Iron metabolism Flashcards
How is iron transported in the blood?
it is bound to transferrin (as Fe3+)
How is iron stored in cells?
It is stored in cells bound to ferritin in hemosiderin
Iron is absorbed as ___ and converted to ___ by ceruloplasmin.
How do we measure iron status?
Serum ferritin (Levels below 15 mg/mL indicate iron deficiency)
First step: ALA produced by gamma-ALA synthase (amino acid decarboxylation reaction)
Requires pyridoxal phosphate
negatively regulated by heme
Second step: 2 gamma-ALA react to form porphobilinogen. Gamma-ALA dehydratase is zinc enzyme sensitive to lead inhibition.
Elevation of gamma-ALA in the absence of elevation of porphobilinogen is diagnostic for ___.
Ferrocheletase deficiency protoporphyrin accumulates, causes photosensitivity
Porphyria cutanea tarda
URO decarboxylase deficiency accumulates uroporphyrinogen III and causes photosensitivity
Inability to export copper from the liver to bile (excretion pathway) and incorporate into ceruloplasmin (major plasma copper carrier)
Copper accumulates in liver, brain, kidneys, cornea
Severe liver damage: cirrhosis, jaundice, hepatomegaly
Caused by mutation in ATP7B (ATPase membrane transporter) Causes accumulation, then damage to hepatocytes. Leaks out of hepatocytes and accumulates in other tissue
Symptoms: Kayser-Fleischer rings (opthalmologic), tremor (neurological), maybe renal
Enzymes with copper
lysyl oxidase, cytochrome C oxidase, superoxide dismutase, and dopamine beta-hydroxylase
True or False: Type I fibers are slow twitch.
True or False: Type I fibers appear white.
False, they appear red.
Cardiac injury markers
Troponin (MI), Creatinine kinase (CK-MB abundant in heart, B dimer in brain, M dimer is muscle isoform) (CK-MB peaks 12-24 hours after AMI, returns to normal in 3-4 days)
Things to remember about muscle metabolism
Uses GLUT4 receptor to taken in glucose
PFK-2 is not regulated by phosphorylation in muscles
Glycogen does not respond to glucagon (no receptors)
Uses Acetyl Coa Carboxylase 2
Malonyl CoA regulates fatty acid oxidation
AMP protein kinase is an important regulator
FA preferred fuel under rest, fasting, or starved condition
Use branched chain amino acids for fuel in amino acid metabolism
Creatine phosphate used for short term energy needs
ATP and citrate levels inhibit glycolysis in skeletal muscles
In cardiac muscle, PFK-2 is phosphorylated and activated by insulin-dependent kinase cascade. Phosphorylation activates PFK-2 kinase activity
(In liver, phosphorylation of PFK-2 inhibits activity)