steriod ring system, an important part of membrane integrity, provides carbon platform with messages above and below rings (methyl or hydroxyl groups)
After absorption in the gut, transported to liver and tissues via chylomicrons
cholesterol is broken down into bile salts by hydroxylases, excreted form of cholesterol
return to the liver after reabsorption in the terminal ileum, recycled form of cholesterol
humans can synthesize up to 1g cholesterol per day
most cholesterol is stored as esters because you can store fatty acids on them, transported via lipoprotein
water soluble, fat glob, apolipoproteins on surface allow for cell recogniton, cholesterol ester, free fatty acids, triglycerides in the core
Biosynthesis of 1 mole of cholesterol
18 moles of aceytl CoA, 36 moles of ATP, 16 moles of NADPH
Site of cholesterol biosynthesis
cytoplasm of hepatic liver cells, starts wth acetyl CoA
Cholesteor biosynthesis pathway
Acetyl CoA (2C)--(HMG CoA reductase)-->mevalonate (6C)--->farnesyl pyrophosphate( 15 C)---> combine 2 farnesyl--->squalene (30C)--->7-dehydro-cholesterol
Rate limiting enzyme for cholesterol biosynthesis
HMG CoA reductase-->takes ester and reduces it down to an alcohol (mevalonate) **IRREVERSIBLE
HMG CoA reductase activity
Phosphorylated is inactive and non-phosphorylated is active
Synthesis of HMG CoA reductase
Hepatic HMG CoA reductase synthetase--> stimulated by well fed state, inhibited by dietary cholesterol intake
inhibit HMG-CoA reductase to prevent cholesterol biosynthesis-->lower intracellular cholesterol and lowers apo B/E recpetor
turns cholecterol in cholesterol ester
Regulation of cholesterol uptake via SREBP
Oxysterols (hydroxylated cholexterol) bind to Liver X receptor (LXR)-->upregulates SREBPs-->SCAP bring SREBP to protease-->cleaved by protease-->activates SREBP in gene expression
Factors that increase intracellular cholesterol concentration
de novo biosynthesis, Hydrolysis of cholesterol esters (cleave esters), Dietary intake of cholesterol and uptake from chylomicrons, receptor mediated uptake of cholesterol containing lipoproteins (LDL)
Inhibition of cholesterol biosynthesis, Downregulate the LDL receptor, Esterification of cholesterol by acyl-CoA, Release of cholesterol to HDL, Conversion of cholesterol to bile salts or steroid hormones
Hormone activation of cholesterol biosynthesis
insulin and tri-iodo-->increases cholesterol biosynthesis, glucagon and cortisol-->decrease cholesterol biosynthesis
Steroid hormones (3 classes)
C21 corticoids in adrenal cortex, C19 androgens in testis, C18 estrogens in ovary
Steroid hormones in cell
penetrate plasma membrane, bind to cytoplasmic locasted receptors-->causes conformational change in transcription factors
Polypeptides hormones in cell
can't cross plasma membrane->bind to cell surface receptor-->termed first messengers-->intracellualr effects are mediated by small molecules like cAMP
Nitric oxide (NO)
vasodilator used for angina, nitro pakcets are nitrated glycerol molecules-->signal the relaxation of smooth muscle in blood vessels by stimulation of guanylate cyclase= changes in intracelluar Ca2+
cleaves specific phospholipis to generate lipids messengers (arachidonic acid, DAG)
C20 unsaturdated fatty acid-->lipid 2nd messenger or inflammatory messenger
synthesized in membranes from AA, signal via G-protein receptors, made via COX1 and COX2 enzymes
Made from AA via lipoxygenases, have roles in inflammation
cleaves DAG or phospholipid-->arachodonic acid
COX1 and COX2
use arachodonic acid make prostaglandins thromboxane, prostacyclin
use arachodonic acid make leukotrienes
use arachodonic acid make HETE (CO/NO inhibit here)
start with AA --> make PGG2--> use peroxidase to make PGH2
Fever inducers (COX1 and COX2 convert AA to PGG2)
non selective COX inhibitors (aspiring, ibuprofen), block COX1 and COX2-->inhibits the synthesis of PGG2 from AA)
Aspirin mode of action
irreversibly acetylates COX1 and COX2, reduces inflammation, blocks the production of thromboxane (vasoconstrictor and clot builder)
Steroidal anti-inflammatory drugs, inhibit PLA2, block all eicosanoids from converting DAG and phospholipids---> Arachodonic acid
type of eicosanoid not made form COX1 and COX2, inflammatory/vasoactive mediators, made from AA via the action of lipoxygenases (which add O to lipid chains)
Deficiency in lipoxygenases
40% of myeloproliferative disorders-->reduced lipoxygenases activity and increased synthesis of thromboxane
AA uses 5-LO and FLAP to make HPETE--> becomes LTA4 uses enzyme LTA4 hydrolase--> LTB4 (power attractant for immune cells)
power attractant for immune cells, involved in ashmatic and allergic reactions
blood glucose levels low-->glucagon is released-->leads to the degradation of glycogen--> and gluconeogenesis--.synthesize glucose from small molecules
pKa (level at reactants=products) of uric acid is 6, at night when we are sleeping-->respiratory acidossi-->shifts products to less soluble side
Synovial fluid analysis (for gout diagnosis)
gross appearance, order cell count and differential (look for neutrophils, microbiology culture, gram stain, crystal analysis if gout is suspected-->need resh specimen because solutes can dissolve
Crystal analysis in gout
polarizing microscope with compensator (MSU found in 90% of acute attacks, lower percent chronically)--can differentiate from pseudogout
Synovial fluid analysis in gout
normal=clear, slightly viscous, WBCs low, no RBCs, no crystals, negative culture, gout fluid=tubid, opqaue, lots of WBCs, negative gram and culture, MSU cyrstals, negative birefringence
Medical problems with increased risk for gout
hypertension, obesity, high alcohol intake, high meat intake, hyperinsulinemia, metabolic syndrome
Purine catabolized to one common free base ______
Final step in Purine metabolism
xanthine oxidized by xanthine oxidase to form uric acid
Fatty acid oxidation (energy provision)
provides half the oxidative energy required for liver, kidney, heart and skeletal muscle
Lipid metabolism (outline of steps)
Lipid mobilization (TAGs hydrolyzed in adipose tissue to fatty acids plus glycerol)-->transport FAs in blood to the tissues-->activation of fatty acids as CoA ester-->transport to mitochondria via carnitine shuttle-->metabolized to acetyl CoA
Triacylglycerol (TAG)-->free fatty acids (FFA)
TAGs---(via DAG)---> glycerol + FFAs
transfer TAGs made in liver
needed for the transportation of long chain fatty (12-20) acidsfrom cytosol into mito matrix
missing the methylmalonyl CoA mutase to convrt odd chain fatty acids to succinyl CoA-->huge build up of methylmalonyl CoA-->metabolic acidosis and developmental retardation
unable to convert B12 to coenzyme form-->flood urine with methylmalonic acid-->huge build up of methylmalonyl CoA-->metabolic acidosis and developmental retardation
Degradation of odd chain fatty acids
propionyl CoA---(biotin as Co2 carrier)-->methylmalonyl CoA---(B12 coenzyme form + methylmalonyl mutase)-->succinyl CoA--->citric acid cycle
Degradation of even chain fatty acids
Phytanic acid & branched chain
alpha-oxidation of phytanic acid (releases CO2)-->now thiokinase can anneal CoA-->proceed to B-oxidation to make acetyl CoA OR propionyl CoA-->succinyl CoA
Jamaican vomiting sickness
ackee plant contains hypoglycin-->inhibits medium and short chain dehydrogenases-->inhibits B-oxidations
no carnitine=no carnitine shuttle=you can't do b-oxidation of long chain FAs-->nonketotic hypoglycemia because you can't produces muscle aches and weakness following exercise
absence of peroxisomes in liver and kidneys-->can't degrade very long chain FAs-->accumulation of long chain FAs in the brain
defect in the enzyme phenylalanine hydroxylase which converts phenylalanine--> tyrosine ( unable to break down phenylalanine)-->build up toxic metabolites 2-hydroxyphenylacetic acid, phenylpyruvid acid, pneyllactic acid
hypomorphic mutation of enzyme defiency
some activity, but loss of function
null mutation of enzyme defiency
deficient in the enzyme that converts biocytin to biotin-->results in problem in the catabolism of branch chain amino acid
Other enzyme realted deficiencies
disfunctional protein (hypomorphi or null), deficient cofactor (vitamin), deficient activator protein, deficient transcription factor
Metabolis Basis of disease
deficiency of product-->substrate for th next reaction-->energy (ATP) OR toxic metabolites
testing for enzyme deficiency in blood
serum amino acids, serum ammonia, acylcarnitine (tandem mass spec)
testing for enzyme deficiency in urine
urinary amino acids (UAA metabolites in TCA cycles), urinary organic acids, urinary acylcarnitine (tandem mass spec), GAGs
errors in mitochondrial fatty acid oxidation
autosomal recessive inherited, potentially fatal disorders, intolerant of exercise
severe hypoglycemia/poor ketogenesis, sudden infant death, intolerance-muscle disease, heart disease (especiallyin long chain fatty acids), fatty liver
most common (1/60-->1/100 people are carriers), autosomal recessive, point mutation in exon 11, high concentration of Mchain FAs, acyl carnitines, acyl glycines in plasma and urine
2 subunits (alpha and beta)
Trifunctional protein alpha subunit (HADHA)
Trifunctional protein beta subunit (HADHB)
ketoacyl CoA thiolase
LCHAD deficiency in fetus
toxic baby syndrome can cause the build of of LCHAD in fetal circulation, late in pregnancy mother will develop HELLP syndrome
hemolysis, elevated liver enzymes, low platelets seen in pregnant mothers, caused by an LCHAD deficiency in the fetus
gas chromatography-mass spectrometry
used to detect urinary organic acids in mitochondrial fatty acid oxidation disorders
How to treat VLCAD deficiency?
give MCADs, bypass the block OR give triheptanoin (C7) triglyceride-->KBs can be produced from odd chain FAs
Where are primary bile salts created?
cytoplasm of liver parenchymal cells
Bile salts are used to...
emulsify fats (soap molecules, hydrophobic on one side hydrophilic on the other)
At physiological pH bile salts are
Rate rate limiting enzyme for bile salt production
7-alpha-hydroxylase enzyme (CYP7A1)
rate limiting enzyme in bile acid production, installs the OH group at position 7
Where are secondary bile salts created?
by bacterial enzyme cleave og primary bile salts in intestines
What controls bile secretions?
How do bile salts get back to liver?
How much bile acids pass through the bile duct each day?
How much of total bile is excreted in feces?
Where do statins inhibit?
HMG CoA reductase
What makes gallstones?
bile supersaturated with cholesterol
made from cholesterol
C21 steroid hormones (Ex.progesterone) made in the adrenal cortex
C19 steroid hormones (Ex.androgens) made in the testis
C18 steroid hormones (Ex.estrogen) made in the ovary
Steroid hormone excretion
preprocessed to be more water soluble then excreted via the kidney --> in urine
Mechanism of action of steroid hormones
act via nuclear action
Type I steroid hormones
act via cytoplasmic receptors to form steroid-receptor complex--->receptor dimerizes-->nuclear localization signal exposed-->complex enter nucleus and binds to SRE (specific response element)-->functions as transcription factor-->enhance/repress gene expression
How do steroid-receptor complexes find DNA sequence?
Zinc Finger on the receptor feels the DNA to find the palandromic
Why are glucocorticoid receptor zinc fingers differ from standard zinc finger?
it has four cysteine instead od 2 cysteines and 2 histidines
synthesized in pancreatic beta cells, anabolic hormone-->acts to decrease glucose in the blood
synthesized in pancreatic alpha cells, catabolic hormone-->action to increase blood glucose
phase 1, five steps (glucose comes into B-cells-->glucose is phosphorylated-->glycolysis-->increase in ATP-->close ATP gated K channel-->depolarization-->open voltage gated Ca channels-->trigger insulin release
Why is insulin response to oral glucose high than IV infusion
because GI hormones help to increase insulin secretion
Insulin binding to membrane receptor in muscle/adipose
dimerizes tyr-kinase receptor-->autophosphorylates-->phosohporylates IRS1-->activated a lot of pathways-->recruits GLUT4 to membrane
What enzyme does muscle lack?
Glucose-6-phosphatase-->can't release glucose in the bloodstream
Is GLUT 2 insulin dependent/independent?
independent, it is always one regardless of insulin level
Is GLUT 4 insulin dependent/independent?
dependent, glucose transport in muscle and adipose tissue depends on insulin levels
What kinds of metabolism does insulin affect?
carbohydrate, lipid, protein, ALSO PROMOTES POTASSIUM UPTAKE
Does GLUT4 mostly reside intracellularly or on the plasma membrane?
intracellularly, 90% is inisde the cell waiting to be mobilized to plasma membrane
How much does insulin affect GLUT4 receptor recruitment to surface?
insulin doubles recruitment of GLUT-4 receptors to plasma membrane
In type II diabetes, what is the most important cause of insulin resistance?
Defective insulin signaling (also, decreased # and affinity of receptors)
How do Type II diabetes patients first present?
impaired glucose tolerance
What causes insulin resistance?
post-receptor signal transduction defects (defective tyr-kin, mutations in genes coding for IRS1, defective translocation of GLUT2 to cell membrane)
mobilizes glucsoe from every available fuel source, increases lipolysis and ketogenesis from acetyl CoA
Glucagon mode of action
binds to its own receptor via G-protein couple proteins-->activates Adenyl Cyclase-->activates cAMP cascade--> activates PKA-->phophorylates PFK2-F2,6BPase-->activates F2,6BPase-->stimulate gluconeogenesis
Does muscle has glucagon receptors?
How do you stimulate gluconeogensis in muscle?
Epinephrine stimulates glycogenolysis and gluconeogenesis (and inhibits glycolysis and lipogenesis)
What receptors does epinephrine bind to?
alpha and beta adrenergic
What is the key enzyme responsible for hyperglycemia with stress?
Foxo1 and Foxa2
fork-head winged-helices, transcription factors that promote gluconeogenesis, synthesis is regulaated by insulin
promotes gluconeogensis in the liver in the fasting states by inducing the PEPCK and G-6-Pase enzymes (insulin phosphorylates foxo1 to blocks gluconeogenesis)
regulates fatty acid oxidation in fasted state by induing genes encoding for enzymes of glycolysis, FA oxidation and ketogenesis (insulin phosphorylates foxa2 to inhibits FA oxidation)
Diabetes lab values
>126 mg/dL fasting glucose or >200mg/dL after glucose tolerance test
Normal lab values for blood glucose
Impaired fasting glucose
allows recycling of lactate (from muscle anaerobic glycolysis) back to glucose (in liver) via gluconeogenesis
allows recycling of alanine (from muscle proteolysis) back to glucose (in liver) via gluconeogenesis
Metabolism during stress
Sympathetic nervous system drives response of stress via what hormones?
Typical US diet high in linoleic (omega 6) vs. linolenic (omega 3) (ratio)
reduce inflammation by upregulating anti-inflammatory proteins, 2 classes (immunologic and metabolic), metabolic increase gluconeogenesis (Ie, cortisol)-->stimulate fat breakdown in adipose tissue to generate FFA
regulate water and salt balance (Na+ retention), aldosterone acts on the kidneys to activate reabsorption of sodium and passive reabsorption of water, active secretion of K, major function in blood pressure and blood volume
mineralocorticoid hormone, aldosterone produced in the adrenal gland and secretion mediated by angiotensin II (also by ACTH) and local potassium levels, that is activated by PKC
rate limiting step in steroid synthesis
conversion of cholesterol to pregenenolone via 20,22 desmolase-->this is limited by the supply of cholesterol in the inner membrane
How is 20,22 desmolase activated
via phosphorylation (cAMP-->PKA-->phosphorylates 20,22-desmolase)
How is 20,22 desmolase activated in cells that make cortisol?
How is 20,22 desmolase activated in cells that make aldosterone?
angiotensin II-->increase IP3 and DAG-->cAMP-->PKC-->phosphorylates 20,22-desmolase
Describe the role of cyt P-450 mixed function oxygenases?
in combination with NADPH, FAD, Fe3+, O2 to form hydroxylated product
What enzyme deficiency causes congenital adrenal hyperplasia?
What is the cause of salt wasting in the case of the virilized baby girl?
The underactivation of renin (converts angiotensinogen-->angiotensin) because of a lack of aldosterone-->results in decreased sodium and water reabsorption by the kidneys
What vitamin is used to make NAD+
Niacin ______ HDL levels
What vitamin in used to make FAD+/FADH
Pyruvate---> Lactate is oxidation or reduction?
pyruvate is getting reduced (NADH gets oxidized-->NAD+)
electron transport chain
substrate level phosphorylation
glycolysis and succinyl CoA-->succinate (releases GTP)
When does the level of ATP in skeletal muscle decrease?
in extreme exercise conditions
How much ATP does the body under resting conditions
some energy generated from anaerobic splitting of a phosphate off of phosphocreatine-->maximum energy tield in about 10 seconds
takes ATP-->ADP (releases energy)
regenerates ATP by: PCr + ADP--> Cr + ATP
Higher intensity exercise
relies mostly on carbs
Lower intensity exercise
relies more on fat
What is the primary fuel source for an ultra marathon?
mostly fats-->you have to slow down
What is the primary fuel source in the first 2 minutes of any exercise?
High energy phosphate bonds
1,3 BPG, PEP, A third is creatine phosphate that has enough energy to synthesize ATP
Total oxidation of glucose gives you
H2O and CO2
Quickest type of regulation
Rate limiting enzyme in glycolysis
What regulates PFK-1 in muscle?
AMP (activates), ATP and citrate (inhibits)
What regulates PFK-1 in liver?
What inhibits Hexokinase
Liver isozyme of pyruvate kinase is inhibited by what?
covalent: phosphorylation by PKA, allosteric: ATP and alanine
allosterically activated by AMP-->know ATP is low-->activates pathways that generate ATP (B-oxidation of fatty acids, glucose transport)-->inhibits those that require ATP (fat synthesis, PCr, Cholesterol synthesis)
Fructose can bypass the regulatory steps in glycosis and enter as ________ and _________
Glyceraldehyde-3-P and DHAP
How does fructose go to DHAP?
Fructose-->Fructose-1-P--(F1P aldolase)--> DHAP
hereditary Fructose Intolerance
F1P aldolase deficiency-->build up in F1P-->decrease in available phosphate-->looks like G1P so acts as competitive inhibitor for glycogenolysis-->HYPOGLYCEMIA
accumulate gal-1-P and galactose-->enlarge liver, jaundice, cataract formation, cataracts (build up of galactitol-->product of galactose in the lens)
Nonpermitted transition in conversion between energy sources
cannot convert FAT to CARBOHYDRATE
Cofactors required for Pyruvate dehydrogenase
TPP (B1), FAD (B2, riboflavin), NAD (B3, niacin), CoA (B5, panthothenate), lipoic acid
What does PDH release when converting pyruvate-->acetyl CoA?
NADH and CO2
PDH is a multienzyme complex, how is it regulated?
PDH kinase and PDH phosphatase
what is oxidative carboxylation?
blowing off CO2
Where is NAD+ needed in gluconeogenesis
it is needed in the malatae shuttle to convert malate back to oxaloacetate in the cytosol
deficiency in protein (onset precipitated by increased demand) not necessarily lacking in diet could be inability in protein synthesis
Major differences between Kwashiorkor and Marasmus
Marasmus has muscle wasting, albumin is moderately diminished and no body fat, Kwashiorkor has Edema and Hepatomegaly in still has some body fat, severely diminished serum albumin, normal insulin and cortisol levels
What do transaminases use as an amino acceptor?
Maple syrup urine disease
autosomal recessive, Deficiency in BCKA DH, so you can't degrade BCAAs, you get elevation in BCAAs, keto-acids and alpha-hydroxyacids in urine, vomiting lethargy, severe brain damage
anti-apoptotic protein, homologue of ced9, BCL2 is associated with mito and somehow associated with blocking the release of cytoC, overexpression in B Cell lymphoma
there are two types of proteinsin the BCL family, BH3 only and BH3+other, can be pro or anti apoptotic
proteases responsible for apoptosis, analogue in C. elegans is ced-3 (but in humans there are 14 different caspases), they are cystein dependent aspartate directed proteases AspHole, exist as zymogen activated by cleavage
What activates caspases
Apaf-1 (ced-4 homologue), ATP, cytochrome C (comprise the apoptosome)-->this starts the activation of the initiator caspase 9
pro-apoptotic, in the BCL family-->cause the release of cytoC
put the helical tail in the active site, sterically occluding their own active site (like CDKs), and inactivating them
have an open, hydrophobic BH3 pocket, and are active
In cell undergoing apoptosis
Hydrophobic pocket is occupied by the BH3 domain of a pro-apoptotic, frees up the pocket of pro-apoptotic protein-->get apoptosis
caused by a dietary deficiency of folate or B12
Aerobic glycolysis generates
2 pyruvate, 2NADH, 2ATP
Anaerobic glycolysis generates
2 lactate and 2 ATP
What enzyme in glycolysis requires NAD+
used NADH to convert pyruvate to lactate-->generates NAD+
Physical inactivity leads to a _________ in protien synthesis
decrease (50% by 14 days)
Stress/burn/trauma leads to a ___________in protein synthesis, a ________ in protein degradation, with an overall net________
increase in synthesis, increase degradation, overall net decrease in protein
Physical inactivity leads to a ______________ protein balance
Stress/trauma/burn leads to a ________________ protein balance
Cortisol generates a _______________ response of muscle
Cortisol cause _____________ in blood sugar resulting in _____________
Stress response in burns results in patients being ____________