Exam II cards Flashcards
fructose is synthesized in the body from glucise via the
polyol pathway
in the lens of the eye if it accumulates can lead to cataracts
fructose
how is fructose metabolized
conversion to intermediates of glycolysis
fructose enters cells via
GLUT 5 transporter
fructose is converted to fructose 1 phosphate via
fructokinase (uses an ATP)
fructose is phosphorylated and cleaved to yield what two intermediates of glycolysis
dihydroxyacetone-P and glyceraldehyde 3-P
where does fructose metabolism occur
liver
function of aldolases in fructose metabolism
all cleave F1,6 bisphoophate
what enzyme is soley responsible for cleaving fructose 1 phosphate
aldolase B
what is the rate limiting enzyme of fructose metabolism
aldolase B
what is the function of muscle and adipose hexokinase when glucose is low
fructose is converted to fructose 6 phosphate
aldolase A is found
muscle
essential fructosuria
deficiency in fructose kinase
hereditary fructose intolerance
deficiency in aldolase B
why is aldolase B deficiency or hereditary fructose intolerance fatal
no aldolase B so fructose 1-6 cannot be cleaved but is also inhibits breakdown of glycogen and gluconeogenesis and results in hypoglycemia, high lactate and low ATP
what are the two steps to the polyol pathway
1) reduction of C1 by aldolase reductoase
2) oxidation of C2 by sorbitol dehydrogenase
the polyol pathway is important in
seminal vesicles
what population has a very high rate of galactose metabolism
neonates
galactose is converted to galactose 1 phosphate via
galactokinase (uses atp)
galactose 1 phosphate is converted to glucose 1 phosphate via
galactose 1 phosphate uridylyltransferase
UDP galactose can be converted to UDP glucose via
Epimerase
when lactose is cleaved in is converted to
glucose and galactose
function of PPP
generated NADPH for redcuing equivalents and ribose 5 phosphate for nucleotide biosynthesis
______is the only source of NADPH for RBC’s
PPP
what is the substrate for PPP
glucose 6 phosphate
pentose intermediates are reversibly interconverted to what
intermediates of glycolysis
1 Glucose 6 phosphate produces what through PPP
2 NADPH, one co2 and one ribulose 5 phosphate
what is the enzyme called that oxidizes aldehyde at C1 of G6P to produce NADPH
G6PD
what are the 4 key enzymes involved in nonoxidative PPP
isomerase, epimerase, transketolase, and transaldolase
type of reaction of nonoxidative phase to produce ribose 5 p
ketose to aldose conversion
what are the 2 pathways of Ribose 6 phosphate
nucleotide synthetic pathway or glycolytic intermediates in the non-oxidative phase of PPP
_________transverse a 2 carbon unit
transketolase
what cofactor does transketolase require
thiamine
what type of deficiency is common in alcoholics
thiamine deficient
xylose 5 phosphate and ribose 5 phosphate can be converted to what and what
glyceraldehyde 3 phosphate and sedoheptulose 7 phosphate
____________transferse a three carbon unit
transaldolase
sendohelptulse 7 phosphate and G3P can be converted to what via transaldolase
erythrose 4 phosphate and fructose 6 phosphate
what is the net result of nonoxidative PPP from 3 moles of ribulose 5P
2 frucot 6P
1 G3P
3 rib 5P
overal net result of PPP
3 G6P to 6 NADPH, 3 CO2, 2 fructose 6P, and 1 g3P
what is the rate limiting step in PPP
glucose 6P dehydrogenase
if a cell needs NADPH only
oxidative reactions to produce NADPH
non oxidative to convert r5P to G6P to produce more NADPH
cell needs NADPH and rib 5P
oxidative reactions
cell needs rib 5 phosphate
only nonaxidative reactions, high NADPH inhibits g6PD
cell needs NADPH and pyruvate
both oxidative and nonoxidative reactions are used
Heinz bodies
NADPH needed for GSSG to GSH, G6PD deficiency leads to formation of these in RBC’s and can lead to hemolysis
ribulose 5 phosphate to ribose 5 phosphate
ribulose 5 phosphate isomerase
ribulose 5 phosphate to xyulose 5 phosphate
ribulose 5 phosphate 3 epimerase
gluconeogenesis occurs
in the liver under fasting or starving conditions
gluconeogenesis is stimulated by
glucagon
glucose 6 phosphate is converted to glucose via
glucose 6 phosphatase
fructose 1,6 P is converted to fructose 6 P via
fructose 1,6 bisphosphatase
carbon sources for gluconeogenesis are
lactate, amino acids and glycerol (from adipose)
ethanol cannot be used for gluconeogenesis becasue
it is metabolized to acetyl CoA
G3P is converted to what for gluconeogenssis
dihyddroxy acetone phosphate via glycerol 3 phosphate dehydrogenase (produces NADH)
pyruvate to OAA via what enzyme
pyruvate carboxylase
what cofactor does pyruvate carboxylase require
biotin
PEPCK is found where
mitochondria and the cytosol
PEPCK activity
OAA to PEP, uses GTP and releases CO2
gluconeogenesis costs how many ATP
6 ATP!
pyruvate carboxylase requires
4 ATP
phophoglycerate kinase requires
2ATP
the most important control point in gluconeoegensis is
between F6P and F1,6BP
pyruvate carboxylase regulation
activated by acetyl CoA
PEP carboxykinase regulation
induced by glucagon, epinpehrine and glucocorticoids
g6 Phosphatase regulation
induced by gene transcritpion during fasting
F1,6 Bphosphatase regulation
induced during fasting
glucokinase regulation
induced by insulin and high Km for glucose
PPFK-1
activated by F2,6, BP. AMP, and inhibited by ATP, citrate
pyruvate kinase regulation
activated by F1,6BP, inhibited by ATP, alanine, inhibited by phosphorylation from protein kinase A)
where is G6 phosphatase found
ER membrane
what is the name of the disease that results from deficiency of glucose 6 phosphatase
von Gierkas disease
hyperglycemia
osmotic dehydration of tissues, hyperoxmolar coma from brain dehydration
hypoglycemia
depletion of ATP, dizziness, drowsiness, coma, blood loss
low F2,6 BP stimulates
F1,6 BPase (gluconeogenssis)
at 16 hours after fed what is constributing to glucose levels
glycogenolysis and gluconeogenesis
cholesterol is important in what
vitamin D membrane formation steroid hormones bile salts lipoproteiins (cholesterol esters)
what are the two sources of cholesterol in our bodies
synthesis and diet
how are lipids transported in the blood
via lipoproteins
what are the structures on the protein surface of a lipoprotein
apoproteins
phospholipids and
cholesterol
what gives rise to the lipid core of lipoproteins
triglycerides and cholesterol esters
what is the precursos lipoprotein to LDL
IDL
what is known as the bad cholesterol
LDL
good cholesterol
HDL
which lipoproteins have the highest cholesterol content
LDL
function ofDL
return endogenous lipids (VLDL) remnants) or are LDL precursors
name of the receptor on LDL
ApoB 100
what is the major way the body eliminates cholesterol
bile salts
HDL is made where
liver
where is LDL made
blood stream
function of LCAT
uses lecithin to convert cholesterol into a cholesterol ester
CEPT function in cholesterol biochemistry
functions to transport cholesterol ester from HDL to VLDL
functions to deliver cholesterol to liver
HDL
functions to deliver cholesterol to tissues
LDL
what percentage of cholesterol comes from our diet
1/3 or 15%
what percentage of our cholesterol comes from liver
85% or 2/3
cholesterol is made primarily in the
liver cytosol
what is the key step in cholsterol synthesis
HMG-CoA reductase
in the blood cholesterol is initially cared by
VLDL
cholesterol is made from
acetyl CoA
What are the steps in cholesterol synthesis
acetyl CoA Mevalonate isoprene squalene cholesterol
what are the three ways HMG-CoA reductase can be regulated
transcriptional
proteolysis
covalent modification
HMG-CoA reductase is inactive when it is
phosphorylated
what activates AMP protein kinase
AMP and glucagon and sterols
what inhibits AMP protein kinase
insulin
what step of cholesterol synthesis uses ATP
mevalonate to isoprenes
what step of cholesterol synthesis uses NADPH
isoprenes to squalene
what is the last intermediate in cholesterol synthesis that does not have a ring
squalene
function of ACAT
converts a cholesterol to cholesterol ester so that it can be packaged into VLDL
CE is more
hydrophobic
what are the two bile acids made from cholesterol synthesis
chenodeoxychlolic acid and cholic acid
what is the rate limiting step of cholesterol synthesis
7 alpha hydroxylase
what two processes occur that allow for cholesterol to accumulate in plaques
oxydized or glycolyated
function of statins
inhibit HMG CoA reductase
Ezetimble
decreases absorption of cholesterl
when there is increased blood glucose from type 2 diabets what happens to cholesterol
LDL-R can become glcated inhibitng its activity
how many carbon longs are eicosanoids
20 hydrocarbon molecules
the most abudant precursor for eicosanoid metabolism is
arachidonic acid
what compound found in plant cells are important precurss for arachidonic acid
linoleate
arachidonic acid can be released by
PLA2 or PLC
what are the three enzymes associated with the arachidonic acid pathway
cyclooxygenase
lipooxygenase
cytochorme P450
cytochorme P450 produces
epoxides
lipooxygenase produces
HPETE
cyclooxygenase produces
prostaglandins and thromboxanes
function of thromboxanes
produced by platelets, stimulates platent aggregation causes vasoconstriction (would healing) bronchoconstriction
function of prostacyclins
vasodilation INFLAMMATION
irreversible inhibit of COX
aspirin
acetaminophen and ibuprofen bind
reversible to COX
primary function of COX1
platelet aggregation and stomach cytoprotection
primary function of COX2
inflammation and hyperalgsia
steroids only have an effect on which COX
COX 2
examples of COX-2 inhibitors
vioxx and celebrex
function of leukotrienes (LTB4
increases vascular permeability, T cell proliferation, Leukocyte aggregation, inflmmatory cytokines
function of LTC4 and LTD4
bronchoconstriction, vascular permeabilty and IFN-Gamma
cortocoid steroids and leukotrienes
supress inflammatory genes and inhhibits cytokine production
leukotriene modifies
may inhibit synthesis or binding to a receptor
singular
blocks cysteinyl luekotrienes
inhaled steroids
block steroid sensitive mediators
LIPOXIN
induces chemotaxis and stimulates superoxide production in leukocytes
which eicosanoids act by the AC-cAMP PKA system
PGe, PGD, and PGI
altered intracellular calcium is mechanism action for what major eicosnaoids
PGF2-alpha
TXA 2
leukotrienes
cytochrome P450 pathway
acts on endocrine, ocular, renal and vascular systems
in some cases inhibits sodium/potassium ATPase
isoprostanes
produced by action of free radicals not by enzymes
what can beused to measure oxidative stress
isoprotane concentration in urine
endocannabinoids
ligands for nervous sistem, retrograde messenger, have an analgesic effect
where is most of ethanol metabolized
in the liver
if ethanol is not metabolismed in the liver where does it goe
enters GI tract or is excreted through the lungs or kidneys
what are the two major pathways of ethanol metabolism in the liver
ADH and MEOS
when alcohol is absorbed in the gut it passes where
liver
ethanol is converted to acetyladehyde via what enzyme
ADH, produces NADH
what enzyme is used during low levels of alcohol consumption
ADH
what enzyme concerts ethanol to produce acetyladehyde but uses NADPH
MEOS in ER
what enzyme is used at high levels of alcohol intake
MEOS
specifically which ADH is associated with low km and is active onlt with ethanol, high tissue capacity
ADH1
what ADH specifically is found primarily in the liver and lower levels of GI tract
ADH2
Where is ADH4 found
highest levels in upper GI tract, gingiva, mouth, esophagus and down to the stomach, not present in the liver
which ADH is not found in the liver
ADH4
MEOS is part of what
cytochorme P450 family
which cytochrome is most active to ethanol
CYP2E1
does MEOS have a higher Km or lower Km than ADH
higher Km, low affinity
where is MEOS found
endoplasmic reticulum
in alcohol metabolism what enzyme is responsible for converted acetalaldehyde to acetate
ALDH
80% of ALDH is found
mitochondria
what converts acetate to acetyl CoA
acetylCoA synthetase I liver and II in skeletal muscle
where is morelikely for acetyl CoA to be syntheiszed from acetate
skeletal muscle MORE than liver
how much energy does ADH produce per ethanol
13 ATP’s
how many ATP’s per ethanol molecule is produced by the MEOS pathway
8 ATPS
most of the toxic effects of alcohol are due to what
acetyladehyde production and NADH
what are the four main effeccts of increasd NADH production in ethanol metabolism
inhibits fatty acid oxidation and promotes VLDL
ketoacidosos-not citrate synthesis
inhibits lactate dehydrogenase- decreases uric acid excretion
inhibits gluconeogenesis
effects of accumulation of acetyladehyde
decreased hepatic protein synthesis
loss of protection against damage from oxidation
methanol is a possible substrate for
ADH
ADH and methanol forms
formaldehyde which is then converted to formate via ALDH
what is the compound that produces methanol toxicity
formate
(T/F) ethanol is both lipid and water soluble
True!
How does olestra work
pancreatic lipase is NOT able to hydrolyze the fatty acids attached to sucrose
when does digestion of lipids take place
not until the intestine
lingual lipase is high in
children who drink alot of cow’s milk
lipids are absorbed by intestinal epithelium and resynthesized to
triacylglycerols
how are lipids transported
via chylomicrons in the lymph
function of colipase
binds to fat and lipase activating pancreatic lipase
function of esterases and phosphilipase A2
removes fatty acids and phosphilipids
pancreatic lipase and colipase are secreted in response to what
cholectyokinin
secretin is secreted in response to
HCL in the intestine and signals for bicarb secretion
what is phospholipase A2 activated by
trypsin
tryglyceride is converted to monoglyceriade and fatty acids via
lipase
bile salts are synthesized where
liver
what is the major component of bile salts
cholic aicd
what is the rate limiting step of bile acid synthesis
first step of 7-alpha hydroxylase, inhibited by bile acids
bile salts are reabsorbed where
illeum
bile salts are stored where
gallbladder
what type of fatty acids do not need bile salts
short and medium chain fatty acids
what are packagaed into micells by bile salts
fatty acids monoacylgylcerols cholesterol lysophospholipids fat soluble vitamins
how are triacylglycerols resynthesized
free fatty acids are esterifired to 2 monoacyglycerol which requires 2 ATP molecules and CoA
which apoprotein is associated with activation of lipoprotein lipase
apoCII
apoB100 and abpoB 48 are related how
located on the same gene
what is the major source of acetyl CoA
dietary glucose
how is OAA produced from pyruvate
pyruvate carboxylase
how is acetyl CoA produced from pyruvate
pyruvate dehydrogenase
what has a higher percentage of triacylglycerols VLDL or chylomicrons
chylomicrons
lipoprotein lipase is activated by
apoprotein CII
in muscle LPL has a low or high Km
low
in adipose LPL has a low or high Km
high
LPL is made in response to
insulin
what causes the release of fatty acids
insulin low, high cAMP, activates protein kinase A
glycerol 3 phosphate reacts with two fatty acids to produce
phosphatidic acid
how is phosphatidylyglycerol produced
condendation of CDP-DAG and G3phopshate
how is a ceramide formed
serine and palmitory CoA
how is the double bond formed in sphingolipids
FAD
short chain fatty acid site of activation
cytosol and mitochondria
medium chain fatty acid site of activation
mitochondrial matrix (kidney and liver)
long chain fatty acid site of activation
ER, outer mito membrane, peroxisomal membrane
very long chain fatty acids site of actiation
peroxisomes
when beta oxidation of fatty acids is blocked where to excess FA go
triacylglycerol synthesis
longchian fatty acids require what to get into the mitochondria
carnitine
Sources of carnitine
comes from the diet, but can also be synthesized from lysinne
beta oxidation of long chain fatty acids is inhibited by
malonyl CoA
what part of beta oxidation does malonyl CoA inhibit
carnitine palmitory transferse I
reaction of propionyl CoA to succinyl CoA requires
propioyl Coa, bicarb, ATP, biotin, and conezyme B12
wehre does omega oxidation of fatty acids occur
endoplasmic reticulum
citrate inhibits
PFK-1
what are the three ketone bodies
acetoacetate
beta hdyrogxy butyrate
acetone
OAA has what affect on ketone body synthesis
decreases synthesis
what are the strictly ketogenic amino acids
leucine and lysine
what are the ketogenic and glucogenic amino acid
phenyalalanine, trophophan and tyrosine