10.1: Storage Lipids

Question 1

fats and oils used as stored energy are

Answer 1

derivatives of fatty acids

Question 2

fatty acids are

Answer 2

hydrocarbon derivatives: carboxylic acids with hydrocarbon tails ranging from 4 to 36 carbons long

oxidation of fatty acids to CO2 and H2O is highly exergonic

can be branched or unbranched, saturated or unsaturated

highly reduced storage forms

Question 3

branched chain fatty acids

Answer 3

major component of bacterial membranes
rare in internal human tissue
-high concentrations in skin and vernix caseosa (waxy white substance coating the skin of term newborns)

Question 4

when naming unbranched fatty acids, numbering begins

Answer 4

at the carboxyl carbon

Question 5

common patterns in fatty acids

Answer 5

-most common fatty acids have even numbers of carbon atoms in an unbranched chain of 12-24 carbons
-in monounsaturated fatty acids, the double bond is usually between C9 and C10
-in polyunsaturated fatty acids, the double bonds are usually C12 and C15, double bonds are usually separated by a methylene group
-double bonds are usually in the cis configuration

Question 6

PUFAs

Answer 6

contain more than one double bond in their backbone

Question 7

PUFAs and Human Nutrition

Answer 7

-humans must obtain the omega-3 PUFA alpha-linolenic acid from their diet
-humans use ALA to synthesize other acids

Question 8

triacylglycerols are

Answer 8

fatty acid esters of glycerol

Question 9

triacylglycerols

Answer 9

the simplest lipids constructed from fatty acids
-composed of 3 fatty acids, each in ester linkage with a single glycerol
-can be simple or mixed
-NONPOLAR, HYDROPHOBIC

Question 10

triglycerides are synthesized by

Answer 10

esterification of fatty acids to glycerol

Question 11

triglyceride synthesization takes place in the

Answer 11

ER of cells by metabolic pathways in which acyl groups of fatty acyl-CoAs are transferred to the hydroxyl groups of glycerol-3-phosphate and diacylglycerol

through dehydration synthesis
glycerol loses an H, 3 fatty acid chain lose OH

Question 12

fatty acids are _____ due to _____-

Answer 12

poor solubility in water due to the nonpolar hydrocarbon chain

carboxylic acid group is polar and ionized at neutral pH, making fatty acids amphipathic

Question 13

______ chain length of fatty acids _____ solubility
_______ double bond number ______ solubility

Answer 13

increased chain length decreases
decreased double bond number decreases

Question 14

melting point of fatty acids at room temperature

Answer 14

saturated fatty acids have a waxy consistency - higher mp
unsaturated fatty acids are oily liquids - lower mp, kinks, less VDW

the extent of packing depends on the degree of saturation

Question 15

triacylglycerols provide stored energy and insulation

Answer 15

vertebrates store triacylglycerols as lipid droplets in adipocytes (fat cells)

plants store triacylglycerols in the seeds

Question 16

lipases

Answer 16

enzymes that catalyze the hydrolysis of stored triacylglycerols, releasing fatty acids for export to sites where they are required as fuel

adipocytes and germinating seeds contain lipases

Question 17

advantages to using triacylglycerols as stored fuels (2)

Answer 17

1. because carbon atoms of fatty acids are MORE REDUCED than those of sugars, oxidation of fatty acids yields MORE ENERGY
2. because triacylglycerols are hydrophobic and unhydrated, the organism doesn’t to have to carry the extra weight of WATER HYDRATION that is associated with stored polysaccharides

Question 18

so, Why not just burn fats?

Answer 18

-the brain prefers sugar
-slower to burn
-slower to digest
-very hard to move around the body

Question 19

triacylglycerols provide insulation

Answer 19

-seals, walruses, penguins, and other warm-blooded polar animals are amply padded with triacylglycerols
-this provides them insulation against low temperatures
-hibernating animals (e.g. bears) accumulate huge fat reserves before hibernation, providing insulation and energy storage

Question 20

partial hydrogenation

Answer 20

-oxidative cleavage of double bonds in unsaturated fatty acids to aldehydes and carboxylic acids causes lipid-rich food to become rancid

-the process that converts many of the CIS double bonds in fatty acids to SINGLE bonds
-this improves shelf life, increases stability, increases melting temperature, and converts some cis double bonds to trans double bonds

Question 21

trans fatty acids

Answer 21

dietary intake of trans fatty acids is linked to a higher incidence of CV disease

1. raise the level of triacylglycerols in the blood
2. raise the level of LDL cholesterol in the blood
3. lower the level of HDL cholesterol in the blood
4. increase the body’s inflammatory response

Question 22

biological waxes - energy stores & water repellants

Answer 22

esters of long-chain (C14 to C36) saturated and unsaturated fatty acids with long-chain (C16 to C30) alcohols

-higher melting point than triacylglycerols
-water-repellant properties
-firm consistency