10.3 Lipids as Signals, Cofactors, and PIgments Flashcards
phosphatidylinositol (PI) and sphingosine derivatives act as
intracellular signals
PI and its phosphorylated derivatives regulate cell structure and metabolism
phosphatidylinositol 4,5-biphosphate (PIP2)
-in the cytoplasmic face of plasma membranes
-serves as a reservoir of messenger molecules that are released in response to extracellular signals
phospholipase C
hydrolyzes PIP2 to IP3 and diacylglycerol (intracellular messengers)
membrane sphingolipids serve as sources of
intracellular messengers
ceramide and sphingomyelin are
potent regulators of protein kinases
ceramide or its derivatives are involved in the regulation of
-cell division
-differentiation
-migration
-programmed cell death
eicosanoids carry
messages to nearby cells
eicosanoids
paracrine hormones, substances that act only on cells near the point of hormone synthesis instead of being transported in the blood
-fatty acid of C20 derivative s
they are a very quick signaling molecule
notice modifications allow for increased solubility to be used as messengers
eicosanoids are involved in
-reproductive function
-inflammation, fever, and pain associated with injury or disease
-formation of blood clots
-regulation of blood pressure
-gastric acid secretion
eicosanoids are derived from
arachidonic acid
four major classes of eicosanoids
prostaglandins
thromboxanes
leukotrienes
lipoxins
prostaglandins (PG)
class of eicosanoids that contain a five-carbon ring
-stimulate contraction of the smooth muscle of the uterus
-affect 1) blood flow to specific organs, 2) the wake-sleep cycle, and the 3) responsiveness of certain tissues to hormones
-elevate body temperature and cause inflammation and pain
thromboxanes (TX)
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 the clot
leukotrienes (LT)
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
lipoxins (LX)
class of eicosanoids that are linear and contain several hydroxyl groups along the chain
potent anti-inflammatory agents
steroid hormones carry messages
between tissues
steroids
oxidized derivatives of sterols
-lack the alkyl chain attached to ring D of cholesterol
-more polar than cholesterol
steroid hormones move through the bloodstream (on protein carriers) to target tissues (enter the cell by simple diffusion across the plasma membrane)
binding to highly specific receptor proteins in the nucleus triggers changes in gene expression
vitamins A and D are
hormone precursors
vitamins
compounds that are essential to the health of humans and other vertebrates but cannot be synthesized
fat-soluble vitamins include the groups ADEK
Vitamin D3 (cholecalciferol)
formed in the skin from 7-dehydrocholesterol in a photochemical reaction driven by the UV component of sunlight
-not biologically active
-converted by enzymes in the liver and kidney to calcitriol
calcitrol
hormone that regulates calcium uptake in the intestine and calcium levels in the kidney and bone
vitamin D deficiency
defective bone formation and the disease rickets
vitamin A1 (all-trans-retinol)
acts in processes of development, cell growth and differentiation, and vision
-can be stored for some time in the body
carotenoids
natural products with a characteristic extensive system of conjugated double bonds, which makes possible their strong absorption of visible light (450-470nm)
beta-carotene pigment is a source of vitamin A
all-trans-retinoic acid
vitamin A1 or beta-carotene can be converted enzymatically to all-trans-retinoic acid
retinoid hormone that acts through a family of nuclear receptor proteins to regulate gene expression
vitamin A deficiencies
in pregnant women, lead to congenital malformations and growth retardation in the infant
in adults, leads to dryness of skin, eyes, and mucous membranes, and night blindness
vitamins E and K and the lipid quinones are
oxidation-reduction cofactors
vitamin E
collective name for a group of lipids called tocopherols
tocopherols
hydrophobic compounds that contain a substituted aromatic ring and a long isoprenoid side chain
-associate with cell membranes, lipid deposits, and lipoproteins
-biological antioxidants
vitamin E deficiencies
cause scaly skin, muscular weakness and wasting, and sterility
very rare in humans
principal symptom is fragile erythrocytes
vitamin K
contains an aromatic ring that undergoes a cycle of oxidation and reduction during the formation of active prothrombin, a blood plasma protein essential in blood clotting
