MBB 222 Study Guide - Midterm Guide: Sigmoid Function, Myoglobin, Hemoglobin

42 views2 pages

browncricket987

20 Dec 2018

School

Simon Fraser University

Department

Molec Biol & Biochem

Course

MBB 222

Professor

Adam Barlev

For unlimited access to Study Guides, a Grade+ subscription is required.

Document Summary

It is either fully loaded or fully unloaded - not much of an intermediate. This communication between the different hemoglobin subunits regarding their oxygenation state (filled or empty) is only possible because of the quaternary structure of the protein. This cooperativity is not observed in myoglobin, which has a single subunit. Myoglobin, on the other hand, must bind to o2 at po2 where hemoglobin releases it, store it, and release it at really low po2 . The difference in o2-binding affinity between hemoglobin and myoglobin ensures that o2 bound to hemoglobin in the lungs is released to myoglobin in the muscles (and other tissues). This oxygen delivery system is efficient because the tissue po2 corresponds to the part of the hemoglobin binding curve where the o2 affinity falls off the most sharply. Understand the effect of bpg, ph and [co2] on hb"s affinity for o2. Lower ph (higher [h+]found in respiring cells): reduces o2 affinity of hemoglobin.

Related Questions

1. The dominant motif found in hemoglobin and myoglobin is: a) twisted beta sheet b) beta barrel c) helix-loop-helix d) 7-TM 2. Myoglobin has how many polypeptide chains? A) 1 b) 2 c) 3 d) 4 3. Structurally and functionally, hemoglobin closely resembles a(n) a) transmembrane protein b) mucopolysaccharide c) bile salt d) allosteric enzyme 4. The oxygen binding site in hemoglobin and myoglobin is called: a) BPG b) heme c) proximal-His d) N-terminal carbamate 5. The proximal His residue in hemoglobin and myoglobin binds to which atom or molecule? A) CO2 b) O2 c) Fe d) BPG 6. The distal His residue in hemoglobin and myoglobin binds to which atom or molecule? A) CO2 b) O2 c) Fe d) BPG 7. BPG binds to: a) N-terminal carbamate b) proximal His c) heme group d) central cavity 8. Indirect activity of CO2 is a result of increased concentration of which chemical species? A) BPG b) H+ c) heme iron d) distal His 9. Direct activity of CO2 is a result of binding to which molecular feature? A) the heme group b) the N-terminal ends of the 4 polypeptide chains c) the central cavity d) the proximal His 10. The sigmoidal, cooperative binding curve commonly observed for hemoglobin is a result of: a) competition between CO2 and O2 for heme binding. B) competition between heme and distal His for O2 binding c) competition between BPG and CO2 for binding at the central cavity site d) T to R transition 11. Hemoglobin has a tendency to release its oxygen to the tissues because: a) in this region pH is high and O2 concentrations are low b) in this region both pH and O2 concentrations are low c) in this region both pH and O2 concentrations are high d) there is much BPG in this region 12. Which statement about fetal hemoglobin is not true? A) fetal hemoglobin has gamma chains instead of beta chains b) fetal hemoglobin binds BPG less strongly than maternal hemoglobin c) fetal hemoglobin binds oxygen less strongly than maternal hemoglobin d) fetal hemoglobin binds oxygen more strongly than maternal hemoglobin 13. Which process is most responsible for the sickling of cells seen in sickle cell disease? A) aggregation of the oxygenated R form of hemoglobin-S to form insoluble fibers b) aggregation of the deoxygenated T form of hemoglobin-S to form insoluble fibers c) Hemoglobin-S does not contain heme d) Hemoglobin-S contains a mutant form of heme which will not bind oxygen 14. A person with sickle-cell trait is very unlikely to catch which disease? A) malaria b) colon cancer c) avian flu d) whooping cough 15. A person with a genetic defect which results in the synthesis of an insufficient amount of the alpha chain of hemoglobin is said to have which disease? A) alpha thalassemia b) beta thalassemia c) pernicious anemia d) Crohnâs disease

Enzyme activity is decreased by:
repression of enzyme synthesis
proteolytic degradation of the enzyme
an increase in [product]
all of the above
--------------------------------------------------------
Which of the following are characteristics of the concerted allosteric model of Monod, Wyman, and Changeux?
a. there are at least two forms of the enzyme, termed T and R
b. there is an equilibrium between the T and R form
c. dimeric proteins can have one subunit in the T form and the other in the R form
d. the greater the L value (T/R), the more sigmoidal the v vs. [S] curve will be
e. regardless of the number of subunits in the enzyme, all must be in the T form or all in the R form
f. the level of cooperativity is greatest when KR >> KT
all but c
all but e
a, b, e, and f
a and b only
a, b, d, and e
------------------------------------------------------
Which of the following are characteristics of the concerted allosteric model of Monod, Wyman, and Changeux?
a. there are at least two forms of the enzyme, termed T and R
b. there is an equilibrium between the T and R form
c. dimeric proteins can have one subunit in the T form and the other in the R form
d. the greater the L value (T/R), the more sigmoidal the v vs. [S] curve will be
e. regardless of the number of subunits in the enzyme, all must be in the T form or all in the R form
f. the level of cooperativity is greatest when KR >> KT
all but c
all but e
a, b, e, and f
a and b only
a, b, d, and e
------------------------------------------
Both hemoglobin and myoglobin share all of the following except:
they provide a protein framework that prevents heme-heme interactions with formation of Fe(III)
they are dimers of dimers with few Î±-Î± or Î²-Î² interactions
they non-covalently bind one heme per globin chain
they have a distal His that sterically hinders CO binding
-------------------------------
A graph of v versus [S] for an enzyme gives a hyperbolic plot. Which one of the following situations cannot give such a plot:
the enzyme obeys Michaelis-Menten kinetics
the enzyme model is an allosteric V system
the enzyme demonstrates positive cooperativity and is in the presence of an activator
the enzyme follows the Monod, Wyman, Changeux model and is in the presence of an inhibitor
All of the above would give a hyperbolic plot

------------------------------------------
Which of the following is something that myoglobin and hemoglobin do not have in common?
oxygenation alters the quaternary structure of both
they both have oxygen bound to the heme at a 120Â° angle
they are both organized into regions of Î± helices
they both have two critical histidines that are crucial to their function
they both contain heme

aquamarinegnat75

MBB 222 Study Guide - Midterm Guide: Sigmoid Function, Myoglobin, Hemoglobin

Document Summary

Get access

Related Documents

MBB 222 Lecture Notes - Lecture 12: Allosteric Regulation, Heme, C-Terminus

MBB 222 Study Guide - Final Guide: Intrinsically Disordered Proteins, Carbonic Anhydrase, Cellular Respiration

MBB 222 Study Guide - Point Mutation, Pyrimidine Dimer, Cytosine

Related Questions