Lipids: Introduction & structures Flashcards
Explain the differences in the structure of triglycerides, phospholipids and cholesterol and describe the various functions of each in the body
FA: simplest of lipids, hydrocarbon chain of varying lengths, amphipathic, with a nonpolar and hydrophobic tail and a polar hydrophilic head. COOH: hydrophilic, Backbone & CH3: hydrophobic
Phospholipids: Amphipathic, attract H2O molecules, commonly expressed on the surface of blood-born lipid particles (chylomicrons) thereby stabilizing the particles in the aqueous medium.
Cholesterol: non-essential, present in animal foods (no kcal), used to form steroids, bile, and Vit D, important part of the cell membrane, increases membrane fluidity at low temps by decreasing phospholipid packing.
Define lipids, describing their classifications and the structures of each class
Macronutrient referred to as fat
C, H, O
Hydrophobic (oil in water)
Classifications: Free FA Triglyceride Phospholipid Cholesteryl Ester
Describe the basic structure of fatty acid
Vary by:
length of the C chain (most common 12-24 C’s)
short: >8
medium: 8-12
long: 14 most common in food and important nutritionally/functionally, take longer to digest, absorb, transport than short or medium chains
Also vary by:
Degree of saturation (with H)
saturated FA
unsaturated FA: monounsaturated & polyunsaturated
Explain polarity. Specifically, describe what makes a fatty acid head and tail polar and nonpolar?
Polar substances are those with an unequal charge distribution.
Contrast fatty acids by carbon length, degree of saturation, and cis and trans isomerization.
Longer FA take longer to digest, absorb, and transport than short or medium chain.
Long chain saturated FA (stearic acid)
more strongly attract one another
relatively straight; pack tightly (in body and food)
solid at room temp (butter) (higher MP)
Level of saturation: more C-C double bonds = more bending
Unsaturated FA: liquid at room temp, lower MP
monounsaturated FA: one double bond, liquid at room temp, Oleic Acid, nonessential, common in diet (olive oil, nuts, avocados), anti-oxidant, antithrombotic, anti-hypertensive properties, lower TAGs.
Molecular configuration Cis and Trans isomerization:
cis: H on the same side, puts a kink in the molecule and lowers its melting point, most common naturally
trans: H on opposite side, linear, similar to saturated; most from partial hydrogenation of fats/oils (cis to trans), a process to add H, raises MP (linoleic acid in margarine), CVD, decreases HDL, increases LDL, decreases cell membrane fluidity
List the four most common fatty acids in the diet and functionally
! Palmitic Stearic Oleic Linoleic Elaidic (trans-unsaturated)
Considering the structures of glucose and palmitate and using nutrient densities of 9 kcal/g and 4 kcal/g for fatty acids and carbohydrates, explain why fatty acids have more kcal/g than carbohydrates.
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Describe the differences between the Delta and Omega stystems for naming fatty acids.
The delta system counts from the carboxyl end.
The omega system counts from the methyl end.
Name the essential fatty acids by their common names and using each system of notation.
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Given any of the three names or a structural drawing of any of the following fatty acids: palmitic, stearic, oleic, a-linolenic, linoleic, arachidonic, and eicosapentaenoic:
- specify the location of each of its double bonds
- identify the fatty acid using each of the naming systems
- describe its level of saturation
- classify it as cis or trans
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Describe the processes of elongation and desaturation of atty acids. List the main desaturases in humans. Use an example fatty acid to explain how the process works and the substrates, enzymes, and products involved.
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Explain why the essential fatty acids cannot be made in the body from other fatty acids
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Given the two essential fatty acids a-linolenic acid and linoleic acid…
- explain why each is essential
- list their delta and omega names, specifying the location of their double bonds
- describe the type of PUFAs that can be formed from each, and list one specific example
- explain why linoleic acid cannot be converted to a-linolenic acid in the human body
- list examples of foods from which each fatty acid is derived
- contrast the physiology of the two fatty acids (and other fatty acids in their respective group) and speculate what the impact might be on health when consuming a diet rich in one type versus the other.
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Describe mono-, di-, and triglyceride, including the structural components of each, the types of bonds that hold them together, and the type of reaction that must occur to form them.
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Describe the difference between simple and mixed triglycerides and explain what determines whether a triglyceride will be simple or mixed
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