In this module:

  1. Enzyme theory & modelling
  2. Enzymes – amylase & starch
  3. Enzymes: catalase
  4. Apple browning
  5. Enzymes: protease pineapple

Enzyme theory & modelling

Enzymes 01: Introduction:

An introduction to some of the enzyme practical work we plan to share.

Enzymes 02: Structure & function:

Looking at enzyme / protein structure. A very brief mention of lock and key and induced fit models of enzyme action to hydrolyse a disaccharide sugar for example.

Enzymes 03: 3-d structure:

Enzyme three-dimensional structure. A simple idea for modelling 3d enzyme structure. Adding additional features such as hydrogen bonding and disulphide bridges to make, dare we say, a more sophisticated model.

Enzymes 04: Denaturing:

Enzymes and denaturing. The effect of temperature and pH on protein structure. Some enzymes can ‘re-nature’ to become functional again.

Enzymes 05: Inhibition:

Enzyme Inhibition: by competition for the active site or by non-competitive inhibitors affecting the enzyme structure.

Enzymes 06: Typical Graphs:

Typical looking graphs displaying enzyme activity, substrate, temperature and pH are the main factors. Time taken and rate of reaction. Mention of the different sources of enzymes, mammalian, fungal or bacterial sources.

Enzymes 07: Where to begin investigating.:

Start any investigation as close as you think will be the optimum be. Get a result as ‘quickly as possible’ then take further readings above and below the optimum to obtain a set of data.

Enzymes 08: Alternative enzyme sources:

Pineapples as a inexpensive sources of protease and yeast for amylase. Lipase from nutrient supplements. Maybe seeing where the enzymes come from might help in setting a context for learners.

Enzymes 09: Protein digestion:

Protein digestion by proteases. Exo and Endopeptidases hydrolysing polypeptides to amino acids eventually.

Enzymes 10: Protease:

Starting off to consider protease sources such as pepsin, trypsin etc. pH is a key factor.

Enzymes 11: Lipase:

A few thoughts of lipase sources and how to prepare for investigations.

Enzymes 12: Lipid digestion:

Lipid structure. Ideas for very simple model of lipids. The hydrolysis of the lipid produces fatty acids. The associated fall in pH (more acidic) could be used to monitor lipid digestion reaction.

Enzymes – amylase & starch

Amylase & starch 01:

The amylase-starch experiment is possibly one of the most quoted and referred to enzyme practicals but boy it can be ‘temperamental’. It shouldn’t be from now on though. Getting started: testing all the reagents so you are sure what you are using.

Amylase & starch 02:

Investigating temperature or pH are popular themes even though changing starch or amylase concentrations are more straightforward. Use of a spotting tile is a common ‘sub-sampling’ technique. Get the iodine solution in the depressions, be aware of the depth / volume though. Judging any reaction end-point be colour is not an exact science. Always begin at the expected optimum rate / fastest time, or you could be in for a very long wait and run out of solution to test!

Amylase & starch 03:

Changing the pH. Begin with what you expect to be optimum. Look at the suppliers note, it might not be anything near the range you expect for salivary amylase and you are way beyond the optimum. Look out for alternative methods you can depend on.

Amylase & starch 04:

Certain sources of amylase can be unreliable to get those blue-black colour changes we are looking for. However, your own salivary amylase is virtually fool-proof unless you smoke tonnes of cigarettes. Checkout certain types of yeast. For a few pennies you have possible the easiest source of amylase activity. Please forward all cost savings to BioTV.

Enzymes: catalase

Catalase 01:

Make sure the hydrogen peroxide is ‘fresh’ or it’s a waste of time.

Catalase 02:

Trial work using liver to check if the hydrogen peroxide is okay.

Catalase 03:

Trial work using liver to check if the hydrogen peroxide is okay. It fizzes nicely so we can continue.

Catalase 04:

Using apple as a source of catalase.

Catalase 05:

Apple, potato liver and yeast as catalase sources. Observe and compare results. Thoughts about common DNA coding for catalase.

Catalase 06:

Using a large volume of hydrogen peroxide to demonstrate a point. Judging chemical reactions. Notice the exothermic temperature rise.

Catalase 07:

Moving on from the previous set up with categoric variables to quantifying concentrations. Using filter papers soaked in apple juice extract as a catalase source to judge the reaction rate.

Catalase 08:

A tried and tested classic set up. Put a measuring cylinder in a beaker as a ‘sink’. Yeast suspensions as a catalase enzyme source. Start at an optimum expected rate of reaction. Make up serial dilutions of substrate. Glowing splints testing for oxygen. As we know hydrogen peroxide produces water and oxygen.

Catalase 09:

Alcohol and liver. Comparing the effect different alcohol concentrations on the way liver catalase reacts with hydrogen peroxide. A possible extension to talk about the health risks of excessive alcohol consumption and liver cirrhosis.

Catalase 10:

A few thoughts to highlight alternative ways to collect data from the catalase reaction. Measuring volumes of oxygen by displacement; oxygen sensors; pressure and temperature sensors. We might be tempted to show these in detail if there is a need.

Apple browning

Apple browning 01:

Possibly the most straightforward enzyme related experiment. A challenge at all levels if you ‘dig deeper’ though. Apple browning is an easy win! The extent of the reaction is obvious and easily extended to a simple pH study. A great way to introduce different variables to test.

Apple browning 02:

Observe the browning results. Look at the effect of pH using familiar acids such as citric acid (lemon juice), acetic acid (vinegar), ascorbic acid (vitamin C) and even talk about the role of antioxidants.

Enzymes: protease pineapple

Protease Pineapple 01:

Pineapple Treats: a way to look at protease activity. Be sure to have a fresh pineapple for this easy route into studying protease enzymes and at very little cost too. Testing for protein and hopefully it is protease. Preparing the pineapple boats made from albustix and film.

Protease Pineapple 02:

A simple set up of pineapple chunks and exposed monochrome film to assay protease digestion. Make sure to use the correct type of film!

Protease Pineapple 03:

Using albustix to detect protein i.e. the enzyme we want. The results of protease activity on the monochrome film.

Protease Pineapple 04:

Adding buffer or different pH solutions to the pineapple chunks. Why buffers are important in pH work.

Protease Pineapple 05:

Extract pineapple juice as enzyme sources. Setting up to investigate temperature and rate of reaction.

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