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FA: random > Glycogen, Lysosomes, FA, Lipids > Flashcards

Glycogen, Lysosomes, FA, Lipids Flashcards

1
Q

Describe how glucagon & epinephrine (Beta) lead to activation of glycogen phosphorylase

A

Glucagon & epi (when bound to Beta receptor) lead to activation of adenylyl cyclase leading to increased cAMP causing action on protein kinase A => this along w/ Ca+-Calmodulin complex activates glycogen phosphorylase kinase which then stimulates glycogen phosphorylase to make glucose

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2
Q

How does epinephrine (alpha) activate glycogen phosphorylase?

A

binding causing ER to release Ca+ that will also activate the Ca+ - calmodulin complex leading to activation of glycogen phosphorylase kinase (both Ca+ & Ca+ - calmodulin complex activate independently) => glycogen phosphorylase kinase then activates glycogen phosphorylase

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3
Q

How does insulin promote glycogen storage &/or prevent its breakdown?

A

insulin (liver & muscle) bind to & activate tyrosine kinase receptor dimer receptor activates glycogen synthase & activates protein phosphatase (inactivates glycogen phosphorylase)

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4
Q

What are the 2 actions of protein kinase A in glycogen regulation?

A

promotes indirect activation of glycogen phosphorylase

directly blocks glycogen synthase

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5
Q

How does muscle get energy during exercise?

A

glycogenolysis to form G-1-P to G-6-P which is rapidly metabolized during exercise

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6
Q

Describe the cycle of producing & breaking down glycogen in the liver to maintain normal blood sugar

A

G-6-P is inside the cell as G-1-P then UDP-glucose pyrophosphorylase converts it to UDP glucose =>
At this point glycogen synthase convert it to glycogen for storage (insulin) => a branching enzyme leads to better storage of glycogen

As the body needs sugar, glycogen phosphorylase is revved up while glycogen synthase is inhibited (both via Protein Kinase A) to produce limit dextrin (4 G-1-P residues)=>
Limit dextrin is attacked by a debranching enzyme (4-a-D-glucanotransferase) resulting in moving 3 from branch to linkage =>
Another debranching enzyme (a-1,6-glucosidase) cleaves off the last glucose 1- phosphate on the branch

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7
Q

Large concept of glycogen storage then breakdown is the bonds

A

Branches have alpha (1,6) bonds for storage;

linkages have alpha (1,4) bonds

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8
Q

How is some glycogen degraded in the lysosomes?

A

the enzyme alpha-1,4-glucosidase

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9
Q

There are 12 types of glycogen storage diseases. What do all result in? (key to remembering main 4)

A

AR diseases that all result in abnormal glycogen metabolism & accumulation of glycogen w/in cells

Very Poor Carbohydrate Metabolism
(Von Gierke, Pompe, Cori, McArdle)

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10
Q

Young child with severe fasting hypoglycemia, increased blood lactate, uric acid & hepatomegaly. What enzyme is deficient? why is liver large? What is Tx?

A

Von Gierke’s disease (type I)
Deficient in Glucose - 6- phosphatase;
hepatomegaly due to large amounts of glycogen in liver
Tx is frequent oral glucose/cornstarch & AVOID fructose & galactose

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11
Q

Infant dies & findings are cardiomegaly & other systemic findings leading to early death. What is the deficient enzyme? What tissues are most damaged?

A

Pompe’s disease (type II)
Deficient in lysosomal alpha-1,4-glucosidase (acid maltase)
Pompe’s trashes the Pump => heart, liver, muscle

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12
Q

Young child comes in with moderate fasting hypoglycemia, increased glycogen in the liver & hepatomegaly but normal lactate in blood. What enzyme is deficient? What physiologic process is still intact?

A

Cori’s disease (type III)
Deficient in debranching enzyme (alpha-1,6-glucosidase);
gluconeogenesis is still intact

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13
Q

A child has increased glycogen in muscle associated with painful cramps. He/she knows to avoid strenuous exercise & lives a normal lifetime. What enzyme is deficient? Why must strenuous exercise be avoided?

A

McArdle’s disease (type V) => McArdle’s = muscle
deficient in skeletal muscle glycogen phosphorylase

glycogen cannot be broken down in muscle so cramps occur which pull in water causing lysis leading to myoglobin in serum & kidney that may cause RHABDOMYOLYSIS

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14
Q

What is the common result in all lysosomal storage diseases? How are they inherited?

A

Result in accumulation of abnormal metabolic products

All are AR except Fabry & Hunter which are XLR

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15
Q

What are the sphingolipidoses?

A 
Fabry;
Gaucher;
Niemann Pick
Tay Sachs
Krabbe
Metachromatic leukodystrophy
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16
Q

A young boy who’s uncle (dead) & him share the same peripheral neuropathy of hands/feet, angiokeratomas, CV/renal disease. What is the deficient enzyme? inheritance? accumulated substrate?

A

Fabry disease => XLR
deficient of alpha-galactosidase A enzyme
Ceramid trihexoside accumulates

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17
Q

What is the most common lysosomal storage disease? What is its treatment?

A

Gaucher disease

Tx is recombinant glucocerebrosidase

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18
Q

A young child has hepatosplenomegaly, pancytopenia, aseptic necrosis of the femur, severe bone pain. On H&E, lipid laden macs are present that resemble crumpled tissue paper. What is the deficient enzyme? inheritance? accumulated substrate?

A

Gaucher disease => AR
Deficient in glucocerebrosidase (Beta-glucosidase)
Glucocerebroside accumulates

Gaucher cells => lipid laden macs are present that resemble crumpled tissue paper

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19
Q

A young Ashkenazi Jew has a cherry red spot on macula. He/she also has hepatosplenomegaly & neurodegenerative disease that is getting worse. Foam cells are also present. What is the deficient enzyme? inheritance? accumulated substrate?

A

Niemann-Pick disease => AR
deficient in sphingomyelinase
Sphingomyelin accumulates

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20
Q

A young Ashkenazi Jew has a cherry red spot on macula. He/she has progressive neurodegeneration w/ developmental delay but has no hepatosplenomegaly. What is the deficient enzyme? inheritance? accumulated substrate? What will be seen w/in the cell?

A

Tay-Sachs disease => AR
Defects in heXosaminidase A
GM-2 ganglioside accumulates

lysosomes w/ onion skin appearance

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21
Q

What is the key to differentiate Tay-Sachs from Niemann Pick disease?

A

Tay Sachs does NOT have hepatosplenomegaly

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22
Q

A young child has peripheral neuropathy, developmental delay. Globoid cells & optic atrophy are present on H&E & exam. What is the deficient enzyme? inheritance? accumulated substrate?

A

Krabbe disease => AR
Deficient in galactocerebrosidase
Galactoscerebroside, psychosine accumulates

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23
Q

A young child has early dementia & ataxia associated with central & peripheral demyelination. What is the deficient enzyme? inheritance? accumulated substrate?

A

Metachromatic leukodystrophy => AR
Deficient in arylsulfatase A
Cerebroside sulfate accumulates

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24
Q

What are the mucopolysaccharidoses?

A

Hurler & Hunter syndrome

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25
Q

A young child has developmental delay, hepatosplenomegaly & airway obstruction. On neuro exam, corneal clouding is seen. The patient also has gargoylism. What is the deficient enzyme? inheritance? accumulated substrate?

A

Hurler syndrome => AR
deficient in alpha-L-uduronidase
Heparan sulfate & dermatan sulfate accumulate

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26
Q

A young child has shown very aggressive behavior towards others & no treatments seem to work & no corneal clouding. A family history shows some men in his family also have the same aggressive behavior. What is the deficient enzyme? inheritance? accumulated substrate?

A

Hunter syndrome => XLR
deficient in iduronate sulfatase
heparan sulfate & dermatan sulfate accumulate

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27
Q

Other than family history, what is another way to differentiate the mucopolysaccharidoses?

A

Hurler has corneal clouding => Hunter does NOT

28
Q

Long chain FA degradation requires what?

A

carnitine dependent transport into mitochondrial matrix

29
Q

What is the result of carnitine deficiency?

A

inability to transport LC-FAs into mitochondria leading to toxic accumulation

causes weakness, hypotonia, & hypoketotic hypoglycemia

30
Q

What is the role of acetyl-CoA in gluconeogenesis? What will a deficiency of acetyl-CoA DH cause?

A

Acetyl-CoA is + allosteric regulator of pyruvate carboxylase in gluconeogenesis

deficiency leads to decreased acetyl-CoA so there is an accumulation of dicarboxylic acids with a decrease in glucose & ketones

31
Q

Describe the process of FA synthesis…location, shuttle, enzymes, cofactors

A

Citrate from Mt matrix leaves via the citrate shuttle to the cell cytoplasm to make Acetyl-CoA via ATP citrate lyase =>
Biotin & CO2 are added to make Malonyl-CoA =>
FA synthesis is now done w/ Palmitate (16C FA)

32
Q

Describe the process of FA degradation…location, shuttle, enzymes, cofactors. What will block this pathway?

A

FA & CoA via FA-CoA synthetase makes Acyl-CoA =>
Acyl-CoA will go from cytoplasm through the carnitine shuttle unchanged into the Mt matrix =>
Acyl-CoA is then Beta-oxidized (broken down into acetyl-CoA groups) =>
Ketone bodies are formed & TCA can start

Malonyl-CoA can block Acyl-CoA from entering carnitine shuttle & trapping it in cytoplasm

33
Q

Where are FA & AA metabolized and into what?

A

in liver, they are metabolized into acetoacetate & Beta-hydroxybutyrate (to be used in muscle & brain)

34
Q

What can cause the production of ketone bodies? How?

A

prolonged starvation & DKA cause OAA to deplete for gluconeogenesis;
Alcoholism has excess NADH so OAA is shunted to malate;

Both cause buildup of Acetyl-CoA so glucose & FFA production is halted & ketone bodies are produced

35
Q

How will a person undergoing ketone production present? What will not be present?

A

Breath smells fruity due to acetone

Urine test for ketones does NOT detect Beta-hydroxybutyrate

36
Q

What are the metabolic processes after a meal (fed state)?

A

Glycolysis & aerobic respiration;

Insulin stimulates storage of lipids, proteins, glycogen

37
Q

What are the metabolic processes between meals (fasting)?

A 
hepatic glycogenolysis (major);
hepatic gluconeogenesis, adipose release of FFA (minor)

Glucagon, Epi stimulate use of fuel reserves

38
Q

In the starvation state of 1-3 days, how is blood glucose maintained?

A

Hepatic glycogenolysis;
Adipose release of FFA;
muscle & liver which shift fuel use from glucose to FFA;
hepatic gluconeogenesis from peripheral tissue lactate & alanine & from adipose tissue glycerol & propionyl-CoA

39
Q

What is the only triacylglycerol component that contributes to gluconeogenesis?

A

propionyl-CoA (from odd chain FFA)

40
Q

During starvation, how long does it take glycogen reserves to be depleted?

A

1 day

41
Q

Starvation after 3 days leads to what source of energy being used? What is key for this source?

A

Adipose stores are used & ketones are primary source for brain;
Once depleted, protein degradation accelerates leading to organ failure & death (amount of stores determine survival)

42
Q

What is the rate limiting step in cholesterol synthesis? How does it work? what induced it?

A

HMG-CoA reductase (induced by insulin) converts HMG-CoA to mevalonate

43
Q

A majority of plasma cholesterol is esterified by what?

A

Lecithin-cholesterol acyltransferase (LCAT)

44
Q

What is the MOA of statins?

A

competitively & reversible inhibit HMG-CoA reductase

45
Q

role of Pancreatic lipase

A

degradation of dietary triglycerides (TG) in small intestine.

46
Q

role of lipoprotein lipase

A

degradation of TG circulating in chylomicrons and VLDLs. Found on vascular endothelial surface

47
Q

role of Hepatic TG lipase (HL)

A

degradation of TG remaining in IDL.

48
Q

role of hormone sensitive lipase

A

degradation of TG stored in adipocytes.

49
Q

role of Cholesterol ester transfer protein (CETP)—

A 
mediates transfer of cholesterol esters to other
lipoprotein particles (VLDL, IDL, LDL
50
Q

What are the major apolipoproteins? function?

A 
E => mediates remnant uptake
A-1 => activates LCAT
C-2=> lipoprotein lipase cofactor
B-48 => mediates chylomicron secretion
B-100=> binds LDL receptor
51
Q

What apolipoproteins function with chylomicron?

A

E
A-1
C-2
B-48

52
Q

What apolipoproteins function with chylomicron remnant?

A

E

B-48

53
Q

What apolipoproteins function with VLDL?

A

E
C-2
B-100

54
Q

What apolipoproteins function with IDL?

A

E

B-100

55
Q

What apolipoproteins function with LDL?

A

B-100

56
Q

What apolipoproteins function with HDL?

A

E
A-1
C-2

57
Q

What are lipoproteins made of? What are the primary carriers of cholesterol?

A

cholesterol, TGs, phospholipids;

LDL transports cholesterol from liver to tissues;
HDL transports cholesterol from periphery to liver

58
Q

What is the role of the chylomicron?

A

Delivers dietary TGs to peripheral tissue;
Delivers cholesterol to liver in the form of chylomicron remnants, which are mostly depleted of their triacylglycerols;
Secreted by intestinal epithelial cells.

59
Q

What is the role of VLDL?

A

Delivers hepatic TGs to peripheral tissue.

Secreted by liver.

60
Q

What is the role of IDL?

A

Formed in the degradation of VLDL;

Delivers TGs and cholesterol to liver.

61
Q

What is the role of LDL?

A

Delivers hepatic cholesterol to peripheral tissues;
Formed by hepatic lipase modification of IDL in the peripheral tissue;
Taken up by target cells via receptor-mediated endocytosis.

62
Q

What is the role of HDL?

A

Mediates reverse cholesterol transport from periphery to liver.
Acts as a repository for apoC and apoE (which are needed for chylomicron and VLDL metabolism).
Secreted from both liver and intestine.

63
Q

Which lipoprotein does alcohol increase the synthesis of?

A

HDL

64
Q

A younger patient has some S/Sx of pancreatitis, hepatosplenomegaly, & eruptive/pruritic xanthomas. What is the risk for atherosclerosis? What is increased in the blood? What is the inheritance? What enzyme is deficient or altered?

A

type I => hyper-chylomicronemia => AR

Deficient in lipoprotein lipase or altered apolipoprotein C-2 causing
elevated Chylomicrons, TG, cholesterol in blood

No increased risk for atherosclerosis

65
Q

A 20 yr old patient comes in after an MI w/ no drug use & exercises regularly. What will be found on physical exam? What is the inheritance? What is defective? What is elevated in the blood?

A

type 2a => familial hyper-cholesterolemia => AD

Absent (homozygous=cholesterol may be 700) or defective (heterozygous=cholesterol may be 300) LDL receptors
causes
elevated LDL & cholesterol

Accelerated atherosclerosis; tendon (achilles) xanthomas;
corneal arcus

66
Q

A patient has had several bouts of pancreatitis along with many people in his family. What is elevated in blood? inheritance? What is the mechanism of pathology?

A

Type IV => hyper-tryglyceridemia => AD

Hepatic overproduction of VLDL causing
elevated blood levels of VLDL & TG

67
Q

Differentiate familial dyslipidemias based on what is elevated in blood

A

type I-hyper-chylomicronemia => CM, TG, cholesterol

Type 2a - familial hypercholesterolemia => LDL, cholesterol

type IV - hyper-triglyceridemia => VLDL, TG

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