Pepsin and Protein

Pepsin and Protein

Question

Is the rate at which Pepsin digests protein affected by temperature?

Prediction

I predict that it is affected by temperature. The optimum temperature

will be between 30°C and 40°C. This is because the average human body

temperature is 37°C. At 0-20°C (which includes the groups 0-10 and

10-20) the pepsin will not digest the protein for a long time. This is

because it is a too cold environment for the enzyme to work most

effectively and quickly. At 20-30°C the pepsin will work slightly more

quickly than at 0-20, but not as well as at 30-40, because it is

reaching the optimum temperature, though it is not quite there yet.

At the higher temperatures (i.e. 40-70°C) the enzymes will not work as

well. You may think that, using the pattern up to 30-40°C, the higher

the temperature, the quicker pepsin works. But this is not the case

because when it gets too hot, the enzymes start to lose their shape.

Enzymes use a very precise "lock and key" method to digest food. For

example pepsin, which is a protease enzyme, has a shape exclusive for

digesting protein molecules, and as soon as it changes its shape (in

this case due to heat) it cannot digest the molecule it was originally

designed to digest. Once it has changed shape it cannot change back

again. The "lock and key" is demonstrated below with diagrams.

The pepsin molecule locks onto the Glucose molecules are very

glucose molecule and breaks it complex but they still need

down into smaller particles. specially designed enzymes

that fit the molecules perfectly

to break them down.

If the temperature is too high and the enzyme changes ...

... middle of paper ...

...ironment

pepsin works quickest in. (see prediction).

The independent variable will be the temperature range - 0-70°C in

jumps of 10°C.This is what to change for the investigation. Nothing

else must change, because then it would be an unfair test. The

dependant variable will be the rate at which pepsin digests the egg

white suspension - in other words how long the mixture takes to go

clear. This will give you the results. For a fair test the controlled

variables will be the amount of egg white suspension (25cm²), the

amount of pepsin (5cm²) and the amount of hydrochloric acid (5 drops

from the pipette) used. Also how often the mixture is checked will be

a controlled variable. To make the results as accurate and reliable as

possible, each temperature range will be repeated 5 times, and an

average will be taken.