Chapter 3 Globular Proteins part I

Question 1

R form is associated with what ?

Deoxygentated or Oxygenated ?

Answer 1

Oxygenated

Question 2

what major type of hemoglobin is found in adults ?

Answer 2

Hemoglobin A

HbA

Question 3

Bohr Effect

Answer 3

• the presence of CO2/H+ affects the affinity of hemoglobin towards Oxygen
• Increased attraction of hemoglobin to oxygen
• more presence of Co2 or H increases the love for Oxygen

Question 4

when hemoglobin is on it’s T form what is going on ?

Answer 4

The molecule is TENSED

movement is constrained by ionic and hydrogen bonds

Question 5

Structure of Heme

1. what is held in the center of heme by four nitrogens ?
2. how many bonds can heme-Fe+2 form?
3. where are these two bonds coordinated ?

Answer 5

1. Iron (Fe+2)
2. two bonds
3. side chains of histidine** residue **of the globin molecule

Question 6

T form is associated with

Deoxygenated or Oxygenated ?

Answer 6

Deoxygenated

Question 7

2,3-BPG

Answer 7

• allosteric effector
• affects the affinity of hemoglobin towards oxygen
• high levels of BPG is found in COPD, chronic hypoxia
• decrease attraction to oxygen
• the removal of BPG returns the affinity of hemoglobin to oxygen

Question 8

Myoglobin Stucture and Function

1. which major organs/tissues contain hemeproteins?
2. how many O2 molecules can myglobin bind ?
3. describe the interior of myoglobin (what is found) ?
4. how is this protein stabilized ?
5. how many polypeptides are involved with this protein?
6. most of this polypeptide chain is folded in how many stretches ?
7. Does myoglobin have more than one heme group ?

Answer 8

1. skeletal and cardiac
2. one O2 molecule
3. non-polar bonds
4. by hydrophobic interactions
5. single chain of polypeptide
6. EIGHT stretches of alpha helix
7. no ! it only contains ONE heme group

Question 9

Binding Heme Group of Myoglobin

1. what does the first histidine bind directly to ?
2. what is the role of second histidine ?
3. Does second histidine have interaction with heme ?

Answer 9

1. Fe+2 of heme
2. stabilize the O2 binding with Fe+2
3. no

Question 10

Quatinary Structure of Hemoglobin

1. what is a dimer ?
2. name the two dimers involved in this structure?
3. how are the two dimers held together ?
4. when there are TWO dimers how many total molecules are at play ?
5. The Two dimers occupy certain positions; what are they?
6. the molecule is allowed for movement when there are what kind of interactions in exactly what part?

Answer 10

1. a molecule or molecular complex consisting of two identical molecules linked together
2. AlphaB1 and Alpha B2
3. by hydrophobic interactions
4. four chains are involved
5. deoxyhemoglobin and oxyhemoglobin
6. weak interactions in between dimers

Question 11

1. When hemoglobin is in its R form; explain what is happening at this point ?
2. How else can you describe the state of the R form ?

Answer 11

1. Biding of oxygen to hemoglobin causes rupture of the polar bonds between the 2 dimers
   * These ruptures allow for movement
2. relaxed : with High-oxygen-affinity (oxyhemoglobin)

Question 12

define the major role of hemoglobin ?

Answer 12

O2 transport

Question 13

Please finish the sentence:

1. An oxygen saturation curve measures oxygen at different
2. which hemeprotein has a higher Po2 level in ALL Po2 values ?
3. The partial pressure to achieve half saturation (P50) of binding sites is: (state which heme group belongs to the corresponding stated values below :

-1 mmHg

26 mmHg

Answer 13

1. partial pressures (Po2)
2. myoglobin
3. myoglobin hemoglobin

Question 14

Hemeproteins

1. hemeproteins contain a constituent other than the amino acid, what is this constituent ?
2. name the two most abundant proteins ?
3. what is the shape/ configuration of hemeproteins ?
4. define their binding ability with O2?

Answer 14

1. prosthetic group
2. myoglobin and hemoglobin
3. three dimensional
4. can be reversible

Question 15

Allosteric Effectors

Answer 15

• factors that affect regulation and cooperativity of hemoglobin binding capacity
• pH
• temperature
• PO2 (Co2)
• DPG/ 2,3-BPG

effects on highs and lows on these factor can result in shifting reactions to the RIGHT (less affinity for oxygen) or to the LEFT (high affinity for oxygen)

Question 16

describe the T Form of Hemoglobin

Answer 16

T form is the LOW-OXYGEN-AFFINITY form of hemoglobin

DEOXYGENATED

Question 17

Hemoglobin traits

1. how many compositions of heme group does it contain?
2. how many O2 molecules can it bind and carry ?
3. what is the shape of hemoglobin ?
4. what elements can hemoglobin transport other than O2?
5. what effectors regulate oxygen-binding properties ?
6. contrast the difference of how many polypeptide chains for hemoglobin and myoglobin ?
7. where is hemoglobin found ?

Answer 17

1. four
2. four
3. tetrameric
4. H and CO2
5. allosteric effectors
6. hemoglobin has FOUR polypeptide chains and Myoglobin has ONE polypeptide chain
7. in red blood cells