A fatty acid can be saturated or unsaturated. If there is no double bonds along the alkyl chain, the fatty acid is saturated. This is because all of the carbon atoms have bonded to as many hydrogen atoms as possible. The alkyl chain is therefore saturated in hydrogen. The presence of a double bond makes a fatty acid unsaturated because it is possible for the alkyl chain to be bonded to more hydrogen atoms. Fats are a common and well-known form of lipids. They are made by bonding fatty acids to an alcohol.
The most common fat is a triacylglycerol. Glycerol is a three carbon alcohol and each of the carbons bond to one fatty acid. The structure of the fatty acids of a fat determine if a fat is saturated or unsaturated. Double bonds in one or more alkyl chains of the fatty acids create an unsaturated fat. A fat molecule with no double bonds in any of its alkyl chains is known as a saturated fat. A double bond creates a bend in an alkyl chain. This reduces how tightly fat molecules can be packed together.
Loosely packed fats have lower melting points which is why unsaturated fats, such as vegetable oils, are commonly liquid at room temperature. Saturated fats on the other hand have higher melting points and are more likely to be found as solids at room temperature. The main function of a fat is to store energy.
They are most common in animals because they contain a very large amount of energy for their weight. For mobile animals carrying extra weight is not ideal so storing energy in lightweight molecules is beneficial. Phospholipids are less well-known than fats and oils but are essential to life on Earth.
They are the molecules used to build the membranes found around and inside cells. Without a plasma membrane a cell would not be able to survive. A phospholipid is similar in structure to a triacylglycerol. It contains TWO fatty acids plus a phosphate group bonded to the three carbons of a glycerol molecule.
The sole difference between a phospholipid and a fat is the replacement of one fatty acid with a phosphate group. A phosphate group has a negative charge so many other molecules can attach themselves to the phosphate group. This makes a large variety of different possible phospholipids. The combination of fatty acids and a phosphate group make phospholipids ideal for making cellular membranes.
The phosphate group is soluble in water and is therefore attracted to water hydrophilic. The fatty acids are insoluble in water and are hydrophobic. A phospholipid membrane contains two layers of phospholipids. In both layers the hydrophobic fatty acids point inwards towards each other. The phosphate groups face outwards towards the water based environments of the cell and the surrounding world. This phospholipid bilayer creates a barrier for substances moving in and out of a cell. If a substance wants to pass through the membrane it must be able to move through the hydrophilic barrier of phosphate groups and the hydrophobic barrier of fatty acids.
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Many substances can only move in and out of cells via membrane channels created by proteins. Steroids are a particular type of lipid with a unique chemical structure. They are characterized by having carbon atoms arranged into four adjacent rings — three rings made from 6 carbon atoms and the final ring made from 5 carbon atoms.
Steroids are produced naturally in the body. Examples include cholesterol and the sex hormones testosterone, progesterone and estrogen.
Cholesterol is the most abundant steroid in the body and is produced in brain, blood and nerve tissue. Learn about animals, plants, evolution, the tree of life, ecology, cells, genetics, fields of biology and more. A confirmation email has been sent to the email address that you just provided. Check your emails and make sure you click the link to get started on our 6-week course. Basic Biology: An Introduction. Also available from Amazon , Book Depository and all other good bookstores.
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Lipids (article) | Macromolecules | Khan Academy
Why not test yourself with our quick 20 question quiz. Lipids Lipids are a group of biological molecules that include fats, oils and some steroids. Why are lipids important? Energy storage Lipids play an important role in storing energy. Insulation Fats are important for heat insulation.
Cholesterol also serves as a precursor for all steroid hormones. In fact, if you look through all the steroid hormones, you'll find that they all have the characteristic 4-ring structure that cholesterol has. Cholesterol also functions as a precursor for the production of bile salts in the liver. These bile salts are subsequently stored in the gallbladder and, when needed, released into the duodenum of the small intestine to aid in the digestion of lipids. Rather, this is a pathological process that leads to a condition called atherosclerosis.
This, in turn, can lead to the hardening of blood vessels, as well as contribute to the formation of blood clots that can impede the flow of blood in that vessel. These clots can also become dislodged and travel throughout the circulatory system, where it can become trapped in other blood vessels. This is a dangerous situation, because it can potentially lead to heart attack or stroke. It is given by the Nernst equation:. Therefore, the potential difference decreases as the ion's charge increases, and is not independent of the concentration gradient.
It increases -- it does not decrease -- with temperature. If you've found an issue with this question, please let us know. With the help of the community we can continue to improve our educational resources. If Varsity Tutors takes action in response to an Infringement Notice, it will make a good faith attempt to contact the party that made such content available by means of the most recent email address, if any, provided by such party to Varsity Tutors. Your Infringement Notice may be forwarded to the party that made the content available or to third parties such as ChillingEffects.
Thus, if you are not sure content located on or linked-to by the Website infringes your copyright, you should consider first contacting an attorney. Hanley Rd, Suite St. Louis, MO Subject optional. Home Embed. Email address: Your name:. Example Question : Macromolecule Fundamentals. Possible Answers: Sphingolipid. Correct answer: Phospholipid. Explanation : Most lipids are made up of a 3-carbon backbone called glycerol. Report an Error.
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Example Question 2 : Lipids. Which of the following is an essential fatty acid? Vitamin A II. Oleic acid III. Alpha-linoleic acid. Correct answer: III only. Explanation : Essential fatty acids are fatty acids that cannot be synthesized by humans; therefore, these fatty acids need to be ingested through food. Possible Answers: There will be increased inflammation in the walls of arteries. There is an increased level of prostaglandins in the blood. There is an increased level of a free 4-membered ring structure in the blood. Correct answer: There is an increased level of a free 4-membered ring structure in the blood.
Explanation : LDL, or low-density lipoprotein, is a lipid transporter that transports lipids in the blood.
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Which of the following is true regarding saturated and unsaturated fatty acids? Possible Answers: Saturated fatty acids can participate in geometric isomerism. Explanation : Fatty acids are long hydrocarbon chains that contain a carboxylic acid moiety on one end. Possible Answers: Phosphatidylethanolamine. Phosphaditic acid.
Correct answer: Phosphatidylserine. Explanation : A triglyceride has three fatty acids; this molecule has two represented by the R chains.
Example Question 6 : Lipids. Possible Answers: Proteins and carbohydrates embedded in the bilayer impart transverse symmetry to the membrane.
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