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Heme structure

It had an Fe atom in center surrounded by amino acids. It has a prosthetic "Heme" group in the middle.

1

What are the two different types of heme groups?

Myoglobin (monomer)- major oxygen-carrying protein in muscles

Hemoglobin- carries oxygen in blood (4 groups=tetramer)

2

The heme group of hemoglobin coordinates with which atom?

Iron

3

How many heme groups are in hemoglobin?

4

4

Myoglobin has _____affinity for oxygen than Hemoglobin.

Higher affinity for oxygen than hemoglobin. As the increase of partial pressure of oxygen the amount of oxygen down to molecules rises very quickly and become saturated at 30mm of oxygen.

Myoglobin takes oxygen from hemoglobin.

5

Hemoglobin has______ affinity then myoglobin does.

Lower affinity for oxygen than myoglobin.

Hemoglobin delivers oxygen to the tissue so it has a lower affinity for oxygen than myoglobin.

Hemoglobin will grab oxygen in the lungs, and let go of the oxygen and give it to the tissue in the body, which is the myoglobin.

6

A prosthetic group of a protein is a non-protein structure that is:

Permanently associated with the protein

7

In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen in the fraction of the binding site occupied can best be described as:

Hyperbolic

8

Cooperativity is:

The way in which hemoglobin and myoglobin react to the partial pressure of oxygen.

9

How will myoglobin react in Hill Curve of we increase oxygen partial pressure?

Myoglobin will not change it because it will stay in the linear line. Myoglobin is a monomer that will not change or be affected if the partial pressure of oxygen is increased. It will not bind more since it is a monomer.

10

How will Hemoglobin change in a Hill curve if the partial pressure of oxygen increases?

Hemoglobin is a tetramer that will start off in a linear line, until at a certain point. At this point the partial pressure of oxygen has increased and caused an increase binding to Hemoglobin.

The affinity increases. At this stage hemoglobin will be higher affinity than myoglobin

11

What happens in cooperativity for hemoglobin, when increasing partial pressure?

Hemoglobin: 1st oxygen binds to the T state and in the low state because it doesn't really want to bin

2nd oxygen weakly binds as well

Then this will flip to the R state and quickly grab 3rd and 4th oxygen for hemoglobin.

This shows the Hill Curve plot.

12

What is the T and R state for hemoglobin?

T state (taut or tense) is low ligand bound affinity

R state( relaxed) is high ligand binding

Changes 15 degrees from T to R state

13

This change in shape is from T and R state are due to:

The Heme is attached to a distal histidine and a proximal histidine. The proximal histidine is directly coordinates with Fe. The distal histidine is not coordinated with Fe but will hydrogen bond with oxygen that does coordinate with Fe.

Heme is associated with proximal and distal Histidines.

14

How does Heme look in the T state?

It looks puckered.

4 atoms in Heme and 1 proximal histidine

No 6th activation site so it is "puckered." No oxygen so Fe is bound to 5 other atoms.

15

How does heme look in the R state?

It is pulled slightly which will change shape slightly. Once oxygen is bound, the Heme goes to plain.

Binding of oxygen causes slight shift in His F8 which will cause amplified shift of entire protein.

16

Are the myoglobin. Alpha hemoglobin, and Beta hemoglobin the same or different?

These three molecules have significant differences BUT they are very similar in shape.

17

When oxygen binds to a heme- containing proteins, the two open coordination bonds of Fe 2+ are occupied by:

One molecule O2 and one amino acid atom

18

Myoglobin and the subunits of hemoglobin have:

Very similar tertiary structures, but different primary structures

19

In hemoglobin, the transition from T State to R state (low to high affinity) is triggered by:

Oxygen binding

20

Carbon monoxide does what to the hemoglobin?

Carbon monoxide will binds to hemoglobin in the place of oxygen. Carbon dioxide hemoglobin is more stable than oxygen hemoglobin and a small amount of carbon monoxide will outcompete for oxygen in the hemoglobin. Carbon monoxide binds more tightly to the heme then iron.

21

How much carbon monoxide and will be present in the average person?

1 % because car exhaust are going to cause this carbon monoxide concentration the body.

1% is CO-Hb

22

How much carbon monoxide will smokers have?

10% of smokers hemoglobin is CO-Hb

23

What is Met- hemoglobin?

It is Fe3+ and does not bind oxygen

24

What binds met – hemoglobin but not Fe2+ hemoglobin?

Cyanide

It binds to cytochromes in the mitochondria tightly but doesn't bind hemoglobin tightly.

Antidotes for Cyanide is to give a substrate that changes the Fe+2 to Fe +3 which will cause the hemoglobin to bind the cyanide and prevent it from getting into the mitochondria of our cells. This is particularly helpful for brain cells.

25

The interactions of ligands with proteins

Are usually transient ( short time)

26

An allosteric interaction between a ligand and a protein is one in which:

Allosteric-
relating to or denoting the alteration of the activity of a protein through the binding of an effector molecule at a specific site.

Binding of a molecule to a binding site effects binding properties of another site on the protein