Chapter 7- Globins

Question 1

List the characteristics of the globins?

Answer 1

heme-containing protein family
globin fold formed by homologous
bind to oxygen

Question 2

What makes globins have the globin fold?

Answer 2

homologous sequence

Question 3

What is the globin fold?

Answer 3

general tertiary structure
almost all alpha helices
has a prosthetic heme
no quaternary structure

Question 4

What is homology?

Answer 4

1. makes it protein related genealogy
2. they are similar because of evolutionary relationships
3. similar because evolved from an ancient common ancestor

example: wings, arms, fins

Question 5

What is a heme?

Answer 5

a macrocyclic porphyrin ring
Nitrogen coordinating with metal ion in center which is iron

Question 6

What kind of structure does hemoglobin have and what does that mean for it?

Answer 6

Has quarternary structure
which enables cooperativity

Question 7

How many oxygens can hemoglobin bind?

Answer 7

4

Question 8

What does cooperativity mean?

Answer 8

in hemoglobin it means that it has varying affinity for oxygen.

Question 9

What does a sigmoidal curve show?

Answer 9

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

Question 10

What does a simple saturated curve indicate?

Answer 10

in the myoglobin example it shows that oxygen binds with high affinity to to myoglobin

Question 11

What is the difference between oxygen binding to myoglobin and oxygen binding to hemoglobin?

Answer 11

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.

Question 12

cooperativity= _____________ structure
no cooperativity= no _____________ structure

Answer 12

quaternary

Question 13

What is to be said about the following in terms of its non cooperativity or its cooperativity?
Myoglobin
Hemoglobin
No cooperativity (hypothetical)

Answer 13

Myoglobin just absorbs O2
Hemoglobin has to have a changing affinity for O2
NO cooperativity means that it will eventually reach 100% saturation overtime

Question 14

Does hemoglobin have a conformational change? If so what does that tell us?

Answer 14

Yes, because it has cooperativity

Question 15

Explain the allosteric model.

Answer 15

The allosteric model has two parts the low affinity O2 state and the high affinity O2 state.

Question 16

What is an allosteric regulator for hemoglobin?

Answer 16

BPG, it modulates hemoglobin’s binding of oxygen

Question 17

What is to be said regarding BPGs charge?

Answer 17

it is heavily negatively charged

Question 18

If we have allostery what do we also have?

Answer 18

allostery regulation

Question 19

What helps us get rid of affinity?

Answer 19

BPG, as an allosteric regulator

Question 20

why does hemoglobin have cooperativity?

Answer 20

because it has quaternary structure

Question 21

BPG binds at what in hemoglobin?

Answer 21

It binds at histidine

Question 22

The Bohr effect explains what?

Answer 22

how hemoglobin delivers oxygen to metabolically active tissues

Question 23

What shifts the curve?

Answer 23

a change in pH
proton changes conformation of protein so its in the high affinity state

Question 24

what delivers more O2 more efficiently?

Answer 24

tissues versus lungs

Question 25

How is the proton released to lower pH according to the Bohr effect?

Answer 25

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

Question 26

How does a fetus get oxygen from its mother’s blood?

Answer 26

from other globin genes in the human genome

Question 27

Describe the protein that the fetus uses in order to get oxygen from the mother.

Answer 27

It uses a different protein that has a different structure and function.

Question 28

Describe the O2 flow from the fetus to its mother.

Answer 28

O2 flows from the mom’s oxyhemoglobin and to the fetus’ deoxyhemoglobin

Question 29

What type of disease is correlated with the shape of the red blood cells? And why?

Answer 29

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