amylase</p> Signup and view all the answers

Match the following steps of the experiment with their purposes:

<p>Adding iodine solution = To test for starch presence Using a syringe for amylase = To measure enzyme volume precisely Starting the stopwatch = To time the reaction accurately Observing color change = To determine starch digestion completion</p> Signup and view all the answers

Which of the following factors can affect enzyme activity?

<p>All of the above (D)</p> Signup and view all the answers

Enzymes function more effectively at lower temperatures.

<p>False (B)</p> Signup and view all the answers

How is the effectiveness of amylase at different pH levels measured?

<p>By timing how quickly the iodine solution changes color.</p> Signup and view all the answers

Flashcards

What are enzymes?

Enzymes are biological catalysts that speed up chemical reactions without being used up or altered in the process. They are proteins essential for all living organisms.

Enzyme Function

Enzymes facilitate chemical reactions by lowering the activation energy required for the reaction to occur, thus speeding up the process.

Enzyme Specificity

Each enzyme only works with a specific substrate due to the enzyme's unique shape that complements the substrate's shape.

Lock and Key Model

This model describes the interaction between an enzyme and its substrate. The enzyme's active site has a shape that perfectly fits the substrate, allowing for a reaction to occur.

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How do enzymes work?

Enzymes work by providing an alternative reaction pathway with a lower activation energy, allowing reactions to proceed much faster.

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Metabolic Reactions

All the chemical reactions necessary for life within an organism. They include processes of breaking down (catabolism) and building up (anabolism) molecules.

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Importance of Enzymes

Enzymes are vital for all living organisms as they control the speed of metabolic reactions, ensuring these processes happen at a rate compatible with life.

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What happens if no digestive enzymes exist?

Without digestive enzymes, it would take an incredibly long time (weeks) to digest a meal. With enzymes, digestion is considerably faster (around 4 hours).

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Enzyme Activity

The rate at which an enzyme catalyzes a reaction. It is influenced by factors like temperature.

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Amylase

A type of enzyme that breaks down starch into simpler sugars.

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Iodine Test

A test to detect the presence of starch. Iodine solution turns blue-black in the presence of starch.

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Optimal Temperature

The temperature at which an enzyme works most efficiently.

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Effect of Temperature on Amylase

Amylase activity increases with temperature until it reaches its optimal temperature. Beyond this, the enzyme denatures and activity decreases.

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Investigating enzyme activity

Studying how factors like temperature, pH, or substrate concentration affect the rate of enzyme-catalyzed reactions.

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Enzyme activity with varying pH

The rate of reaction catalyzed by an enzyme changes with different pH levels. Each enzyme has an optimal pH where it works most efficiently.

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Iodine solution in enzyme experiment

Iodine solution is used as an indicator to detect the presence of starch. It turns blue-black in the presence of starch and remains orange-brown when starch is absent.

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How does iodine solution indicate starch digestion?

As amylase breaks down starch, the iodine solution changes color from blue-black to orange-brown. This indicates that the starch has been digested.

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Optimum pH for enzyme activity

The pH value at which an enzyme shows the highest activity. At this pH, the enzyme's active site is in its most favorable shape for binding to the substrate.

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How does changing pH affect enzyme activity?

Extreme pH values can denature enzymes, altering their shape and making them less effective or inactive. This happens because the pH changes the interactions within the enzyme structure, disrupting the active site.

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Why is it important to understand enzyme activity?

Understanding how factors affect enzyme activity is crucial in various fields, including medicine, biotechnology, and food science. It helps us understand how enzymes function in our bodies and how they can be used in different applications.

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What is the active site of an enzyme?

The specific region on an enzyme's surface where the substrate binds and the catalytic reaction takes place. Its shape is crucial for the enzyme's function.

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Active Site

The region on an enzyme where the substrate binds and the chemical reaction occurs. It has a specific shape complementary to the substrate.

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Enzyme-Substrate Complex

The temporary structure formed when an enzyme and its substrate bind together in the active site. This is essential for the reaction to happen.

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What happens after the reaction?

After the reaction is complete, the products are released from the enzyme's active site. The enzyme is unchanged and ready to catalyse another reaction.

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How do enzymes speed up reactions?

Enzymes catalyse reactions by lowering the activation energy required for the reaction to start. This means the reaction can happen faster.

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What if no digestive enzymes?

Without digestive enzymes, food would take weeks to break down. Enzymes make digestion much faster, typically around 4 hours.

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Why are enzymes important?

Enzymes are vital for all living organisms. They control the speed of metabolic reactions, making sure these processes happen at the right pace for life.

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Optimum pH

The pH at which an enzyme works most efficiently. For most enzymes, this is pH 7, but it varies depending on where the enzyme functions in the body.

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Effect of pH on Enzymes

Extreme high or low pH values can disrupt the bonds holding an enzyme's protein structure together. This alters the shape of the active site, preventing the substrate from binding and reducing enzyme activity.

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Denaturation

Irreversible damage to an enzyme's structure caused by extreme changes in pH or temperature, rendering it inactive.

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Duodenum Enzyme

Enzymes produced in the duodenum (small intestine) have an optimum pH of around 8 or 9, due to the alkaline environment.

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Stomach Enzyme

Enzymes produced in the stomach have an optimum pH of around 2, because the stomach is acidic.

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Enzyme Shape

Enzymes are proteins with a specific shape, vital for their function. This shape is maintained by bonds, especially around the active site.

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Enzyme Activity & Temperature

Increasing temperature from 0°C to the optimum increases enzyme activity. This is because molecules move faster, leading to more collisions with the substrate.

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Low Temperatures & Enzymes

Low temperatures slow down enzyme activity but don't denature them. Enzymes can regain full activity when warmed to the optimum temperature.

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Effect of Temperature on Enzyme Activity Graph

The graph shows a bell-shaped curve. Enzyme activity increases with temperature until it reaches the optimum. Beyond the optimum, activity rapidly decreases due to denaturation.

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Why is Enzyme Shape Important?

The specific shape of an enzyme's active site determines which substrate it can bind to. Only the correct substrate can fit and undergo the reaction.

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What happens to the active site during denaturation?

During denaturation, the enzyme loses its shape, including the active site. This means the substrate can no longer bind to the enzyme, and the reaction cannot occur.

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Study Notes

Enzymes

  • Enzymes are biological catalysts
  • Catalysts speed up the rate of a chemical reaction without being changed or used up in the reaction
  • Enzymes are proteins
  • Enzymes are essential for all living organisms as they maintain reaction speeds of all metabolic reactions (all the reactions that keep an organism alive) at a rate that can sustain life
  • For example, without digestive enzymes, digesting a single meal would take around 2-3 weeks instead of around 4 hours.

Enzyme Action & Specificity

  • Enzymes are specific to one particular substrate(s)
  • The active site of the enzyme is complementary in shape to the substrate
  • This is because the enzyme is a protein, and it has a specific 3-D shape
  • This is known as the lock and key hypothesis
  • When the substrate moves into the enzyme's active site they become known as the enzyme-substrate complex
  • After the reaction occurs, the products leave the active site as they no longer fit
  • The enzyme is unchanged and can catalyse further reactions

How Enzymes Work

  • Enzymes and substrates randomly move about in the solution
  • When an enzyme and substrate collide, and the substrate fits into the active site of the enzyme, an enzyme-substrate complex is formed
  • A reaction occurs, and products form, which are released from the active site
  • The enzyme is unchanged and ready to catalyse further reactions

Enzyme Investigations: Effect of Temperature on Amylase

  • Starch solution is heated to a set temperature
  • Iodine is added to wells on a spotting tile
  • Amylase is added to the starch solution and mixed
  • Every minute, droplets of the solution are added to a new well of iodine solution
  • This is repeated until the iodine stops turning blue-black (meaning there's no more starch left/it has been completely broken down)
  • The time taken for the reaction to complete is recorded
  • The experiment is repeated at different temperatures
  • The quicker the reaction is completed, the faster the enzyme is working

Enzyme Investigations: Effect of pH on Amylase

  • Single drops of iodine solution are placed on a tile
  • A test tube is labelled with the pH to be tested
  • 2cm³ of amylase is placed in the test tube using a syringe
  • 1cm³ of buffer solution is added to the test tube
  • 2cm³ of starch solution is added to the mixture, and a stopwatch is started
  • After 10 seconds a drop of the mixture is placed on the first drop of iodine. This should turn blue-black.
  • This is repeated every 10 seconds until iodine solution remains orange-brown
  • The experiment is repeated at different pH values
  • The shorter the time taken for the iodine to remain orange-brown, the better the enzyme is working at that pH.

Enzymes & Temperature (Extended Tier Only)

  • Enzymes are proteins with a specific shape held in place by bonds
  • This specific shape is crucial for the active site to ensure the substrate fits
  • Enzymes work fastest at their optimum temperature. For humans, this is 37°C
  • Heating to temperatures beyond the optimum breaks the bonds holding the enzyme together, causing it to lose its shape—this is called denaturation
  • Substrates cannot fit into denatured enzymes' distorted active sites because their shape is lost
  • Denaturation is irreversible.
  • Once denatured, enzymes cannot regain their proper shape or activity

Enzymes & pH (Extended Tier Only)

  • Most enzymes have a pH optimum of 7
  • Some have different optimum pHs due to their production environment (e.g., stomach enzymes have a lower pH optimum)
  • If the pH is too high or too low, it can destroy bonds that hold the amino acid chain together, changing the shape of the active site
  • This will cause the substrate to not fit into the active site, reducing enzyme activity
  • Changing the pH too far from the optimum will cause denaturation of the enzyme.

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Cambridge IGCSE Biology Enzymes PDF

Description

Test your understanding of enzyme activity, their roles, and the effects of pH and temperature on their function. This quiz covers key concepts such as the function of amylase, the significance of iodine in experiments, and the optimum conditions for enzyme activity. Challenge yourself with matching components of enzyme reactions and understanding the broader implications of enzymes in biology.

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