Chapter 7- Globins Flashcards
List the characteristics of the globins?
heme-containing protein family
globin fold formed by homologous
bind to oxygen
What makes globins have the globin fold?
homologous sequence
What is the globin fold?
general tertiary structure
almost all alpha helices
has a prosthetic heme
no quaternary structure
What is homology?
- makes it protein related genealogy
- they are similar because of evolutionary relationships
- similar because evolved from an ancient common ancestor
example: wings, arms, fins
What is a heme?
a macrocyclic porphyrin ring
Nitrogen coordinating with metal ion in center which is iron
What kind of structure does hemoglobin have and what does that mean for it?
Has quarternary structure
which enables cooperativity
How many oxygens can hemoglobin bind?
4
What does cooperativity mean?
in hemoglobin it means that it has varying affinity for oxygen.
What does a sigmoidal curve show?
that the binding protein has quaternary structure
that oxygen binding to hemoglobin at one site increases the likelihood that oxygen will bind at the remaining unoccupied sitesW
What does a simple saturated curve indicate?
in the myoglobin example it shows that oxygen binds with high affinity to to myoglobin
What is the difference between oxygen binding to myoglobin and oxygen binding to hemoglobin?
because myoglobin only has 1 binding once it is in the presence of O2 then it will bind readily
in hemoglobin it has 4 binding sites and has varying affinity for oxygen.
cooperativity= _____________ structure
no cooperativity= no _____________ structure
quaternary
What is to be said about the following in terms of its non cooperativity or its cooperativity?
Myoglobin
Hemoglobin
No cooperativity (hypothetical)
Myoglobin just absorbs O2
Hemoglobin has to have a changing affinity for O2
NO cooperativity means that it will eventually reach 100% saturation overtime
Does hemoglobin have a conformational change? If so what does that tell us?
Yes, because it has cooperativity
Explain the allosteric model.
The allosteric model has two parts the low affinity O2 state and the high affinity O2 state.
What is an allosteric regulator for hemoglobin?
BPG, it modulates hemoglobin’s binding of oxygen
What is to be said regarding BPGs charge?
it is heavily negatively charged
If we have allostery what do we also have?
allostery regulation
What helps us get rid of affinity?
BPG, as an allosteric regulator
why does hemoglobin have cooperativity?
because it has quaternary structure
BPG binds at what in hemoglobin?
It binds at histidine
The Bohr effect explains what?
how hemoglobin delivers oxygen to metabolically active tissues
What shifts the curve?
a change in pH
proton changes conformation of protein so its in the high affinity state
what delivers more O2 more efficiently?
tissues versus lungs
How is the proton released to lower pH according to the Bohr effect?
CO2 is made into H2CO3 (bicarbonate) at biological pH (7.5) will release a H+ to lower the pH
this would not be possible if hemoglobin didn’t have quaternary structure
How does a fetus get oxygen from its mother’s blood?
from other globin genes in the human genome
Describe the protein that the fetus uses in order to get oxygen from the mother.
It uses a different protein that has a different structure and function.
Describe the O2 flow from the fetus to its mother.
O2 flows from the mom’s oxyhemoglobin and to the fetus’ deoxyhemoglobin
What type of disease is correlated with the shape of the red blood cells? And why?
sickle cell disease
it occurs in low O2 conditions, it doesn’t carry O2 well and it is stuck in the capillaries. The O2 delivery is greatly diminished
