ch.21 Lipids
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| Lipids | Heterogeneous class of naturally occurring organic compounds
Insoluble in water but soluble in organic solvents like dichloromethane
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| Lipid Examples | Fatty acids, triglycerides, sphingolipids, glycolipids
prostaglandins, leukotrienes, thromboxanes
Cholesterol, steroid hormones, bile acids
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| Function of Lipids: Storage & membrane components | Storeage: 2x the energy of carbs by weight
Membrane components: membranes divide aqueous cytoplasma into cells & intracellular compartments
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| Function of Lipids: Chemical Messengers | Primary Messengers- signals from one part of the body to the other ex) steroid hormones, sex hormones
Secondary Messengers- intracellular messengers ex) prostoglandins
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| Triglycerides | A triester of glycerol with 3 fatty acids
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| Structure of Triglycerides | 2 or 3 fatty acid components present
hydrophobic character caused by long hydrocarbon chains
The ester group is polar but buried in a non-polar environment, making triglycerides insoluble in water
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| 2 kinds of Complex Lipids | Phospholipids and Glycolipids
Complex lipids form the membranes around cells and around small structures within cells
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| Phospholipids | Contains an alochol, 2 fatty acids and phosphate
Glycerophospholipids-alcohol is glycerol
Sphingolipids- alcohol is sphingosine
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| Glycolipds | Complex lipids that contain a carbohydrate
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| Complex lipids in aqueous solution | spontaneously form into a lipid bilayer, a back to back arrangement of lipid monolayers (2 layers, tail to tail)
The hydrocarbon tails in the interior can be rigid of rich in saturated fatty acids or fluid if rich in unsaturated fatty acids
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| Cholesterol | *Most abundant & important steroid in body
*A component in plasma membrane in all animal cells
*the precursor of all steroid hormones & bile acids
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| What are lipoproteins? | Carriers of cholesterol
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| High Density Lipoproteins (HDL) | "good Cholesterol" consists of 33% protein & 30% cholesterol
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| Low density lipoprotein (LDL) | "bad Cholesterol" contains 25% proteins & 50% cholesterol
*leaks lipids that get stuck in blood vessles
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| Very Low density lipoproteins (VLDL) | Carries Triglycerides(fats) synthesized by liver, Delivers fat cells for storage will morph into LDL eventually
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| Chyomicrons | Carry dietary lipids synthesized in intestines
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| What is the starting material for the synthesis of steroid hormones? | Cholesterol, it is converted first to progesterone and then to both sex hormones & adrenocorticoid hormones
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| Female sex hormones | synthesized in the ovaries from progesterone
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| Prostaglandins | family of compounds that have the 20-carbon skeleton of prostanoic acid
* autocrine and endocrine hormones
*mediate vasodilation, bronchodilation, neuron sensitization
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| Prostaglandins not stored in tissues but synthesized ... | from membrane bound 20-carbon polyunsaturated fatty acids in response to specific physiological triggers ex) arachidonic acid
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| Thrombaxanes | derived from arachodonic acid
*induces platelet aggregation & vasconstriction
*aspirin inhibits the synthesis of thromboxane by inhibiting the COX enzyme
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| COX-1 | catalyzes the normal physiological production of prostaglandins
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| COX-2 | responsible for production of prostaglandins in inflammation-reason why we take asprin
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| Which hormone inhibits further ovulation once an egg has been fertilized? | progesterone
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| How many rings are associated with the steroid structure? | 4
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| Which of the following transports cholesterol to the liver? | HDL
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| Lipid membranes have how many layers? | 2
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| What is the IUPAC name of glycerol? | 1,2,3-propanetriol
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| In glycerophospholipids where is the phosphate group attached to glycerol? | at a terminal carbon only
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| Which of the following has the largest percentage of cholesterol and cholesterol esters? | LDL
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| Myelin, the coating of nerve axons, is what type of lipid? | sphingolipid
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| Which of the following reactions is the source of trans fatty acids found in some processed food? | Hydrogenation
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| Which of the following carries cholesterol to the cells? | LDL
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| What is the function of a steroid hormone primary messenger? | deliver signals from one part of the body to another
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| Which alcohol is a component of all triglycerides? | glycerol
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| Which hormone triggers ovulation? | luteinizing hormone
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| Which of the following is associated with thromboxanes? | platelet clumping
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| Which of the following is used to define lipids? | their insolubility in water
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| Which of the following is a function of unsaturated fatty acids in membranes? | they give the interior of the membrane liquid like structure
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| What do we mean by an essential fatty acid? | a fatty acid which must be part of our diets since we cannot synthesize it
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| Which of the following describes the distribution of the polar & nonpolar portions of lipids in the lipid bilayer? | both polar heads are on the outside of the bilayer and both hydrophobic tails are on the inside of the bilayer
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| Which of the following is the result of high cholesterol levels inside cells? | less LDL is taken into the cells from the plasma
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| Asprin and other NSAIDs do which of the following? | inhibit both COX-1 and COX-2 activity
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| Where in the body are leukotrienes most commonly found? | White blood cells
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