Hemoglobin and iron metabolism Flashcards
 What is the Relationship between hemoglobin and heme? 
Hemoglobin contains heme
Is a conjugated globular proteins which constitutes 33% of RBC weight by volume
Hemoglobin
What is the weight percentage of hemoglobin in RBCs?
33%
_____% of hemoglobin synthesis occurs during nucleated stages of maturation
____% occurs during the reticulocyte stage
66
33
One hemoglobin molecule contains….
-two pairs of two different polypeptide chains (dimers) ie: 4 globin chains arranged as a tetramer
-Four molecules of protoporphyrin IX
-For iron atoms (Fe2+) that combine with protoporphyrin IX to form 4 heme rings
-one 2,3-BPG molecule (from RLP pathway) may or may not occupy the center of the entire hemoglobin molecule
what does 2,3-BPG help with?
Oxygen offloading
Normal hemoglobin production is dependent upon what three processes?
• adequate iron delivery and supply
• Adequate synthesis of protoporphyrins
• Adequate globin (to hold iron and heme) synthesis
Apo….
Vacant of iron
Fe has extremely ____ Bioavailability in food.
Low
*10-20 mg of iron/day, only 1-2 mg is absorbed
How does the body compensate for low bioavailability of iron? 
Recycles iron from degraded RBCs (Which has been stored in splenic macrophages) 
-no mechanism for excretion
about _____ of iron is in storage form - ferritin or hemosiderin in macrophages (very small amount in transferrin (Plasma carrier protein))
1/4
Where is iron stored? 
In macrophages in the spleen
Is ferritin or hemosiderin easier to use? 
Ferritin
Ferritin is made of a cylindrical protein called ______________, Plus the many iron atoms stuffed into it
Apoferritin
Apoferritin + Fe =
Ferritin
What is Apoferritin?
Ferritin without iron
When Fe is needed, _____ is released from ferritin and guts mucosal cells, this Fe Attaches to a special Fe transport proteins called transferrin.
Fe3+ (needs to be in this form)
Fe transport Protein
Transferrin 
Transparent can transport up to _____ Fe3+ Simultaneously through the plasma; It delivers Fe3+ into RBCs 
2 atoms
-transferrin is returned to cell surface for recycling
-Fe3+ is reduced to ferrous (Fe2+) in cytoplasm of RBC
A plasma proteins that transports ferric iron (Fe3+) to the developing RBCs
Transferrin
Iron (ferrochelatase) is actively carried across the RBC membrane to the mitochondria, where it is matched with _______________ to make heme. 
Protoporphyrin IX
He leaves the mitochondria and travels to the cytosol (Cytoplasm) To join the globin chains 
Protoporphyrin synthesis:
Begins with _______________
-By-product of the tricarboxylic acid cycle
succinyl coenzyme-A (COA)
Protoporphyrin synthesis:
CoA combines with glycine to form ______________
Where does it occur?
aminolevulinic acid
(ALA)
Mitochondria of pronormoblast and requires B6
Protoporphyrin synthesis:
ALA and ALA dehydrates combine to form __________.
Prophobilinogen (PBG)
Protoporphyrin synthesis:
Pathway continues until protoporphyrin IX Combines with _______________ to make heme. 
Ferrochelatase/heme synthase
The globin genes are transcribed into ______ In the nucleus of an immature (& still nucleated) RBC
mRNA
Chromosome 16 contains the ________ and _______ Globin genes. 
Alpha and Zeta (16 AZ) 
Chromosome 11 contains the _______ Globin genes and all others.
Beta (11B)
In Cytoplasm, mature mRNA transcript is translated at a __________ Into a polypeptide chain, which immediately begins to assume it’s secondary confirmation (And then it’s tertiary and then quaternary shapes) 
Ribosome
Refers to linear amino acid structure (Beads on a string). The amino acid in a polypeptide chain are numbered beginning with number one at the N(amino) Terminal, and ending at C – terminal
Primary hemoglobin structure (chain) 
- changes to secondary very quickly
Refers to the polypeptide chain arrangement in helical‘s and non-helical‘s.
Secondary structure
Of the secondary structure each chain is divided into _____ helicals and ____ nonhelical segments.
8, 7
The helices are separate and structurally rigid segments, designated by the letters ______ through ______. 
A, H
The non-helical segments are more _________ and lie between helical segments. This arrangement for a slight but real physical bending of the polypeptide chain
Flexible
This structure is it involves bending of non-helical. Refers to the roughly globular shape (like a pretzel)  that the secondary level of structure assumes spontaneously due to non-hydrogen bonds (such as sulfhydryl bridges) Formed between neighboring amino acid side chains
Tertiary Hemoglobin structure
(hold heme ring into these pockets)
At what point is one heme group inserted inside each of the four globin chains?
Tertiary structure
This structure refers to tetramer formed by association of two pairs of polypeptide chains
Quaternary structure
Quaternary structure:
Complete hemoglobin molecule is spherical, has ______ Heme groups attached to ______ Polypeptide chains, and can carry ______ Molecules of oxygen.
4, 4, 4
globin chains are assembled from…
Two pairs of polypeptide chains (Four chains per hemoglobin molecule)
What are the four primary chains that can be produced? 
Alpha, beta, gamma, delta
 many hemoglobin forms can be formed depending upon…
The combination of the two pairs of globin chains
What is fetal hemoglobin (F) composed of? And in what proportions? 
Two alpha and two gamma (AG)
Newborns- 80%
Adults- <1%
What is A1 hemoglobin composed of? And in what proportions?
Two alpha and two beta (AB)
Newborn- 20%
Adult-97%
What is hemoglobin A2 composed of? And in what proportions?
Two alpha and two delta (AD)
Newborn- <0.5%
Adult- 2.5%
During the first three months after conception, embryo produces what three embryonic hemoglobins?
Portland, Gower 1, and Gower 2
What globin chains is Portland composed of?
Zeta 2, gamma 2 (GZ)
What globin chains is Gower I composed of?
Zeta two, epsilon two
What globin chains is Gower II composed of?
Alpha two, epsilon two (AE)
When does fetal hemoglobin begin to be produced?
In the second trimester, Hepatic phase 
By birth, hemoglobin-F comprises about ______% of total hemoglobin with the remainder being hemoglobin A1
80
When is essentially all of a child’s Hemoglobin in the adult forms?
 by the first birthday
Hemoglobin can be modified by ___________ Binding of various sugars with the globin chains. What is the most common?
Non-enzymatic
Hgb A1c
a glycosylated hemoglobin that can tell how well diabetes is being managed. Glucose attaches to the N-terminal valine of the beta chain
Hgb A1c
What cells typically contain more hemoglobin A1C? What percentage is normal? 
Older cells (4-6% of Hgb A)
*increased with diabetes! (proportional to the mean glucose level over 2 to 3 months)
What is the main mission of RBCs?
• contain, transport, and protect hemoglobin molecules so that oxygen can be carried
Each hemoglobin molecule consists of ______ Globin chains and ______ heme groups, Each with a center iron molecule
4, 4
Each globe and chain has a ______________”pocket” Containing a heme group 
Hydrophobic (Protects heme and keeps it in the Fe2+ form)
The iron from each heme is directly bonded to ____________ Of the globin chain
2 histidines 
What is the function of proximal histidine?
To increase the oxygen affinity of the heme ring
What is the function of distal histidine?
To protect the iron in the ferrous state (hydrophobic pocket) Which diminishes the binding of carbon monoxide (CO)
- The exterior of the chain is hydrophilic which makes the molecule soluble
What is the first step of hemoglobin molecule assembly?
A Ferric (Fe3+) Fe Molecule (Originally obtained from ferritin, but being transported by transferrin) Is chemically reduced to the ferrous (Fe2+) Form in the nucleated RBC cytoplasm
Second step of hemoglobin molecule assembly?
Fe2+ is transported into mitochondrion and inserted into center of a protoporphyrin IX molecule (At this point the molecule can be called heme)
Protoporphyrin IX + Fe =
Heme
Step three of hemoglobin molecule assembly
Finished heme is released from the mitochondria back into the cytoplasm
Step four of hemoglobin molecule assembly
In the cytosol, finished alpha and beta globin polypeptide chains are released from nearby Ribosomes
Step five of hemoglobin molecule assembly
One heme molecule is inserted into each globin polypeptide
Step six of Hemoglobin molecule assembly
Alpha and beta chains quickly form dimers and then dimers quickly form a tetramer (4° Structure) 
Step seven of hemoglobin molecule assembly? 
One 2,3-BPG/DPG molecule is inserted into the central cavity of each finished hemoglobin molecule as needed
When Fe is low, [FEP] goes _____.
Up
What to test measure Excess protoporphyrin Left over in mitochondria when iron supply is diminished. It becomes complex to zinc, then shipped out into cytoplasm 
FEP (Free Erythrocyte Protoporphyrin)
Zinc Proto-porphyrin
What are the three major functions of hemoglobin
• transport of oxygen
• Transport of CO2
• Buffering the blood
What are the allosteric affects of hemoglobin?
• cooperative binding binding of oxygen
• regulation of oxygen affinity by 2,3-BPG
•Bohr effect 
The binding of one O2 molecule causes it increased infinity of the other heme groups for additional O2 molecules. What is this called?
Heme-heme interaction
The more O2 hemoglobin binds, the ___________ it’s Affinity for O2 becomes
Greater
At any time a heme molecule may be carrying ___________ O2 molecules. As O2 binds to a heme group, that heme group shifts slightly, and this overall shape change then encourages another oxygen molecule to bind to another nearby heme. 
1, 2, 3, or 4
Hemoglobin saturated with O2
Oxyhemoglobin
Hemoglobin without bound O2
Deoxyhemoglobin
Hemoglobin with CO2
Carbaminohemoglobin
Hemoglobin with CO2 bound
Carboxyhemoglobin
oxygen __________ occurs in tissues and is regulated, in part, by the oxygen affinity of hemoglobin
Tension
(you get tense when you need oxygen) 
Oxygen _________ occurs in the RBC and is modulated by the concentration of phosphates in cell
Affinity
-in areas of Hypoxic tissue, as oxygen moves from Hemoglobin into the tissues, the amount of reduced hemoglobin decreases resulting in reduced oxygen affinity
If tissue hypoxia persists, the depletion of ________ Leads to increased glycolysis and production of more _________, Which will further lower hemoglobin oxygen affinity
2,3-BPG (both blanks)
What pathway produces 2,3-BPG?
RLP
This is an allosteric regulator of hemoglobin, which diminishes the affinity of hemoglobin for oxygen
2,3-bisphosphoglycerate (2,3-BPG)
It binds between beta chains of hemoglobin A1 via salt bridges when hemoglobin is in a more unoxygenated state (aka. Tense or “T” form) 
2,3-BPG
The binding process of 2,3-BPG moves Beta change slightly further apart and results in a shape change causing _________ O2 Affinity, such that any remaining bound O2 is preferencially “offloaded”into the tissues
Decreased
Explain the process of relaxed or “R” form
What’s the deoxyhemoglobin reaches the lungs, however, the binding of O2 to heme is a greater Force then the weak bonds holding the 2,3-BPG Inside the hemoglobin. As a result hemoglobin A-1 becomes oxygenated (“relaxed” form) and the resulting heme-heme Interaction causes 2,3-BPG to be Expelled
 what happens when salt bridges are broken?
Beta chains move closer and the shape change then permits further binding of additional O2 molecules. This results in increased O2 uptake and increased oxygen affinity
Breaking of the salt bridge allows what to happen?
Allows oxygen to be bound
• The salt Bridge keeps 2,3-BPG in place?
Tense form equals..
______ 2,3-BPG and
______ oxygen infinity
______ Oxygen offloading (in tissues) 
Increased
Decreased
Increased
Relaxed form equals…
______ 2,3-BPG
______ Oxygen affinity
______ Oxygen uptake (in lungs)

No
Increased
Increased
What contributes to hemoglobins ability to bind large quantities of oxygen, but also to release oxygen we needed
This is a result of the quaternary structure changes
- look at oxygen disassociation curve
The affinity of hemoglobin for O2 depends on the….:
Partial pressure of O2 (PO2)
What is P50 value?
O2 needed to saturate 50% of hemoglobin
What does the oxygen disassociation curve plot?
Plots the O2 content of hemoglobin (% Saturation) Versus the PO2
(Myoglobin to the left and hemoglobin to the right)
A shift to the right of the oxygen disassociation curve is…..
__________ Oxygen affinity
Decreased (Tends to offload oxygen)
- Giveaway 02 with my right hand
In hypoxia, where would a shift to the right occur?
In the tissues
What Can cause a shift to the right on the oxygen disassociation curve?
•Increase CO2
• decrease pH
• Increased 2,3-DPG
• Increase in body temperature
-Oxygen binding heme protein present in cardiac and skeletal muscle
-greater oxygen affinity than hemoglobin, and not as effective in releasing oxygen to the tissues
-Normally flushed through kidneys
-can be distinguished from Hemoglobinin the urine
Myoglobin
What are the three methods carbon dioxide is transported from the tissues to the lungs
• dissolution directly into the blood (Not often)
• Binding to hemoglobin- carbaminohemoglobin (Not often)
• Carried as a bi carbonate ion (about 75%) 
_____ and _____ promote the release of oxygen from the hemoglobin molecule
• Enhances the release of oxygen in tissues
H+ and CO2
Each red blood cell contains this enzyme that catalyzes the conversion of CO2 (Given up by tissues) and H2O, to produce carbonic acid (H2CO3)
Carbonic anhydrase (CA) 
In the lungs, binding of oxygen releases H+ and displaces bound _________
Hgb-CO2
HCO3- + H ———-> CO2 + H2O
About ____% Of the blood CO2 is converted to bicarbonate and H + ions
90
About ____% of CO2 in arterial blood is physically dissolved in plasma
5
About ____% of CO2 known as carbaminohemoglobin, Is carried in blood bound to amino groups of plasma proteins.
5
What are the two ways the amount of oxygen reaching the tissues can be regulated by?
• changing the number of circulating RBCs with a change in the rate of erythropoiesis
•Altering the affinity of hemoglobin for oxygen
what are the six factors that affect hemoglobin‘s affinity for O2
• body temperature
• pH (Bohr effect)
•2,3-BPG/DPG
•CO2
•Fetal Hgb
•Abnormal Hgb Variants 
An increase in body temperature will cause _____________ in O2 Solubility. 
Decrease
*Helps movement of O2 off hemoglobin 
 Phenomenon in which increase pH causes a left shift
Bohr effect
*High pH, 02 uptake in hemoglobin is favored
( think “pH is Bohring”) 
In the lungs where pH is higher, 02 uptake by hemoglobin is…..
Increased
- PH is lower in the tissues that causes O2 release by hemoglobin
2,3-BPG/DPH =tense form = __________ O2 affinity and ___________ 02 offloading. 
Decreased, Increased
*in tissues (think tense in the tissues)
Phenomenon in which increased CO2 causes right shift, encouraging 02 release (And vice versa)
Haldane effect
Increased CO2 causes ________ shift, Encouraging 02 release
Right
(Haldane effect is due to CO2)
 does A1 or F hemoglobin upload O2 more easily? 
F hemoglobin
How does abnormal hemoglobin variants affect affinity for O2?
These Hemoglobin may shift more to the right or to the left than A1 Hgb would
carboxyhemoglobin results from the binding of ____ To hemoglobin.
CO (not CO2)
CEO binds to hemoglobin at a rate of ______X Higher than regular O2. so asphyxiation Results in a matter of minutes
What shift would this cause?
200
Left
What color is carboxyhemoglobin? 
Hallmark cherry red color (Does not offload Easley) 
What is the most common source of carboxyhemoglobin?
Death can result when concentrations reach what percentage of normal hemoglobin?
Auto exhaust
50-70% (normal is less than 1%)
Form of hemoglobin that contains iron in the ferric state (Fe3+)
Methmoglobin 
(measured spectrophotometry in whole blood)
What is the color of methmoglobin? 
What is it commonly associated with?
Brownish to bluish color
Nitrites and genetic disorders
(measured spectrophotometry in whole blood)
Accumulation of methmoglobin produces a shift to the ________, Resulting in….
Left
oxygen not being delivered efficiently to the tissues
What hemoglobin conversion is permanent for the life of the cell and has a green pigment?
sulfhemoglobin
(measured spectrophotometry in whole blood)
-Formed by the oxidation of hemoglobin by drugs or chemicals
-displays 100 times less affinity for oxygen then unmodified hemoglobin
Sulfhemoglobin (usually from sulfa drugs) 
In extravascular hemolysis, hemoglobin is broken down into….
Heme, iron, and globin 
Extravascular hemolysis:
Heme iron is stored as __________ or __________ within macrophages until needed ——> transferrin and cycle Continues. 80% of transferrin
-Globin is broken down and returns to the amino acid pool
Ferritin, hemosiderin
Extravascular hemolysis:
Component of heme converts to bilirubin (released into the plasma and excreted by the liver in bile) 
Protoporphyrin
Extravascular hemolysis:
Is exsecreted from the liver into the small intestine via the bile duct where it is converted by bacterial flora to urobiligen
Conjugated bilirubin
Most urobilinogen is excreted in the stool as _________. 10% to 20% is reabsorbed by the gut. 
Urobilin
With liver disease, the enterohepatic cycle is impaired and increased amounts of ____________ Is excreted in the urine. 
Urobilinogen
In intravascular hemolysis cell contents are released into the plasma. ____________ and ___________ work to salvage they released hemoglobin, so the iron is not lost.
They carry the hemoglobin to the liver, where it is broken down to bilirubin. 
Haptoglobin, hemopexin
A decrease in serum __________ may be used to indicate intravascular hemolysis.
If haptoglobin is depleted, free hemoglobin is filtered by the renal glomerulus. 
Haptoglobin
