Chapter 5: Protein Function Flashcards
What are the two types of interactions?
- Protein acting as a reaction catalyst, or enzyme.
2. Neither the chemical configuration nor the composition of the bound molecule has changed.
Where does a ligand bind?
The binding site at a protein
What is an induced fit?
The structural adaptation occurs between protein and ligand.
Describe two things about Oxygen?
- Poorly soluble in aqueous solution.
2. Transitions metals have a strong tendency to bind.
What is a heme?
Protein-bound prosthetic group
Would a molecule of Oxygen bind to one of the hemes of a hemoglobin molecules in the T state, which has no molecules of Oxygen bound?
Yes, but the molecules of Oxygen would bind weakly because the T state has a low affinity for Oxygen.
What happens when one molecules of Oxygen binds to hemoglobin?
The affinity of neighboring subunits of Oxygen increases.
Can a molecule of Oxygen dissociate from one of the hemes of a hemoglobin molecule in the R state, which has four molecules of Oxygen bound?
Yes, but dissociation is difficult because the R state has a high affinity for Oxygen.
What happens when one molecule of Oxygen dissociates from hemoglobin?
The affinity for Oxygen of neighboring subunits decreases.
Under which condition does hemoglobin primarily exist in the T state?
Low Oxygen concentration
Based on how Oxygen binding affects the affinity of neighboring hemoglobin subunits , Oxygen is an _____ allosteric modulator.
Activating homotropic.
Which methods of energy production contributes to a decrease in pH?
Both aerobic and anaerobic metabolism.
What increases and decreases during vigorous exercise, in terms of physiological factors.
CO2 concentration increases.
Oxygen concentration decreases and pH decreases.
Physiological changes favoring the T state.
- Decreased pH
- Increased CO2 concentration.
- Decreased Oxygen concentration.
The combination of decreased O2 concentration, an increased CO2 concentration, and a decrease pH led to the football player’s sickle cell crisis.
Based on this information, the football player’s sickle cell crisis was most likely triggered by the aggregation of hemoglobin in which state?
The T state
Considering the structure of 2,3‑BPG, what type of residues do you suspect line the cavity between the β subunits where 2,3‑BPG binds?
Positively charged residues. Because 2,3-BPG is deprotonated and negatively charged.
Which state of hemoglobin would predominate if the blood concentration of 2,3 BPG increases?
The T State.
Because 2, 3 BPG sits in the central cavity between the Beta subunits of the T state tetramer. That cavity is closed in the R state.
What would be the net effect of increasing the concentration of 2,3 BPG in the blood?
Hemoglobin’s affinity for Oxygen would decrease.
Why are the His residues in the central cavity Hba important for the binding of 2,3 BPG?
The His residues can become protonated and positively charged, enabling the to strongly interact with the negatively charged groups of 2,3 BPG.
How should replacing His residues found in HbA with Her residues found in HbF affect the binding of 2,3 BPG to HbF?
HbF should have a lower affinity for 2,3 BPG relative to HbA.
Since CO2 binds to hemoglobin like Oxygen, what is the effect of one molecule of CO binding to hemoglobin?
The affinity of neighboring subunits for both Oxygen and CO increases.
Which conformational state for hemoglobin should have a higher affinity for CO?
The R state.
Favoring conditions of R state of hemoglobin.
High Oxygen concentration and high CO concentration.
