lecture nine - blood proteins, hemoglobin

Question 1

5 major classes of extracellular proteins found in the blood?

Answer 1

albumin, alpha-globulin, beta-globulin, gamma-globulin, fibrinogen

Question 2

albumin

Answer 2

osmotic regulation and fatty acid transportation

Question 3

alpha-globulin

Answer 3

lipoprotein, used in ion and hormone transportation, protease inhibitors, hormone inhibitors, also involved in the body’s inflammatory response

Question 4

beta-globulin

Answer 4

lipoprotein, heme and iron transportation; heme cofactors

Question 5

gamma-globulin

Answer 5

used for antibodies; the body’s first line of defense against a variety of foreign organisms and molecules

Question 6

fibrinogen

Answer 6

used for blood clotting

Question 7

which class consists of only one protein

Answer 7

albumin

Question 8

which class (x2) contain multiple proteins

Answer 8

alpha globulin and beta globulin

Question 9

which blood proteins contain lipoproteins

Answer 9

alpha- and beta-globulin

Question 10

highest concentrated blood protein

Answer 10

albumin

Question 11

what is the function of fibrinogen?

Answer 11

used to produce fibrin which is used in blood clotting, inactive precursor protein and is activated in proteolysis (by fibrin) during the blood clotting processes

Question 12

two major functions of serum albumin

Answer 12

two major functions: osmotic regulation and fatty acid transport

Question 13

what does it mean that albumin has an osmotic effect?

Answer 13

osmotic effect because it helps regulate when water flows into and out of the cell

Question 14

what is the physiological function of the binding of fatty acids by albumin?

Answer 14

fatty acids bind to the hydrophobic areas of albumin, this prevents fatty acid plaques from forming in the bloodstream

Question 15

what are lipoproteins?

Answer 15

complexes of protein and lipids that are involved in the transport of phospholipids, triglycerides, and cholesterol through the bloodstream

Question 16

HDL

Answer 16

more protein, less lipid; small but very dense

Question 17

VLDL

Answer 17

highest amount of lipids, least amount of proteins; least dense

Question 18

LDL

Answer 18

intermediate amounts of lipid and protein; large and less dense

Question 19

chylomicrons

Answer 19

large lipoproteins that transport triglycerides from intestine to the lymph

Question 20

which lipoprotein helps limit the amount of cholesterol in the blood/plays a positive role in reducing the deposition of cholesterol in the arteries?

Answer 20

HDL limits the amount of cholesterol in the blood by picking up lipids from the bloodstream and carrying back to the liver; or gives to LDL

Question 21

what lipoprotein fraction increases the deposition of cholesterol in the arteries?

Answer 21

LDL increases deposition of cholesterol in the arties

Question 22

lipoprotein fraction that has the largest particles, lowest density, and carries triacylglycerols from the intestinal cells to adipocyte tissue

Answer 22

VDL

Question 23

how do certain protein components serve as “address labels” during the delivery of lipoprotein particles to tissues?

Answer 23

apoproteins are specific cell-targeting proteins of lipoproteins

Question 24

how do LDL particles get transported into target cells?

Answer 24

receptor-mediated endocytosis: LDL binds to a receptor and this causes endocytosis – takes LDL into the cell
LDL is then broken down into the cell and the components are used for the biosynthesis of other molecules

Question 25

what are the chemical features of cholesterol, and in what modified form cholesterol is deposited in atherosclerotic plaques?

Answer 25

VERY nonpolar lipid molecule
3 fused 6-m rings, 1 fused 5-m ring
NOT aromatic, NOT planar
cholesterol esters are deposited in the fatty acid plaques of atherosclerosis

Question 26

good cholesterol

Answer 26

HDL; decresed risk of cardiovascular disease

Question 27

bad cholesterol

Answer 27

LDL; correlates with increased risk of CV disease

Question 28

familial hypercholesterolemia

Answer 28

hereditary, defect in LDL receptors; reduces/prevents ability to carry out receptor-mediated endocytosis

Question 29

HDL deficiency

Answer 29

results from lack of ABC1 protein
in cells lacking this protein, there is a lack of uptake of cholesterol by HDL particles, and the cholesterol-poor HDL particles are rapidly destroyed

Question 30

major function of red blood cells

Answer 30

constitute 40% of the volume of human blood; highly differentiated cells whose major function is to transport oxygen from the lungs to the tissues

Question 31

how does hemoglobin contribute to function of RBCs?

Answer 31

the biconcave disks are loaded with hemoglobin protein; hemoglobin binds the oxygen to the red blood cell by means of being carried by the iron ion of the heme group of hemoglobin

Question 32

what does it mean that Hemoglobin is a tetrameric protein consisting of two alpha and two beta subunits?
does this have anything at all to do with alpha and beta sheets?

Answer 32

there are four chains and each chain has a heme group
NO, this has nothing to do with alpha and beta sheets

Question 33

what is a heme cofactor, and how do the four heme cofactors play a role in the transport of oxygen by hemoglobin?

Answer 33

heme cofactor is present in hemoglobin and myoglobin
it is a tetrapyrrole structure with a ferrous ion at the center; the tetrapyrrole group has a series of alternating single and double bonds which gives it the ability to delocalize electrons
interaction of the organic tetrapyrrole structure with the iron ion promotes the ability of iron to bind molecular oxygen

Question 34

hemoglobin vs myoglobin

Answer 34

hemoglobin contains two alpha and two beta subunits; myoglobin only contains alpha subunits

myoglobin exists in the muscle with the role to pick up oxygen released from hemoglobin and hold onto it until needed for metabolic purposes

hemoglobin exists in the blood and oversees transporting oxygen around the body

Question 35

what features of hemoglobin allow it to exhibit allosteric regulation in contrast to myoglobin which does not exhibit this behavior?

Answer 35

when one subunit in hemoglobin binds oxygen, a conformational (allosteric) change occurs in the whole complex, and the other subunits exhibit increased affinity for oxygen
when oxygen binds to iron in the center of the heme group of one subunit, this changes the entire complex and so all the subunits change to bind to oxygen

Question 36

explain hemoglobin exhibiting positive cooperativity

Answer 36

binding of the first oxygen influences the binding of the next 3 oxygens in a favorable way

Question 37

tense vs relaxed state of hemoglobin with respect to its allosteric oxygen binding properties?

Answer 37

the tense state has poor oxygen binding
the relaxed state has increased binding ability and so upon binding of one oxygen molecule, all 4 subunits switch to the relaxed state

Question 38

how does the hyperbolic binding of oxygen to myoglobin and the sigmoidal binding of oxygen to hemoglobin relate to the physiological functions of these two proteins?

Answer 38

myoglobin functions in muscle tissue, its role is to pick up oxygen released from hemoglobin and hold onto it until it is needed for metabolic purposes; exhibits a classical hyperbolic oxygen binding response

hemoglobin is required to bind oxygen when the blood diffuses through the lungs and to release the oxygen when the blood circulates in tissues; needs to be able to pick up oxygen efficiently from the capillaries of the lungs but it also needs to release the oxygen efficiently in the tissues

Question 39

sigmoidal-S shape binding response is characteristic of

Answer 39

an allosteric protein

Question 40

what happens to the iron atom in the heme cofactor of hemoglobin when oxygen binds, and how does this change trigger an allosteric transition in the hemoglobin protein?

Answer 40

the size of the iron atom is reduced, and the iron enters the plane of the heme complex
the associated histidine imidazole group is pulled toward the face of the heme ring, and the movement of that histidine imidazole draws the F-alpha-helix closer to the heme ring

Question 41

the major form of hemoglobin proteins found in embryos, fetuses, and adult red blood cells

Answer 41

embryos = HbE (2 sigma, 2 epsilon subunits)
fetuses = HbF (2 alpha, 2 gamma subunits)
birth - end of life = HbA (2 alpha, 2 beta)

Question 42

Bohr effect

Answer 42

says that a decrease in pH promotes oxygen release from hemoglobin

Question 43

how do changes in pH influence the oxygen binding affinity of hemoglobin?

Answer 43

because of the high CO2 concentration in the tissues, the pH is lower than in the lungs; the lower pH decreases the affinity of hemoglobin for oxygen and promotes oxygen release into the tissues

Question 44

how does the binding of 2,3-bisphosphoglycerate change the oxygen binding curve for hemoglobin?

Answer 44

BPG stimulates O2 release by stabilizing the quaternary structure of deoxyhemoblobin; this increases the sigmoidal allosteric nature of hemoglobin

Question 45

what genetic change in the structure of hemoglobin occurs in sickle cell anemia, and how does this change alter the molecular interactions of hemoglobin molecules?

Answer 45

in sickle cell anemia, the hemoglobin beta chain, glutamate is replaced with valine, resulting in a hydrophobic “sticky” patch on the surface
this sticky patch can cause HbS tetramer (rope-like structure that distorts the RBC into the classic sickle shape) to polymerize and form long, stiff rods within the red blood cells
this can lead to extensive cell lysis, and prevent oxygen from being able to bind, which leads to death of the molecules