Metabolism Flashcards
What does kwashiorkor look like?
Child with a swollen belly
What is mneumonic for Kwashiorkor?
Malnutrition
Edema
Anemia
Liver change (fatty -from decreased synthesis of apolipoprotein)
What is marasmus?
Energy malnutrition resulting in tissue muscle wasting, loss of subcutaneous fat, edema
What is the difference between marasmus and kwashiorkor?
They have enough calories but lack protein in kwashiorkor.
They lack calories altogether in marasmus
What metabolism happens in the mitochondria?
Fatty acid oxidation
Acetyl-CoA production
TCA cycle
Oxidative phosphorylation
What metabolism happens in the cytosol?
Glycolysis Fatty acid synthesis HMP shunt Protein synthesis Steroid synthesis Cholesterol synthesis
What processes take place in both the mito and the cytosol?
HUG
Heme synthesis
Urea cycle
Gluconeogenesis
What is the rate determining enzyme of glycolysis?
Phosphofructokinase
What enzyme commits glucose to glycolysis?
Hexokinase/glucokinase
Adds and phosphate group using ATP
What is the rate determining enzyme in gluconeogenesis?
Fructose 1,6 - bisphosphatase
What is the rate determining enzyme of the TCA cycle?
Isocitrate dehydrogenase
What is the rate determining enzyme of glycogen synthesis?
Glycogen synthase
What is the rate determining enzyme of glycogenolysis?
Glycogen phosphorylase
What is the rate determining enzyme of HMP shunt?
G6PD
What is the rate determining enzyme of de novo pyrimidine synthesis?
Carbamoyl phosphate synthetase II
What is the rate determining enzyme of de novo purine synthesis
Glutamine-PRPP amidotransferase
What is the rate determining enzyme of the urea cycle?
Carbamoyl phosphate synthetase I
What is the rate determining enzyme of fatty acid synthesis?
Acetyl CoA carboxylase
What is the rate determining enzyme of fatty acid oxidation?
Carnitine acyltransferase I
What is the rate determining enzyme of kerogenesis?
HMG-CoA synthase
What is the rate determining enzyme of cholesterol synthesis?
HMG-CoA reductase
How many molecules of ATP are made by aerobic metabolism of glucose?
32 via malate-aspartate shuttle
30 via glycerol-3-phosphate shuttle
How many molecules of ATP are made by anaerobic glycolysis?
2 ATP per glucose molecule
What type of reactions is NAD used in?
Catabolic process
What kind of reactions is NADPH used in?
Anabolic processes such as steroid and fatty acid synthesis
Also: respiratory burst
P-450
Glutathione reductase
What is the difference between hexokinase and glucokinase?
Hexokinase is ubiquitous with high affinity and low capacity.
It is not induced by insulin
Glucokinase is seen in only the liver and beta cells of the pancreas. It has low affinity and high capacity. It can be induced by insulin.
What inhibits hexokinase?
Glucose-6-phosphate
What inhibits glucokinase?
Fructose-6-phosphate
ATP
Citrate
What stimulates phosphofructokinase-1?
AMP
Fructose 2,6 bisphospate
What inhibits phosphofructokinase 1?
ATP
Citrate
Which steps in glycolysis require ATP?
The commitment step (glucose –> glucose-6-phosphate by glucokinase/hexokinase)
The rate limiting step (G6P –> fructose 6 phosphate by phosphofructokinase)
Which steps in glycolysis make ATP?
Steps 7 and 10
1,3 bisphosphoglycerate to 3-phosphoglycerate. By phosphoglycerate kinase
Phosphoenol pyruvate to pyruvate via pyruvate kinase
Which 2 enzymes are involved in the production of ATP in glycolysis?
Phosphoglycerate kinase
Pyruvate kinase
What stimulates phosphoglycerate kinase and pyruvate kinase?
Fructose 1,6 bisphosphate
Which enzymes regulate fructose 2,6 bisphosphate?
Fructose bisphosphatase 2
Phosphofructokinase 2
Which enzyme is active during the fed state?
Phosphofructokinase 2
What does PFK-2 do?
Activates PFK-1 to convert F6P to F1,6BP
What does fructose bisphosphatase 2 do?
Activates fructose 1,6 bisphosphatase to convert fructose 6 phosphate to glucose 6 phosphate
What are the levels of glucagon, insulin, cAMP, protein kinase A and the PFK-2 and FBPase-2 during the fed state?
High insulin Low glucagon Low cAMP Low protein kinase A Low FbPase2 High PFK2 Net result = increased glycolysis
What are the levels of glucagon, insulin, cAMP, protein kinase A and the PFK-2 and FBPase-2 during the fasting state?
Low insulin High glucagon High cAMP High protein kinase A Low PFK2 High FBPase-2 Net result: decreased glycolysis
What are the signs of arsenic poisoning?
Vomiting
Rice water stool
Garlic breath
What does arsenic inhibit?
Lipoid acid
What is the product pyruvate dehydrogenase complex reaction?
Pyruvate + NAD + CoA –> acetyl-CoA + NADH + CO2
What cofactors are involved in the pyruvate dehydrogenase complex?
Pyrophosphate - B1 FAD - B2 NAD - B3 CoA - B5 Lipoid acid
What is PDC deficiency caused by?
X-linked mutation in gene for E1-alpha subunit
What does PDC deficiency result in?
Backup of substrate: pyruvate and alanine
What are the findings of PDC deficiency?
Neuro deficits starting in infancy
What is the treatment for PDC deficiency?
Increase intake of ketone is nutrients : fat and lysine/leucine
What is the function of PDC?
To transition from glycolysis to the TCA
What are the 4 products pyruvate can be converted to?
Alanine
Acetyl-CoA
Oxaloacetate
Lactate
What enzyme converts pyruvate to alanine?
Alanine amidotransferase with the help of B6
What enzyme converts pyruvate to lactate?
Lactate dehydrogenase
What is lactate used in?
Anaerobic glycolysis and the cori cycle
What enzyme converts pyruvate to oxaloacetate?
Pyruvate carboxylase (b7) with CO2 and ATP
What can oxaloacetate be used in?
TCA or gluconeogenesis
What enzyme converts pyruvate to acetyl-CoA?
Pyruvate dehydrogenase with B1,2,3,5
Which organs use anaerobic glycolysis?
RBCs, WBCs, kidney medulla, lens, cornea, testes
What are the products of the TCA cycle?
3 NADH, 1FADH2, 2 CO2, 1 GTP per acetyl CoA = 10 ATP
And we get 2 acetyl CoA molecules per 1 glucose so multiply everything by 2
What is the starting and end product of the TCA cycle?
Citrate Is Krebs’ Starting Substrate For Making Oxaloacetate:
Citrate –> Isocitrate –> alpha-Ketoglutarate –> Succinyl-CoA –> Succinate–> Fumarate–> Malate –> oxaloacetate
What are the irreversible reactions in the TCA cycle?
Acetyl CoA –> citrate by citrate synthase
Isocitrate to alpha Ketoglutarate by Isocitrate dehydrogenase (rate limiting step, produces NADH2)
Alpha Ketoglutarate to succinyl CoA by alphaketoglutarate dehydrogenase (makes NADH2)
Which steps produce NADH2?
Isocitrate to alpha-Ketoglutarate
Alpha-Ketoglutarate to Succinyl CoA
Malate to oxaloacetate
Which step produces FADH2?
Succinate to Fumarate
Which step uses substrate level phosphorylation to generate GTP?
Succinyl CoA to Succinate
What is complex I?
NADH dehydrogenase
What is an inhibitor of complex I?
Rotenone
Amytal
What is the consequence of electron transport inhibitors?
They decrease the proton gradient and block ATP synthesis
What is complex II?
Succinate dehydrogenase
What is complex III?
Cytochrome b-c
What is an inhibitor of complex III?
Antimycin A
What is complex IV?
Cytochrome c oxidase
What inhibits complex IV?
Cyanide
What is complex V?
ATP synthase = f0/f1
F0= integral membrane protein with delta stalk attached to F1
F1= made of alpha/beta subunits - converts ADP to ATP
What inhibits complex V?
Oligomycin
What do complex 3 and 4 do
Pump hydrogen ions from the matrix to the inter membrane space creating a negative charge inside the matrix and thus a larger proton gradient
What is oligomycin?
It is an ATP synthase inhibitor
What is the MOA of oligomycin?
Increases the proton gradient and stops ATP synthesis
Which complex uses CoQ?
Complex III
What is the effect of 2,4 dinitrophenol, aspirin, and thermogenin on the ETC?
Uncouple the ETC –> increase membrane permeability causing a decrease in the proton gradient stopping ATP, but continuing electron transport –> produces heat!
What are the irreversible enzymes in gluconeogenesis?
Pathway Produces Fresh Glucose:
Pyruvate carboxylase = pyruvate to oxaloacetate
Phosphoenol carboxykinase = oxaloacetate to PEP
Fructose 1,6 bisphosphatase = F1,6BP to F6P
Glucose-6-phosphatase = G6P to glucose
What does the G6Pase reaction need in gluconeogenesis?
GTP
What does the pyruvate carboxylase reaction in gluconeogenesis need?
Acetyl-CoA, biotin, ATP
What is the function of the HMP shunt pathway?
To provide a source of NADPH from glucose 6 phosphate
Provide ribose for nucleotide synthesis and glycolysis intermediates
Where does the HMP shunt occur?
In the cytoplasm
Does the HMP shunt require ATP?
No
At what sites does the HMP shunt occur?
Lactating mammary glands
Liver
Adrenal cortex
RBCs
What is the irreversible phase of the HMP shunt?
Oxidative
G6p –> 2 NADPH, CO2, ribulose-5-p by G6PD (rate limiting)
What is the reversible phase of the HMP shunt?
Nonoxidative
Ribulose-5-P –> ribose-5-p, G3P, F6P by phophopentose isomerase with B1
What is respiratory burst?
The production of reactive oxygen species for the killing of bacteria by immune cells
What is the end product of respiratory burst?
Bleach = HOCL
What is the first step in respiratory burst?
Oxidation of oxygen to a superoxide radical using NADPH
What is the mech of superoxide dismutase?
Converts superoxide radical to H2O2
What does myeloperoxidase do?
Converts H2O2 to bleach
What does bacterial catalase do?
Converts H2O2 to water and oxygen so that it cannot be used by the host to make ROIs
What does G6PD do in respiratory burst?
Generates more NADPH for respiratory burst using G6P
How do we deal with our H2O2?
Reduce it using glutathione
What replenishes/reduces glutathione?
NADPH
What is the inheritance pattern of G6PD deficiency?
X linked recessive
What is the clinical presentation of G6PD deficiency?
Back pain then hematuria after infection, antibiotics, fava beans.
What do you see in the peripheral blood smear in G6PD deficiency?
Heinz bodies
Bite cells
What is the problem in G6PD deficiency?
Can’t reduce NADP to NADPH and therefore you can’t reduce glutathione so cells are susceptible to oxidative damage
What is the inheritance pattern of essential fructosuria?
Auto recessive
What is the defect in essential fructosuria?
Defect in fructokinase
What are the findings of essential fructosuria?
Fructose in blood and urine
Otherwise asx
What is the inheritance pattern of fructose intolerance?
Auto recessive
What is the defect in fructose intolerance?
Defect in aldolase B that results in the accumulation of fructose-1-phosphate thereby depleting the phosphate pool. Causes inhibition of glycogenolysis and gluconeogenesis
What are the sx of fructose intolerance?
Hypoglycemia
Jaundice
Cirrhosis
Vom
What is the treatment of fructose intolerance?
Decrease intake of fructose and sucrose
What is the inheritance pattern of galactokinase deficiency?
Auto recessive
What are the signs of galactokinase deficiency?
Infantile cataracts
Lack of tracking objects
Lack of development of social smile
Galactose in the blood
What is the defect in classic galactosemia?
Absence of galactose-1-phosphate uridyltransferase that causes toxic buildup of galacitol
What is the inheritance pattern of classic galactosemia?
Auto recessive
What are the findings of classical galactosemia?
Infantile cataracts, mental retardation, failure to thrive, jaundice, hepatomegaly
What is the treatment for classic galactosemia?
Exclude galactose and lactose from the diet
Where does galactitol deposit in the body?
Lens of the eye
What does aldose reductase do?
Converts glucose to its alcohol form, sorbitol
What does sorbitol dehydrogenase do?
Converts sorbitol to fructose
What is the consequence of an sorbitol dehydrogenase deficiency?
Sorbitol accumulates in the cells and sets up a gradient for water to come in –> osmotic damage = cataracts, retinopathy, peripheral neuropathy
Which organs are most susceptible to sorbitol accumulation and why?
Schwann cells, kidneys, eyes because they only have aldose reductase - no sorbitol dehydrogenase
What is the problem in lactase deficiency?
Loss of a brush border enzyme
What are the sx?
Bloating, cramps, osmotic diarrhea
Who is more likely to have lactase deficiency?
Asians and blacks
What are the essential amino acids?
Met, Val, His, Ile, Phe, Thr, Trp, Leu, Lys
What are the essential glucogenic amino acids?
Met, Val, His
What are the essential glucogenic/ketogenic amino acids?
Ile, Phe, Thr, Trp
What are the essential ketogenic amino acids?
Leu, Lys
What are the acidic amino acids?
Asp
Glu
These are negatively charged and bodily pH
What are the basic amino acids?
Arg, Lys, His
What is the most basic protein?
Arg
Which amino acid has no charge at bodily ph?
His
What is the urea cycle?
Ordinarily Careless Crappers Are Also Frivolous About Urination.
Ornithine + Carbamoylase to Citrulline via ornithine transcarbamoylase
Then Aspartate plus ATP with Citrulline converted to argininosuccinate via argininosuccinate synthetase
Argininosuccinate - Fumarate = Arginine
Arginine + water = urea via arginase
Where does the urea cycle occur?
In the liver
What does the Cori cycle do?
Uses lactate from anaerobic glycolysis for gluconeogenesis
What is the glucose-alanine cycle?
Used as a secondary transport of ammonium from muscles
Used for gluconeogenesis during starvation
What other amino acid is used for transport of ammonium in the body?
Glutamate/alpha ketoglutarate
What is the rate limiting step in the urea cycle?
The first step using CO2, NH4, and 2 ATP to make carb amigo phosphate
What is the problem in hyperammonemia?
Excess NH4 results in depletion of alpha-ketoglutarate and therefore inhibits the TCA cycle so ATP production is impaired