Podcast
Questions and Answers
What is the main function of hemoglobin?
What is the main function of hemoglobin?
Hemoglobin can pass through capillary membranes.
Hemoglobin can pass through capillary membranes.
False
What are the two types of chains in a hemoglobin molecule?
What are the two types of chains in a hemoglobin molecule?
alpha and beta chains
Hemoglobin consists of ___ alpha chains and ___ beta chains.
Hemoglobin consists of ___ alpha chains and ___ beta chains.
Signup and view all the answers
What molecule can enter red blood cells, release its ribose moiety, be phosphorylated, and eventually be converted to 2,3-BPG?
What molecule can enter red blood cells, release its ribose moiety, be phosphorylated, and eventually be converted to 2,3-BPG?
Signup and view all the answers
Which gas binds to hemoglobin 210 times more readily than oxygen?
Which gas binds to hemoglobin 210 times more readily than oxygen?
Signup and view all the answers
Methemoglobin carries a positive charge and can combine with neutral atoms such as O2, CO2, or CO.
Methemoglobin carries a positive charge and can combine with neutral atoms such as O2, CO2, or CO.
Signup and view all the answers
Myoglobin serves as an intracellular storage site for ____ in muscle tissue.
Myoglobin serves as an intracellular storage site for ____ in muscle tissue.
Signup and view all the answers
Match the following substances with their role in the body:
Match the following substances with their role in the body:
Signup and view all the answers
Study Notes
Here are the study notes:
Porphyrins
- Porphyrins are cyclic compounds formed by the linkage of four pyrrole rings through methenyl bridges (-HC=)
- Porphyrin rings are numbered with Roman numerals I through IV, starting at the top and proceeding clockwise
- Methenyl bridges are lettered with Greek letters, alpha through delta, again proceeding clockwise
- Common substituents are often abbreviated, e.g. A = acetic acid, P = propionic acid, M = methyl, V = vinyl
Hemoproteins
- Hemoproteins are proteins that contain heme (iron-protoporphyrin)
- Examples of hemoproteins in humans and animals:
- Hemoglobin (Hb) in red blood cells (RBCs)
- Myoglobin (Mb) in muscle tissue
- Cytochrome c in electron transport chain
- Cytochrome P450 in xenobiotic metabolism
- Catalase in hydrogen peroxide degradation
- Tryptophan pyrrolase in tryptophan oxidation
Hemoglobin (Hb)
- Hemoglobin is the key molecule of oxygen transport
- It is the main constituent of RBCs and responsible for the red color of blood
- Hemoglobin has a large molecular weight and is electrically neutral
- Normal blood concentration of Hb is 12-16 gm/dL (female) and 14-18 gm/dL (male)
- Hemoglobin carries oxygen from lungs to tissues and carbon dioxide from tissues back to lungs
Hemoglobin Structure
- Hemoglobin molecule consists of four polypeptide chains: two alpha chains and two beta chains
- Each chain has a heme molecule containing a ferrous iron atom
- The protein portion of each chain is called globin
- Alpha and beta globin chains are very similar in structure, but distinct from each other
- Histidine residues in the globin chains form a fifth coordination bond with the heme iron ion
Types of Hemoglobin
- Embryonic Hb (a2e2)
- Fetal Hb (a2g2)
- Adult Hb (a2b2)
Functions of Hemoglobin
- Oxygen transport (oxy Hb)
- Carbon dioxide transport (carbamino Hb)
- CO transport (carboxy Hb)
Oxygen Binding to Hemoglobin
- Iron is displaced from one imidazol ring and one oxygen is attached instead
- Each Hb subunit contains a pocket for the heme that provides a non-polar environment for oxygen binding
Bohr Effect
- Decreased oxygen affinity of Hb in tissues due to high CO2 and H+ concentrations
- CO2 is transported as bicarbonate, formed by the enzyme carbonic anhydrase
- Protons generated from CO2 and water react with Hb, lowering its oxygen affinity
- In lungs, high oxygen concentration and low CO2 and H+ concentrations increase oxygen affinity of Hb
2,3-Diphosphoglycerate (2,3-DPG)
- A metabolite found in the anaerobic glycolysis pathway
- Binds to partially deoxygenated Hb, reducing its oxygen affinity
- Increases in response to chronic hypoxia or anemia
- Essential for the normal oxygen transport function of Hb
Carbon Monoxide (CO)
- A byproduct of incomplete combustion of fuels
- Has a 210 times greater affinity for Hb than oxygen
- Displaces oxygen from Hb, inhibiting oxygen transport
- Can cause carbon monoxide poisoning
Methemoglobin (MetHb)
- Formed when the iron of Hb is oxidized to the ferric state
- Cannot combine with oxygen, CO2, or CO
- Can be reduced back to Hb by MetHb reductase in the presence of NADPH
- Cyanide toxicity can be treated with sodium nitrite, which oxidizes some Hb to MetHb, which then reacts with CN- to form a non-toxic compound
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Learn about the structure and characteristics of porphyrins, a type of cyclic compound formed by the linkage of four pyrrole rings.
