Hemoglobina parte 2(grupo hemo, union del hemo a la gb, efecto de cooperatividad )

Summary

The transcript explains the structure and function of hemoglobin and myoglobin, highlighting the importance of the heme group, iron in its ferrous state, and its interaction with oxygen. It explores the cooperative binding of oxygen by hemoglobin, with each molecule able to bind four oxygen molecules, and how this process is influenced by oxygen concentration. The difference between oxyhemoglobin and methemoglobin is also covered, with the latter being unable to bind oxygen due to iron in the ferric state. The effect of pressure and interactions within the protein structure is discussed, including the transition between tense and relaxed forms of hemoglobin.

Takeaways

• 😀 The heme group in myoglobin and hemoglobin consists of a complex of protoporphyrin IX and ferrous iron (Fe²⁺).
• 😀 The heme group is tetrahedral in structure, with iron at the center and nitrogen atoms from porphyrins surrounding it.
• 😀 The iron in the heme group is essential for its ability to bind oxygen, forming a reversible interaction with O₂.
• 😀 When iron is in the Fe²⁺ state, the hemoglobin is able to bind oxygen, while in the Fe³⁺ state (methemoglobin), it cannot bind oxygen.
• 😀 Hemoglobin is capable of binding up to four oxygen molecules, with the binding of one oxygen molecule facilitating the binding of subsequent ones due to cooperativity.
• 😀 Cooperativity means that as one molecule of oxygen binds to hemoglobin, it induces a conformational change that makes it easier for the next oxygen molecules to bind.
• 😀 The oxygen-hemoglobin binding is reversible and depends on the partial pressure of oxygen in the surrounding environment.
• 😀 In areas of high oxygen concentration (like the lungs), hemoglobin binds oxygen, while in low oxygen areas (like tissues), it releases oxygen.
• 😀 The cooperativity effect also aids in oxygen release, where the release of one oxygen molecule facilitates the release of others.
• 😀 Hemoglobin undergoes conformational changes between two states: the tense (T) state, where oxygen binding is harder, and the relaxed (R) state, where oxygen binds more easily.

Q & A

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

The heme group in both myoglobin and hemoglobin consists of a porphyrin complex with a central ferrous (Fe2+) iron atom. The iron is coordinated with nitrogen atoms from a porphyrin ring and forms a tetrapyrrole structure, making the heme group essential for oxygen binding.

What role does iron play in the heme group?

Iron in the heme group is responsible for binding oxygen. In its ferrous (Fe2+) state, iron can interact with oxygen, allowing the heme group to carry oxygen molecules.

What happens when iron in the heme group is oxidized to Fe3+?

When the iron in the heme group is oxidized to Fe3+ (ferric state), it can no longer bind oxygen. This results in the formation of methemoglobin, which is unable to transport oxygen efficiently.

What is the difference between oxyhemoglobin and methemoglobin?

Oxyhemoglobin occurs when iron is in the ferrous (Fe2+) state and is capable of binding oxygen, while methemoglobin occurs when iron is oxidized to the ferric (Fe3+) state, rendering it incapable of binding oxygen.

What is cooperativity in hemoglobin?

Cooperativity in hemoglobin refers to the phenomenon where the binding of one oxygen molecule to hemoglobin increases the affinity of the molecule for subsequent oxygen molecules. This makes oxygen binding more efficient as more molecules of oxygen are attached.

How does the interaction between oxygen and hemoglobin depend on the oxygen concentration?

The binding of oxygen to hemoglobin is reversible and depends on the partial pressure of oxygen. Higher oxygen pressure (such as in the lungs) promotes the binding of oxygen, while lower oxygen pressure (such as in tissues) triggers the release of oxygen.

What is the significance of the T and R states in hemoglobin?

The T (tense) state of hemoglobin is associated with lower affinity for oxygen, while the R (relaxed) state has a higher affinity for oxygen. The transition between these states facilitates oxygen binding and release.

How does the release of one oxygen molecule affect the rest of the oxygen molecules in hemoglobin?

The release of one oxygen molecule from hemoglobin facilitates the release of additional oxygen molecules. This is due to the cooperative interactions between the subunits of the hemoglobin molecule.

Why is the interaction between the heme group and the globin important for oxygen transport?

The interaction between the heme group and the globin protein ensures that oxygen is efficiently bound and released. The structural changes in the hemoglobin molecule as it binds oxygen are crucial for its function as an oxygen carrier.

What role does the iron in the heme group play in the cooperative binding of oxygen?

The iron in the heme group acts as the binding site for oxygen. The cooperative effect in hemoglobin allows each oxygen binding to increase the affinity of the remaining heme sites for oxygen, making oxygen uptake and release more efficient.