We are searching data for your request:
Upon completion, a link will appear to access the found materials.
I know that in the human body cellulose cannot be broken down by enzymes; however, I am confused as to which molecules amylase enzymes during fermentation.
I also looked at https://en.wikipedia.org/wiki/Amylase where it says that "All amylases are glycoside hydrolases and act on α-1,4-glycosidic bonds." so now I am confused.
Does amylase work to break down starch into glucose exclusively?
If not… Does amylase enzyme break down corn cob extract which contains xylans, cellulose, lignin and some sugar for fermentation? Does amylase enzyme break down corn stem which contains cellulose, hemicellulose and lignin for fermentation?
Your incomprehension is due to the fact that both starch and cellulose are polysaccharides.
As it is said in the wiki page. Amylase is active only on alpha linkage like starch or glycogen. If you want to break beta linkage like in cellulose you need a cellulase enzyme, which humans do not have.
Amylase is found in high concentration in the pancreas of virtually all animals. However, it is also found in the liver, salivary glands, and small intestinal mucosa of many species the quantity of amylase in these organs varies considerably with different species. Removal of amylase from blood in all species is relatively rapid, but the mechanism of clearance is species-specific. In many animals, amylase is excreted by the kidney the liver appears to be involved in other animals. Amylase produced by the pancreas enters the small intestine to assist in digestion by hydrolyzing complex carbohydrates ionized calcium is required for this process.
Serum amylase levels increase substantially during acute bouts of pancreatitis, but because of its lack of organ specificity in exotic species, the diagnostic value of amylase levels is minimal.
A substance that helps a chemical reaction to occur is called a catalyst, and the molecules that catalyze biochemical reactions are called enzymes. Most enzymes are proteins and perform the critical task of lowering the activation energies of chemical reactions inside the cell. Most of the reactions critical to a living cell happen too slowly at normal temperatures to be of any use to the cell. Without enzymes to speed up these reactions, life could not persist. Enzymes do this by binding to the reactant molecules and holding them in such a way as to make the chemical bond-breaking and -forming processes take place more easily. It is important to remember that enzymes do not change whether a reaction is exergonic (spontaneous) or endergonic. This is because they do not change the free energy of the reactants or products. They only reduce the activation energy required for the reaction to go forward (Figure 1). In addition, an enzyme itself is unchanged by the reaction it catalyzes. Once one reaction has been catalyzed, the enzyme is able to participate in other reactions.
Figure 1 Enzymes lower the activation energy of the reaction but do not change the free energy of the reaction.
The chemical reactants to which an enzyme binds are called the enzyme’s substrates. There may be one or more substrates, depending on the particular chemical reaction. In some reactions, a single reactant substrate is broken down into multiple products. In others, two substrates may come together to create one larger molecule. Two reactants might also enter a reaction and both become modified, but they leave the reaction as two products. The location within the enzyme where the substrate binds is called the enzyme’s active site. The active site is where the “action” happens. Since enzymes are proteins, there is a unique combination of amino acid side chains within the active site. Each side chain is characterized by different properties. They can be large or small, weakly acidic or basic, hydrophilic or hydrophobic, positively or negatively charged, or neutral. The unique combination of side chains creates a very specific chemical environment within the active site. This specific environment is suited to bind to one specific chemical substrate (or substrates).
Active sites are subject to influences of the local environment. Increasing the environmental temperature generally increases reaction rates, enzyme-catalyzed or otherwise. However, temperatures outside of an optimal range reduce the rate at which an enzyme catalyzes a reaction. Hot temperatures will eventually cause enzymes to denature, an irreversible change in the three-dimensional shape and therefore the function of the enzyme (Figure 8). Enzymes are also suited to function best within a certain pH and salt concentration range, and, as with temperature, extreme pH, and salt concentrations can cause enzymes to denature.
Figure 2 Heat applied to an egg during cooking irreversibly denatures the proteins. (credit: “K-Wall”/Flickr)
Typically, enzymes function optimally in the environment where they are typically found and used. For example, the enzyme amylase is found in saliva, where it functions to break down starch (a polysaccharide – carbohydrate chain) into smaller sugars. Note that in this example, amylase is the enzyme, starch is the substrate, and smaller sugars are the product. The pH of saliva is typically between 6.2 and 7.6, with roughly 6.7 being the average. The optimum pH of amylase is between 6.7 and 7.0, which is close to neutral (Figure 3). The optimum temperature for amylase is close to 37ºC (which is human body temperature).
Figure 3 The effect of pH and temperature on the activity of an enzyme. Amylase is shown in blue in both graphs. (top) Amylase (blue) has an optimum pH of about 7. The green enzyme, which has an optimum pH of about 2.3, might function in the stomach where it is very acidic. (bottom) Amylase (blue) has an optimum temperature of about 37 degrees C. The orange enzyme, which has an optimum temperature of about 15 degrees C (about 60F) might function in a plant found outdoors.
For many years, scientists thought that enzyme-substrate binding took place in a simple “lock and key” fashion. This model asserted that the enzyme and substrate fit together perfectly in one instantaneous step. However, current research supports a model called induced fit (Figure 9). The induced-fit model expands on the lock-and-key model by describing a more dynamic binding between enzyme and substrate. As the enzyme and substrate come together, their interaction causes a mild shift in the enzyme’s structure that forms an ideal binding arrangement between enzyme and substrate.
When an enzyme binds its substrate, an enzyme-substrate complex is formed. This complex lowers the activation energy of the reaction and promotes its rapid progression in one of multiple possible ways.
- On a basic level, enzymes promote chemical reactions that involve more than one substrate by bringing the substrates together in an optimal orientation for reaction.
- Enzymes promote the reaction of their substrates is by creating an optimal environment within the active site for the reaction to occur. The chemical properties that emerge from the particular arrangement of amino acid R groups (side chains) within an active site create the perfect environment for an enzyme’s specific substrates to react.
- The enzyme-substrate complex can also lower activation energy by compromising the bond structure so that it is easier to break.
- Finally, enzymes can also lower activation energies by taking part in the chemical reaction itself. In these cases, it is important to remember that the enzyme will always return to its original state by the completion of the reaction.
One of the hallmark properties of enzymes is that they remain ultimately unchanged by the reactions they catalyze. After an enzyme has catalyzed a reaction, it releases its product(s) and can catalyze a new reaction.
Figure 9 The induced-fit model is an adjustment to the lock-and-key model and explains how enzymes and substrates undergo dynamic modifications during the transition state to increase the affinity of the substrate for the active site.
It would seem ideal to have a scenario in which all of an organism’s enzymes existed in abundant supply and functioned optimally under all cellular conditions, in all cells, at all times. However, a variety of mechanisms ensures that this does not happen. Cellular needs and conditions constantly vary from cell to cell, and change within individual cells over time. The required enzymes of stomach cells differ from those of fat storage cells, skin cells, blood cells, and nerve cells. Furthermore, a digestive organ cell works much harder to process and break down nutrients during the time that closely follows a meal compared with many hours after a meal. As these cellular demands and conditions vary, so must the amounts and functionality of different enzymes.
Since the rates of biochemical reactions are controlled by activation energy, and enzymes lower and determine activation energies for chemical reactions, the relative amounts and functioning of the variety of enzymes within a cell ultimately determine which reactions will proceed and at what rates. This determination is tightly controlled in cells. In certain cellular environments, enzyme activity is partly controlled by environmental factors like pH, temperature, salt concentration, and, in some cases, cofactors or coenzymes.
Enzymes can also be regulated in ways that either promote or reduce enzyme activity. There are many kinds of molecules that inhibit or promote enzyme function, and various mechanisms by which they do so. In some cases of enzyme inhibition, an inhibitor molecule is similar enough to a substrate that it can bind to the active site and simply block the substrate from binding. When this happens, the enzyme is inhibited through competitive inhibition, because an inhibitor molecule competes with the substrate for binding to the active site.
On the other hand, in noncompetitive inhibition, an inhibitor molecule binds to the enzyme in a location other than the active site, called an allosteric site, but still manages to block substrate binding to the active site. Some inhibitor molecules bind to enzymes in a location where their binding induces a conformational change that reduces the affinity of the enzyme for its substrate. This type of inhibition is called allosteric inhibition (Figure 10). Most allosterically regulated enzymes are made up of more than one polypeptide, meaning that they have more than one protein subunit. When an allosteric inhibitor binds to a region on an enzyme, all active sites on the protein subunits are changed slightly such that they bind their substrates with less efficiency. There are allosteric activators as well as inhibitors. Allosteric activators bind to locations on an enzyme away from the active site, inducing a conformational change that increases the affinity of the enzyme’s active site(s) for its substrate(s) (Figure 10).
Figure 10 Allosteric inhibition works by indirectly inducing a conformational change to the active site such that the substrate no longer fits. In contrast, in allosteric activation, the activator molecule modifies the shape of the active site to allow a better fit of the substrate.
Many enzymes do not work optimally, or even at all, unless bound to other specific non-protein helper molecules. They may bond either temporarily through ionic or hydrogen bonds, or permanently through stronger covalent bonds. Binding to these molecules promotes optimal shape and function of their respective enzymes. Two examples of these types of helper molecules are cofactors and coenzymes. Cofactors are inorganic ions such as ions of iron and magnesium. Coenzymes are organic helper molecules, those with a basic atomic structure made up of carbon and hydrogen. Like enzymes, these molecules participate in reactions without being changed themselves and are ultimately recycled and reused. Vitamins are the source of coenzymes. Some vitamins are the precursors of coenzymes and others act directly as coenzymes. Vitamin C is a direct coenzyme for multiple enzymes that take part in building the important connective tissue, collagen. Therefore, enzyme function is, in part, regulated by the abundance of various cofactors and coenzymes, which may be supplied by an organism’s diet or, in some cases, produced by the organism.
Enzymes must have pairs with suitable substrates because enzymes have specific properties. This means that even though there are many substrates, the enzyme will choose a suitable substrate for it, aka already paired. In addition to specific properties, enzymes also have several other properties. The second property is that enzymes can work back and forth. In addition to turning the substrate into a product, enzymes can also turn the product into a substrate again, according to the body’s needs. Then as long as the enzyme is not damaged, the enzyme can be used over and over again. So actually the body only needs enzymes in small amounts. Well, whether or not enzymes work smoothly depends on several factors, such as temperature, pH, inhibitors, and activators.
you can also see how enzyme work on this video :
Amylase Enzyme: An Essential Digestive Component
As nutritional science advances, we are learning more and more about the important role that carbohydrates play in our overall health – whether you are eating too much of them, the wrong kind of them, or need to load up on them for athletic activity. In all three of these scenarios, nutrient absorption, or malabsorption, plays a key role. A major part of making sure that you actually get all the nutrients you need from the food you eat is having the enzymes that help process them. This is where amylase comes in. As lipase helps you digest fats and protease helps you digest protein, amylase is essential to breaking down carbohydrates.
The Role of the Amylase Enzyme
Among the “trinity” of digestive enzymes, amylase is unique in that you see its effects much more quickly than you do either of its counterparts. This is because amylase comes from two distinct parts of your body: the pancreas and salivary glands in the mouth. The end goal of amylase is to break down carbohydrates into simple sugars that the body can use for energy, and this starts in the mouth. As food is chewed and mixed with saliva, amylase starts working to break down food into smaller molecules.1 In the stomach, this amylase is neutralized by gastric acid, and the starch, only partially broken down, goes on to the small intestine.
In the intestine, the starch is broken down further by the next set of amylase enzymes, this time released by the pancreas. The final result is glucose, which moves on into your bloodstream to be used for energy.2 Low levels of glucose in the blood can lead to fatigue and muscle weakness, and glucose is the preferred type of fuel for the brain and nervous system. However, different types of carbohydrates manifest this energy in different ways. For example, simple carbs, like those found in refined sugars, break down quickly, giving a quick burst of energy followed by fatigue.3 For more complex carbohydrates, amylase breaks things down more slowly, leading to more consistent energy levels. Good foods in this category include:
Added Benefits of Amylase Enzymes
Amylase’s primary function is digestion, but it may play a role in other facets of health as well, perhaps not directly, but as an indicator. One study showed that people with metabolic syndrome are more likely to have low serum amylase levels.4 Another study showed that levels of salivary alpha-amylase were extremely sensitive to psychosocial stress. This means that amylase may have future use as a means to help measure stress levels.5 Amylase has one additional small but important role – processing and digesting dead white blood cells.
Amylase is an important part of your digestive health, but the best way to get the most out of it is to combine it with other factors in order to get the maximum effect. One way to do this is through supplements like Enzymedica’s Chewable Digest. Naturally orange flavored and sweetened with sugar-free Xylitol, this contains amylase, lipase, cellulase and protease Thera-blend™ enzymes, which help you digest a variety of different foods. Thera-blend combines several strains of enzymes to get stronger and faster results.
There are a number of potential issues that can lead to enzyme deficiencies or imbalances. Some of the most common are issues with the pancreas, but alcoholism and certain medications can impact the levels of amylase that you have in your body. Also, we naturally start producing lower levels of amylase as we age. If you find that eating starchy foods is giving you inordinate amounts of discomfort, it would be worthwhile to meet with your doctor and have your amylase levels checked. Being cautious now can save you from larger issues later.
What molecules does amylase enzyme work on? - Biology
Enzymes pass out into the gut, where they catalyse the breakdown of food molecules.
Different enzymes catalyse different digestion reactions.
Enzymes and their reactions catalysed
|amylase||starch to sugars |
|protease||proteins to amino acids|
|lipase||fatty acids to glycerol |
Different parts of the gut produce different enzymes. This is shown in the table below:
|enzyme || Where produced |
|amylase ||salivary glands, small intestine, pancreas|
|protease ||pancreas, stomach, small intestine |
|lipase ||pancreas, small intestine |
Overall, this means that:
Amylase catalyses the breakdown of starch into sugars in the mouth and small intestine.
Proteases catalyse the breakdown of proteins into amino acids in the stomach and small intestine.
Lipases catalyse the breakdown of fats and oils into fatty acids and glycerol in the small intestine.
Different enzymes work best at different pH values. The digestive enzymes are a good example of this.
The stomach produces hydrochloric acid which helps to begin digestion. Tjhis acid kills many harmful microorganisms that might have been swallowed along with the food. The enzymes in the stomach work best in acidic conditions - in other words, at a low pH.
The small intestine
After the stomach, food travels to the small intestine. There, the enzymes work best in alkaline conditions. But the food is acidic after being in the stomach. A substance called bile neutralises the acid to provide the alkaline conditions needed in the small intestine.
- lipase - breaks down fats
- protease - breaks down proteins
- carbohydrase - breaks down carbohydrates
Enzymes are proteins which speed up reactions in living organisms. They’re really useful because they allow reactions which would be really sluggish happen in a matter of milliseconds. They also allow reactions to happen at a lower temperature so they can take place at body temperature. There are two ways scientists think enzymes work - the ‘lock-and-key’ model and ‘induced-fit’ model.
Enzyme function and structure
Enzymes are biological catalysts - they speed up the rate of chemical reactions happening inside our body. They work by reducing the activation energy of a reaction. Activation energy is defined as the minimum amount of energy needed for a reaction to happen. If less energy is needed, then reactions can take place as lower temperatures than would be needed without an enzyme. Without the enzymes in our bodies, the reactions that happen inside of us would not be possible at normal body temperature. Remember that enzymes are unchanged at the end of a reaction which means they can be reused.
Enzymes can be classed as either intracellular if they catalyse reactions inside cells e.g. RNA polymerase, or extracellular if they catalyse reactions outside of cells e.g. amylase. All enzymes are globular proteins and have regions called active sites. The active site of an enzyme has a specific shape and allows the substrate to bind. Other enzymes may have regulatory regions where an inhibitor can bind, which we refer to as the allosteric site.
Mechanisms of enzyme action
Scientists have two ideas to explain the way in which enzymes work: the ‘lock-and-key’ model and the ‘induced-fit’ model. They are models because they are our best-accepted theories based on the evidence we have available.
Lock and Key model
The lock and key model is the simpler of the two theories of enzyme action. This model suggests that the substrate fits into the enzyme’s active site in the same way in which a key fits into a lock. The shape of the substrate and the active site are perfectly complementary to each other. Catalysis happens in the following stages:
The substrate binds to the enzyme’s active site, forming an enzyme-substrate complex (ES complex).
The enzyme converts the substrate into product, forming an enzyme-product complex (EP complex).
The product is released from the enzyme’s active site.
The Induced Fit model
The induced fit model suggests that the shapes of the enzyme’s active site and its substrate are not exactly complementary, but when the substrate enters the active site, a conformational change (change of shape) occurs which induces catalysis. The induced fit model can be broken down into the following stages:
The substrate enters the enzyme’s active site, forming an ES complex.
The enzyme undergoes a conformational change which causes the conversion of substrate into product, forming an EP complex.
The product is released from the enzymes active site.
Comparing the two models of enzyme action
The advantage of the lock-and-key model is that it explains why most enzymes display such high specificity to their substrates. Each enzyme will catalyse only a certain type of reaction and will only bind to a single specific substrate out of the millions of different molecules that are floating around our bodies. However, not all enzymes catalyse a single chemical reaction. For example, lipase exhibits broader specificity and can bind to a variety of lipids, which only the induced fit model is able to explain. In addition, the induced fit model is better able to explain how catalysis actually occurs. A conformational change, which would place stress on the bonds within the substrate can explain how bonds would break in order for the products to form. This makes the induced fit model the more widely accepted model of the two.
Factors which affect rate of reaction
As enzyme concentration increases, the rate of reaction increases since more active sites will be available to bind to substrate molecules. This means that there will be more frequent collisions between the enzyme and substrate, so there will be more formation of enzyme-substrate complexes. However, a point will be reached when increasing enzyme concentration does not result in further increases in reaction rate. At this point, something else has become a limiting factor, such as the availability of substrate.
As substrate concentration increases, the rate of reaction increases since there are more substrate molecules to fill the enzyme’s active sites. There will be more frequent collisions so more formation of ES complexes. At some point a ‘saturation’ point is reached where all of the enzyme’s active sites are occupied with substrate molecules, so the addition of more substrate molecules will have no effect on the rate of reaction. At this point, the reaction is proceeding as fast as possible, which is referred to as Vmax. The only way the reaction can go any faster is by increasing enzyme concentration.
At low temperatures, the rate of reaction will be slow because the enzyme and substrate have low amounts of kinetic energy. This means that there won’t be many collisions so there will be reduced formation of ES complexes. As the temperature is increased, the number of collisions increases, increasing the formation of ES complexes and increasing the rate of reaction. If the temperature becomes really high, hydrogen bonds will begin to break within the protein, causing it to unravel and become denatured. If enzymes are denatured, they lose the shape of their active sites which means they cannot bind to their substrate, decreasing the rate of reaction.
Each enzyme has its own optimum pH at which it works best. Pepsin, the enzyme which digests protein in the stomach, works best in acidic environments whereas the enzymes responsible for the digestion of carbohydrates work better at a more neutral pH. Deviations from the optimum pH change the charge on the enzyme, which affects ionic bonding within its structure. Deviations in pH also break hydrogen bonds. This causes it to change shape and become denatured, decreasing the rate of reaction as pH deviates from the enzyme’s optimum conditions.
Chemical digestion could not take place without the help of digestive enzymes. An enzyme is a protein that speeds up chemical reactions in the body. Digestive enzymes speed up chemical reactions that break down large food molecules into small molecules.
Did you ever use a wrench to tighten a bolt? You could tighten a bolt with your fingers, but it would be difficult and slow. If you use a wrench, you can tighten a bolt much more easily and quickly. Enzymes are like wrenches. They make it much easier and quicker for chemical reactions to take place. Like a wrench, enzymes can also be used over and over again. But you need the appropriate size and shape of the wrench to efficiently tighten the bolt, just like each enzyme is specific for the reaction it helps.
Digestive enzymes are released, or secreted, by the organs of the digestive system. These enzymes include proteases that digest proteins, and nucleases that digest nucleic acids. Examples of digestive enzymes are:
- Amylase, produced in the mouth. It helps break down large starch molecules into smaller sugar molecules.
- Pepsin, produced in the stomach. Pepsin helps break down proteins into amino acids.
- Trypsin, produced in the pancreas. Trypsin also breaks down proteins.
- Pancreatic lipase, produced in the pancreas. It is used to break apart fats.
- Deoxyribonuclease and ribonuclease, produced in the pancreas. They are enzymes that break bonds in nucleic acids like DNA and RNA.
Bile salts are bile acids that help to break down fat. Bile acids are made in the liver. When you eat a meal, bile is secreted into the intestine, where it breaks down the fats (Figure below).
Figure (PageIndex<1>): Bile is made in the liver, stored in the gallbladder, and then secreted into the intestine. It helps break down fats.
Hormones and Digestion
If you are a typical teenager, you like to eat. For your body to break down, absorb and spread the nutrients from your food throughout your body, your digestive system and endocrine system need to work together. The endocrine system sends hormones around your body to communicate between cells. Essentially, hormones are chemical messenger molecules.
Digestive hormones are made by cells lining the stomach and small intestine. These hormones cross into the blood where they can affect other parts of the digestive system. Some of these hormones are listed below.
- Gastrin, which signals the secretion of gastric acid.
- Cholecystokinin, which signals the secretion of pancreatic enzymes.
- Secretin, which signals secretion of water and bicarbonate from the pancreas.
- Ghrelin, which signals when you are hungry.
- Gastric inhibitory polypeptide, which stops or decreases gastric secretion. It also causes the release of insulin in response to high blood glucose levels.
Science Friday: Stained Glass Conservation
Stained glass from the Middle Ages is often hundreds of years old. Unfortunately, many of these relics are in need of cleaning and maintenance. In this video by Science Friday, conservator Mary Higgins discusses the methods used to protect the stained glass.
Amylase is naturally produced in humans by the salivary glands and pancreas. It can also be naturally found in plants and animals.
Like most things, amylase production slows as we get older, which increases our risk for digestive troubles, malnutrition, and poor health. It is therefore important to keep levels up as we get older, and this can be easily done through plant-based digestive enzyme supplements as well as eating a variety of foods, including:
&diams Fruits, like bananas and mango
&diams Fermented foods, such as sauerkraut and kefir
&diams Whole grains, like quinoa and rice
&diams Legumes, like chickpeas and soybeans
Amylase is responsible for breaking down and processing carbohydrates into simple sugars that you body can utilize. Despite the bad reputation that carbohydrates get, they are essential for health and energy production.
Since there are refined carbohydrates that are not beneficial for you, it is important to understand which are necessary and which you should avoid. Because you need carbohydrates, you also need amylase enzymes.
The effects of amylase can be seen much quicker than those of lipase digestive enzymes (helps digest fats) and protease (helps digest proteins). The reason for this is because amylase comes from two locations in your body&mdashthe pancreas and the salivary glands.
The breakdown of carbohydrates begins in the mouth with your saliva, but when they get to the stomach, the amylase is neutralized by stomach acid, and the breakdown of carbohydrates ceases. Once carbohydrates get to the intestines, digestion resumes, as amylase produced by the pancreas is now available and creates glucose.
Any disruptions to this carbohydrate breakdown can result in health complications. For example, low glucose levels in the blood can cause fatigue and muscle weakness. The brain and nervous system both favor glucose-supplied energy, so without adequate levels in the blood, the function of these systems can also become impaired.
When it comes to choosing which carbohydrates to eat for energy, it is best to choose those that supply consistent levels. Refined carbohydrates (simple sugars) supply energy bursts, but these are often followed by crashes and fatigue.
Complex carbohydrates, like nuts, seeds, whole-grains, and most vegetables, offer sustained levels of energy and no spikes or crashes in blood glucose levels. However, without amylase, the energy levels may not be attainable at all.
This activity covers the lock and key hypothesis and enzyme activity. Enzymes like RNA polymerase are at the centre of most of the cells biochemical activity. This lesson answers the question, "How do enzymes work?" Students complete research, work with an online animation, make structured notes using a worksheet then test their knowledge with a range of questions including a data analysis.
How does the random movement of particles help enzymes to function?
What is most important about the shape of an enzyme to enable it to catalyse reactions with its substrate?
In what way do simple diagrams of complex 3D enzyme structures help us to understand how enzymes work?
Activity 1 - How do enzymes work? (Lock and key hypothesis)
Watch the animation below which shows a simple model of enzyme function.
Summary of the main points about enzymes
Enzymes are proteins which work as biological catalysts.
They speed up the rate of a chemical reaction without themselves being changed.
The actual structure of enzymes is complex they are often large proteins with a specific 3D shape.
The most important part of the shape on an enzyme is the active site.
The active site must fit the shape of the enzyme&rsquos substrate.
The active site is where the substrate molecules bind and undergo a chemical reaction.
Each enzyme has a particular shape of active site. They can each only catalyse one specific reaction.
This is known as &ldquoenzyme-substrate specificity.&rdquo
Activity 2 - Structured questions about Enzymes
Complete the Enzyme worksheet which will help to make a record of important notes about enzymes.
Activity 3 - Measuring rates of reactions and identification of substrates of enzymes.
One of the easiest methods of measuring the rate of and enzyme catalysed reaction is to measure the amount of product produced by the reaction in a given time.
It is also possible to measure the time taken for the substrate to disappear.
In fact the best method of measuring the reaction rate usually depends on easiest way to measure a substrate or a product.
The rate of catalase activity is easily measured, without an indicator but using a measure of the volume of oxygen gas produced.
The rate of amylase is often measured using the disappearance of its substrate. Iodine indicator can identify the moment when all the starch has been hydrolysed.
Biologists often use experiments to study the rate of enzyme catalysed reactions.
This enzyme simulation from Jon Darkow in Ohio provides a great introduction to factors which affect enzyme reaction rates.
Click the link, and follow the steps below.
Follow the instructions in this box to carry out a simple activity using this simulation.
Answer the questions as you progress through each step.
Enzyme simulation questions
- Ad just each of the red "Initial" substrate sliders one at a time and identify which are the substrates of amylase and trypsin.
- Amylase catalyses a reaction with the substrate .
- Trypsin catalyses reaction with the substrate .
What is the optimum temperature of Amylase? .
What is the optimum temperature of Trypsin? .
What is the optimum temperature of taq DNA polymerase? .
What is unusual about the optimum temperature of Taq polymerase
(Taq Polymerase is an enzyme found in the bacterium, T.aquaticus, living in hot springs?
Change the pH using the slider.
Use this to work out:
The optimum pH of pepsin is .
The optimum pH of Amylase is .
The optimum pH of Trypsin is .
The optimum pH of Taq polymerase is .
Use the lock and key hypothesis to explain in more detail why substrate concentration, temperature and pH affect the rate of enzyme catalysed reactions.
Extension activities - Video and short online quiz about enzymes
Watch this short video introduction to university work on enzyme research from Birmingham University in the UK.
More information is available here.
Test yourselves using the Multiple choice quiz on enzymes
Many students will have experience of enzyme experiments but few seem to have a clear memory of how to speed up an enzyme controlled reaction, and what denaturing really is. These concepts are clearly addressed in this lesson.
Activity 1 is a revision of the lock and key model. It is important to note that this lesson is designed for SL students. The content has been carefully selected to cover the IB SL guide but not the extra HL details. This is so that SL students don't have to learn details which will not appear in the SL exam.
HL students could save time by going directly onto the HL details of induced fit, and the extra details of the 3D structure of enzymes. This is shown in the animation in activity 1 but not mentioned.
Activity 2 is really about making nots about a topic which most students have studied before.
There are model answers to the enzyme's worksheet here:
Activity 3 incudes a simulation which could take students much further into working on rates of reactions. In this instance the questions are focused on the interactions between enzymes and their substrates, or the way that environmental variables affect the rate of reaction.