Porphyrins and Hemoglobin Structure

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Questions and Answers

What is a porphin?

A type of hereditary disease
A cyclic compound formed by the linkage of 4 pyrrole rings (correct)
A protein that contains heme as a prosthetic group
A complex of one porphyrin and ferrous iron

What is the function of the heme group in hemoglobin and myoglobin?

To interact with oxygen and form damage oxygen radicles
To reversibly bind oxygen (correct)
To catalyze the breakdown of hydrogen peroxide
To serve as an electron carrier

What is the result of a deficiency of one of the enzymes needed for heme synthesis?

Increased production and excretion of porphyrins and/or their precursors (correct)
Decreased production and excretion of porphyrins and/or their precursors
Only increased production of porphyrins
No effect on porphyrins and/or their precursors

What type of porphyria is caused by lead poisoning?

Any type of porphyria (B) Signup and view all the answers

What is the function of the heme group in catalase?

To catalyze the breakdown of hydrogen peroxide (B) Signup and view all the answers

What is the result of anemia in patients with porphyria?

Decreased production of heme (B) Signup and view all the answers

What is the result of photosensitivity in patients with porphyria?

Formation of damage oxygen radicles (D) Signup and view all the answers

What is the inheritance pattern of congenital erythropoietic porphyria?

Autosomal recessive (D) Signup and view all the answers

What is the primary function of myoglobin in muscle cells?

To act as a reservoir and carrier for oxygen (B) Signup and view all the answers

What is the structure of the myoglobin molecule?

A compact molecule with 80% α-helix structure (D) Signup and view all the answers

How many oxygen molecules can myoglobin bind?

One (A) Signup and view all the answers

What is the partial pressure of oxygen needed to achieve half-saturation of the binding sites on myoglobin?

1 mm Hg (A) Signup and view all the answers

What happens to the oxygen dissociation curve when the pH is raised or the concentration of CO2 in the lungs is lowered?

It shifts to the left (A) Signup and view all the answers

What is the Bohr effect?

The decrease in oxygen binding capacity of hemoglobin at low pH (B) Signup and view all the answers

What happens to the oxygen dissociation curve in the Bohr effect?

It shifts to the right (D) Signup and view all the answers

What is the effect of 2,3-bisphosphoglycerate (2,3 BPG) on the oxygen affinity of hemoglobin?

It decreases the oxygen affinity (A) Signup and view all the answers

What is the purpose of 2,3-BPG in the RBCs?

To release oxygen efficiently in the tissues (B) Signup and view all the answers

What is the primary difference in oxygen binding between myoglobin and hemoglobin?

Myoglobin has a higher oxygen affinity than hemoglobin (C) Signup and view all the answers

What happens to the oxygen affinity of hemoglobin in the absence of 2,3-BPG?

It increases (C) Signup and view all the answers

What is the function of the heme group in myoglobin?

To bind oxygen (B) Signup and view all the answers

What is the function of Hb A2?

It is synthesized in the adult at low levels compared to Hb A (D) Signup and view all the answers

What can happen to Hb A?

It can become modified by the covalent addition of a hexose (D) Signup and view all the answers

What occurs due to an imbalance in the synthesis of globin chains in thalassemias?

A defect in either α or β-globin chain synthesis (C) Signup and view all the answers

What leads to the formation of α2β2 (Hb A) in normal conditions?

Coordination in the synthesis of α and β-globin chains (A) Signup and view all the answers

Which enzyme catalyzes the first step in the degradation of heme?

Heme oxygenase (D) Signup and view all the answers

What pigment is produced as a result of the first step in the degradation of heme?

Biliverdin (C) Signup and view all the answers

How is bilirubin transported to the liver?

Bound to albumin (D) Signup and view all the answers

What increases the solubility of bilirubin in the hepatocyte?

Addition of glucuronic acid (B) Signup and view all the answers

What is formed when bilirubin diglucuronide is hydrolyzed and reduced by bacteria in the gut?

Urobilinogen (C) Signup and view all the answers

What is the primary location where red blood cells are degraded after approximately 120 days in circulation?

Reticuloendothelial system (D) Signup and view all the answers

What pigment gives feces its characteristic brown color?

Stercobilin (D) Signup and view all the answers

What is the main cause of hemolytic jaundice?

Massive lysis of red blood cells (B) Signup and view all the answers

What is the fate of reabsorbed urobilinogen in the portal blood?

Participates in the enterohepatic urobilinogen cycle (B) Signup and view all the answers

Which type of jaundice involves an obstruction of the bile duct?

Obstructive jaundice (C) Signup and view all the answers

What causes the urine to turn dark in hepatocellular jaundice?

Increase in urobilinogen (C) Signup and view all the answers

Why do newborns often develop jaundice?

Immature liver function (B) Signup and view all the answers

What enzyme's activity is low at birth, contributing to jaundice in newborns?

Hepatic bilirubin glucuronyltransferase (B) Signup and view all the answers

What is the end product of heme catabolism?

Bilirubin (B) Signup and view all the answers

Flashcards

What is a porphin?

A cyclic compound formed by the linkage of 4 pyrrole rings

Heme group function

To reversibly bind oxygen