Saturday, October 23, 2010

How to teaching basic biochemistry, topic 3.

This is an outline of my approach to teaching basic biochemistry ( notice we are not dealing with HL topics at this stage)

Ask the student to complete 3.2.1,  3.2 .4,  3.2.6 and 3.2 7 as homeLearning in preparation for your lesson (see Flip-learning post below). I would test this immediately that the students arrive, MCQ, demo materials etc.  Lets move to the main course of the lesson.

The syllabus statements read:

3.2 Identify amino acids, glucose, ribose and fatty acids from diagrams showing their structure(2).


3.2.5 Outline the role of condensation and hydrolysis in the relationships between monosaccharides, disaccharides and polysaccharides; between fatty acids, glycerol and triglycerides; and between amino acids and polypeptides(2).

Notice the command term is identify which means to to give the differences between two or more different items and outline which means to give a brief summary.

I'm going to go through my routine for 3.2.2 and 3.2.5. I would teach carbohydrates first, then proteins and then lipids. Notice I am saving time by not teaching the objective 1 statements but would test them during this lesson or as a separate starter to this lesson. Here's the carbohydrate routine just repeat for the others

Phase 1
  1. Using a molecular modeling kits get the student to select the carbon, hydrogen and oxygen sufficient to build glucose (C6H12O6)
  2. I would then provide the student with a sample of solid glucose (not a solution) and ask them to note down the physical properties (sweet, solid, crystalline).
  3. Ask them to join all six carbons in a row, introduce the word hexose. (ask students to draw this on paper)
  4. Now ask them to join C1 to C5 through an oxygen (emphasis valency and once more ask students to draw this on paper)
  5. Add H and OH to each Carbon
  6. Add in additional groups such as are required on C6 (ask students to draw this on paper)
  7. Peer review/ Immediate teacher feedback
  8. You could at this stage do a pentose but I prefer to return to this later, so I go straight into phase 2
Phase 2
  1. Ask the student to add the glucose to a boiling tube, add water and describe what happens (add to properties)
  2. Add sufficient Benedict's reagent until blue, place in waterbath (usual lab safety)
  3. There should be a strong positive result. Record
Notice that we have introduced student to a physical substance they can touch, and not a clear prepared solution they cannot relate to in any way. Also emphasis that the Benedict's test is of reducing sugar which suggest that the sugar is reactive.

Phase 3 (addressing 3.2.5)

Pair students
  1. Provide with sample of solid maltose
  2. Ask to describe the properties
  3. Introduce the idea of a polymer (disarccharide)
  4. Provide diagram of maltose and ask the pair of student to combine their glucose molecules, this should produce a 'water' molecule. Link to condensation reaction. Peer instruction/ Teacher feedback
  5. Students draw diagram of maltose
  6. Ask student to add maltose to a boiling tube, add water, what happens...dissolves (add to list of properties)
  7. Carry out a Benedict's test.
Phase 4
  1. Provide students with a sample of sucrose
  2. Build molecule
  3. Repeat Benedict's test
  4. Draw molecules and describe properties
Phase 5
  1. In student pairs rebuild maltose.
  2. Now progressively add maltose to maltose (student groups getting bigger).
  3. Provide the students with a sample of starch /solid.
  4. Ask student to describe properties.
  5. Add to the boiling tube and try to dissolve (it doesn't).
  6. Carry out a Benedict's test
  7. Introduce the Iodine solution (KI (aq)) test.
At this point you could proceed to the overall molecular shape or you could introduce the concept of hydrogen bonding. I just go straight to the helix shape/ possibly introduce amylopectin

Phase 6
  • A group review of carbohydrates
  • I link this to the way plants make, transport and store carbohydrate.

Protein biochemistry can be dealt with in the same way and extended out to the Higher Level work as necessary. Lipid chemistry can be demonstrated in exactly the same way but contrasting this as non polymer.

All of this would take me 5 x 40 mins of class time.