10.3 Lipids as Signals, Cofactors, and PIgments

Question 1

phosphatidylinositol (PI) and sphingosine derivatives act as

Answer 1

intracellular signals

PI and its phosphorylated derivatives regulate cell structure and metabolism

Question 2

phosphatidylinositol 4,5-biphosphate (PIP2)

Answer 2

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

Question 3

phospholipase C

Answer 3

hydrolyzes PIP2 to IP3 and diacylglycerol (intracellular messengers)

Question 4

membrane sphingolipids serve as sources of

Answer 4

intracellular messengers

Question 5

ceramide and sphingomyelin are

Answer 5

potent regulators of protein kinases

Question 6

ceramide or its derivatives are involved in the regulation of

Answer 6

-cell division
-differentiation
-migration
-programmed cell death

Question 7

eicosanoids carry

Answer 7

messages to nearby cells

Question 8

eicosanoids

Answer 8

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

Question 9

eicosanoids are involved in

Answer 9

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

Question 10

eicosanoids are derived from

Answer 10

arachidonic acid

Question 11

four major classes of eicosanoids

Answer 11

prostaglandins
thromboxanes
leukotrienes
lipoxins

Question 12

prostaglandins (PG)

Answer 12

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

Question 13

thromboxanes (TX)

Answer 13

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

Question 14

leukotrienes (LT)

Answer 14

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

Question 15

lipoxins (LX)

Answer 15

class of eicosanoids that are linear and contain several hydroxyl groups along the chain

potent anti-inflammatory agents

Question 16

steroid hormones carry messages

Answer 16

between tissues

Question 17

steroids

Answer 17

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

Question 18

vitamins A and D are

Answer 18

hormone precursors

Question 19

vitamins

Answer 19

compounds that are essential to the health of humans and other vertebrates but cannot be synthesized

fat-soluble vitamins include the groups ADEK

Question 20

Vitamin D3 (cholecalciferol)

Answer 20

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

Question 21

calcitrol

Answer 21

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

Question 22

vitamin D deficiency

Answer 22

defective bone formation and the disease rickets

Question 23

vitamin A1 (all-trans-retinol)

Answer 23

acts in processes of development, cell growth and differentiation, and vision
-can be stored for some time in the body

Question 24

carotenoids

Answer 24

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

Question 25

all-trans-retinoic acid

Answer 25

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

Question 26

vitamin A deficiencies

Answer 26

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

Question 27

vitamins E and K and the lipid quinones are

Answer 27

oxidation-reduction cofactors

Question 28

vitamin E

Answer 28

collective name for a group of lipids called tocopherols

Question 29

tocopherols

Answer 29

hydrophobic compounds that contain a substituted aromatic ring and a long isoprenoid side chain
-associate with cell membranes, lipid deposits, and lipoproteins
-biological antioxidants

Question 30

vitamin E deficiencies

Answer 30

cause scaly skin, muscular weakness and wasting, and sterility

very rare in humans

principal symptom is fragile erythrocytes

Question 31

vitamin K

Answer 31

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