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Chem/Phys Final Exam 4 > Hemoglobin > Flashcards

Flashcards in Hemoglobin Deck (38)
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1

Hemoglobin is an allosteric oxygen-binding protein. What does this mean?

Allosteric- combines at another site, not at the active site
- The cooperative binding is due to this effect, binding to one site affects the binding at another site*

2

Main task of hemoglobin?

1. Carry oxygen from the lungs to tissue for cellular respiration
2. It consists of 4 subunits total:
- 2 alpha subunits (141 amino acids each)
- 2 beta subunits (146 amino acids each)

Therefore, it is a tetramer (tetra=four)
Each subunits contains a heme moiety which can bind 1 oxygen

3

A single hemoglobin molecule can bind up to _________ oxygen molecules

4

4

When hemoglobin binds to oxygen, what happens to the subunits?

1. Slightly shift and a conformational change occurs

5

Note the conformation difference between oxy and deoxyhemoglobin including the size of the cleft?

1. Cleft gets smaller in oxyhemoglobin

6

Oxygen molecules bind to hemoglobin in a _________ fashion

1. Cooperative Fashion
-the first oxygen bind to hemoglobin with the lowest affinity
- each successive oxygen binds with higher affinity
-initially hemoglobin is reluctant to take up oxygen, but oxygen affinity increases with each oxygen molecule uptake
- this causes oxygen uptake curve to be sigmoidal (s shaped)

7

In the lung, where oxygen tension is relatively high, what happens to hemoglobin?

1. It is nearly saturated with oxygen

8

In deep tissues where oxygen tension is low, what happens to hemoglobin?

1. It releases half of its oxygen

9

Ligation of protoporphyrin IX with an iron atom (Fe) results in the formation of what?

1. Heme
-Note that the 4 bonds to Fe are to the nitrogens (coordination site) of the protoporphyrin group
-in hemoglobin, the 5th Fe bond is to a histidine residue in the protein portion, the 5th coordination site
-When O2 is present, it binds to the 6th coordination site of Fe

10

What charge does Heme have?

+2 charge, positive charge

11

Deoxyhemoglobin

1. Fe 2+ is not bound in deoxy form, but will bind O2 and CO when each is present
2. Ferrous iron- no ligand on 6th site of iron

12

Oxyhemoglobin

1. Ferrous iron is bound to oxygen
2. After one O2 is bound, others bind more readily because of conformational change

13

Carboxyhemoglobin

1. Ferrous iron is bound to CO
- this forms a stronger bond that with O2

14

Methemoglobin

1. The iron is in the ferric form and will not bind to O2 or CO.
2. Oxidation of Fe 2+ to Fe 3+ is caused by oxidants such as chlorite S, nitrates, NO

15

Fe++ or Fe 2+

Ferrous iron

16

Fe +++ or Fe +3

Ferric iron (non functional hemoglobin)

17

Sulfmethemoglobin

Fe 3+ --- SH
Rare, in H2S toxicity, blood is purple to green color
Can occur due to medication

18

Cyanmethemoglobin

Fe 3+ ----- CN
Occurs in cyanide poisioning
Iron must be ferric before it will bind to CN
This property of methemoglobin an be used in cyanide poisioning to sequester CN
Has negative charge

19

Fetal Hemoglobin

1. Differences in protein portion
2. Normally present in fetus before birth, it has slightly higher affinity for O2 than adult hemoglobin (left shift)
3. Mother nature making sure baby is taken care of before the mother

20

Oxygen Saturation

Percentage based on volume
SaO2= [Blood oxygen content (ml/dl)/ blood oxygen capacity (ml/dl)]X 100

21

SaO2 refers to _______ oxygen in red blood cells

Arterial oxygen
Small amount of dissolved oxygen is substrated
SaO2 is independent of the amount of Hb present or forms of Hb present

22

Blood oxygen content equation

1. Concentration of Hb X % saturation of hemoglobin + O2 solubilized in the plasma

Equation:
Oxygen content (ml/dl)= Hb (g/dl) X So2 X 1.34 (ml/g) + (.003 x Po2)

23

SO2

Percentage of oxygen saturation (%)

24

PO2

Partial pressure of oxygen (mmHg)

25

1.34

Molar oxygen capacity of Hb (ml O2 bound at full saturation)

26

.003

Solubility coefficient of oxygen in plasma (ml/dl/mmHg)

27

Blood Oxygen Content in "Volumes Percent"

1. A normal person has about 15 grams of hemoglobin/100 ml of blood
2. Each gram of Hb can bind a maximum of 1.34 ml of O2

28

On average, the hemoglobin in 100 ml (dl) of blood can bind up to ______ ml of O2?

1. 20 ml
2. 20 ml of O2/dl blood= 20%

29

PO2 and Volume % in Oxygen in Blood

1. FUll saturatio= 20%
2. The effect of PO2 on the quantity of oxygen bound w/ hemoglobin in blood
3. Note: in normal venous blood hemoglobin has released not more than half of the oxygen
4. Sigmoid curve

30

Right shift of Oxygen-hemoglobin dissociation curve- what does it mean and what causes this?

1. Right shift= hemoglobin has less affinity for oxygen
2. Shift to the right is caused by: increased H ions, increased CO2, increased temperature, increased 2,3 DPG, a metabolic product. DPG binds to the enlarged cleft of deoxyhemoglobin
The effect of H+, CO2, and DPG favors release of oxygen in tissues where it is needed