Bio Quick Question. Easy. - Topic

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Sep 15 2013 01:29pm

A student has just gotten done browning some ground beef to add to the homemade marinara sauce he has spent all morning cooking. If this student was to pour some of the liquid left over in the skillet into a test tube and perform a Sudan IV test as outlined in your lab manual, can this student expect to see a floating red layer when he is finished performing the test?

i know sudan iv tests for fats. but does it only test for 1 type of fat? or all fats in general? cause beef is saturated fat, not unsaturated.

thanks.

This post was edited by noob_whacker on Sep 15 2013 01:47pm

EBAZ

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Sep 15 2013 02:12pm

There will not be a red ring or layer seeing how it only tests for one kind of lipids.

Dmon_Hunter

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Sep 15 2013 04:13pm

Quote (EBAZ @ Sep 15 2013 03:12pm)

There will not be a red ring or layer seeing how it only tests for one kind of lipids.

That is a strange reply.

The Sudan IV dye is lipophilic, meaning it mixes well with .. lipids (fat). It is not specific for one kind of lipid, as long as the lipid is sufficiently liquid. The saturated fat (like beef fat) tends to be more solid than the unsaturated fat (like oil). However, the dye will be soluble and make a color in both types of fat.

Here's the dye's chemical structure:

Notice how hydrophobic that molecule is with those aromatic rings, except for a lonely hydroxyl group over there.

Back to the OP -- you did not provide sufficient details on the manual experiment, such as temperature and other details, for us to help you.

My best guess is this: the WARM liquid left over the skillet is poured into a test tube. To this WARM liquid, the Sudan IV test is performed. Typically lipids float on water, as their density is lower and they don't mix with water. So, yes there will be a floating red layer in that experiment.

However, if the liquid is left to cooled down, then the lipid will float on top of the aqueous tasty mariana sauce and SOLIDIFY to look like parafilm. Even in this case, the lipid will turn redish.

Does this help?

noob_whacker

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Sep 16 2013 12:18am

Quote (Dmon_Hunter @ Sep 15 2013 05:13pm)

http://forums.d2jsp.org/html/emoticons/headscratch.gif That is a strange reply.

The Sudan IV dye is lipophilic, meaning it mixes well with .. lipids (fat). It is not specific for one kind of lipid, as long as the lipid is sufficiently liquid. The saturated fat (like beef fat) tends to be more solid than the unsaturated fat (like oil). However, the dye will be soluble and make a color in both types of fat.

Here's the dye's chemical structure:

http://i44.tinypic.com/2j0jdxz.png

Notice how hydrophobic that molecule is with those aromatic rings, except for a lonely hydroxyl group over there.

Back to the OP -- you did not provide sufficient details on the manual experiment, such as temperature and other details, for us to help you.

My best guess is this: the WARM liquid left over the skillet is poured into a test tube. To this WARM liquid, the Sudan IV test is performed. Typically lipids float on water, as their density is lower and they don't mix with water. So, yes there will be a floating red layer in that experiment.

However, if the liquid is left to cooled down, then the lipid will float on top of the aqueous tasty mariana sauce and SOLIDIFY to look like parafilm. Even in this case, the lipid will turn redish.

Does this help?

thanks alot. yeah.

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