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24 Cards in this Set

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What is included in the Lipidome?
-Glycerolipids
-Sphingolipids
-Glycolipids
-Steroids
-Fatty Acids
-Polyprenes
Define LIPIDS.
Operational definition: Organic biomolecules that are soluble in organic, apolar solvents but, as a rule, insoluble or sparingly soluble in water.
FATTY ACIDS
R-CO2H <---> R-CO2- + H+

How long is a short, medium, and long chain FA?
Chain Length (C2-C24+)

-short chain fatty acids (C2 - C6)
-medium chain fatty acids (C8 - C12)
-long chain fatty acids (C14 - C24+)
SATURATED FATTY ACIDS

What are three representative Short-chain fatty acids?
1. CH3-CO2H acetic acid

2. CH3-CH2-CO2H propionic (propanoic) acid

3. CH3-CH2-CH2-CO2H butyric (butanoic) acid
PATHOPHYSIOLOGIC SIGNIFICANCE OF SATURATED FATTY ACIDS
High dietary intake is associated with increased LDL, decreased HDL, increased risk of atherosclerosis.

C12-C16 have the most pronounced effect.
PATHOPHYSIOLOGIC SIGNIFICANCE OF TRANS UNSATURATED FATTY ACIDS
Natural unsaturated FA are predominantly cis.
DB are isomerized by intestinal flora (ruminant) or industry.
Trans FA have different physical properties.
Trans FA have different biological activities (similar to saturated fatty acids).
Exception: Conjugated Linoleic Acid
How many carbons are in the most common unsaturated fatty acids?
The most commonly occurring unsaturated fatty acids in mammals have 18 carbons.
PHYSIOLOGICAL SIGNIFICANCE OF UNSATURATED FATTY ACIDS
-Families of fatty acids (ω3, ω6, ω7, ω9)
-Essential fatty acids (linoleic, linolenic)
-Membrane properties
-Prostaglandin precursors
-Certain UFA lower LDL/raise HDL cholesterol in the blood
-Resolvins
Influence of carbon number on melting points of fatty acids. # Carbons and # DBs.
More carbons = higher melting temp

Cis DB = lower melting temp
Trans DB = lower melting temp
What do ionized FA do in solution?
Ionized fatty acids are only sparingly soluble but they form aggregate structures that are readily dispersed in water.
Fatty acids are amphiphiles, forming micelles at alkaline pH. Which portions face inward and which outward?
Hydrophobic tail. Apolar. Inside

Hydrophilic head. Polar. Outside

Forms a Micelle
Reactions of Fatty Acids, the carboxyl group and the double bond.
1. Reactions involving the carboxyl group
-Esterification
-Amidation
-Hydrolysis

2. Reactions involving the double bonds
-Hydrogenation
-Autooxidation
How do FA form esters and amides?
FA + alcohol --> Ester

FA + amine --> Amide

Both are condensation reactions!
What is saponification?

Remember that hydrolysis is the reverse of esterification.
Saponification is the hydrolysis of an ester under basic conditions to form an alcohol and the salt of a carboxylic acid (carboxylates).
Why Hydrogenation? Making unsaturated FA into saturated FA.
1. Cultural factors (butter/margarine vs. oil)

2. Desirable physical properties (pie crust)

3. Chemical stability
Disadvantages of Hydrogenation
1. Increased saturated fat content

2. Altered biological activity

3. Cis-trans and positional isomerization (partial hydrogenation only)
Undesirable Effects of Lipid Autooxidation
In foods: Toxic products (free radicals, aldehydes)
Unpleasant odors, flavors (aldehydes, organic acids)

In vivo: Membrane damage
Dysfunctional lipoproteins
Toxic products (aldehydes, polymers)
What is the RULE OF THUMB for FA oxidation and double bonds?
Susceptibility of a fatty acid to autooxidation increases about 10-fold for each double bond.
NOMENCLATURE

COMPLEX LIPIDS: ESTERS, AMIDES AND ETHERS

GLYEROL-BASED ESTERS AND ETHERS
Protonated fatty acid – stearic acid
Ionized acid – potassium stearate
Derivatized fatty acid - _______stearate
Compound derivatized with fatty acid – stearoyl _________
What are Sphingolipids?
Sphingolipids are membrane lipids and precursors to important signaling molecules
Pathophysiologic Significance of sphingolipids.
Specific character of the cell surface
-Blood group markers
-Differentiation markers
-Transformation markers
-Cell-cell interactions
-Receptors

Hereditary Gangliosidoses due to deficiency in glycosidases
Pathophysiologic Significance of Cholesterol.
1. Relationship to atherosclerosis and CHD
-Epidemiology
-Arterial plaques

2. Membrane constituent

3. Precursor to bile acids, steroid hormones and vitamin D
What is the function of bile?
Bile acids are metabolites of cholesterol that function as biological detergents in fat digestion.

The liver oxidizes about 500 mg/day of cholesterol to bile acids. This is the major route for removal of cholesterol from the body.
Where are steroids synthesized and in what proportion compared to bile?
Steroid hormones are biologically active metabolites of cholesterol synthesized in gonads and adrenals.

The mass of cholesterol converted to androgens, estrogens, glucocorticoids and mineralocorticoids is very small in comparison to bile acid synthesis.