Help with permiability of membranes question (AS)

I was doing a worksheet on the effect of temperature on permbiality of membranes.
First few questions were fairly simply, then there was this one:

4 Liver cells contain membrane-bound organelles called peroxisomes. These organelles contain catalase, an enzyme that breaks down hydrogen peroxide to release oxygen gas.
A student carried out an investigation on catalase using the following procedure:
• two identical sized cubes were cut from a piece of fresh liver
• one cube was frozen overnight and then defrosted
• the other cube was stored in the refrigerator
• both cubes were returned to room temperature and were placed in separate test tubes containing equal volumes of 2% hydrogen peroxide solution.
The student observed that the cube of liver that had been frozen and defrosted, bubbled significantly more than the cube that had been refrigerated. Suggest an explanation for this result. (2 marks)

Any ideas?? We haven't gone into stuff about freezing at all! :s-smilie:

ANy help is appreciated <3

Reply 1

doc.dolittle

2

Original post by 666satinsdoll666

I was doing a worksheet on the effect of temperature on permbiality of membranes.
First few questions were fairly simply, then there was this one:

4 Liver cells contain membrane-bound organelles called peroxisomes. These organelles contain catalase, an enzyme that breaks down hydrogen peroxide to release oxygen gas.
A student carried out an investigation on catalase using the following procedure:
• two identical sized cubes were cut from a piece of fresh liver
• one cube was frozen overnight and then defrosted
• the other cube was stored in the refrigerator
• both cubes were returned to room temperature and were placed in separate test tubes containing equal volumes of 2% hydrogen peroxide solution.
The student observed that the cube of liver that had been frozen and defrosted, bubbled significantly more than the cube that had been refrigerated. Suggest an explanation for this result. (2 marks)

Any ideas?? We haven't gone into stuff about freezing at all! :s-smilie:

ANy help is appreciated <3

Basically when you freeze it, it damages the plasma membrane of the liver and increases the permeability of the membrane to H2O2. So when the liver breaks down the H2O2, more O2 is released.

Reply 2

Reality Check

22

Spelling of 'permeability' is important.

Not doing it for you, but if you freeze something, what effect do you think this has on the cell membranes? Have you ever seen a piece of lettuce that's got pushed to the back of the fridge or something accidentally and ended up being frozen? What does it look like after?

In other words, what effect do extremes of temperature have on membranes, do you think? This could lead you to your answer, given that the gas is produced by breaking down a chemical which is contained in membrane bound organelles...

Reply 3

Ambitious1999

20

Original post by 666satinsdoll666

I was doing a worksheet on the effect of temperature on permbiality of membranes.
First few questions were fairly simply, then there was this one:

4 Liver cells contain membrane-bound organelles called peroxisomes. These organelles contain catalase, an enzyme that breaks down hydrogen peroxide to release oxygen gas.
A student carried out an investigation on catalase using the following procedure:
• two identical sized cubes were cut from a piece of fresh liver
• one cube was frozen overnight and then defrosted
• the other cube was stored in the refrigerator
• both cubes were returned to room temperature and were placed in separate test tubes containing equal volumes of 2% hydrogen peroxide solution.
The student observed that the cube of liver that had been frozen and defrosted, bubbled significantly more than the cube that had been refrigerated. Suggest an explanation for this result. (2 marks)

Any ideas?? We haven't gone into stuff about freezing at all! :s-smilie:

ANy help is appreciated <3

Also some of the catalase enzyme is release into the extra cellular space through the membrane that's been made more permeable by the freezing. So the peroxide can react with the enzyme straight away.

Help with permiability of membranes question (AS)

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