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Chapters 6-10
ACS Biochemistry Review
38
Biochemistry
Undergraduate 3
05/11/2015

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Term
Homologs
Definition
derived from common ancestor
Term
Paralogs
Definition
homologs present within one species--often differ in their detailed biochemical functions
Term
Orthologs
Definition
homologs present within different species with similar biochemical functions
Term
How to calculate alignment score?
Definition
+10 points for each identity between aligned sequences
-25 points for gaps (regardless of size)
Term
Which protein structure is most conserved evolutionarily?
Definition
Tertiary is more conserved than primary
Term
Common example of convergent evolution?
Definition
Chymotrypsin and subtilisin (the serine proteases)
Term
Oxygen carrying efficiency of hemoglobin vs. myoglobin?
Definition
Hemoglobin: 90%
Myoglobin: 7%
Term
Structural differences between hemoglobin and myoglobin?
Definition
Hemo = four polypeptide chains
Myo = single polypeptide
Term
Hemoglobin binds oxygen _____, which means...
Definition
cooperatively, binding of oxygen to a site in one chain increases likelihood that other chains will bind oxygen
Term
Which state of iron in heme is capable of binding oxygen? What is it bound to?
Definition
Fe2+
lies in center of protoporphyrin, bound to four pyrrole nitrogen atoms
Term
In myoglobin, the fifth coordination site is occupied by... This is referred to as the...
Definition
the imidazole ring of a histidine residue
proximal histidine
Term
Oxygen binding occurs at the ___ coordination site.
Definition
sixth
Term
Oxygen binds with high affinity to...
Definition
myoglobin
Term
The cooperative binding and release of oxygen by hemoglobin enables it to deliver nearly __ times as much oxygen as myoglobin
Definition
10
Term
Deoxyhemoglobin is in the (T/R) state
Definition
T
Term
Oxhemoglobin is in the (T/R) state
Definition
R
Term
2,3-BPG binds tightly to the __ state of hemoglobin, lowering the oxygen affinity of hemoglobin
Definition
T
Term
Fetal hemoglobin binds oxygen ___ tightly than adult hemoglobin, owing to...
Definition
more
weaker 2,3-BPG binding
Term
Bohr effect: decreased pH leads to...
Definition
decreased oxygen affinity
Term
Bohr effect: increased CO2 leads to...
Definition
decreased oxygen affinity
Term
Vmax
Definition
reaction rate when enzyme is fully saturated with substrate
Term
Km
Definition
Michaelis constant, substrate concentration at which reaction rate is half maximal
Term
How to calculate Vmax
Definition
kcat X total concentration of enzyme
Term
kcat
Definition
turnover number, the number of substrate molecules converted into product per unit time at a single catalytic site when the enzyme is fully saturated
Term
Do allosteric enzymes conform to Michaelis-Menten kinetics?
Definition
No, sigmoidal curve
Term
Irreversible inhibition
Definition
inhibitor covalently linked to enzyme or bound so tightly that dissociation is very slow
Term
Reversible inhibtion
Definition
Characterized by more rapid equilibrium between enzyme and inhibitor
Term
Competitive inhibitor
Definition
Prevents substrate from binding to active site
Term
Uncompetitive inhibition
Definition
inhibitor combines only with the enzyme-substrate complex
Term
Oxioreductases
Definition
oxidation-reduction
Term
Transferases
Definition
group transfer
Term
Hydrolases
Definition
hydrolysis reactions
Term
Lyases
Definition
addition or removal of groups to form double bonds
Term
Isomerases
Definition
isomerization
Term
Ligases
Definition
ligation of two substrates at the expense of ATP hydrolysis
Term
Five basic strategies of enzymes to form and stabilize the transition state:
Definition
1) Use of binding energy
2) Covalent catalysis
3) General acid-base catalysis
4) Metal ion catalysis
5) Catalysis by approximation
Term
What is the crucial component of active sites of carbonic anhydrases?
Definition
Zn2+ ion
Term
Myosins are examples of ____. Their function is to...
Definition
P-loop NTPase enzymes
catalyze hydrolysis of ATP to form ADP and Pi
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