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CMBM Exam 2 > Dietary Lipids > Flashcards

Dietary Lipids Flashcards

1
Q

Short-chain (SCFA)

A
  • 2-3 carbons
  • Soluble
    • do not require bile salts (i.e. mixed micelles for their absorption by the mucosa)
    • more readily absorbed in the stomach than other fatty acids
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2
Q

Medium-chain (MCFA)

A
  • 4-11 carbons
  • Fairly soluble
    • do not require bile salts (i.e. mixed micelles for their absorption by the mucosa
    • preferentially transported via portal vein to the liver because of their smaller size and greater solubility compared to LCFAs
  • not carnitine dependent for entry into mitochondria
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3
Q

Long-chain (LCFA)

A
  • 12-20 carbons
  • insoluble
  • most important for brain development in the first year (palmitic, oleic, or linoleic acids)
  • LC-PUFAs play a vital role in overall development of immunity in infants
  • carnitine shuttle required for their transport into mitochondrial matrix
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4
Q

Very long-chain (VLCFA)

A
  • > 20 carbons
  • insoluble
  • exclusively oxidized in peroxisomes
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5
Q

Fatty acids that contribute to the membrane fluidity

A
  • MUFA and PUFA
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6
Q

Effects of length and degree of unsaturation on melting point

A
  • The longer the chain length, the higher the melting point

- The more unsaturation (i.e., the larger # of double bonds), the lower the melting point

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7
Q

Dietary studies have shown that diets enriched with monounsaturated fat (MUFA) have what beneficial effects?

A
  • reduce total cholesterol and LDL levels
  • cardioprotective effects
  • blood pressure lowering effects
  • improving insulin sensitivity
  • providing anti-thrombotic effects
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8
Q

What fatty acids are crucial to optimal to the development of the brain and eyes?

A
  • docosahexaenoic acid (DHA; synthesized in liver and brain)

- arachidonic acid (AA)

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9
Q

The Essential fatty acids

A
  • Linoleic acid (LA)

- α-linolenic acid (ALA)

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10
Q

Essential fatty acids are essential because?

A
  • body cannot introduce double bonds past carbon 9 (counting from carboxyl as #1)
  • Mammals do not have the enzymes (desaturases) that introduce double bonds at ∆ 12 and ∆ 15, but plants synthesize both from oleic acid
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11
Q

Linolenic acid is what type of fatty acid?

A
  • an ω-3 fatty acid
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12
Q

Two important ω-3 fatty acids

A
  • EPA, eicosapentaenoic acid (20:5∆ 5,8,11,14,17), and DHA, docasahexaenoic acid (22:6∆ 4,7,10,13,16,19,), are metabolic derivatives of ALA and necessary for synthesis of a number of regulatory compounds in the body. ALA===>EPA, DHA
  • EPA and DHA may reduce the risk of a heart attack. Fish oil contains DHA and EPA
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13
Q

Fatty acid derivatives serve as

A
  • hormones and precursors of cellular regulators
  • The essential FAs, linoleic acid (LA) and α-linolenic acid (ALA), combine with cholesterol to form eicosanoids and steroid hormones
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14
Q

linoleic acid (LA, ω-6) may be converted into

A
  • other polyunsaturated acids, particularly γ-linolenic acid (GLA), eicosatrienoic acid, and eicosatetraenoic acid (AA or arachidonic acid)
    • these compounds affect key cellular and physiological processes in the body ranging from cell signalling to inflammation
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15
Q

ω-3 fatty acids are essential in

A
  • growth and development throughout the human life cycle

- ω-3 PUFAs inhibit tissue eicosanoid biosynthesis and reduce inflammation

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16
Q

Arachidonic acid (AA)

A
  • major constituent of membrane phospholipids and an essential precursor to a number of important biological compounds known as eicosanoids that regulate body functions, such as immune function, blood clotting and blood pressure
  • Modifications of AA form the prostaglandins, the inflammatory hormones that aspirin interferes with; leukotrienes are produced in the body from AA by the enzyme 5-lipoxygenase
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17
Q

Eicasanoids

A
  • derived from the 20 carbon AA
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18
Q

Essential Fatty Acid Deficiency Side Effects

A
  • hemorrhagic and scaly dermatitis
  • skin dryness and atrophy
  • weakness
  • impaired vision
  • tingling sensations
  • mood swings
  • edema
  • high blood pressure
  • high triglycerides
  • hemorrhagic folliculitis
  • hemotologic disturbances (ex: sticky platelets)
  • immune and mental deficiencies
  • impaired growth
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19
Q

Excessive amounts of omega-6 polyunsaturated fatty acids and a very high omega- 6/omega-3 ratio have been linked with pathogenesis of many diseases

A
  • cardiovascular disease
  • cancer
  • inflammatory
  • autoimmune diseases
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20
Q

The ratio of omega-6 to omega-3 in modern diets is approximately

A

15: 1
- ratios of 2:1 have been associated with reduced mortality from cardiovascular disease, suppressed inflammation in patients with rheumatoid arthritis, and decreased risk of breast cancer

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21
Q

When membranes are NOT very fluid, this interferes with

A
  • ion channels (transmembrane proteins), and prevents rapid passage of ions; how local anaesthetics such as lidocaine work
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22
Q

Cholesterol effects on membrane fluidity

A

has conflicting effects:

  • the steroid rings help stiffen the membrane, making it less fluid
  • prevent the other lipids from packing tightly
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23
Q

Trans fatty acids effects on cellular membrane

A
  • are incorporated into the cell membranes create denser membranes that alter the normal functions of the cell
  • replace the cis-unsaturated FAs normally found there
  • makes the membranes less fluid
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24
Q

Triglyceride (TG or triacylglycerol)

A
  • major forms of fat stored in adipose cells
  • highly concentrated metabolic energy storage form because they are anhydrous and exclude water
  • consists of a 3-carbon glycerol backbone and 3 fatty acids
    • Glycerol is an alcohol composed of 3 carbon atoms
    • Each of the 3 fatty acids within each TG can be different sizes and can be either saturated or unsaturated
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25
Q

Trans fatty acids health effects

A
  • increase LDL cholesterol, decrease HDL cholesterol and promote both cardiovascular disease and cancer growth
  • raise levels of triglycerides in the blood
    • Both of these conditions are associated with insulin resistance which is linked to diabetes, hypertension, and cardiovascular disease
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26
Q

Which oil can play a significant role in reducing blood cholesterol levels when consumed regularly as part of the diet

A
  • linoleic acid
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27
Q

Neutral, uncharged lipids, (nonpolar)

A
  • triacylglycerol (TG)

* cholesteryl esters (CE)

28
Q

Amphipathic lipids, (polar)

A
  • phospholipids (PL)
  • cholesterol (C)
  • monoacylglycerols (MG)
  • diacylglycerols (DG)
  • sphingolipids
  • glycolipids
29
Q

Glycerol

A
  • Glycerol is an alcohol composed of 3 carbon atoms

- forms the backbone of triacylglycerol and glycerophospholipids (phospholipids)

30
Q

Sphingosine

A
  • 18C amino alcohol

- forms the backbone of glycosphingolipids (glycolipid) and sphingophospholipids (phospholipids)

31
Q

Glycerolipids

A
  • Monoacylglycerol (MG), polar (Monoglyceride)
32
Q

Glycerophospholipids

A
  • Phospholipids (PL)
  • Phosphatidylcholine
  • Plasmalogens (in nervous tissues)
33
Q

Phospholipids (PL)

A

Glycerophospholipid class

  • amphipathic, having both polar and non-polar components
  • make up an important part of the membrane lipid bilayer in every cell
  • assist in transporting fat in our bloodstream
  • consist of a Glycerol backbone and 2 FA with a phosphate and head group (an alcohol: ethanolamine, choline, serine, inositol, etc.)
  • The phosphate group is soluble in water (hydrophilic), giving PL its amphipathic property
34
Q

Phosphatidylcholine

A

Glycerophospholipid class
- a common phospholipid and is also called a glycerolphospholipid
or a phosphoacylglycerol
- Lecithin (means egg yolk in Greek) is full of vitamin B and an example of a phosphatidylcholine
- makes surfactant

35
Q

Plasmalogens (in nervous tissues)

A

Glycerophospholipid class

  • contain polar head group of ethanolamine, serine, or choline and an ester long chain alcohol group
  • form a significant fraction of the membranes in nervous tissue
  • Some of the steps in plasmalogen biosynthesis are localized in peroxisomes, and some peroxisomal disorders impair plasmalogen biosynthesis
  • can protect mammalian cells against the damaging effects of reactive oxygen species
  • have been implicated as being signaling molecules and modulators of membrane dynamics
36
Q

Sphingolipids

A
  • have a sphingosine backbone rather than a glycerol backbone
  • major components of nervous tissue and are also found in biological membranes:
    • Ceramide- contains sphingosine with a fatty acid joined to its amino group
    • Sphingomyelin- contains a ceramide and phosphocholine/phosphoethanolamine
    • Glycolipids or glycosphingolipids- contain a ceramide and a carbohydrate group (either galactose or glucose)
37
Q

4 major classes of glycolipids

A
  • Cerebrosides: contain a single moiety, principally galactose
  • Sulfatides: sulfuric acid esters of galactocerebrosides
  • Globosides: contain 2 or more sugars
  • Gangliosides: similar to globosides except also contain sialic acid
38
Q

Sphingolipids two general structures

A
  1. Sphingophospholipids
    • Sphingomyelin= Ceramide + phosphate + choline
  2. Glycosphingolipids
    • Galactocerebroside= Ceramide + galactose
39
Q

Sphingophospholipids

A
  • Sphingolipids are important components of the myelin sheath, a multilayered membranous structure that protects and insulates the nerve fibers
  • Sphingomeylin is the primary sphingolipid in human
40
Q

Glycosphingolipids

A
  • Cerebrosides are glycosphingolipids which are important components in muscle and nerve cell membrane
  • Myelin is the well-known cerebroside
  • Two major types are glucocerebrosides and galactocerebrosides
    • Galactocerebrosides are typically found in neural tissue, while glucocerebrosides are found in other tissues
41
Q

Sterol

A
  • type of lipid found in both plant and animal foods and are produced by the body
  • Plant sterols are not well absorbed by the body, and they reduce the absorption of the major dietary sterol, cholesterol
42
Q

Cholesterol

A
  • synthesized in the liver
  • part of every cell membrane, particularly in neural cells that make up our brain, spinal cord, and nerves
  • vital to metabolism
  • important sterol compounds are synthesized using cholesterol
    • sex and adrenal hormones, bile acids, and Vitamin D
  • most common sterol in our diets
  • polar lipid that has a characteristic steroid ring system
  • predominantly hydrophobic, a single hydroxyl group allows cholesterol to interact with water at a membrane surface; therefore it is considered amphipathic
    • This hydroxyl group can be esterified to a FA to form cholesterol ester, a hydrophobic, nonpolar lipid
43
Q

Bile acids

A
  • cholic acid and chenocholic acid, the primary bile acids
    • produced from cholesterol
  • made in the liver peroxisome by the cytochrome P450-mediated oxidation of cholesterol
  • conjugated with either glycine or taurine, which increases water solubility and prevents passive re- absorption once secreted into small intestine
  • The acid groups on conjugated bile acids are often converted to salts
  • have a spatial configuration that gives them a polar “side” and a non-polar “side”
  • Liver cleaves cholesterol to make free cholesterol and puts it into bile salts and phosphatidylcholine, and conjugated bilirubin
  • Addition of bile salts with cholesterol increases solubility to 100,000 fold
44
Q

Pancreatic lipid enzymes

A
  • triacylglycerol lipase, colipase, bicarbonate, cholesteryl esterase, and phospholipases
45
Q

Triacylglycerol lipase

A
  • in complex with colipase breaks down triacylglycerols in the emulsified fat droplet; this occurs at the surface of the fat droplet
  • triacylglycerol digestion produces products such as monoacylglycerols (MG) and fatty acids (FA), which are solubilized in small bile salt micelles
46
Q

Micelle

A
  • small aggregates (4-8 nm in

diameter) of mixed lipids and bile acids suspended within the ingesta

47
Q

Bile salts

A
  • converted acid groups on conjugated bile acids
  • major component of bile
  • Sodium, calcium, and potassium are often used to produce bile salts
  • Sodium glycocholate and sodium taurocholate are examples of bile salts
48
Q

Bile Acid Synthesis Defect

A
  • Generally, the genetic defect is a deficiency of the hydroxylase enzyme needed to make bile acid
49
Q

Bile Acid Synthesis Defect symptoms

A
  • can result in progressive liver disease
  • Cholestasis
  • Jaundice
  • Liver fibrosis
  • abnormal bile acid precursors in urine
50
Q

Bile Acid Synthesis Defect treatment

A
  • oral bile acid therapy is used which causes suppression of the 7α- hydroxylase preventing further synthesis of cholestatic intermediates
51
Q

The Enterohepatic Circulation

A
  • circulation of bile acids and salts from the liver to the ileum of small intestine and back to the liver
    • Humans cannot break down and metabolize cholesterol’s complex ring structure (the “sterol ring”) for energy; the rings must either be recycled or eliminated
    • Most bile acids (> 95%) are recycled and 5% excreted
  • Majority of bile acids are recycled as primary or secondary conjugated bile salts by active transport from the proximal or distal ileum
    • Secondary conjugated bile salts happen after flora bacteria dehydroxylate bile salts. These are taken back to the liver via the portal system and carried on albumin through the blood stream
    • Additional bile acids are recycled by passive diffusion after they are deconjugated from the amino acids glycine and taurine
  • Excretion
    • In healthy people, the amount of bile acid synthesized from cholesterol
      approximately equals the amount of bile salts excreted (0.8 g/ day ~5%)
52
Q

Ezetimibe

A
  • cholesterol absorption inhibitor

* prevents uptake of cholesterol from the small intestine into the circulatory system

53
Q

Lingual lipase

A
  • acid stable lipase
  • Short and medium chain FAs from TG are targets of this enzyme
  • Digestion by lingual lipase is very limited due to the short time food stays in the mouth
54
Q

Gastric lipase

A
  • acid stable lipase degrading short and medium chain FAs

- Gastric digestion can account for up to 30% of total triacylglycerol hydrolysis

55
Q

Triacylglycerol lipase or Pancreatic Lipase

A
  • digests triacylglycerols
    • cuts ester bonds at primary alcohols of TG
  • The major products:
    • 2-Monoacylglycerol
    • Fatty acids
56
Q

Orlistat

A
  • anti-obesity drug which inhibits pancreatic and gastric lipase, thereby decreasing fat absorption and resulting in weight loss
57
Q

Colipase

A
  • secreted as a zymogen, procolipase, which is activated by trypsin in the intestine
  • binds lipase anchoring it at the lipid aqueous phase, bringing it in contact with the oil droplet and orienting the enzyme’s active site toward its substrate
  • increases lipase activity
58
Q

Cholesteryl esterase

A
  • degrades cholesterol esters to cholesterol + 1 FA

- activity is increased in the presence of bile salts

59
Q

Phospholipases

A
  • digests phospholipids
  • Phospholipase A2 is secreted as a zymogen and is activated by trypsin in the intestine
  • activity is greatly increased in the presence of bile salts
  • degrades phosphatidylcholine in two steps to one free fatty acid and lysophosphatidylcholine and then to glycerylphosphorylcholine + 2 free fatty acids
60
Q

Cholecystokinin (CCK)

A
  • produced by cells in the mucosa of the jejunum and lower duodenum
  • When partially digested lipids and proteins enter the upper small intestine, CCK acts on the gallbladder and the exocrine cells of pancreas, causing them to release bile salts and digestive enzyme, respectively
  • decreases gastric motility, resulting in a slower release of gastric contents into small intestine
61
Q

Secretin

A
  • released in response to the low pH in the chyme entering intestine
  • causes the pancreas to secrete bicarbonate to neutralize the pH of the intestinal contents
62
Q

Chylomicron

A
  • spherical particles consisting of a core of triglycerides (85%) and cholesterol esters (CE) with a shell of apolipoproteins, phospholipids, and unesterified cholesterol
  • major protein of chylomicron is apo B48
63
Q

Chylomicron Production Deficiency

A
  • severe neural degeneration
  • interrupts transfer of vitamin E from the intestine to neurons and other tissues
    • Vitamin E injections can overcome this block (oral doses greater than 1000X of normal)
64
Q

DHA (docosahexaenoic acid synthesized in liver and brain) and AA (arachidonic acid) are both crucial to

A
  • optimal development of the brain and eyes
  • omega-3 fatty acid
  • along with EPA is derived from ALA
65
Q

Surfactant

A
  • Proteins, phospholipids, and phosphatidylcholine (80%) make up lung surfactant
  • phosphatidylcholine coats alveoli of lungs and reduces surface tension, preventing lung collapse
66
Q

Prior to secretion bile acids are conjugated with

A
  • glycine or taurine

* increases water solubility and prevents passive re- absorption once secreted into small intestine

67
Q

cholestyramine

A
  • block the re-absorption of bile acids
    • Since more cholesterol is converted to bile acids in response, this helps to eliminate significant quantities of cholesterol from body

CMBM Exam 2 (13 decks)

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