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91 Cards in this Set
- Front
- Back
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What is a Lipid?
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A naturally occurring molecule from a plant or animal soluble in non-polar organic solvents
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Name the functions of Lipids.
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- energy storage
- membrane components - thermal insulation and padding - chemical messengers - protection from mechanical shock |
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What is the defining factor of Lipids?
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Solubility
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What is a Fatty Acid?
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A long-chain carboxylic acid
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How many carbon atoms are contained within animal fats and vegetable oils?
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12-22 Carbon atoms
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What are waxes defined as?
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Carboxylic acid esters
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Where are waxes secreted from in animals?
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They are secreted by sebaceous glands in the skin
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What is the main function of waxes?
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Perform mostly external protective functions
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What are Triacylglycerols (TAGs)?
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Carboxylic acid triesters of glycerol, a three-carbon trialcohol
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What makes up the fats stored in our bodies and most dietary fats and oils?
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Triacylglycerols
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What type of Lipid is a major source of biochemical energy?
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Triacylglycerols
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What are Glycerophospholipids?
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Triesters of glycerol that contain charged phosphate diester groups
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What type of Lipid is abundant in cell membranes?
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Glycerophospholipids
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Together with other types of Lipids, which Lipid helps to control the flow of molecules into and out of cells?
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Glycerophospholipids
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What are Sphingomyelins?
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Amides derived from an amino alcohol (spingosiine), also contain charged phosphate diester groups
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Sphingomyelins are essential to what?
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They are essential to the structure of cell membranes
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Where are Sphingomyelins most abundant?
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Nerve cell membranes
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What are Glycolipids?
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Different amides derived from sphingosine that contain polar carbohydrate groups; on cell surfaces the carbohydrate portion is recognized by and connects to intracellular messengers
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What are Steroids?
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Tetracyclic moolecules that act as hormones and contribute to the structure of cell membranes
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Steroids contains fatty acids within their structure. True or False?
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False
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What is an Eicosanoids?
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Eicosanoids are carboxylic acids that are a special type of intracellular chemical messenger
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Which particular steroid plays an important role in maintaining cell membrane shape?
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Cholesterol
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What are naturally occurring fats and oils defined as?
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Triesters formed between glycerol and fatty acids
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What is a Saturated Fatty Acid?
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A long-chain carboxylic acid containing only carbon-carbon single bonds
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What are Polyunsaturated Fatty Acids?
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Fatty acids that have more than one carbon=carbon double bond
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What two polyunsaturated fatty acids are essential to the human diet?
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Linoleic and Linolenic Acids
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Why is Linoleic and Linolenic acid essential to the human diet?
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Because the body does not synthesize them and they are needed for the synthesis of other lipids
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In nature, what are the simplest fatty acid esters?
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Waxes
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A wax is a mixture of fatty acid-long-chain alcohol esters. How many carbons do the fatty acids usually contains?
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The fatty acids usually have an even number from 16 to 36 carbons
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How many carbon atoms do alcohols usually contain?
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24-36 carbons
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What are the most plentiful lipids in nature?
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Animal fats and vegetable oils
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All fats and oils are composed of what?
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triesters of glycerol with three fatty acids
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What main type of fatty acid do vegetable oils contain?
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Vegetable oils consist almost entirely of unsaturated fatty acids
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What main type of fatty acid do animal fats contain?
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Animal fats contain a large percentage of saturated fatty acids
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What is the primary reason for the different melting points of fats and oils?
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Differences in composition
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In IUPAC nomenclature, the carboxyl C is labelled what?
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C1
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In common nomenclature, what are the carbon atoms labelled as?
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the carbon adjacent to the carboxyl carbon is designated 'α' and the other carbons are lettered β, γ, etc.
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What does the Greek letter ω (omega) specify when labeling fatty acids?
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ω (omega) specifies the carbon atom furthest from the carboxyl group, counting from the methyl end of the fatty acid
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In a graphical representation of a fatty acid, what does the zig-zag line represent?
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The zig-zag line indicates the number of carbons
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What are the common properties of TAGs in natural fats and oils?
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- non-polar
- hydrophobic molecule - no ionic charges |
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What is an oil?
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A mixture of TAGs that is a liquid because it contains a high proportion of unsaturated fatty acids
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What is a Fat?
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A mixture of TAGs that is a solid because it contains a high proportion of saturated fatty acids
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Why is Linolenic acid considered an omega 3?
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Because the double bond is located after C3
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Describe the shape of hydrocarbon chains in saturated acids.
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Flexible and uniform in shape, allowing them to nestle together
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Describe the shape of hydrocarbon chains in unsaturated acids.
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Rigid kinds wherever they contain cis double bonds.
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How does the rigid kinks in the hydrocarbon chains of unsaturated acids affect its shape?
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The kinks make it difficult for such chains to fit next to each other in the orderly fashion necessary to form a solid.
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What affects the melting point of triacylglycerols?
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- the length of the chain; the shorter the fatty acid chain, the lower the melting point
- amount of double bonds; high amount of double bonds, low melting point |
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When C=C double bonds of vegetable oil are hydrogenated, what is yielded?
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Saturated fats; when hydrogenated a H and C is added to the double bond, converting the double bond to a single bond
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What is saponification?
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Saponification is the hydrolysis of fats and oils carried out by strong aqueous bases to form soaps (also known as fatty acid salts)
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Saponification is the reversal of a condensation reaction. What happens to the fatty acids and glycerol in saponification?
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The fatty acids break off from the glycerol backbone
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How is a Micelle formed?
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A spherical cluster formed by the aggregation of soap or detergent molecules so that their hydrophobic ends are in the centre and their hydrophilic ends are on the surface
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What is a Micelle?
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A micelle is a spherical cluster made by long chain fatty acids with sodium ions at the end
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What is a phospholipid?
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A lipid that has an ester link between phosphoric acid and an alcohol (either glycerol or sphingosine)
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What are the two types of cell membranes?
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Phospholipids and Glycolipids
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Describe the structure of sphingosine.
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- 18 C containing structure
- has 2 hydroxyl groups at C1 and C3 - amino group attached to C2 (involved in structure forming amine linkages) |
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What are glycolipids?
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- derived from sphingosine (like phospholipids)
- contains no phosphate group but have an attached CHO that is a monosaccharide or a short chain of monosaccharides |
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What lipids are classified as Sphingolipids and why?
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- glycolipids, sphingomyelins, and phospholipids
- all have sphingosine in their structure |
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What is the general structure of membrane lipids?
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- polar head and two tails
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What is the general structure of a triacylglycerol?
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- no polar head
- 3 fatty acid chains attached to a glycerol backbone |
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What are Phosphatidylcholines, AKA lecithins?
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Glycerophospholipids with a phosphate ester link to the amino alcohol choline
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What are the fucntions of Phosphatidylcholines (lecithins)?
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- emulsifying agents
(substances that surround non-polar liquids and hold them in suspension in water) |
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What are Sphingomyelins?
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Sphingosine derivatives with a phosphate ester group at C1 of sphingosine. Also classified as a phospholipid as it contains a phosphate group.
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Sphingomyelins are the major components of what?
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Major components of the coating around nerve fibres (the myelin sheath) and are present in large quantities in brain tissue)
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What are Cerebrosides?
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Glycolipids which contain a monosaccharides - membrane lipid found in brain tissue.
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Where are cerebrosides abundant?
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Nerve cell membranes in the brain, where the sugar is D-galactose. Also found in other cell membranes, where the sugar unit is D-glucose
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Cerebrosides are also classified as what?
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- Glycolipids as they contain a monosaccharide
- Sphingolipids as they contain sphingosine |
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The polar heads and hydrophobic tails of phospholipids and glycolipids allow them to form what?
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- Membrane bilayers
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What is the function of a membrane bilayers?
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- act as barriers separating the interior of cells from the environment
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Glycolipids extend their CHO segments into the fluid surrounding the cells. What does this allow them to function as?
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They function as receptors that are essential for recognizing chemical messengers, other cells, pathogens, and drugs
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What is Cholesterol?
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- A steroid which is a member of the class of lipids that all contain the same four-ring system
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What are the major functions of steroids?
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- Cholesterol
- Hormones - Bile acids that are essential for the digestion of fats and oils in the diet |
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What are the two most important functions of Cholesterol?
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- component of cell membranes
-starting material for the synthesis of all other steroids |
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Describe the structure of Cholesterol.
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- nearly a flat molecule
- except for its -OH group, it is hydrophobic |
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What does Cholesterol provide in a cell membrane?
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within a cell membrane, cholesterol molecules are distributed among the hydrophobic tails of the phospholipids; because cholesterol molecules are more rigid than the hydrophobic tails, they help to maintain the structure of the membrane
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What is a Lipid Bilayer?
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The basic structural unit of cell membranes; composed of two parallel sheets of membrane lipid molecules arranged tail to tail.
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What is a Liposome?
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A spherical structure in which a lipid bilayer surrounds a water droplet.
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By what is the Lipid Bilayer formed?
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The bilayer is formed by two parallel layers of lipids oriented so that their ionic head groups protrude into the aqueous environments on either side of the bilayer; their non-polar tails cluster together in the middle of the bilayer where they can interact and avoid water.
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What happens when phospholipids are shaken vigorously?
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They spontaneously form liposomes, small spherical vesicles with a lipid bilayer surrounding an aqueous centre
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What type of proteins are only associated with one face of the bilayer?
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Peripheral Proteins
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What proteins extend completely through the cell memebrane and may twist in and out of the membrane many times before ending on the outside with a hydrophilic sugar group?
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Integral proteins
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The overall structure of cell membranes is represented by what?
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The fluid-mosaic model
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Why is the membrane described as a 'fluid-mosaic'?
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The membrane is described as fluid because it is not rigid and molecules can move around within it, and as a mosaic because it contains many kinds of molecules.
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Brain tissue is high in what type of lipid?
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Phosphatidylserines
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Heart tissue is high in what type of lipid?
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Phospatidylglycerol
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Lung tissue is high in what type of lipid?
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Sphingomyelins
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What is Active Transport?
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Movement of substances across a cell membrane using energy.
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Describe the movement of a substance across a membrane by active transport.
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Energy from the conversion of ATP to ADP is used to change the shape of an integral protein (the Na/K pump), simultaneously bringing two K ions into the cell and moving three Na ions out of the cell.
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What is Passive Transport?
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Movement of a substance across a cell membrane without the use of energy, from a region of higher concentration to a region of lower concentration.
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What is Simple Diffusion?
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Passive transport by the random motion of diffusion through the cell membrane or through channel proteins. Lipid soluble and small hydrophilic molecules move by simple diffusion.
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What is Facilitated Diffusion?
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Passive transport across a cell membrane with the assistance of a protein that changes shape.
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Both passive (facilitated diffusion) and active mediated transport systems share what characteristics?
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1. Transporters include:
- uniport (1 type of solute), - symport (2 solutes in the same direction), - antiport (2 solutes in opposite directions) 2. Saturation kinetics 3. Substrate specificity (highly specific) 4. Inhibitability (inhibited by certain drugs) |
