Energy Metabolism- Lipids

Question 1

Lipids

Answer 1

heterogeneous group of water-INsoluable organic molecules;
vitamins A,D,E,K;
major source of E for body;
provide hydrophobic barriers (compartmentalization);
hydrophobic so are found in compatmentalized form (membrane lipids) or bound to plasma proteins (lipoproteins, albumin)

Question 2

Common lipids

Answer 2

fatty acids, triacylglycerol, phospholipid, steroid, glycolipid

Question 3

Amphiphatic character

Answer 3

hydrophobic and hydrophilic sides

Question 4

Molecules with high physiological relevance

Answer 4

prostaglandins, steroid hormones

Question 5

Dietary lipids

Answer 5

cholesterol esters, phospholipids, fatty acids

Question 6

Lipid digestion: beginning

Answer 6

starts in the stomach (lipases are acid-stable)

Question 7

Lipid structure

Answer 7

hydrophobic hydrocarbon chain: CH3(CH2)n

hydrophilic carboxyl group: COO-

Question 8

Lipid digestion: emulsification

Answer 8

occurs in duodenum;
breaks lipids so lipase can “eat” the cells;
bile acids emulsify fat droplets

Question 9

Lipid digestion: control

Answer 9

CCK (cholecystochinin) stimulates pancreas–> pancreas enzyme secretion
CCK stimulates gall bladder–> bile acid secretion
Secretin stimulates pancreas to make morebicarbonate

Question 10

Long chains

Answer 10

digestion produces free fatty acids (FFA), cholesterol, and 2 monoacylglycerol (MAG) which form long chains (micelles)

Question 11

Short and medium chains

Answer 11

directly released to portal circulation where they bind to albumin

Question 12

Mixed micelles

Answer 12

lumen of small intestine; long chains

Question 13

Chylomicron

Answer 13

a lipoprotein; generated in ER;
so big it can’t go to capillaries so bypasses portal vein and liver; goes to lymphatic system–>renal system;
directly sends lipids to body (bypass liver);
gets FFA’s–> used up by muscles for E;
gets glycerol–>sends to liver to make G3P–>gluconeogenesis

Question 14

Re-esterification

Answer 14

once absorbed, lipids go to ER for synthesis:
MAG–>TAG
Lysophospholipids–>phospholipids
Cholesterol–>fatty acids

Question 15

Composition of plasma lipoproteins

Answer 15

triacylglycerol, protein, phospholipids, cholesterol (used for hormones), and cholesteryl esters

Question 16

Use of dietary lipids by tissues

Answer 16

TAGS from chylomicrons: free fatty acids used by muscles for E, fat cells storage, in blood bind to plasma
TAGS from chylomicrons: glycerol sent to liver to make G3P
Chylomicron remnants absorbed by liver by process receptor-mediated endocytosis

Question 17

Relevance of fatty acids

Answer 17

E: during fast, FA’s bind to albumin leading to oxidation
Structural: phospholipids and glycolipids in the plasma membrane
Hormone precursor: prostaglandins
E reserve: TAG in adipose tissues

Question 18

Structural aspects of lipids: Saturated

Answer 18

no double bonds

Question 19

Structural aspects of lipids: Unsaturated

Answer 19

double bonds (kinks)

Question 20

Structural aspects of lipids: Configuration

Answer 20

double bonds more frequent in CIS configuration

cis has important role in membrane

Question 21

Phospholipids: structure

Answer 21

two fatty acid chains (one saturated, one unsaturated)
phosphate group
alcohol group
substituent
unsaturated more important bc makes more flexible membrane

Question 22

Fatty acids of physiological relevance

Answer 22

Glycerine, phosphoglyceride, sphingomyelin;
Number of carbons=double bonds and positions
alpha: carboxyl group
beta: carbon 3
gamma: carbon 4
omega: terminal methyl group

Question 23

Essential FA’s

Answer 23

cannot be synthesized in body- we must eat them!
linoleic acid (w-6 FA)–> arachodonic acid
alpha-linoleic acid (w-3 FA)–> growth & development

Question 24

De novo synthesis

Answer 24

rxn occurs in cytosol;
need acetyl CoA to make citrate (in mitochondria), citrate gets pumped into cytosol;
result is palmitate (fully saturated fatty acid)

Question 25

De novo synthesis enzyme

Answer 25

acetyl CoA carboxylase: takes acetyl CoA & makes malonyl CoA, is a rate limiting step; fatty acid synthase makes rest of synthesis occur

Question 26

Use of new fatty acids

Answer 26

store (in fat cells) or mobilize (use enzyme hormone sensitive lipase); storage simulated by INSULIN

Question 27

Hormonal regulation of fat degradation in adipocyte

Answer 27

glycerol released during TAG degradation CAN'T be metabolized by adipocytes (they lack enzyme glycerol kinase)--> transported to liver; free FA's bind in blood to albumin and are transported to tissue used for E in mitochondria

Question 28

Beta-oxidation

Answer 28

occurs in mitochondria; how make E from fatty acids; takes C from fatty acid (palmitoyl CoA) to produce 8 ACoA, 7 NADH, 7 FADH2; carrier that transports C's (from fatty acids) into mitochondria: the carnitine translocase; from there generates NET 129 ATP

Question 29

Beta-oxidation net gain

Answer 29

129 ATP

Question 30

Ketone bodies

Answer 30

important source of E during fasting; high levels lead to acidosis; LIVER

Question 31

Ketone bodies synthesis

Answer 31

liver (mitochondria) can convert ACoA into ketone bodies such as acetoacetate, 3-hydroxybutyrate, and acetone; in peripheral tissues, can be converted into ACoA which enters TCA; SO, synthesis in liver and use in peripheral tissues

Question 32

Synthesis of phosphlipids for the plasma membrane occurs...

Answer 32

in the smooth ER

Question 33

Fatty acids of physiological relevance

Answer 33

hydrophilic (polar) head, hydrophobic tail; | glycerophospoholipids

Question 34

orientation of phospholipids in aqueous milieu

Answer 34

lipid-bilayer: hydrophobic tail in, polar head out | liposom: wheel formation, water inside and outside, polar heads facing out towards water (bc they're hydrophilic)

Question 35

Synthesis of phospholipids

Answer 35

all cells EXCEPT ERYTHROCYTES (RBC's) can synthesize phospholipids; occurs in sER, goes to golgi apparatus, then membranous organelles; donation of phosphatidic acid from CDP-DAG to an alcohol

Question 36

Glycerophospholipids

Answer 36

phosphatidic acid + alcohol; serine + PA = phosphatidylserine ethanolamine + PA = phosphatidylethanolamine (cephalin) choline + PA = phosphatidylcholine (lecithin) inositol + PA = phosphatidylinositol gylerol + PA = phosphatidylglycerol

Question 37

Cardiolipin

Answer 37

phospholipid of physiological relevance; inner mitochondrial membrane; maintenance for e- transport chain

Question 38

Platelet-activating factor (PAF)

Answer 38

phospholipid of physiological relevance; activates inflammatory cells, platelet aggregation; cause anaphylactic reactions

Question 39

Sphingomyelin

Answer 39

phospholipid of physiological relevance; | component of myelin in nerve fibers

Question 40

Role of inositol triphosphate (IP3) and diacylglycerol (DAG) in intra-cellular signaling

Answer 40

hormone is 1st receptor in step 1 | IP3 & DAG are 2nd messengers in step 5

Question 41

Blood typing

Answer 41

ABO blood group antigens are GLYCOSPHINGOLIPIDS | sphingosin

Question 42

Prostaglandins & Thromboxanes

Answer 42

play many roles in physiology; | synthesis: eicosanoids; eicosa= 20 carbons