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45 Cards in this Set
- Front
- Back
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What are the 2 main functions of Myoglobin?
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1) Stores Oxygen in diving mammals.
2) Acts to facilitate Oxygen transport in tissues by increasing solubility. |
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Describe the physical structure of:
Myoglobin |
- 153 Amino acids long
- Eight α-helices ("a" through "h") - Heme group (sits in the middle) binds the oxygen. |
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Describe the physical structure of:
a Heme group |
- Four pyrrole groups (A, B, C, D)
- Connected by methene bridges - Substitutions - Binding is characterized by "K" - Fe²+ is octahedrally coordinated |
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What benefit does the protein structure surrounding the Heme group provide?
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1) It carries the Heme group (which would be insoluble otherwise)
2) Helps Coordinate the Fe²+ (holds it in the center) 3) Prevents oxidation of Fe²+ to Fe³+ 4) Provides space for the oxygen (prevents other molecules from binding there) |
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O₂ binding equation:
The variable "K" = ? |
[Mb]*[O₂] / [Mb*O₂]
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What is the geometric shape of a red blood cell?
Why is this shape good? |
Biconcave shape (doughnut with center filled in)
This shape increases the surface area, and allows conformational flexibility so RBC's can fit through blood vessels while stacked together. |
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Why do we need blood to transport O₂?
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Because in organisms larger than 2mm, diffusion is too slow a process to supply the tissues with O₂
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Why do we need hemoglobin to transport O₂ through our blood?
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Hemoglobin helps to increase the solubility of O₂ in the blood.
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To be the most efficient in it's transporting of O₂, hemoglobin must:
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- Take up as much O₂ in the lungs as possible.
- Leave as much O₂ behind as possible in the tissues. |
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What type of binding curve characterized hemoglobin's binding specificity?
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A sigmoidal (S-shaped) binding curve.
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What type of binding curve is Myoglobin characterized by?
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A hyperbolic curve.
[7.4] pg. 180 |
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Why is the sigmoidal binding curve the most efficient for hemoglobin?
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Lecture 14 (slide 11/13)
- With just a *high* affinity, no O₂ would be released into the tissues - With just a *low* affinity, not very much O₂ would be released into the tissues. - Thus an intermediate curve with a high binding specificity at the pressures within the lungs, and a low binding specificity at the pressure of the tissues is the most efficient. |
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How many binding sites for O₂ does Hemoglobin have?
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4
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Binding of O₂ to Hemoglobin:
Binding of O₂ to one subunit of Hemoglobin _____ the O₂ binding affinity of the other subunits. |
...INCREASES...
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Binding of O₂ to Hemoglobin:
Release of O₂ from one subunit of Hemoglobin _____ the O₂ binding affinity of the other subunits. |
...DECREASES...
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O₂ binding to Hemoglobin:
Decreasing the pH _____ the affinity for O₂ binding. |
...DECREASES...
i.e. more acidic environments decrease O₂ binding affinity |
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O₂ binding to Hemoglobin:
Increasing the pH _____ the affinity for O₂ binding. |
...INCREASES...
i.e. more basic environments increase O₂ binding affinity |
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CO₂ in the blood is carried as a _____ ion.
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...bicarbonate...
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What are the 2 conformational states that Hemoglobin may be found in?
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T-state
R-state |
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Oxygen binding to Hemoglobin triggers a conformational change from the (T/R) state to the (T/R) state.
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...from *T-state* to the *R-state*.
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At low pH (acidic environment), protonation of Hemoglobin occurs. This stabalizes the (T/R) state.
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T-state is stabalized.
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O₂ binding to Hemoglobin:
Describe the Bohr Effect |
Protonation of Hemoglobin occurs at low pH.
When protonated, the N-terminal amino group (α-subunit) and C-terminal His (β-subunit) participate in ionic bonding which *stabalizes* the T-form (i.e. deoxygenated form) of Hemoglobin. In higher pH environments (more basic environments), the absence of ion-pairs stiumlates Hemoglobin to bind more O₂. |
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Decreasing the pH shifts the Hemoglobin binding curve to the (right/left)?
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...right.
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Describe what happens (in terms of O₂ binding affinity to Hemoglobin) when CO₂ binds to Hemoglobin.
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N-terminal NH₂ groups react with CO₂ to form a carbamate.
The carbamate *stabalizes* the T-form, promoting O₂ release (also inhibiting further O₂ binding) |
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What are the 3 main characteristics that makes the lungs an environment that promotes O₂ *binding* to Hemoglobin?
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1 - High pH
2 - Low pCO₂ 3 - High pO₂ |
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What are the 3 main characteristics that make tissues an environment that promotes O₂ *release* from Hemoglobin?
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1 - Low PH
2 - High pCO₂ 3 - Low pO₂ |
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2,3-BPG _____ the affinity of Hemoglobin for O₂
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...decreases...
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Where does 2,3-BPG bind to on Hemoglobin?
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2,3-BPG binds to the basic groups on the β-chains.
i.e. right in the center. |
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Other than affecting the affinity of O₂ binding to Hemoglobin, what 2 things does 2,3-BPG play a role in?
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1 - Altitude adaptation
2 - Delivery of O₂ to the fetus |
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Define:
Allosteric Effects (need to know definition verbatim for test) |
Binding of a molecule to one site affects the activity of the protein at a different site.
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Allosteric Effects:
Describe how the following 4 molecules affect the binding affinity of O₂ to Hemoglobin. - O₂ - H+ - CO₂ - 2,3-BPG |
O₂ binding at one site increases the binding affinity at other sites for O₂.
- H+ decreases the affinity of Hemoglobin for O₂ - CO₂ decreases the affinity of Hemoglobin for O₂ - 2,3-BPG decreases the affinity of Hemoglobin for O₂ |
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What are the 3 types of muscle?
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1 - Striated muscle
2 - Smooth muscle 3 - Cardiac muscle (involuntary) |
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From smallest to largest, list the 4 categories for striated muscle.
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Lecture 15 (slide 25/35)
myofibril --> individual muscle fibre --> bundles of muscle fiber --> muscle |
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What two types of filaments do myofibrils contain?
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Thick filaments
Thin filaments |
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Anatomy of the Myofibril:
I-Band contains only ____ filaments |
Lecture 26 (slide 26/35)
...thin... |
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Anatomy of the Myofibril:
The Z-Disk is located in the middle of the _____. |
Lecture 26 (slide 26/35)
...I-Band. |
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Anatomy of the Myofibril:
1 sarcomere is the distance between two consecutive _____. |
Lecture 26 (slide 26/35)
...Z-Disks. |
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Anatomy of the Myofibril:
The M-Disk is located in the middle of the _____. |
Lecture 26 (slide 26/35)
...H-Zone. |
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Anatomy of the Myofibril:
Thin filaments are anchored to the _____. |
Lecture 26 (slide 26/35)
...Z-Disk. |
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Anatomy of the Myofibril:
List the 6 terms you need to know to draw the anatomy of a myofibril. |
Lecture 26 (slide 26/35)
M-Disk Z-Disk H-Zone I-Band A-Band length of 1 Sarcomere |
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Anatomy of the Myofibril:
During muscle contraction, the length of the _____ and _____ shortens. |
...I-Band...
...H-Zone... |
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Muscle is largely composed of which 2 proteins?
Which filaments are these individual proteins found on? |
Actin (on thin filament)
Myosin (on thick filament) |
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How many subunits make up Myosin?
Name them. |
[7.25] pg. 201
Myosin is made up of 6 subunits. 2 Heavy chains 4 Light chains (2 light chains per heavy chain) |
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Thin filaments are polymers of _____.
The polymerized form of this is _____. |
...G-Actin.
...F-Actin. |
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Describe the 6-step process that allows Myosin and Actin to generate force in a muscle.
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[7.32] pg. 206
Lecture 15 (slide 34/35) 1 - ATP binds to myosin head, actin binding site opens myosin head releases actin 2 - Active site closure followed by ATP hydrolysis causing cocking of myosin head. 3 - Weak binding of myosin to actin 4 - P_i release resulting in strong binding of myosin to actin 5 - POWER STROKE! 6 - ADP release *Through repetition of this process, myosin heads "walk" up thin-filaments toward the Z-Disk. |
