Tuesday, Jun. 27, 2017

Teaching for understanding and retention: investigative learning approach

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May 24, 2017

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The mediocre teacher tells. The good teacher explains. The superior teacher demonstrates. The great teacher inspires.
–William Arthur Ward

As teachers all of us strive to live up to this idea and thus keep innovating our lesson plans to make them more powerful.

Teaching is a passion for us at the Biology department at TGES, Rajkot. We try to come up with lesson plans that help students gain more from our classroom teaching. The reason for us to think differently was the assessment papers. While checking papers we realized that some students had completely misunderstood certain concepts, despite what we considered flawless teaching sessions. We thus comprehended a gap in what we taught and what the students imbibed. Somewhere it is difficult to gauge, how far what we teach actually reaches the students in the desired format.

This made us realize that if things have to be imbibed properly, mere psychological presence of the student is not enough. It requires engaging them in the learning process, thus inspiring students towards inquiry-based learning. This, we found, facilitated long-term retention of the concept.

These experiences drove us to create lesson plans differently, thus giving rise to the idea of Investigative Learning Approach (ILA). This idea envisaged by us has brought a radical change in our teaching pedagogy. The outcome of this has been very encouraging as we found the students changing from passive listeners to inquirers and the classroom becoming a more interesting place. With the success of our ILA strategies, we are happy to share these ideas with the teaching community.

Investigative learning approach-1: Enzymes

We started this for the chapter ‘Enzymes’ (ISC) Grade 11. This involves, students investigating the properties and factors affecting enzyme action by performing experiments in groups and deriving conclusions that then result in their understanding the concepts. Drawing conclusions based on the data collected by students creates better understanding by engaging and empowering the students thus allowing better retention of concepts.

We have tried to include experiments with chemicals/materials that are readily available. Some of these experiments are a part of the practical syllabus for ISC. However, most of the time it is seen that students simply follow the protocol without thinking about the concept. Our idea is to integrate these experiments with the theory thus facilitating better understanding.

To engage and involve students it is important to trigger their curiosity and generate interest for the topic. We began our session by introducing some real life connection related to the topic Enzymes. We gave an Eclair to each student and asked them how is it that the centre is soft and the covering is solid and hard.[This is due to the use of enzyme invertase that acts on sucrose breaking it down to glucose and fructose making it soft]. We could also discuss other examples like why is commercially available fruit juice transparent as compared to home made fruit juice or the difference between regular washing powders and biological washing powders. There are washing powders with enzymes as their constituent. These examples stimulate the thinking mode among the students.

What is a biocatalyst?

Now, we began the lesson by a discussion about production of ammonia. Students know Haber’s process and the conditions required for it i.e about 400-500 degree celsius temperature and 200 atm pressure. We compared this to the production of ammonia in the liver cells where ammonia is produced without such high temperature and pressure. How is this possible?

Another example is the production of carbonic acid from water and carbon dioxide. In this, the reaction is very slow, about 200 molecules of H2CO3 are formed in an hour. However inside a cell, this reaction speeds up dramatically with approximately 600,000 molecules being formed every second. How is this possible?

This leads to the term biocatalyst. We then explained biocatalyst and gave the definition.

Difference between catalyst and biocatalyst

To understand the difference between biocatalyst and catalyst we let the students perform an experiment working in groups. We asked them to compare the action of inorganic catalyst (MnO2) and organic catalyst (catalase). Both MnO2 and catalase, work on the same substrate (hydrogen peroxide). Potato extract was used as source for catalase. They had to put both in two different test tubes containing same amount of H2O2 and observe the difference. The effervescence from the tubes was a clear indicator of which acts faster.

Interpretation: The tube with catalase shows faster and more effervescence.

Chemical nature of enzymes

A major misconception among students is that ‘enzymes are living’.

Instead of just explaining that enzymes are chemicals, made up of proteins, students were asked to perform biochemical tests. This included selecting a pure enzyme, and performing a test for carbohydrate, lipid and protein for it.

By interpreting the results of these tests, they were able to confirm that enzymes are proteins. We also clarify that all enzymes are not protein in nature because RNase also shows catalytic property.

Structure of Enzyme: It’s shape matters…

Most enzymes are proteins. The unit biomolecules covers the structure of proteins. Students are thus familiar with the tertiary structure of protein.

To clarify that enzymes are globular in shape, we use a ribbon to give them the idea of the folding in levels of protein structure. This gives them visual clarity about the globular structure of enzymes.

The active site of the enzyme and its significance is explained here.

How do enzymes work?
The mechanism of action of enzymes can be explained by – the Lock and Key hypothesis and the induced fit hypothesis ; we used magnetic cardboard pieces to explain the lock and key mechanism for enzyme specificity.

Enzymes and activation energy

Enzyme speeds the rate of reaction, by decreasing the activation energy. This can be observed if we allow hydrolysis of a particular substance with enzyme and without enzyme. We selected hydrolysis of starch by keeping the test tubes in water bath set at 80 degree celsius for different time interval and one with enzyme, the product of hydrolysis – sugar was observed by Benedict’s test. Students were asked to perform this experiment and deduce the results.


To bring the concept of enzyme specificity, we decided on another experiment that would show that only a specific enzyme will act on a specific substrate. Starch was selected as the substrate and different enzymes like lipase, amylase, protease and sucrase were added to check their action on starch. Hydrolysis of starch was checked by using Benedict’s test. [Other than this, we can use amylase which can be used with different substrates- starch, sucrose and egg albumin or catalase from potato with H2O2, water and sugar solution]

Factor affecting enzyme action:

Chemically most enzymes are protein. The integral protein conformation decides their catalytic activity. Enzymes will lose their catalytic activity by any factor that dissociates or breaks it into its subunits.
There are different factors , pH, temperature and substrate concentration that affect enzyme action.

In order to show that pH affects enzyme action we chose an experiment with catalase and H2O2. Students were given different pH solutions [4.2, 6.8, 7.2, 8.2 and 9]. Potato discs were used as source for catalase. These discs were added in tubes containing pH and H2O2. The release of oxygen caused the discs to rise up and float.

Fig: Activity of catalase (in potato disc) in different pH solutions of H2O2

Similarly different temperatures and substrate concentration on enzymes were tested. Students performed experiments to draw conclusions and thus know how these factors affect enzyme action. The conceptual part is explained after every experiment.
Some questions that may be given at the end of the chapter for assessment-

  • What happens if there is no enzyme in a cell?
  • Why do we need so many enzymes, why can’t we have just one for all reactions?
  • Are enzymes water soluble?
  • Enzymes are reused. Is enzyme production inside cells a continuous or once in a life time process?
  • Enzymes speed up the reaction rate. What controls this speed?

This is a part of the lesson plan that includes, experiments/activities to make the topic of Enzyme interesting and engaging. Students were very enthusiastic about the Biology classes during this entire chapter. The detailed plan for this lesson with experimental protocols is available with us and we will be more than happy to share it.

Acknowledgements-
Lab technicians- Mrs Madhuri Parmar and
Ms Anila Patel
Photo credits- Ms. Manmitha Deepthi

Dr. Deepthi Uthaman
An educator by choice, her Ph.D. is on reproductive endocrinology. Her school and college life gave the opportunity to assimilate knowledge and experience diverse traditions and cultures from different Indian states.
She has taught students from grade VIII to post-graduate level and has worked as the Principal of a residential school.
Her teaching pedagogy emerged to new horizons after attending the IB & CIE workshops, PBL training (Buck Institute of Education, California) and the Wide world online training for TFUT (Harvard School of education).
Currently she is Biology facilitator and HoD, at TGES, and is passionate about implementing new teaching strategies in her classes. She is also passionate about sharing her knowledge and experiences with her teammates help them grow professionally. She can be reached at deepthi.uthaman@tges.org

Gajendra Khandelwal
An educator with extensive and varied experience in teaching science is enthusiastic about teaching. He is M. Sc in Botany, B Ed and a CSIR NET (Life science) qualified teacher.
He has experience teaching varied boards like CBSE, ISC, CIE, IGCSE, and IB that contribute to his innovative teaching strategies. Attending the IB & CIE workshops, PBL training (Buck Institute of Education, California) and the Wide world online training for TFUT (Harvard School of education) has also contributed to his novel lesson plans.
Currently he is a senior Biology facilitator at TGES, handling IB and ISC classes.He is passionate
about teaching and learning and likes sharing his ideas and strategies with colleagues helping them enhance their classroom strategies. He can be reached at gajendra.khandelwal@tges.org

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