concept 1d part2

Question 1

dietary fat

Answer 1

consists mainly of triacylglycerols

remained comprised of cholesterol, cholesterol esters, phospholipids, and free fatty acids

Question 2

lipid digestion

Answer 2

minimal in mouth and stomach
transported to the small intestines essentially intact where emulsification occurs
then pancreas secretes enzymes into the small intestine
these enzymes hydrolyze lipid components to 2-monoacylglycerol, free fatty acids, and cholesterol

Question 3

emulsification

Answer 3

mixing of 2 normally immiscible liquids (for lipids its fat and water)
formation of emulsion increases surface area of lipid leading to greater enzymatic interactions and processing
aided by bile

Question 4

bile

Answer 4

contains bile salts, pigments, and cholesterol
secreted by the liver and stored in the gallbladder
aids in emulsification

Question 5

pancreatic secretions

Answer 5

pancreatic lipase, colipase, and cholesterol esterase

secreted into the small intestine to hydrolyze lipid components to 2-monoacylglycerol, free fatty acids, and cholesterol

Question 6

micelles

Answer 6

clusters of amphipathic lipids that are soluble in the aqueous environment of intestinal lumen
water-soluble spheres w/ a lipid-soluble interior
vital in digestion, transport, and absorption of lipid-soluble substance from duodenum to ileum
formed by free fatty acids, cholesterol, 2-monoacylglycerol, and bile salts

Question 7

structure of micelles

Answer 7

collections of lipids with their hydrophobic ends oriented toward center and charged ends oriented toward the aqueous environment
collect lipids within their hydrophobic center

Question 8

absorption

Answer 8

micelles diffuse to brush border of intestinal mucosal cells and are absorbed
digested lipids pass through the brush border , where they are absorbed into the mucosa and re-esterified to form triacylglycerols and cholesterol esters and packaged
more water-soluble short-chain fatty acids absorbed by simple diffusion directly to bloodstream

Question 9

chylomicrons

Answer 9

packed triacylglycerols and cholesterol lipids after absorption
along with apoproteins, fat-soluble vitamins, and other lipids

Question 10

pathway of chylomicrons

Answer 10

leave the intestine via lacteals, the vessels of the lymphatic system
re-enter the bloodstream via the thoracic duct, a long lymphatic vessel that empties into the left subclavian vein at the base of the neck

Question 11

postabsorptive state

Answer 11

at night
utilizing energy stores instead of food for fuel
fatty acids are released from adipose tissue and used for energy
decreased insulin, increased epinephrine, increased cortisol

Question 12

hormone-sensitive lipase (HSL)

Answer 12

activated by decreased insulin
hydrolyzes triacylglycerols yielding fatty acids and glycerol
also activated by epinephrine and cortisol

Question 13

mobilization of triacylglycerols

Answer 13

hydrolyzed in adipose tissue to glycerol and fatty acids then transported to the liver
glycerol participates in glycolysis or gluconeogenesis to form glucose
fatty acids undergo beta-oxidation to form acetyl-CoA for the citric acid cycle and ketone bodies

Question 14

lipoprotein lipase (LPL)

Answer 14

necessary for the metabolism of chylomicrons and very-low-density lipoproteins
enzyme that can release free fatty acids from triacylglycerols in lipoproteins

Question 15

free fatty acid transport

Answer 15

transported through the blood in association with albumin, a carrier protein

Question 16

lipoprotein

Answer 16

transport mechanism for lipids within the circulatory and lymphatic systems
include chylomicrons and VLDL which transport triacylglycerols
HDL, IDL, and LDL which transport cholesterol and cholesteryl esters

Question 17

structure of lipoproteins

Answer 17

phospholipid sphere with hydrophilic tail on inside and hydrophobic tail pointing out
cholesterol in the membrane
triacylglycerol (lipids) on the inside of the sphere
apoprotein B-100 spanning the membrane

Question 18

types of lipoproteins

Answer 18

chylomicrons (least dense) 
very-low-density lipoproteins (VLDL)
intermediate-density lipoproteins (IDL)
low-density lipoproteins (LDL)
high-density lipoproteins (HDL) (most dense)

Question 19

chylomicrons

Answer 19

transport dietary triacylglycerols and cholesterol from intestines to tissues
least dense lipoprotein
highly soluble in lymphatic fluid and blood
assembly occurs in intestinal lining, results in nascent chylomicron containing lips and apolipoproteins

Question 20

very-low-density lipoprotein (VLDL)

Answer 20

transport triacylglycerols from liver to tissues
metabolism similar to chylomicrons
produced and assembled in the liver
also contain fatty acids that are synthesized from excess glucose

Question 21

intermediate-density lipoprotein (IDL)

Answer 21

picks up cholesterol from HDL to become LDL
picked up by the liver
VLDL with triacylglyceol removed
some processed in the bloodstream

Question 22

low-density lipoproteins (LDL)

Answer 22

delivers cholesterol into cells
for biosynthesis, cell membranes
bile acids and salts are made from cholesterol in the liver

Question 23

high-density lipoproteins (HDL)

Answer 23

picks up cholesterol accumulating in blood vessels
delivers cholesterol to liver and steroidogenic tissues
transfers apolipoproteins to other lipoproteins
synthesized in the liver and intestines, released as a dense protein-rick particle in blood

Question 24

apoproteins

Answer 24

aka apolipoproteins
form of protein component of lipoproteins
receptor molecules and involved in signaling
5 types

Question 25

types of apoproteins

Answer 25

apoA-I: activates LCAT, enzyme that catalyzes cholesterol esterification apoB-48: mediates chylomicron secretion apoB-100: permits uptake of LDL by the liver apoC-II: activates lipoprotein lipase apoE: permits uptake o chylomicron remnants and VLDL by the liver

Question 26

cholesterol

Answer 26

ubiquitous component of all cells in the human body | role in synthesis of cell membranes, steroid hormones, bile acids, and vitamin D

Question 27

cholesterol sources

Answer 27

most derive it from LDL or HDL | some is synthesized de novo which occurs in the liver and driven by acetyl-CoA and ATP

Question 28

citrate shuttle

Answer 28

carries mitochondrial acetyl-CoA into the cytoplasm where synthesis occurs NADPH, from pentose phosphate pathway, supplies reducing equivalents

Question 29

synthesis of mevalonic acid

Answer 29

in the smooth ER is the rate-limiting step in the cholesterol biosynthesis catalyzed by 3-hydroxy-3-methylglutaryl (HMG) CoA reductase

Question 30

regulation for cholesterol synthesis

Answer 30

increased levels of cholesterol inhibits further synthesis by feedback inhibition mechanism insulin promotes cholesterol synthesis control over de novo cholesterol synthesis is dependent on regulation of HGM-CoA reductase gene expression in the cell

Question 31

specialized enzymes in cholesterol synthesis

Answer 31

lecithin-cholesterol acyltransferase (LCAT) | cholesteryl ester transfer protein (CEPT)

Question 32

lecithin-cholesterol acyltransferase (LCAT)

Answer 32

enzyme found in the blood stream that is activated by HDL apoproteins adds a fatty acid to cholesterol produces soluble cholesteryl esters, in HDL HDL cholesteryl esters can be distributed to other lipoproteins like LDL

Question 33

cholesteryl ester transfer protein (CETP)

Answer 33

facilitates the transfer process | HDL cholesteryl esters distributed to IDL, which becomes LDL by acquiring these cholesterol esters from IDL

Question 34

fatty acids

Answer 34

``` long-chain carboxylic acids carboxyl carbon is C1 C2 is alpha-carbon found in the body occur as salts capable of forming micelles or esterified to other compounds, membrane lipids ```

Question 35

saturated fatty acids

Answer 35

fatty acid with no carbon-carbon double bonds | saturated with Hs

Question 36

unsaturated fatty acids

Answer 36

fatty acids with carbon-carbon double bonds have one or more humans only synthesis a few of these rest are from essential fatty acids in diet double bonds generally in cis configuration

Question 37

2 essential fatty acids

Answer 37

alpha-linolenic acid linoleic acid poly-unsaturated fatty acids role in cell membrane fluidity, critical for proper function of cell

Question 38

omega numbering system

Answer 38

also used for unsaturated fatty acids designation describes the position of the last double bond relative to the end o the chain identifies the major precursor fatty acid

Question 39

synthesis

Answer 39

used as fuel for body and supplied primarily bb diet excess carbohydrate and protein acquired from diet converted to fatty acids and stored as triacylglycerol for energy contemplate synthesis, do not rely directly on coding of nucleic acid (lipid and carbohydrate)

Question 40

fatty acid biosynthesis

Answer 40

occurs in liver products subsequently transported to adipose tissue for storage adipose synthesizes small amount

Question 41

fatty acid biosynthesis enzymes

Answer 41

acetyl-CoA carboxylase fatty acid synthase stimulated by insulin

Question 42

palmitic acid (palmitate)

Answer 42

primary end product of fatty acid synthesis

Question 43

acetyl-CoA shuttling

Answer 43

acetyl-CoA accumulates in mitochondrial matrix, needs to be moved to the cytosol for fatty acid biosynthesis Acetyl-CoA is product of PDH complex couples with oxaloacetyate to form citrate at beginning of citric acid cycle isocitrate dehydrogenase is rate-limiting, as cell becomes e energetically satisfied, slows the citric acid cycle causes citrate accumulation, can diffuse across membrane cytosol citrate lyase splits it back to acetyl-CoA and oxaloacetate

Question 44

acetyl-CoA carboxylase

Answer 44

activates acetyl-CoA in the cytoplasm for incorporation into fatty acids rate-limiting enzyme of fatty acid biosynthesis requires biotin and ATP to function adds CO2 to acetyl-CoA t po form malonyl-CoA activated by insulin and citrate

Question 45

fatty acid synthase

Answer 45

palmitate synthase palmitte is only fatty acid that humans can synthesize de novo large multiple enzyme complex found in cytosol rapidly induced in the liver following a meal of carbohydrates bc of elevated insulin

Question 46

acyl carrier protein (ACP)

Answer 46

part of the multienzyme complex, fatty acid synthase | requires pantothenic acid (vitamin B5)

Question 47

activation of fatty acid synthase

Answer 47

1. activation of the growing chain 2. activation of malonyl-CoA with ACP 3. bond formation b/w these activated molecules 4. reduction of a carbonyl to a hydroxyl group 5. dehydration, removal of H2O 6. reduction to a saturated fatty acid

Question 48

triacylglycerol synthesis

Answer 48

triglyceride synthesis formed by attaching three fatty acids (as fatty acyl-CoA) to glycerol occurs primarily in the liver, and some in adipose tissue from fatty acids and glycerol 3-phosphate in liver packaged and sent to adipose tissue as VLD lipoproteins, leaving only small amount of stored triacylglycerols

Question 49

beta-oxidation

Answer 49

catabolism of most fatty acids | in the mitochondria, peroxisomal beta-oxidation also occurs

Question 50

alpha-oxidation

Answer 50

catabolism of branched-chain fatty acids | depending on branch points

Question 51

omega-oxidation

Answer 51

oxidation in which endoplasmic reticulum produces dicarboxylic acids

Question 52

activation of fatty acid metabolism

Answer 52

first become activated by attachment to CoA catalyzed by fatty-cyl-CoA synthetase product is fatty acyl-CoA or acyl-CoA

Question 53

fatty acid entry into mitochondria

Answer 53

short chain and medium chain fatty acids diffuse freely into mitochondria, where they are oxidized long chain fatty acids (14-20C) are also oxidized in the mitochondria but require transport via a carnation shuttle very long-chain fatty acids are oxidized elsewhere

Question 54

carnitine acyltransferase I

Answer 54

rate-limiting enzyme of fatty acid oxidation

Question 55

beta-oxidation in mitochondria

Answer 55

reverses the process of fatty acid synthesis by oxidizing and releasing molecules of acetyl-CoA (rather than reducing and linking) repetition of four steps

Question 56

process of beta-oxidation

Answer 56

``` each 4-step cycle accomplishing this releases one acetyl-CoA reduces NAD+ and FAD NADH and FADH2 are oxidized in ETC producing ATP acetyl-CoA is entered into the citric acid cycle (muscles and adipose) or stimulates gluconeogenesis by activating pyruvate carboxylase (liver) ```

Question 57

4 steps of beta-oxidation

Answer 57

1. oxidation of the fatty acid to form a double bond 2. hydration of the double bond to form a hydroxyl group 4. splitting of the beta-ketoacid into a shorter acyl-CoA and acetyl-CoA process continues until the chain has been shorted to 2 carbons, creating final acetyl-CoA

Question 58

beta-oxidation of odd# fatty acids

Answer 58

undergo beta-oxidation in same manner until final cycle final step yields one acetyl-CoA and on propionyl-CoA (from 5C fragment) propionyl-CoA is converted to methylmalonyl-CoA

Question 59

propionyl-CoA carboxylase

Answer 59

``` converts propionyl-CoA to methylmalonyl-CoA requires biotin (vitamin B7) ```

Question 60

methylmalonyl-CoA

Answer 60

``` converted into succinyl-CoA catalyzed by methylmalonyl-CoA mutase requires cobalamin (vitamin B12) ```

Question 61

succinyl-CoA

Answer 61

a citric acid cycle intermediate | can be converted to malate to enter the gluconeogenic pathway in cytosol

Question 62

oxidation of unsaturated fatty acids

Answer 62

require 2 additional enzymes bc double bonds can disturb stereochemistry needed for oxidative enzymes to act on fatty acid catalyzed by enoyl-CoA isomerase once enough is liberated to isolate the bond within the first 3 carbons

Question 63

enoyl-CoA isomerase

Answer 63

rearranges cis double bonds at the 3,4 position to trans double bond at the 2,3 position

Question 64

2,4-dienoyl-CoA reductase

Answer 64

further reduction required for oxidation of polyunsaturated fatty acids enzyme that is used to convert 2 conjugated double bonds to just one double bond at the 3,4 position then undergo the same arrangement as monounsaturated fatty acids

Question 65

ketone bodies

Answer 65

liver converts excess acetyl-CoA from beta-oxidation of fatty acids during fasting state acetoacetate and 3-hydroxybutyrate used for energy in various tissues muscles metabolize ketons as rapidly as liver releases them this prevents accumulation in bloodstream

Question 66

after a week of fasting

Answer 66

ketones reach a concentration in the blood that is enough for the brain to begin metabolizing them known as ketogenesis and ketolysis

Question 67

ketogenesis

Answer 67

occurs in the mitochondria of liver cells when excess acetyl-CoA accumulates in fasting state HMG-CoA synthase forms HMG-CoA HMG-CoA lyase breaks down HMG-CoA into acetoacetate which is reduced to 3-hydroxybutyrate aceton is minor side product and will not be used as energy for tissues

Question 68

ketolysis

Answer 68

acetoacetate picked up from blood is activated in the mitochondria catalyzed by succinyl-CoA acetoacetyl-CoA transferase (aka thiophorase)

Question 69

thiophorase

Answer 69

succinyl-CoA acetoacetyl-CoA transferase enzyme in tissues outside the liver 3-hydroxybutyrate is oxidized to acetoacetate liver cannot catabolized ketone bodies that it produces

Question 70

protein catabolism

Answer 70

rarely used as energy source but important for other functions under extreme energy deprivation, can be used for energy proteins must be digested and absorbed

Question 71

digestion of proteins

Answer 71

begins in the stomach with pepsin continues with the pancreatic proteases secreted by zymogens completed by the small intestine brush-boarder enzymes dipeptidase and amino peptidase

Question 72

produce of protein digestion

Answer 72

amino acids dipeptides tripeptides

Question 73

aborption of amino acids

Answer 73

and small peptides through the luminal membrane accomplished by secondary active transport linked to sodium at the basal membrane simple and facilitated diffusion transports amino acids into bloodstream

Question 74

glucogenic amino acids

Answer 74

all but leucine and lysine | can be converted into glucose thought gluconeogenesis

Question 75

ketogenic amino acids

Answer 75

leucine, lysine, isoleucine, phenylalanine, threonin, tryptophan, and tyrosine can be converted into acetyl-CoA and ketone bodies

Question 76

urea cycle

Answer 76

occurs in the liver | body's primary way of removing excess nitrogen from the body