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Example Questions
Example Question #1 : Help With Organic Lipids
What is the name of the pictured fatty acid?
Arachidonic acid
Palmitoleic acid
Eicosapentaenoic acid
Linoleic acid
Oleic acid
Arachidonic 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.
Example Question #261 : Biochemistry
Identify the common name of the fatty acid shown here.
Arachidonic acid
Palmitic ccid
Linoleic acid
Oleic acid
Myristic acid
Oleic acid
Oleic acid is a fatty acid consisting of 18 carbon molecules and a single unsaturated (double) bond after carbon 9, as pictured.
Example Question #261 : Biochemistry
What hormone does this structure represent?
Progesterone
Estrogen
Cholesterol
Luteinizing hormone
Testosterone
Cholesterol
The structure represents cholesterol. The hydroxyl group attached to the terminal cyclohexane and the 6-carbon chain on the opposite end are easily recognizable substituents.
Example Question #262 : Biochemistry
Organic peanut butter contains both saturated and unsaturated fats.
What is the difference between saturated and unsaturated fats?
Unsaturated fats do not contain glycogen and saturated fats do
Unsaturated fats contain double bonds and saturated fat do not
Unsaturated fats do not contain cholesterol and saturated fats do
Unsaturated fats are lipids and saturated fats are carbohydrates
Unsaturated fats contain double bonds and saturated fat do not
Unsaturated fats are said do be unsaturated because of their lack of saturation with hydrogen atoms, due to carbon's ability to make four bonds, and one or more carbons in the hydrocarbon tail of an unsaturated fatty acid contains a double bond to another carbon. Both unsaturated and saturated fats are lipids, but neither contain cholesterol nor glycogen.
Example Question #2 : Identification By Structure
Which of the following associations about lipids is false?
Steroid - multiple rings
Phospholipid - hydrophobic fatty acid tail
Isoprene - five-carbon atoms
Triacylglycerols - no hydrophobic fatty acid tails
Glycolipids - hydrophobic fatty acid tails
Triacylglycerols - no hydrophobic fatty acid tails
Triacylglycerols, like phospholipids and glycolipids, have long, hydrophobic, fatty acid tails. Steroids are characterized by their ABCD ring structure. Isoprene, the building block of steroids and polyisoprenoids, has five carbon atoms.
Example Question #2 : Identifying Specific Lipid Structures
Based on the structure of the molecule shown below, what is the most likely identification of this compound?
Methionine
Cortisol
NADH
Epinephrine
Insulin
Cortisol
For this question, we're presented with the molecular structure of some unknown compound, and we're asked to identify which answer choice offers the most likely identity for this compound.
Since there's no way for us to know exactly what this molecule is (unless you have it memorized!), we'll need to look at each answer choice.
Insulin is a peptide hormone whose main function is to allow cells in the body to take up glucose from the blood.
Epinephrine is also a hormone, but in addition it can act as a neurotransmitter. One of epinephrine's main roles is in the fight-or-flight response, where it acts to mobilize the body's energy reserves in preparation for a demanding situation.
NADH is a cofactor involved in a variety of catabolic pathways, such as glycolysis. Its main role is to act as a carrier of high-energy electrons, which it can donate into the electron transport chain to produce cellular energy in the form of ATP.
Methionine is one of the twenty amino acids found in organisms. It thus acts as a key constituent in many proteins.
Cortisol is a steroid hormone, often called the "stress hormone." It plays a variety of roles in the body, some of which influence the body's metabolism of glucose (cortisol is a type of glucocorticoid hormone).
When looking at the structure given in the question stem, we can see that this is a pretty big molecule! While we don't need to have the exact structure of cholesterol memorized, we can recall that cholesterol is a big molecule that has multiple rings in its structure, just as this compound does. Thus, we can be reasonably sure that this compound is most likely a derivative of cholesterol. Many derivatives of cholesterol function as steroid hormones, which are largely hydrophobic molecules that are able to transverse cellular membranes. Since we know that cortisol is a steroid hormone, we can assume that this structure most likely represents cortisol.
Example Question #1 : Identifying Specific Lipid Structures
What is the most accurate description of the given compound?
This compound is a lipid
The structure is an amino acid
This compound is a nucleic acid
This compound is a protein
This compound is a carbohydrate
This compound is a lipid
This question is presenting is with the molecular structure of some unknown compound, and is asking us to identify the most appropriate classification for it.
From the picture, we can see that this structure has a carbon backbone. On the carbon backbone, we have three long hydrocarbon chains attached to the backbone via an ester linkage. Thus, this compound is a triglyceride (also known as a triacylglycerol).
From our understanding of biochemistry, we know that triglycerides are a type of lipid, thus making this the correct answer.
The structure shown is not a protein or a nucleic acid, as both of these compounds contain nitrogen or phosphate as part of their molecular structure, respectively. Proteins are linked by a characteristic series of amino acids, each of which has a unique side chain group. Nucleic acids, on the other hand, contain a sugar-phosphate backbone connected by phosphodiester linkages, along with nitrogenous bases.
Furthermore, this structure is not a carbohydrate, as these structures generally have a carbon:hydrogen:oxygen ratio of .
Example Question #1 : Identifying Specific Lipid Structures
From what type of molecule is vitamin A derived from?
Squalene
Triacylglycerol
Vitamin K
Glucose
Cholesterol
Squalene
An isoprene unit repeats many times to form molecules called terpenes. Squalene is a triterpine - made from six isoprene units. Vitamin A is known as a terpinoid because it is derived from squalene.
Example Question #2 : Identifying Specific Lipid Structures
Arachidonate is a precursor for all of the following except __________.
leukotrienes
prostacyclin
cholesterol
thromboxanes
prostaglandins
cholesterol
Arachidonate is a precursor for many biologically important molecules. If acted on by lipoxygenases it can be converted to leukotrienes. If acted on by prostaglandin synthase and then subsequently by another (or several other) enzymes it can be converted to prostacyclin, prostaglandins, or thromboxanes. However, it is not a precursor for cholesterol.
Example Question #1 : Identifying Specific Lipid Structures
What is the difference between linoleic and alpha-linolenic acid and what is their importance?
I. They are essential fatty acids.
II. Linoleic acid is unsaturated, has 2 double bonds and has an 18-carbon chain.
III. Alpha-linolenic acid is an eighteen-carbon molecule with 3 double bonds.
IV. Apha-linolenic acid is a seventeen-carbon molecule with 3 carbon double bonds.
II and IV
I, II, and III
I and IV
I, II, III, and IV
II, III, and IV
I, II, and III
Essential fatty acids cannot be produced by the body and need to be obtained thru diet. Linoleic acid is unsaturated, has 2 double bonds while alpha-linolenic acid has 3 double bonds. Both have a backbone structure of 18 carbons.
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