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Example Questions
Example Question #1 : Lipid Structures And Functions
Which of the following statements about oleic acid is false?
Its IUPAC name is (9Z)-Octadec-9-enoic acid
It is a fatty acid with an omega-9 unsaturation
Its condensed molecular formula is
None of the other answers is false
There are 16 carbon atoms in its longest chain
There are 16 carbon atoms in its longest chain
Oleic acid (which composes much of olive oil) has a double bond between its 9th and 10th atoms. Hence it has an omega-9 unsaturation. It has 18 carbon atoms, not 16, which gives it a condensed molecular formula:. Because it is a cis-isomer, the IUPAC name contains a Z, and becuse it is an unsaturated carboxylic acid, it ends in -enoic acid.
Example Question #1 : Lipid Classifications
Which of the following factors contribute to increasing the melting point of a fatty acid?
Adding methylene groups
Decrease fatty acid chain length
Introducing cis-double bonds
Increased number of double bonds
Increased fatty acid chain length
Increased fatty acid chain length
Double bonds cause unsaturation, thus decreases the melting point. Cis-double bonds as well as methylation also introduce kinks within the chain, decreasing the melting point. Increasing the fatty acid chain length creates saturation, thus causes the melting point to increase. Therefore, decreasing fatty acid chain length has the adverse effect.
Example Question #162 : Biochemistry
How many hydrogens are bound to a carbon atom in the middle of a saturated fatty acid chain?
In a saturated fatty acid, all of the covalent carbon to carbon bonds are single bonds. So a carbon atom in the middle of the chain will have two covalent bonds to other carbon atoms, and can therefore bond to two hydrogen atoms.
Example Question #2 : Fatty Acids
Select the most accurate description of alpha-linolenic acid.
Is an eighteen-carbon chain omega-6 fatty acid
Is a twenty-carbon chain omega-3 fatty acid
Is a precursor for arachidonic acid (AA)
Is a precursor for eicosapentaenoic acid (EPA)
Can be synthesized de novo in the body
Is a precursor for eicosapentaenoic acid (EPA)
Alpha-linolenic acid is an essential fatty acid that must be consumed in the diet (cannot be synthesized by the body). It is an eighteen-carbon omega-3 fatty acid that is used to synthesize eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two important long chain polyunsaturated fatty acids. Alpha-linoleic acid is the precursor to arachodonic acid (AA).
Example Question #3 : Fatty Acids
Which of the following is not an omega-3 fatty acid?
docosapentaenoic acid (DPA)
Alpha-linolenic acid (ALA)
Dihomo-gamma-linolenic acid (DGLA)
Docosahexaenoic acid (DHA)
Eicosapentaenoic acid (EPA)
Dihomo-gamma-linolenic acid (DGLA)
Dihomo-gamma-linolenic acid (DGLA) is a twenty-carbon omega-6 fatty acid that is a desaturation product of linoleic acid. The rest of the answer choices are indeed omega-3 fatty acids.
Example Question #1 : Lipid Classifications
Omega-6 fatty acids are primarily found in __________.
poultry
salmon
flax seeds
chia seeds
krill
poultry
Omega-6 fatty acids are primarily found in vegetable oils (ex. soybean oil or corn oil), chicken, and eggs. Note that poultry feed is very heavy on corn products and thus increases the omega-6 fatty acid proportion of almost all farm raised animals. Fish, chia seeds, and flax seeds are high in omega-3 fatty acids.
Example Question #163 : Biochemistry
Omega-3 fatty acids __________.
can be used to synthesize anti-inflammatory (or less-inflammatory) eicosanoids
have a double bond at the 6th carbon
are found in most vegetable oils
are considered pro-inflammatory
are a substrate for the synthesis of series 2 prostaglandins
can be used to synthesize anti-inflammatory (or less-inflammatory) eicosanoids
Omega-3 fatty acids can be utilized as a substrate for the synthesis of series 3 prostaglandins (a subclass of eicosanoids), and are generally considered "anti-inflammatory" for this reason. Furthermore, omega-3 fatty acids are so named for having a double bond at the 3rd carbon from the omega end. They are generally found in fish and flax and chia seeds, while omega-6 fatty acids are in poultry and vegetable oils.
Example Question #7 : Lipid Classifications
If arachidonic acid is used as a substrate for eicosanoid synthesis, what type of eicosanoid can be produced?
Prostaglandin I3 (PGI3)
Thromboxane A3 (TXA3)
Thromboxane A1 (TXA1)
Thromboxane A2 (TXA2)
Thromboxane A2 (TXA2)
Arachidonic acid (AA) is used as a substrate for series 2 eicosanoid synthesis, including thromboxane A2 (TXA2). Series 3 eicosanoids are synthesized from alpha-linolenic acid (ALA), and series 1 are synthesized from dihomo-gamma-linolenic acid (DGLA).
Example Question #2 : Fatty Acids
Which of the following is true of eicosanoids produced from alpha-linolenic acid?
They produce a strong platelet aggregation response
They produce a weak platelet aggregation response
Their production is increased by adding vegetable oil in the diet
They are considered pro-inflammatory
A decreased amount is recommended for those with high risk of heart disease
They produce a weak platelet aggregation response
Alpha-linolenic acid (ALA) is an omega-3 fatty acid that is utilized to produce series 3 eicosanoids. Series 3 eicosanoids lead to a weak platelet aggregation response, and are considered anti or less-inflammatory. Thus, a diet rich in omega-3 fatty acids is recommended for those with heart disease risk. Omega-3 fatty acids are primarily found in fish or flax and chia seeds, not vegetable oil, which is rich in omega-6 fatty acids.
Example Question #1 : Lipid Classifications
Micelle formation is a result of which of these?
Hydrophobic interactions with the polar head of free fatty acids
Hydrogen bonding between water and the carbon chain end of free fatty acids
Covalent bonding between fatty acids and water
Hydrogen bonding between water and the polar head of free fatty acids
Hydrophobic interactions with the carbon chain end of free fatty acids
Hydrophobic interactions with the carbon chain end of free fatty acids
The hydrocarbon tail of free fatty acids is nonpolar, and so it interacts unfavorably with water molecules. So, when free fatty acids are placed in a polar environment, the nonpolar tails are driven together and inward in order to avoid water molecules. A micelle is formed from the circular formation of free fatty acids.
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