Enzymes. Topic 3.6 and AHL 7.6. http://www.livingscience.co.uk/joomla/index.php?option=com\_content&view=article&id=57:enzymes&catid=42:enzymes&Itemid=54. I.A. Investigation: Factors affecting enzyme activity investigations.
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Topic 3.6 and AHL 7.6
Factors affecting enzyme activity investigations
You will be looking at the decomposition of H2O2 by catalase in yeast. How could you get catalase? What is catalase?
Two periods to investigate different lab protocols.
Your ORIGINAL lab design will be due the following day.
Class period to work on lab design with students using a similar design (I’ll explain).
Two lab periods for YOUR INDIVIDUAL data collection.
Due one week later
Remember to use the report format you have used before.
I’ll put a link here to it in the future on the website I haven’t set up.
The Lock-and Key hypothesis: the substrate and the active site match each other in two ways:
If the lock-and-key model were true, one enzyme would only catalyze one reaction. In reality, some enzymes can catalyze multiple reactions.
to original shape
An enzyme stresses the bonds in the substrates, reducing the activation energy required for a reaction to occur.
Enzymes are globular proteins. Their structure can be altered by changes in pH or temperature – if the shape of the active site is changed substantially, they will not function.
Use this animation to test the affect of the following factors on enzyme activity:
When you have finished this, complete the enzyme activity sheet.
As temperature increases, rate of reaction increases as molecules have more energy, move faster and therefore collide and react more frequently.
Above optimal temperature any more increase denatures the protein. The active site changes, and the enzyme is non-functional.
A thermophile, such as bacteria in boiling pools (think Yellowstone National Park) can withstand MUCH higher temps before it denatures.
Try this virtual lab:
Look at this example of two digestive enzymes. If there is a deviation from the optimum pH, the hydrogen bonds between the amino acids in the structure of the enzyme are broken.
Lactose (milk sugar) can cause allergies in some people. This is usually because they can’t produce the enzyme lactase in quantity.
No ice cream for YOU!
*or biochemical pathways
Inhibition can be competitive or non-competitive
Inhibitor fits into the allosteric site* causing a conformational change in the active site. The substrate cannot attach to react.
Inhibitor fits the active site and prevents the substrate from entering.
*allosteric site = Other site
Even with competitive inhibition, the same maximum rate of reaction will be achieved if more substrate is added because we have not change the number of enzymes available.
Normal metabolism of ethanol (alcohol):
Antabuse (disulfiram) competes with the aldehyde oxidase and prevents the acetaldehyde from being converted to acetic acid.
A build up a acetaldehyde follows, resulting in a strong feeling of nausea and other hang over symptoms. A great deterrent from drinking!!
Antabuse is administered as a daily pill, so how well it works depends on how much a person is motivated! If they stop taking it they can drink again.