Chapter 3, Globular Proteins Flashcards
Heme contains conjugated double bonds (double bonds alternating with single bonds); these double bonds are responsible for the color of what?
human blood
Protein without a prosthetic group is called…?
apoprotein
Myoglobin functions in the storage and transport of oxygen in the heart and skeletal muscle cells.
- The oxygen diffuses through the ________ membrane and binds to (deoxy) myoglobin, generating oxymyoglobin.
- The oxymyoglobin diffuses to the __________ and releases the oxygen.
- The deoxymyoglobin then diffuses to the _______ _______, and is available to pick up additional oxygen.
- myocyte
- mitochondria
- plasma membrane
The 4 nitrogens of the heme group bind the Fe2+ nearly in the plane of the ring, leaving the 2 remaining positions of Fe2+ available for binding perpendicular to the plane of the heme. One binds a ________ residue of globin, while the other is available to bind to ________.
histidine, oxygen
Hemoglobin is found only in ________ and its primary function is the transport of oxygen from the _______ to the _______ of tissues.
erythrocytes (RBCs)
lungs to the capillaries
What is the diameter and lifespan of erythrocytes?
Diameter - 7.3 microns
Lifespan - 120 days
How many hemoglobins are there per erythrocyte?
280 million
What do we refer to as the percentage of blood volume occupied by red blood cells?
Hematocrit
- 38-46% Female
- 42-53% Male
Each hemoglobin subunit has a ________ core and a ________ exterior.
hydrophobic core
hydrophillic exterior
Hemoglobin has 4 polypeptide chains, each with its own heme. Major adult human hemoglobin consists of __ alpha and __ beta chains.
2 alpha, 2 beta
Hemoglobin (Hb) is a tetramer consisting of 4 subunits. It is also a dimer of a dimer (alpha-beta)1 and (alpha-beta)2. How are the alpha and beta chains primarily bound to each other?
hydrophobic interactions
What are the two attachments to the iron other than the heme?
*Proximal histidine binds directly to iron
*Distal histidine is involved in stabilization of oxygens binding to iron
(Association and Dissociation is known as Oxygenation)
Dimer 1 and 2 are held together by weak ionic and hydrogen bonds. Describe the relationship between oxygenation and strength of the subunits.
Interactions between subunits are weaker in oxyhemoglobin than deoxyhemoglobin. The addition of oxygen makes them weaker.
What is the difference between T and R structures of hemoglobin?
T = Taut is used to describe the structure of DEOXYhemoglobin R = Relaxed is used to describe the structure of OXYhemoglobin
Which as a greater affinity for oxygen, T or R?
R (relaxed) has a higher affinity for oxygen and more freedom of movement
Describe the curves myoglobin and hemoglobin.
myoglobin - hyperbolic
hemoglobin - sigmoidal
Hemoglobin exhibits changes in ligand (oxygen) affinity under the influence of small molecules. This makes it what type of protein?
allosteric
Allosteric effectors may be either positive or negative effectors. Name the four that were discussed.
- H+
- CO2
- 2,3-BPG
- O2
A decrease in pH results in _________ oxygen affinity of hemoglobin and, therefore, a shift to the _______ in the oxygen dissociation curve.
decrease, right
Carbon monoxide shifts the oxygen dissociation to the _______.
left
An H+ is the way to let the body know you need more oxygen. Therefore, high acidity will ________ the release of oxygen from hemoglobin. This is known as what?
- increase
* The Bohr Effect
Actively metabolizing tissues can also release lactic acid and thusly ________ the release of oxygen from oxygenated hemoglobin.
increase or enhance
BPG binds to which conformation (T/R), which stabilizes it and decreases the oxygen-binding affinity.
T = Taut = DEOXYhemoglobin
A pneumonic device to help remember the different variables that shift the oxygen dissociation curve to the RIGHT, is what?
BE CATCH
B, 2,3-BPG
E, Exercise
C, CO2
A, Acidity
T, Temperature
CH, Carbaminohemoglobin
The weaker the binding to 2,3-BPG, the ________ the affinity for oxygen.
higher
Hb__ is the major hemoglobin found in the fetus and newborn. Hb__ synthesis starts in the bone marrow at about the eighth month of pregnancy and gradually replaces HbF.
HbF, HbA
Under physiological conditions, HbF has a higher affinity for oxygen than does HbA, as a result of HbF binding only weakly to what?
2,3-BPG
CarbaminoHb stabilizes which form of hemoglobin?
T
The ferrous iron in heme binds CO with an affinity over 200x greater than it binds oxygen, forming carbon monoxyhemoglobin. Oxygen is displaced by CO (competitive __________). Hb shifts to the R-conformation. The binding of CO at a single Hb oxygen binding site induces a conformational change in the molecule, increasing the oxygen affinity at the remaining three sites.
competitive antagonism
With carbon monoxide poisoning, you’re holding onto the oxygen, so your lips are ________. Hemoglobin has more oxygen, but the tissues don’t. If your lips are ________, from hypoxia, you’re not holding onto the oxygen and it’s being released more quickly.
red, blue
Carbon monoxide poisoning can be treated by ________ oxygen.
hyperbaric
Hb switching is controlled by a developmental _________.
clock
Why is the lifespan of a Hb molecule the same lifespan of the erythrocyte?
Bc it doesn’t have a nucleus
When glucose binds molecules non-specifically, they are known as Altered _________ End Products.
Glycation
Why was globin the first gene studied?
Bc it’s so readily available.
Alpha-Globin-like genes = Chromosome ___
Beta-Globin-like genes = Chromosome ___
Alpha - 16
Beta - 11
Does splicing remove the introns or the exons?
The introns are spliced and the exons make up the mRNA
- The human genome contains how many billion nucleotides?
- The human genome contains how many different genes?
- What percentage of the genome codes for proteins?
- 3.2 billion
- 20-25,000 genes
- Less than 2%
Mutations that reduce water solubility can lead to what disease?
Sickle-Cell anemia
Mutations that affect the processing/stability of the mRNA, or lead to increased proteolytic degradation of the globin chains are known as?
Thalassemia
Hemoglobin point mutations causing amino acid substitutions:
- Hemoglobin A -
- Hemoglobin S -
- Hemoglobin C -
A - Glu (Glutamate)
S - Val
C- Lys
- Hemolytic anemia
- Acute chest syndrome
- Stroke
- Jaundice - caused by massive death of red blood cells and accumulation of bilirubin
Symptoms of Sickle-Cell
Sickle Cell Disease Process:
- Point mutation in the Beta-Globin chain
- At low oxygen tension, the deoxy beta-globin of Hb S forms a network of fibrous polymers that distort the red blood cell
- The polymers are relatively unstable
- The repeated episodes of polymerization and depolymerization can damage the red blood cell
- The RBC membrane becomes rigid and can fail to move through small blood vessels
- Hemolysis occurs
Know this.
The median age of death among individuals who have sickle cell is 48 yeas for females and 42 for males. Patients who had ________ levels of fetal hemoglobin experienced a higher life expectancy.
higher
It has been speculated that administration of tiny amounts of _______ _______ might theoretically alleviate some of the problems of sickle cell.
carbon monoxide
There is a selective advantage for __________, who are less susceptible to malaria.
heterozygotes
Methemoglobinemia is characterized by the presence of higher than normal levels of _______ ______ in hemoglobin. Methemoglobinemia cannot effectively bind _________.
- Higher levels of Ferric Iron (Fe3+)
* Cannot bind oxygen
What is known as the most common single gene disorder in the world?
Thalassemia
The structure of the hemoglobin among individuals who have thalassemia is normal, however, the rate of synthesis is _________.
reduced
Beta-Thalassemia has two forms, minor and major. Minor is when you have one defective beta-globin gene and major is when you have both genes defective. Those with minor make some beta chains, and usually don’t require treatment. Those with major, appear healthy at birth, but become severely anemic and require blood transfusions. These mutations are found on which chromosome?
11
Alpha-thalassemia has several levels of chain deficiencies because each individual’s genome contains four copies of the alpha-globin gene.
- If one gene is defective, the individual is a _______ carrier.
- If two genes are defective, the individual has the _______.
- If three genes are defective, the individual has Hb H disease.
- If all four genes are defective, Hb ______ disease with hydrops fetalis and fetal death results, because alpha-globin chains are required for synthesis of Hb F.
- silent carrier
- trait
- Hb H disease
- Hb Bart
