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91 Cards in this Set

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