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M1 > Lipids > Flashcards

Lipids Flashcards

1
Q

Fatty acids are

A
  • water-insoluble hydrocarbons used for cellular energy storage.
  • highly reduced and thus provide a rich source of stored chemical energy for cells.
  • Storage of hydrophobic fats as triacylglycerols is also highly efficient because water is not needed to hydrate the stored fats.
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2
Q

Membrane lipids are:

A
  • composed of hydrophobic tails attached to polar head groups.
  • Cellular membranes are composed of a variety of lipids, including glycerophospholipids and sterols.
  • These lipids are used for structuring membranes as well as for displaying molecules on the membrane surfaces for signaling and molecular recognition.
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3
Q

Many lipids are present in the cell at ________ amounts than those making up membranes or being stored as fat.

These lipids can function as:

A

smaller;

  • cellular messengers
  • hormones
  • electron carriers
  • pigments
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4
Q

The chemical properties of lipids are related to their __________ and _____________

A

structure and composition

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5
Q

Biological Lipids Features:

Lipids function are also diverse:

A

Biological lipids:

  • Chemically diverse
  • Generally insoluble in water.

Lipids functions are also diverse:

  • Stored energy
  • Components of biological membranes.
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6
Q

Other lipid functions:

A
  • electron carriers
  • hydrophobic anchors for proteins
  • emulsifying agents in the digestive tract
  • hormones
  • intracellular messengers
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7
Q

Fatty acids are:

  • Water-insoluble hydrocarbons with attached _______used for cellular energy storage
  • Generally ________and thus provide a rich source of________
  • Storage of hydrophobic fats (fatty acids) as triacylglycerols is not _______highly_______ because water is not needed to hydrate the stored fats
A
  • COO-
  • highly reduced; stored chemical energy
  • hydrated; efficient
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8
Q
  • fatty acids = ____________
  • oxidation of fatty acids (to CO2 and H2O) is highly ______________
A
  • hydrocarbon derivatives
  • exergonic (energy producing)
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9
Q

fatty acids = __________ with hydrocarbon tails ranging from __ to ___ carbons long

  • can be _______ or ______
  • can be _______ or _______
A

carboxylic acids; 4 to 36 (C4 to C36)

  • saturated or unsaturated
  • branched or unbranched
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10
Q

Poor solubility in water dur to the ____________

  • increased chain length _______ solubility
  • decreased double bond number ________ solubility

carboxylic acid group is _______ and _______ at neutral pH

A

nonpolar hydrocarbon chain

  • decreases
  • decreases

polar and ionized

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11
Q

Nomenclature for Unbranched Fatty Acids

A
  • the chain length and number of bonds, separated by a colon
  • numbering begins at the carboxyl carbon
  • positions of double bonds are indicated by ∆ and a superscript number
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12
Q

Common Patterns in Fatty Acids

A
  • even numbers of carbon atoms (12 to 24 carbons)
  • mostly straight chains
  • Can be unsaturated
  • if monounsaturated, the double bond is usually between C-9 and C-10 (∆9)
  • if polyunsaturated fatty acids:
    • the double bonds are usually ∆12 and ∆15
    • double bonds are usually separated by a methylene group
  • double bonds are usually in the cis configuration
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13
Q

Polyunsaturated Fatty Acids (PUFAs)

A

Contain more than one double bon in their backbone

  • omega-3 (w-3) fatty acids= double bond between C-3 and C-4 relative to the most distant carbon (w)
  • omega-6 (w-6) fatty acids= double bond betweeen C-6 and C-7 relative to w
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14
Q

humans must obtain the omega-3 PUFA α-linolenic acid (ALA; 18:3(∆9,12,15)) from_________

A

their diet

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15
Q

humans use ALA to synthesize:

A
  • eicosapentaenoic acid (EPA; 20:5(∆5,8,11,14,17))
  • docosahexaenoic acid (DHA; 22:6(∆4,7,10,13,16,19))
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16
Q

the optimal dietary ratio of omega-6 to omega-3 PUFAs is between _____ and _____

A

1:1 and 4:1

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17
Q

triacylglycerols are fatty acid esters or glycerol

A
  • composed of three fatty acids in ester linkage with a single glycerol
  • May consist of
    • (one kind of fatty acid)
    • mixed (two or three different fatty acids)
  • non-polar, hydrophobic
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18
Q

Triacylglycerols Provide ________________

A
  • Stored Energy and Insulation
    • vertebrates store triacylglycerols as lipid droplets in adipocytes (fat cells)
    • plants store triacylglycerols in the seeds
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19
Q

Advantages of Using Triacylglycerols as Stored Fuels

A
  • Generally highly or more reduced state
  • Stored in unhydrated form
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20
Q

Lipases

A

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

adipocytes and germinating seeds contain lipases

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21
Q

Dietary intake of _________ is linked to a higher incidence of cardiovascular disease

A

trans fatty acids

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22
Q

trans fatty acids do what?

A
  • raise the level of triacyglycerols in the blood
  • raise the level of LDL (“bad”) cholesterol in the blood
  • lower the level of HDL (“good”) cholesterol
  • increase the body’s inflammatory response
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23
Q
  • Double layer of lipids that acts as a barrier to polar molecules and ions
  • amphipathic
  • hydrophobic regions associated with each other
  • hydrophilic regions associate with water
A
  • biological membranes
  • membrane lipids
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24
Q

Four general types of membrane lipids

A
  1. phospholipids = have hydrophobic regions composed of two fatty acids joined to glycerol or sphingosine
  2. glycolipids = contain a simple sugar or a complex oligosaccharide at the polar ends
  3. archaeal tetraether lipids = have two very long alkyl chains ether-linked to glycerol at both ends
  4. sterols = compounds characterized by a rigid system of four fused hydrocarbon rings
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25
Q

Derivatives of phosphatidic acid

A

glycerophospholipids

26
Q

glycerophospholipids

A
  • two fatty acids are attached in ester linkage to the first and second carbons of glycerol
  • a highly polar or charged group is attached through a phosphodiester linkage to the third carbon
27
Q

The Fatty Acids in Glycerophospholipids

A
  • can be any of a wide variety
  • in general, glycerophospholipids contain:
    • a C16 or C18 saturated fatty acid at C-1
    • a C18 or C20 unsaturated fatty acid at C-2
28
Q

In glycerophospholipids a phosphodiester bond joins the head group to __________

The phosphate group can bear a __________ charge

A

glycerol

negative, neutral, or positive charge

29
Q

ether lipids

A

one of the two acyl chains is attached to glycerol in ether

  • chain may be saturated
  • chain may contain a double bond between C-1 and C-2 as in plasmalogens
30
Q

platelet-activating factor

A

an ether lipid that serves as a potent molecular signal

  • releases from leukocytes called basophils
  • stimulates platelet aggregation and serotonin release
  • plays a role in inflammation and the allergic response
31
Q

sphingolipids

A

class of membrane phospholipids and glycolipids

  • have a polar head group and two nonpolar tails
  • contain no glycerol
  • contain one molecule of the long-chain amino alcohol sphingosine or one of its derivatives
32
Q

ceramide

A

compound resulting when a fatty acid is attached in amide linkage to the NH2 on C-2

structurally similar to a diacylglycerol

33
Q

Ceramides are the structural parent of all sphingolipids

A

C-1, C-2, and C-3 of sphingosine are structurally analogous of the three carbons of glycerol in glycerophospholipids

34
Q

sphinogomyelins

A

subclass of sphingolipids that contains:

  • phosphocholine or
  • phosphoethanolamine as their polar head group
35
Q

glycosphingolipids

A

have head group consist of one or more sugars connnected directly to the -OH at C-1 of the ceramide moiety

  • do not contain phosphate
  • occur largely in the outer fce of plasma membranes
36
Q

cerebrosides

A

have a single sugar linked to ceramide

  • those with galactose are found in the plasma membranes of cells in neural tissue
  • those with glucose are found in the plasma membranes of cells in nonneural tissues
37
Q

globosides

A

glycosphingolipids with 2 or more sugars, usually D-glucose, D-galactose, or N-acetyl-D-galactosamine

sometimes called neutral glycolipids, as they have no charge at pH 7

38
Q

gangliosides

A
  • oligosaccharides as their polar head groups and
  • 1 or more residues of N-acetylneuraminic acid (Neu5Ac), a sialic acid, at the termini
    • 1 sialic acid residue = GM (M for mono-) series
    • 2 sialic acid residues= GD (D for di-) series
    • 3 sialic acid residues= GT (T for tri-) series (and so on)
39
Q

Sphingolipids at cell surfaces are sites of

A

biological recognition

  • prominent in the plasma membranes of neurons
  • human blood groups (O, A, B) are determined in part by the oligosaccharide head groups of these glycosphingolipids
40
Q

Phospholipids and Sphingolipids Are Degraded in Lysosomes
Phospholipid degradation…

A
  • phospholipases of the A type remove one of the two fatty acids
  • lysophospholipases remove the remaining fatty acid
  • lysosomal enzymes catalyze the stepwise removal of sugar units of gangliosides
41
Q

Abnormal Accumulations of Membrane Lipids

A

genetic defects in any of these hydrolytic enzymes leads to the accumulation of gangliosides in the cell

42
Q

Sterols:

Steroid nucleus:

A

structural lipids present in the membranes of most eukaryotic cells

  • Steroid nucleus:
    • consists of four fused rings
    • almost planar
    • relatively rigid
43
Q

cholesterol

A

major sterol in animal tissues

  • amiphipathic
  • polar head group
  • nonpolar hydrocarbon body
  • membrane constituents
44
Q

polar derivatives of cholesterol that emulsify dietary fats in the intestine to make them more readily accessible to digestive lipases

A

bile acids

45
Q

Sterols Serve as Precursors for Products with Specific Biological Activities

A
  • steroid hormones
  • regulate gene expression
  • bile acids
46
Q

steriods

A

oxidized derivates of sterols

  • lack the alkyl chain attached to ring D of cholesterol
  • more polar than cholesterol
47
Q

steriod hormones move through the bloodstream (on protein carries) to target tissues binding to highly specific receptor proteins in the nucleus which triggers changes in

A

gene expression

48
Q

Steroids derived from cholesterol

A
  • Testosterone
    • Male sex hormone produced in the testes
  • Cortisol
    • Hormone produced in the adrenal cortex; regulates glucose metabolism
  • Prednisone
    • Synthetic steroid used as an anti-inflammatory agent
  • Beta-Estradiol
    • Female sex hormone produced in the ovaries and placenta
  • Aldosterone
    • Hormone produced in the adreanl cortex; regulates salt excretion
  • Brassinolide ( a brassinosteroid)
    • Growth regulator found in vascular plants
49
Q

Vitamin D3 (cholecalciferol)

A

formed in the skin from 7-dehydrocholesterol in a photochemical reaction driven by the UV component of sunlight

  • not biologically active
  • converted by enzyme in the liver and kedney to calcitriol
50
Q

calcitrol

A

hormone that regulates calcium uptake in the intestine and calcium levels in the kidney and bone

51
Q

Phosphatidylinositols and Sphingosine derivatives act as _____________

A

intracellular signals

phosphatidylinositol (PI) and its phosphorylated derivatives regulate cell structure and metabolism

52
Q

in the cytoplasmic face of plasma membranes ____________serves as a reservoir of messenger molecules that are released in response to extracellular signals

A

Phosphatidylinositol 4,5-Bisphosphate (PIP2)

phospholipase C hydrolyzes PIP2 to IP3 and diacylglycerol (intracellular messengers)

53
Q

ceramide and sphingomyelin are potent regulators of __________

ceramide or its derivatives are involved in the regulation of:

A

protein kinases

  • cell division
  • differentiation
  • migration
  • programmed cell death
54
Q

Eicosanoids Carry Messages to Nearby Cells

eicosanoids =

involved in:

A

paracrine hormones, substances that act only on cells near the point of synthesis instead of being transported in the blood

involved in:

  • reproductive function
  • inflammation, fever, and pain associated with injury or disease
  • formation of blood clots
  • regulation of blood pressure
  • gastric acid secretion
55
Q

Eicosanoids are derived from

A

arachidonic acid

56
Q

four major classes of eicosanoids

A
  1. prostaglandins
  2. thromboxanes
  3. leukotrienes
  4. lipoxins
57
Q

prostaglandins (PG)

functions:

A

class of eicosanoids that contain a five-carbon ring

array of functions:

  • stimulate contraction of the smooth muscle of the uterus
  • affect blood flow to specific organs, the wake-sleep cycle, and the responsiveness of certain tissues to hormones
  • elevate body temperature and cause inflammation and pain
58
Q

thromboxanes (TX)

A

class of eicosanoids that have a six-membered ring containing an ether

produced by platelets (also called thrombocytes)

act in the formation of blood clots and reduction of blood flow to the site of a clot

59
Q

Leukotrienes (LT)

A
  • class of eicosanoids that contain three conjugated double bonds
  • powerful biological signals
    • leukotriene D4 induces contraction of the smooth muscle lining the airways to the lung
60
Q

Lipoxins (LX)

A
  • class of eicosanoids that are linear and contain several hydroxyl groups along the chain
  • potent anti-inflammatory agents

M1 (48 decks)

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