Iron metabolism

Question 1

How is iron transported in the blood?

Answer 1

it is bound to transferrin (as Fe3+)

Question 2

How is iron stored in cells?

Answer 2

It is stored in cells bound to ferritin in hemosiderin

Question 3

Iron is absorbed as ___ and converted to ___ by ceruloplasmin.

Answer 3

Fe2+,

Fe3+

Question 4

How do we measure iron status?

Answer 4

Serum ferritin (Levels below 15 mg/mL indicate iron deficiency)

Question 5

Heme synthesis

Answer 5

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.

Question 6

Elevation of gamma-ALA in the absence of elevation of porphobilinogen is diagnostic for ___.

Answer 6

lead poisoning

Question 7

Erythropoeitic protoporphyria

Answer 7

Ferrocheletase deficiency protoporphyrin accumulates, causes photosensitivity

Question 8

Porphyria cutanea tarda

Answer 8

URO decarboxylase deficiency accumulates uroporphyrinogen III and causes photosensitivity

Question 9

Wilson Disease

Answer 9

Excess copper
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

Question 10

Enzymes with copper

Answer 10

lysyl oxidase, cytochrome C oxidase, superoxide dismutase, and dopamine beta-hydroxylase

Question 11

True or False: Type I fibers are slow twitch.

Answer 11

True

Question 12

True or False: Type I fibers appear white.

Answer 12

False, they appear red.

Question 13

Cardiac injury markers

Answer 13

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)

Question 14

Things to remember about muscle metabolism

Answer 14

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

Question 15

PFK-2 regulation

Answer 15

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)

Question 16

Activation of ___ inhibits ATP-requiring pathways and stimulates ATP-producing pathways.

Answer 16

AMP-PK

Question 17

AMP-PK induces insulin-independent recruitment of ____ receptors in active skeletal muscle (Skeletal muscle makes up for 70% of plasma glucose uptake)

Answer 17

GLUT4

Question 18

AMP-PK phosphorylation ____ acetyl-CoA carboxylase and ___ malonyl-CoA decarboxylase lowering malonyl CoA, resulting in ____.

Answer 18

inactivates,
activates,
increased mitochondrial fatty acid beta-oxidation

Question 19

ACC

Answer 19

Acetyl Coa Carboxylase

Question 20

ACC1

Answer 20

Acetyl Coa Carboxylase 1:
located in liver and adipose tissue
biosynthesis of fatty acids

Question 21

ACC2

Answer 21

Acetyl Coa Carboxylase 2:
located in muscle
regulatory purpose - forms malonyl CoA
little biosynthesis of fatty acids

Question 22

Malonyl CoA

Answer 22

Relieves inhibition of CPT-1 by Malonyl CoA when phosphorylated by AMP-PK; muscles

Question 23

____ stimulates glycogenolysis in muscle.

Answer 23

Epinephrine

Question 24

Epinephrine activates ____.

Answer 24

Adenylate cyclase

Question 25

AMP activates ____ in muscle.

Answer 25

phosphorylase b and PFK-1

Question 26

2 ADP are converted to ___ and ___ by ____ during muscle contraction.

Answer 26

ATP and AMP
by adenylate kinase
(Increases AMP concentration, which activates glycogenolysis)

Question 27

___ can be used to generate ATP in muscles.

Answer 27

Creatine phosphate

Question 28

Creatine synthesis

Answer 28

Glycine converted to Guanidinoacetate in the kidney (also converting arginine to ornithine). Guanidinoacetate is converted to Creatine using SAM in the liver. It then travels to the brain, heart, and skeletal muscle

Question 29

True or false: Lactate is used by skeletal muscle.

Answer 29

False

Question 30

True or false: Lactate can be used by cardiac muscle.

Answer 30

True

Question 31

Difference between creatine and creatinine

Answer 31

Creatinine is formed when creatine phosphate cyclizes. Creatinine is cyclic.