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33 Cards in this Set

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LIGAND
ANY MOLECULE RERVERSIBLY BINDING IN A SPECIFIC MANNER TO A PROTEIN
BINDING SITE
SPECIFIC REGION OF THE PROTEIN INVOLVED IN THE REVERSE BINDING TO LIGAND
BINDING SITE COMPLEMENT
BINDING SITE IS COMPLEMENTARY TO LIGAND IN SIZE, SHAPE, CHARGE, & HYDRO- PHILIC/ PHOBIC CHARACTERISTICS
INDUCED FIT
PROTEIN-LIGAND BINDING IS OFTEN COUPLED TO A CONFORMATIONAL CHANGE IN PROTEIN THAT MAKES BINDING SITE MORE COMPLEM. TO LIGAND... TIGHTER BINDING OF FLEX PROTEIN TO LIGAND
COOPERATIVITY
DESCRIBES SITUATIONS WHERE BINDING AT ONE SITE EITHER INC. OR DECREASES BINDING @ ANOTHER SITE (eg. on another subunit) BY CHANGING CONFORMATION
MYOGLOBIN
Protein consisting of a single polypeptide chain with a heme prosthetic group that binds oxygen reversibly
FUNCTION OF MYOGLOBIN DDEPENDS ON PROTEIN'S ABILITY TO ??
PROTEIN'S ABILITY TO BIND OXYGEN AND TO RELEASE IT WHEN AND WHERE ITS NEEDED.
THE REVERSIBLE BINDING OF A PROTEIN (P) TO A LIGAND (L) CAN BE DESCRIBED BY ??
A SIMPLE EQUILIBRIUM EQUATION
P+L == PL
P+L== PL RXN IS CHARACTERRIZED BY ??
Ka = ASSOCIATION CONSTANT

HIGHER Ka = HIGHER AFFINITY OF THE L FOR THE P
RATIO OF BOUND TO FREE PROTEIN IS DIRECTLY PROPORTIONAL TO ??
CONCENTRATIOON OF A FREE LIGAND

Ka[L]= [PL]/[P]
BINDING EQUILIB. FROM STANDPOINT OF THE FRACTION @, OF WHAT??
OF LIGAND- BINDING SITES ON THE PROTEIN THAT OCCUPIED THE LIGAND
WHAAT DOES THE FRACTION (theta) @= ?? (3 forms)
@= binding sites occupied/ total binding sites

@= [PL]/ [PL]+[P]

@= [L]/[L]+(1/Ka)
[@] IS A ? FUNCTION OF ??
HYPEROBLIC FUNCTION x=y/(y+z)of [L]
DISSOCIATION CONSTANT [Kd]
EQUILIB CONSTANT FOORR RELEASED LIGAND

[L] AT WHICH HALF OF THE AVAIL. LIGAND BIND SISTES ARE OCCUPIED...AT @=0.5

Kd=1/Ka
3 EQUATIONS WITH Kd
Kd= [P][L]/[PL]

[PL]=[P][L]/Kd

@=[L]/[L]+Kd
EQ. FOR BINDING OF OXYGEN TO MYOGLOBIN
@=[O2]/[O2]+Kd

substitute concentraation of dissolved o2 for[l] b/c itss a gas
Kd= to [O2]0.5 so,
@=[o2]/[o2]+[o2]0.5
[VOTILE SUBSSTANCE] IN SOL'N IS PROPORTIONAL TO /??
LOCAL PAARTIAL PRESSURE OF THE GAS

@=pO2/pO2+P50
HEMOGLOBIN TRANSPORTS
Hb TRANSPORTS O2 IN RED BLOOD CELLS IN BLOOD
Hb MUST AQUIRE O2?? AND THEN???
AQUIRE O2 IN LUNGS ANAD RELEASE IT IN TISSUE
Hb TRANSPORT OF O2 IN RBC REQUIRES HIGH ENOUGH AND LOW ENOUGH AFFINITY IN???
HIGH ENOUGH AFFINITY IN LUNGS, BUT LOW ENOUGH AFFINITY IN TISSSUE TO RESPOND TO SMALL CHANGES IN [O2]
Hb TRANSPORT OF O2 IS ACCOMPLISHED BY????
COOPERATIVE EFFECTS FROM O2 BINDING TO DIFF. Hb SUBUNITS
RELATIONSHIP B/W Hb SUBUNITS AND MYOGLOBIN
STRUCT. RERLATED BUT SUBUNITS AFFECT O2 BINDING

BOTH BIND heme SAME WAY AND USE CONSERVED His ON BOTH SIDES OF heme TO PROTECT AND STABILIZE Fe2+ & o2 binding
HEMOGLOBIN'S STRUCTURE
Mr 64,500 roughly spherical diameter= 5.5nm
TETERAMERIC PROTEIN WITH 4 heme GROUPS (1 ON EACH POLYPEPTIDE CHAIN)
ADULT Hb STRUCTURE
2 TYPES OF GLOBIN:
2 ALPHA CHAINS (141 residues each)
2 BETA CHAINS (146 residues each)
R-STATE CONFORMATION OF Hb
HAS HIGH AFFINITY FOR O2

STABILIZED BY O2 BINDING
WHAT IS SHAPE OF HEME GRROUP?
COMPLEX ORGANIC RING STRUCTURE= PROTOPORPHYRIN =
AND IS BOUND TO A Fe2+ atom
WHERE IS HEME GROUP IN MYOGLOBIN?
HEME IS BOUND IN A POCKET MADE UP LARGELY OF THE E&F HELICES, although amino acid residues from other seg.s of protein alsso participate.
AMINO ACID RESIDUE DESIGNATION IN MYOGLOBIN MOLECULE?
INDIV A.A. RESIDUE IS DESIGNATED BY EITHER:
ITS POSITION IN A.A. SEQ OR ITTS LOCATION W/IN THE SEQ. OF A PARTICULAR ALPHA-HELICAL SEGMENT.
IN OXY-BINDING CURVES FOR Mb, WHY pO2 AND NOT [O2]?
IN EXPERIMENTS USING OXY AS A LIGAND, BINDING TO Mb, IT IS THE PARTIAL PRESSURE OF OXY IN GAS PHASE ABOVE THE SOL'N, pO2, THAT IS VARIED
LOCAL PARTIAL PRESSSURE OF THE SOL'N GAS IS PROPORTIONAL TO/????
CONCENTRATION OF VOLITILE SUBSTANCE
WHAT DOES TERM [PL] MEAN IN TERMS OF SPECIFIC MOLECULES????
[PL]= P(PROTEINS) L(LIGANDS)

LIGAND-BINDING SITES ON THE PROTEIN THAT ARE OCCUPIED
HEME BINDS TO CO2 20,000X MORE BETTER THAN TO O2; WHY WE DONT GETT CO2 POISONING?
IT ONLY BINDS ABOUT 200X BETTER WHEN HEME IS BOUND IN MYOGLOBIN- STERIC HENDERANCE
WHY IMPORTANT THAT ERYTHROCYTES ARE SMALL CELLS?
RED BLOOD CELLS- OXYGEN IS BOUND ANAD TRANSPORTED BY Hb IN RBC AND HUMAN ERYTH. ARE SMALL (6-9 um) BICONCAVE DISKS