Biology Design Lab Help

[Guest Evil Mouse]

I decided that I will investigate the effect of temperature on the enzyme bromelain. The independent variable is temperature but I'm not sure about what the dependent variable could be. I will use jello as the substrate.

[Sandwich]

...rate of reaction, no? So you'll have to find some way of measuring the activity of the enzyme such that you can record a rate of reaction, usually based on observations of the substrate.

[Guest Evil Mouse]

could my lab then be to find out at what temperature does the denaturation of bromelain occur?

so ill have lets say 5 bowls with jello then Ill heat 5 pieces of bromelain at different temperatures put them in each bowl with the jello then place the bowls in a freezer for about 2 hours

then ill observe which jello had stiffened and which remained in liquid form

would that be a good idea for the lab?

[Sandwich]

I just looked up bromelain and it's not even an enzyme, it's a piece of pineapple, apparently, which contains a series of proteases. Obviously this is instantly a bad experiment because you are actually looking at a combination of many variables.

A standard enzyme experiment (of a sufficiently high quality of science to be IB level) involves:

- a purified enzyme (i.e. not a mixture of enzymes)

- the specific substrate for that enzyme

If you're testing temperatures it's considered standard to do a temperature curve. So you do 1 at 20 degrees, 1 at 30 degrees, 1 at 40 degrees (obviously with intervals and degrees relevant to the enzyme you're testing, a human body enzyme is going to work best around body temperature, a plant enzyme at lower temperatures etc). From this you obtain data about when the enzyme is denatured, its optimum temperature of operation and generally how well it works at other temperatures.

When measuring your substrate you need a much better method of mechanism than "yes" "no". An enzyme doesn't either work or not work, it works to different degrees at different temperatures. So "is it solid or not solid?" is a very poor method of measuring this. If you can't find a good way to measure the activity of the enzyme on the jelly, use something other than jelly OR find a different enzyme/substrate concentration.

You have to consider things like surface area exposed to the enzyme, amount of stirring/mixing of the enzyme and substrate and a whole load of other variables for the science to be 'good' - i.e. yield a true result and not a result which comes from a flawed/muddled design. So the whole thing needs to be controlled and monitored very well - and importantly monitorable. If you can't control for something, re-think.

[Guest Evil Mouse]

how could I measure the rate at which the gelatin (substrate) is broken down?

[Sandwich]

...that's for you to figure out! It's YOUR design lab!

often provides answers.

[rosirosiful]

I am doing my lab report on photosynthesis

I scanned the extracts of my plants with the spectrophotometer

the thing is that I was going to calculare the quantity of chlorophyll a and b for different colors of light, but I think that the formulas I got are not correct

chlorophyll a= 12.7 * A663 - 2.69 * A645 * (volume of extract/ milliliter*grams)

chlorophyll b= 22.9 * A645 - 4.68 * A663 * (volume of extract/ milliliter*grams)

I don´t know if they are correct because the source is not very reliable

then I read about the jefrey and humphrey's formulas, but there says that they are for 90% acetone and I used 96% ethanol, can I use them anyway?? or which formulas can I use??

also, how can I get these error numbers: ?