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Ch5 hemoglobin / antigen / muscle protein - Coggle Diagram
Ch5 hemoglobin / antigen / muscle protein
Myoglobin (storage)
Structure
Not release O2 in tissue
For effective transport, affinity must vary with pO2
Ligand
Things bind to proteins called
On binding sites
Reversible (可拆)
Noncovalent
Induced fit
Tighter binding
Allow high affinity for different ligand
Both protein and ligand can change their conformation
Kd
Strong binding:Kd < 10nM
Weak binding:Kd > 10 μM
How can affinity to O2 change
With multiple binding sites
Binding sites must be able to interact with each other
Cooperativity
Positive cooperativity
Recognized by sigmoidal binding curves(O2結合曲線會受到positive cooperativity 影響)
Negative cooperativity
Scale
n > 1 = positive
n=1 = no cooperativity
n < 1 = negative
General: positive homotropic regulation
Hemoglobin (transport)
Myoglobin *4(subunit幾乎一樣)
T(tense)state
Lower affinity for O2
H+ bind to Hb and stabilize T state
R( relaxed) state
Higher affinity for O2
O2 binding triggers T—R(low—high affinity)
pH effect on O2 binding (base 親）
Hemoglobin and CO2 export：15～20%of CO2 is exported in the form of amino terminal residue
2,3-BPG
Stabilize the T state
bind to the central cavity of Hb
allow O2 release in tissue
Sickle-cell anemia(鐮狀紅血球貧血症）
Cause:mutation in hemoglobin
Giu6->Val in the beta chain of Hb
Homozygous (all mutation 早夭）
Heterozygous (part mutation)
Allosteric Regulation(異位調控）
Binding of a ligand will affect different binding site on the same protein
Bohr effect :H+ & CO2 will decrease the affinity of hemoglobin to O2, and make hemoglobin release O2
Immune system
Cellular immune system
Antibodies bind to surface of invading cells
Phagocyte(吞噬細胞):eat invaders
Macrophages:ingest bacteria tagged by antibodies
Humoral immune system
Antigens
One antigen can have several epitopes(抗原結合位)
Antibodies
IgG
Muscle Protein
Muscle fiber
Myofibril
I band (Z disk)/A band(M line)
Combine
Thin filament of actin(真正在移動I band）
Actomyosin cycle
ATP bind to myosin head
ATP hydrolyze
Myosin head attach to actin filaments, cause release of Pi(接上2️⃣)
ADP released(2️⃣➡️3️⃣)
Regulation of muscle contraction
Troponin and tropomyosin can avoid continuous muscle contraction
Nerve impulse trigger release of Ca2+
Thick filaments of myosin
Protein interactions modulate by chemical energy
Use of chemical energy cause conformational changes in proteins, generally required for their function
Conformational changes (binding, hydrolysis, release of ATP&ADP)
