Help with Organic Lipids - Organic Chemistry
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Which of the following lipids is polyunsaturated?
I. (9Z,12Z,15Z)-octadeca-9,12,15-trienoic acid
II. Octadecanoic acid
III. (9Z,12Z)-octadeca-9,12-dienoic acid
IV. (9Z)-9-Octadecenoic acid
Which of the following lipids is polyunsaturated?
I. (9Z,12Z,15Z)-octadeca-9,12,15-trienoic acid
II. Octadecanoic acid
III. (9Z,12Z)-octadeca-9,12-dienoic acid
IV. (9Z)-9-Octadecenoic acid
This question tests your knowledge of what an unsaturated lipid is, as well as your ability to obtain structural information from IUPAC names.
Firstly, a polyunsaturated lipid is a long carboxylic acid hydrocarbon chain that features multiple unsaturations, or double bonds. Remember from nomenclature that the stem "-en" indicates double bonds, or alkenes, while "-an" indicates alkanes, or fully saturated hydrocarbons. The relevant stems in the answer choices are italicized below:
I. (9Z,12Z,15Z)-octadeca-9,12,15-_trien_oic acid
II. Octadec_an_oic acid
III. (9Z,12Z)-octadeca-9,12-_dien_oic acid
IV. (9Z)-9-Octadec_en_oic acid
As you can see, "trien" and "dien" in I and III indicate these lipids are polyunsaturated, while "an" in II indicates a fully saturated lipid and "en" in IV indicates a monounsaturation. The lipids are drawn below as well, with the alkenes in polyunsaturated lipids circled in red, and the alkene in the monounsaturated lipid circled in green.
This question tests your knowledge of what an unsaturated lipid is, as well as your ability to obtain structural information from IUPAC names.
Firstly, a polyunsaturated lipid is a long carboxylic acid hydrocarbon chain that features multiple unsaturations, or double bonds. Remember from nomenclature that the stem "-en" indicates double bonds, or alkenes, while "-an" indicates alkanes, or fully saturated hydrocarbons. The relevant stems in the answer choices are italicized below:
I. (9Z,12Z,15Z)-octadeca-9,12,15-_trien_oic acid
II. Octadec_an_oic acid
III. (9Z,12Z)-octadeca-9,12-_dien_oic acid
IV. (9Z)-9-Octadec_en_oic acid
As you can see, "trien" and "dien" in I and III indicate these lipids are polyunsaturated, while "an" in II indicates a fully saturated lipid and "en" in IV indicates a monounsaturation. The lipids are drawn below as well, with the alkenes in polyunsaturated lipids circled in red, and the alkene in the monounsaturated lipid circled in green.
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What is the name of the pictured fatty acid?
What is the name of the pictured fatty acid?
The pictured structure represents arachidonic acid due to the 20-carbon carboxylic acid chain with characteristic unsaturated (double) bonds after carbons 5, 8, 11, and 14.
The pictured structure represents arachidonic acid due to the 20-carbon carboxylic acid chain with characteristic unsaturated (double) bonds after carbons 5, 8, 11, and 14.
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Other than the traditional numerical system, the X marking the terminal carbon in the structure shown here can be labeled how?
Other than the traditional numerical system, the X marking the terminal carbon in the structure shown here can be labeled how?
Fatty acids can be labeled numerically from 1-X, or they can be labeled in reverse starting with omega-1 as the terminal carbon.
Fatty acids can be labeled numerically from 1-X, or they can be labeled in reverse starting with omega-1 as the terminal carbon.
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Identify the common name of the fatty acid shown here.
Identify the common name of the fatty acid shown here.
Oleic acid is a fatty acid consisting of 18 carbon molecules and a single unsaturated (double) bond after carbon 9, as pictured.
Oleic acid is a fatty acid consisting of 18 carbon molecules and a single unsaturated (double) bond after carbon 9, as pictured.
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What type of lipid is shown below?
What type of lipid is shown below?
A triglyceride consists of three fatty acid chains bound to a glycerol backbone via ester bonds, as shown by the pictured structure.
A triglyceride consists of three fatty acid chains bound to a glycerol backbone via ester bonds, as shown by the pictured structure.
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Three fatty acid chains can be bound to a glycerol backbone via ester bonds to form a triglyceride. What type of chemical reaction is this?
Three fatty acid chains can be bound to a glycerol backbone via ester bonds to form a triglyceride. What type of chemical reaction is this?
The reaction described is an esterification in which water is a product—as is characteristic of a condensation reaction—and in which an ester bond is formed to connect the fatty acid chain and the glycerol molecule.
The reaction described is an esterification in which water is a product—as is characteristic of a condensation reaction—and in which an ester bond is formed to connect the fatty acid chain and the glycerol molecule.
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An unknown molecule was found to have a molecular formula of 
. This molecule can be identified as a __________.
An unknown molecule was found to have a molecular formula of
This question is a little bit tricky. At first glance, we would jump to the conclusion that this molecule is a long hydrocarbon chain attached to a carboxylic acid and, therefore, a fatty acid. The premise is correct. However, our conclusion is false because, by convention, a fatty acid must contain a carbon chain of at least 12 carbons. The given formula does not match the description for a steroid or triacylglycerol. The correct answer is none of these.
This question is a little bit tricky. At first glance, we would jump to the conclusion that this molecule is a long hydrocarbon chain attached to a carboxylic acid and, therefore, a fatty acid. The premise is correct. However, our conclusion is false because, by convention, a fatty acid must contain a carbon chain of at least 12 carbons. The given formula does not match the description for a steroid or triacylglycerol. The correct answer is none of these.
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What is the primary biological function of a fatty acid?
What is the primary biological function of a fatty acid?
The primary biological function of a fatty acid is to serve as a medium for the derivation of other important lipids such as waxes, triacylglycerols, phospholipids, and other necessary lipids.
The primary biological function of a fatty acid is to serve as a medium for the derivation of other important lipids such as waxes, triacylglycerols, phospholipids, and other necessary lipids.
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Before the advent of synthetic soap, hand soap was made from animal fat, namely triacylglycerols. What property of triacylglycerols make them an ideal component in hand soap?
Before the advent of synthetic soap, hand soap was made from animal fat, namely triacylglycerols. What property of triacylglycerols make them an ideal component in hand soap?
A triacylglycerol is derived from the hydrolysis of glycerols and fatty acids. Triacylglycerols have hydrophobic hydrocarbon tails and hydrophilic heads (amphipathic). The hydrophobic tails dissolve into dirt/grease on the skin while the hydrophilic tails work with running water to suspend and remove the dissolved impurities.
A triacylglycerol is derived from the hydrolysis of glycerols and fatty acids. Triacylglycerols have hydrophobic hydrocarbon tails and hydrophilic heads (amphipathic). The hydrophobic tails dissolve into dirt/grease on the skin while the hydrophilic tails work with running water to suspend and remove the dissolved impurities.
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Based on the formula and structure of this molecule, this molecule can be classified as a __________.
Based on the formula and structure of this molecule, this molecule can be classified as a __________.
The correct answer is the lipid, wax. Lipids can often be identified based on their structure alone. The general structure of wax is an ester with two long carbon chains on each end of the ester, as seen in this problem. Additionally, fatty acids can be identified simply as long carbon chains with a carboxylic acid on one end, while the general structure of steroids can be seen as four connected hydrocarbon rings.
The correct answer is the lipid, wax. Lipids can often be identified based on their structure alone. The general structure of wax is an ester with two long carbon chains on each end of the ester, as seen in this problem. Additionally, fatty acids can be identified simply as long carbon chains with a carboxylic acid on one end, while the general structure of steroids can be seen as four connected hydrocarbon rings.
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The following terpene is classified as which of the following?
The following terpene is classified as which of the following?
The molecule's skeletal structure contains two isoprene (2-methylbutyl) units, and therefore the molecule is a monoterpene.
The molecule's skeletal structure contains two isoprene (2-methylbutyl) units, and therefore the molecule is a monoterpene.
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Which of these two fatty acids has the lower melting point and why?
Which of these two fatty acids has the lower melting point and why?
Fatty acids that contain a higher degree of unsaturation (more alkene bonds) will introduce more "kinks" into the hydrocarbon chain. This "kinked" chain does not stack nicely with other fatty acids of its kind and therefore are more likely to slip past each other at lower temperatures. This is primarily due to the van der Waals forces within the unsaturated fatty acids being disrupted with the introduction of double bonds. As a result, unsaturated fatty acids generally have a lower melting point than saturated fatty acids.
Fatty acids that contain a higher degree of unsaturation (more alkene bonds) will introduce more "kinks" into the hydrocarbon chain. This "kinked" chain does not stack nicely with other fatty acids of its kind and therefore are more likely to slip past each other at lower temperatures. This is primarily due to the van der Waals forces within the unsaturated fatty acids being disrupted with the introduction of double bonds. As a result, unsaturated fatty acids generally have a lower melting point than saturated fatty acids.
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