Chapter 6 Bio Myo and Hemoglobin Flashcards
Myoglobin general
Globular protein found in skeletal muscle and cardiac muscle. Higher O2 affinity than hemoglobin. Store O2 and uses it as a reserve for when demand cannot be met by Hb.
High amounts of myoglobin allow organism to hold their breath for an extended time under water.
Myoglobin structure
O2 is bound on a heme group found on its single polypeptide chain. 80% alpha helix. No quaternary structure, monomer of 1 chain. Folding of Mb chain places the nonpolar residues on the interior. Polar aa residues are exterior, making Mb a H20 soluble globular protein.
Globular proteins
Hydrophilic and H20 soluble
Heme group
prosthetic group, non protein part. Sits on a crevice lined by nonpolar aas. Fe contain protein responsible for the colour of meat.
Muscle injury myoglobin
Myoglobin is released into the blood within 2-3 hours. 10 hours after injury, Mb levels peak. Sometimes excreted through urine.
Mb can bind only one molecule of O2 since it contains one heme group.
Hemoglobin (Hb)
4 polypeptide chains, 2 alpha and 2 beta
1,2,3 structure similar to Mb. Each chain has a heme group with it’s own Fe2+ ion. When Hb is deoxygenated, BPG is held in the central cavity.
Hb can bind to __ also.
Carbon monoxide and Carbon dioxide.
HbCO and HbCO2
Carboxyhemoglobin and carbaminohemoglobin
Hemoglobin main job
Transport O2 from the lungs to the tissue capillaries. Exclusively found in RBC. Tetramer
HB Cooperative binding
When O2 binds to Hb, many salt bridges are broken which causes conformation to change. O2 binds more easily. HB is an allosteric protein.
Binding in Mb is not cooperative.
When 4 O2 molecules are bound, the other subunits release more readily.
Release of O2 Mb vs Hb
Mb shows no change in O2 binding over a wide pH and CO2 range.
Hb dumps its O2 off when in need (during rapid muscle contraction).
Bohr effect
CO2 and H promotes the release of O2 or Hb has decreased it’s affinity for O2. Hb’s oxygen binding decreases as the amount of CO2 and H+ increase.
Low pH effect on hemoglobin
Shifts its curve to the right. It dumps off it’s O2.
BPG (2,3-DPG) and Hb
Increase binding capacity of Hb by a factor of 26. BGP molecule is synthesized from an intermediate in the glycolysis pathway. It binds to the positively charged groups on the beta chain of the deoxy form of Hb.
Hb shift to the right
Hb is releasing of fO2 to the tissues in need
Fetal Hb
Has a higher O2 affinity than does adult Hb
1) Adult has 3 alpha chains and 2 beta chains
Fetal Hb has 2 alpha chains and 2 gamma chains
2)Fetal Hb binds BPH less strongly than does adult Hb
HbFetal and BPG
HbF does not hold BPG as tightly. Preferred conformation will be to have O2 dumped off
Hb curve for HbFetal is shifted to the left since it will keep its O2
Mb vs Hb O2 dissociation curves
Mb- hyperbolic
Hb- sigmoidal
Mb holds on to O2 tigheter and with higher affinity
The Haldane Effect
The deoxyform of Hb increases its ability to carry CO2. The removal of O2 from Hb will increase its affinity for CO2.
Hb-CO2 = carbamino hemoglobin. Co2 binds to the amino groups of lysine and arginine residues in H.
What shifts the Hb curve to the right?
Increase in temp, BPG, CO2, H+ or decrease in Ph, acidity. Bohr effect
Shift left = fetal Hb, alkalosis
Carbon monoxide and Hb
Hb binds to CO 240x more readily than with O2. There is a lower potential for Hb to bind O2
Sickle Cell Anemia
Glutamic acid is converted to Valine.
Mutation is on a Hb Beta chain.
Electrophoresis
Anode is +
Cathode is -
