Bio Chem Exam 3

Front 1

triacylglycerol

Back 1

fats or triglycerides

major form of metabolic energy storage

Front 2

what determines rate of digestion?

Back 2

surface area and actions of bile acids

Front 3

What are bile acids?

Back 3

-Solubilize fat globules (liver digestion and absorption of liver products)
-cholesterol derivatives synthesized by liver and secreted as glycine or taurine conugates into the gallbladder for storage. They are then secreted into small intestines

Front 4

What is triacylglycerol lipase?

Back 4

-pancreatic lipase
-catalyze hydrolysis of 1 and 3 positions of triaclglycerols to form 1,2-diacylgycerols and 2-acylglycerols

Front 5

What is interfacial activation?

Back 5

-enzyme activity of lipase increases when it contacts lipid-water inteface

Front 6

What is colipase?

Back 6

-90 residue protein that forms 1:1 complex with lipase.
-helps form hydrophobic tips of 3 loops (phosphatidylcholine, bile acids, colipase) to form hydrophobic plateau which helps with binding lipase to lipid surface.
-forms 3 hydrogen bonds to opened lid to stabilize it

Front 7

Pancreatic Lipase (449 residues)

Back 7

-Active site is in N-terminal domain (1-336)
-without micelles, active site is covered by 25-residue helicial lid
-with micelles, lid allows exposure of active site
-B5 loop forms oxyanion hole and generates a hydrophobic surface near entrance of active site
-colipase binds to C-terminal domain (337-449) to help form hydrophobic plateau to bind lipase to lipid surface

Front 8

what does phosphatidylcholine participate in?

Back 8

helps bind lipase to interface with bile acids and colipase

Front 9

What is B5 loop?

Back 9

it is part of the pancreatic lipase and it helps form the oxyanion hole and generates a hydrophobic surface near entrance of active site.

Front 10

where is the active site of the pancreatic lipase?

Back 10

it's in the N-terminal domain

Front 11

where does colipase bind to in the pancreatic lipase?

Back 11

it binds to the C-terminal domain

Front 12

phospholipase A2

What's so special about it?

Back 12

-this enzyme contains a hydrophobic channel that provides direct access for substrate to active site of enzyme.
-soluble and dispersed phospholipids must first surmount kinetic barriers to bind to enzymes (substrates have to go through a lot to get direct access).

Front 13

What does the intestinal mucosal do?

Back 13

it absorbs fatty acids produced by lipid digestion

Front 14

micelles of Bile acid

Back 14

transport lipid degradation products to intestinal wall and helps absorption of vitamins K,A,D,E

Front 15

What does I-FABP do?

Back 15

-cytoplasmic protein
-increases effective solubility of water-soluble substances
-protects cell from detergent-like effects

Front 16

What is I-FABP?

Back 16

-intestinal fatty acid-binding protein
-fatty acids bind to I-FABP inside intestinal cells

Front 17

What is the structure of I-FABP?

Back 17

-131 residues
-10 antiparallel B strands stacked in two B sheets.

Front 18

How does fatty acid bind to I-FABP?

Back 18

-fatty acid takes up the space between the two B strands.
-fatty acid's carboxyl group interacts with Arg106, Glu115, and two bound water molecules

Front 19

What are lipoproteins?

Back 19

-they are globular micelle-like particles that consist of a nonpolar core of triacylglycerols and cholesteryl esters surrounded by an amphilic coating of protein, phospholipid, and cholesterol
-20 A thick monolayer of protein, phospholipid, and cholesterol on particle surface
-densities increase with decrease particle diameter because density of outer coating is great than inner

Front 20

What are the 5 types of lipoproteins?

Back 20

1.chylomicrons
2.VLDL
3.IDL
4.LDL
5.HDL

Front 21

Chylomicrons

Back 21

-packaged triacylglycerols
-released into intestinal lymph and transported through lymphatic vessels before draining into large veins and then into bloodstream

Front 22

VLDL

Back 22

-very low density lipoproteins
-transport endogenous triacyglycerols and cholesterol from liver to tissues

Front 23

IDL

Back 23

-Intermediate density lipoprotein
-transport endogenous triacyglycerols and cholesterol from liver to tissues

Front 24

LDL

Back 24

-low density lipoprotein
-transport endogenous triacyglycerols and cholesterol from liver to tissues

Front 25

HDL

Back 25

-high density lipoprotein
-transport cholesterol from tissue to liver
-smallest lipoprotein

Front 26

What is apolipoproteins/apoproteins?

Back 26

they are the protein part of lipoproteins

Front 27

What is apoB-100?

Back 27

-apolipoprotein B-100
-4536 residue monomer
-LDL has this
-high hydrophobicity

Front 28

properties of apoproteins

Back 28

-water soluble
-associate weakly with lipproteins
-high helix content, which increases when they bind with lipoproteins
-contact with hydrophobic surface favors formation of helices

Front 29

helices in apoprotein

Back 29

have hydrophilic and hydrophobic side chains so lipoproteins are like logs on water

Front 30

what is apoA-I?

Back 30

-apolipoproteinA-I
-occurs in chylomicrons and HDL

Front 31

What does chylomicrons do?

Back 31

-deliver triaclglycerols to muscles and adipose tissue and cholesterol to liver
-bind to inner surface of capillaries

Front 32

what does lipoprotein lipase do to chylomicrons?

Back 32

triacylglycerol in chylomicrons are hydrolyzed by lipoprotein lipase where tissues then take up freed monoacylglycerol and fatty acids

Front 33

what happens after chylomicrons are used up?

Back 33

they shrink and become remnants which dissociate from capillaries and get taken up by liver again

Front 34

What do VLDL do?

Back 34

they transport endogenous triacylglycerols and cholesterol

Front 35

what does lipoprotein lipase do to VLDL?

Back 35

lipoprotein lipase degrades VLDL in capillaries, which gives fatty acids. The fatty acids are used by cells or used to remake triacylglycerols while the glycerol is transported to liver/kidneys to convert to glycolytic intermediate dihydroxyacetone phosphate

Front 36

what is dihydroxyacetone phosphate?

Back 36

glycerol from degradation of VLDL is transported to liver/kidneys to convert this this glycolytic intermediate, which is 3 carbons. oxidation of this gives very little energy

Front 37

what happens to VLDL remnants?

Back 37

turns into IDL and then to LDL. Half of the products is taken up by liver.

Front 38

how do cells take up LDL?

Back 38

through receptor mediated endocytosis

Front 39

how does cell get cholesterol?

Back 39

body synthesizes it or take it from LDL, rich in cholesterol and cholesteryl esters

Front 40

what does LDL receptors do?

Back 40

they isolate LDL by binding specifically to apoB-100 on the cell surface

Front 41

what are clathrin-coated pits?

Back 41

group of LDL receptors

Front 42

what are clathrin-coated vesicles?

Back 42

they form after apoB-100 of LDL binds to receptor and is transported into cell

Front 43

what happens to clathrin-coated vesicles after it enters cell?

Back 43

fuses with endosomes (internal pH~5), results in LDL to dissociate from receptor and receptor goes back to membrane surface,

Front 44

what happens to endosome with LDL after receptors go back to membrane surface?

Back 44

endosome with LDL fuses with lysosomes

Front 45

what happens in lysosomes after it fuses with endosomes with LDL?

Back 45

LDL's apoB-100 degrade to amino acids and cholesteryl esters are hydrolyzed to give cholesterol and fatty acids

Front 46

what controls rate of LDL receptor synthesis?

Back 46

intracellular concentration of free cholesterol

Front 47

what happens with defects in LDL receptor system?

Back 47

abnormal high levels of cholesterol leading to risk of heart disease

Front 48

where is LDL receptor synthesized and how does it get to cell surface?

Back 48

made in the endoplasmic reticulum and processed in golgi apparatus and inserted into plasma membrane, to become part of clathrin-coated pits

Front 49

what are clathrin triskelions?

Back 49

outside of clathrin-coated vesicles are clathrin triskelions. when vesicle fuse with endosome, triskelions recycle back to cell surface

Front 50

ACAT

Back 50

-acyl-CoA:cholesterol acyltransfersase
-converst cholesterol into cholesteryl esters

Front 51

HMG-CoA reductase

Back 51

-part of getting cholesterol
-catalyze cholesterol biosynthesis

Front 52

what does a lot of cholesterol do to HMG-CoA, LDL receptors, and ACAT?

Back 52

decreases HMG-CoA and LDL receptors while increases ACAT

Front 53

What does HDL do and how?

Back 53

transports cholesterol from tissues to liver by taking it from cell surface of membrance (HDL is in the plasma)

Front 54

LCAT

Back 54

-lecithin-cholesterol acyltransferase
-converts cholesterol into cholesteryl esters
-activated by apoA-I

Front 55

SR-BI

Back 55

HDL binds to receptor SR-BI and gives components to liver cell.

Front 56

how do you dipose of cholesterol?

Back 56

convert to bile acids in liver

Front 57

what does serum albumin do?

Back 57

free fatty acids bind to serum albumin for transport to tissues

Front 58

what is the Franz Koop Experiment?

Back 58

suggested that fatty acids are oxidized on B-carbons: B-oxidation

Front 59

what does acyl-CoA synthetase do?

Back 59

-several forms specific for different chain lengths
-associated with mitochondrial outer membrane

Front 60

reaction of activation of fatty acids

Back 60

Fatty Acid + ATP + CoA <=> Acyl-CoA + AMP + PPi

Front 61

activation of fatty acids

Back 61

reaction driven by hydrolysis of PPI, overall gibs free engery = -34 kJ/mole.