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Have you ever put a piece of white bread in your mouth and left it there? Without chewing or swallowing, the bread will slowly begin to dissolve, producing a sweet taste. This happens because of salivary amylase. It breaks down the complex carbohydrates in the bread and turns them into smaller, sweet-tasting sugar molecules.

The Definition of Amylase

First things first, what is amylase? It is a protein made by the salivary glands in and around the mouth of humans, where it triggers the process of digestion. Amylase is classified as an enzyme as it helps the body to catalyse the hydrolysis of carbohydrates into sugars.

Learn more about Digestive Enzymes and Digestion by checking out our articles!

Amylase is a digestive enzyme that speeds up the breakdown of starch into maltose.

Hydrolysis is the process of splitting a compound using water.

Amylase is also produced in the pancreas, where dietary starch is further broken down into simple sugars. These sugars are then further converted by the body (by other enzymes) into energy in the form of glucose.

Plants, along with some types of bacteria, produce amylase too.

Amylase as an Enzyme

Amylase is an enzyme. Enzymes are specialised proteins that speed up chemical reactions (in this case, digestion) by acting as biological catalysts.

Learn more about Enzymes by checking out our article!

Amylase breaks down long chain saccharides (sugars, starch in this case) into smaller sugars such as maltose. It does this using a water molecule to break the glycosidic bonds in the starch compound.

A catalyst is a substance that increases the rate of reaction without being used up.

A glycosidic bond is a type of covalent bond that links sugars together.

Enzymes help to increase the rate of reaction by lowering the activation energy of a reaction.

The activation energy is the minimum energy required for a chemical reaction.

The feasibility of a reaction typically relies on a high temperature. So that reactions can take place at lower temperatures, enzymes reduce the amount of activation energy required - this increases the rate of reaction.

Enzymes are three-dimensional globular proteins. Every enzyme has a specific active site. This is where a specific substrate (the interacting substance) binds to the enzyme.

Think of an enzyme as a lock and the substrate as a key. Only a specific 'key' (substrate) can 'open' (interact with) the enzyme.

Every enzyme has an optimum temperature and pH where it functions best.

  • Amylase functions best at 37ºC and pH 7.

Outside these conditions, the enzymes can become denatured. The bonds that maintain the protein's shape break, and the enzyme will no longer function properly. But a denatured enzyme isn't a problem for the body. If an enzyme becomes denatured, it will synthesise more.

The Structure of Amylase

Amylase is a globular protein. First, let's recap the four categories of protein structure:

  • Primary proteins - the sequence of amino acids in a polypeptide chain determines the primary structure of a protein.

Amino acids are organic acids that contain:

  • a carboxyl functional group (-COOH)
  • an amine functional group (-NH2)
  • a side chain specific to the amino acid (-R)

Amino acids commonly act as monomers, small units of larger molecules. Linking a few amino acids together creates a peptide. A large chain containing numerous amino acids is a polypeptide.

  • Secondary proteins - hydrogen bonds form between the amino acids in the chains, altering the shape.
    • There are two types of secondary proteins: spiral alpha-helix shapes and folded beta-sheets.
  • Tertiary proteins - the protein bends and folds from a secondary protein into a complex, three-dimensional shape.
  • Quaternary proteins - these proteins are made of different polypeptide chains.

Amylase, like all human enzymes, is a tertiary protein. It has some special structural traits that help it carry out its role effectively.

  • It has a globular (roughly spherical) shape. Tightly folded polypeptide chains cause these globular shapes. This shape allows amylase to form an active site where the substrate molecule can bond.

  • The outside of the amylase enzyme contains hydrophilic (water-loving) groups that make it soluble. This allows amylase to be easily transported around the body.

The Function of Amylase

Amylase catalyses the breakdown of starch molecules (polysaccharides) into maltose molecules (disaccharides) - but how does it do that?

The amylase enzyme collides with starch molecules and forms an enzyme-substrate complex. Amylase allows the starch molecule to break down into many smaller maltose molecules. The maltose molecules are released, and the enzyme is free to act again.

A polysaccharide is a large carbohydrate molecule, made up of lots of sugar molecules.

A disaccharide is a sugar molecule made up of two glucose units.

Amylase supports digestion in the mouth and the pancreas. Breaking down large, complex carbohydrates into smaller sugars makes it easier for the body to digest them and gain the energy they provide.

Sources of complex carbohydrates include bread, pasta, potatoes, and rice.

Amylase pasta starchy carbohydrate StudySmarterFig. 2 - Complex carbohydrates are an essential part of our diets. They provide energy for our bodies and brains, aid with digestion, and may reduce our risk of heart disease, unsplash.com

Maltose molecules are made of only two glucose units; the body can break them down quickly to form single glucose molecules. Glucose molecules are the body's primary source of energy from food.

Amylase is the primary component of saliva. But saliva doesn't just help us digest our food – it also plays a vital role in looking after our teeth. Saliva neutralises acids, prevents plaque build-up and kills bacteria.

Amylase Testing with an Example

It's normal to have a small amount of amylase in your blood and urine.

  • The healthy range of amylase in blood is 30 to 110 units per litre.

  • In urine, it's 2.6 to 21.2 international units per hour.

If your amylase levels are outside the usual range, you may be experiencing a health problem. High amylase levels typically indicate an issue with your pancreas. Low amylase levels suggest problems with your pancreas, liver, or kidneys. Low levels can also indicate cystic fibrosis.

Cystic fibrosis is a genetic disease occurring in 0.04% of the population (equivalent to 1 in every 2500 people). It is a multi-system disease affecting the pancreas, intestines, reproductive tract and lungs. Sufferers find it challenging to absorb adequate nutrients, leading to fatigue-related problems.

Amylase tests can be used to diagnose or monitor several diseases, such as:

  • Cystic fibrosis

  • Infection

  • Pancreas problems (e.g., pancreatitis, gallstones, cancer)

  • Eating disorders

  • Alcoholism


How is an Amylase Conducted?

Amylase is an enzyme that increases the rate of starch digestion. Like all enzymes, amylase functions best at a specific temperature and pH.

During your GCSEs, you will carry out an experiment to see how pH affects the rate of reaction of amylase.

Method:

  • Set up test tubes at different pHs by using a buffer solution.

  • Add amylase and starch to each test tube, then add a drop of iodine solution. Iodine turns blue-black in the presence of starch.

  • When the iodine has returned to its natural orange colour, all the starch has been broken down into maltose.

  • Use a stopwatch to time how long it takes for the iodine solution to change colour — the quicker the colour change, the faster the rate of reaction.

Control Variable

Enzymes are affected by pH and temperature. We only want to test the effect of pH, so the temperature should stay the same. It can be controlled using a water bath or electric heater to keep the test tubes at 35°C.

Risk Assessment

  • Wear eye protection.

  • Avoid chemical contact with the skin.

Results

Present your results in a table. Calculate the rate of starch breakdown using the following equation: 1 / time in seconds

Finally, plot a graph of the rate of reaction against pH.

pHTime taken for starch to break down (seconds)Rate of starch breakdown (1/t)
5850.012
6300.033
7250.040
8400.025
91000.010

Amylase testing experiment rate of reaction graph StudySmarterFig. 3 - The rate of reaction is highest at its optimum pH.

Amylase - Key takeaways

  • Amylase is a digestive enzyme that catalyses the breakdown of starch into maltose. It is produced in the salivary glands and the pancreas.

  • Enzymes are biological catalysts. They speed up the rate of chemical reactions without being used up.

  • Amylase has a globular shape and hydrophilic groups on the outside that make the enzyme soluble.

  • Amylase plays an essential role in digestion. It breaks down complex carbohydrates into smaller, simple sugars, making them more accessible for the body to digest. Salivary amylase also supports dental health.

  • Abnormal amylase levels in blood or urine can indicate a health problem - especially those that affect the pancreas.


1. Anne Marie Helmenstine, Amino Acid Definition and Examples, ThoughtCo, 2019

2. CGP, AQA A-Level Biology Revision Guide, 2015

3. Cleveland Clinic, Amylase Test, 2022

4. David J. Culp, Murine Salivary Amylase Protects Against Streptococcus mutans-Induced Caries, Frontiers in Physiology, 2021

5. Edexecel, Salters-Nuffield Advanced Biology, 2015

6. Keith Pearson, What Are the Key Functions of Carbohydrates?, Healthline, 2017

7. Regina Bailey, Salivary Amylase and Other Enzymes in Saliva, ThoughtCo, 2019

Frequently Asked Questions about Amylase

Amylase aids digestion by breaking down large carbohydrate molecules into simple sugars.

Amylase is produced in the salivary glands and the pancreas.

An abnormally high amylase level indicates a problem with your pancreas.

Blood amylase is typically between 30 and 110 units per litre, whilst urine amylase is between 2.6 and 21.2 international units per hour.

Final Amylase Quiz

Question

What is amylase?

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Answer

Amylase is a digestive enzyme that catalyses the breakdown of starch into maltose.

Show question

Question

What is an enzyme?

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Answer

An enzyme is a protein that acts as a biological catalyst.

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Question

What is a catalyst?

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Answer

A catalyst is a substance that increases the rate of reaction without being used up.

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Question

How do enzymes increase the rate of reaction?

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Answer

Enzymes lower the activation energy of a reaction.

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Question

Where does the substrate bind to an enzyme?

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Answer

The substrate binds to the enzyme at the active site.

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Question

What are the optimal conditions for amylase?

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Answer

Amylase's optimal conditions are 37ºC and pH 7.

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Question

What type of protein has a three-dimensional structure?

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Answer

Primary protein

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Question

Enzymes are soluble. Why?

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Answer

It allows them to be easily transported around the body.

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Question

What is a polysaccharide?

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Answer

A polysaccharide is a large carbohydrate molecule, made up of lots of sugar molecules.

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Question

How does amylase aid digestion?

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Answer

Amylase breaks down large complex carbohydrates into smaller, simple sugars, making them easier for the body to digest.

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Question

Which of these is not a source of complex carbohydrates?

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Answer

Chicken breast

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Question

Where is amylase produced?

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Answer

Salivary glands

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Question

Small amounts of amylase are present in some body fluids. Which ones?

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Answer

Blood

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Question

Amylase tests can indicate problems with what organ?

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Answer

The pancreas

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Question

How many glucose units are found in a maltose molecule?

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Answer

2

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