Hemoglobin/Myglobin, O2 and Enzyme Regulation Flashcards
hemoglobin, myoglobin and enzyme regulation
What are the main functions of myoglobin?
- carry oxygen in muscle cells
- store oxygen in muscle cells
- deleiver oxygen to mitochondria
- binds oxygen at LOW levels
What are the main functions of hemoglobin?
- carry oxygen in the blood
- binds oxygen in the lungs
- releases oxygen to the tissues
- sensitive to small changes in oxygen levels
- carries CO2 from the tissues to the lungs
Oxygen binds to the _______ of myoglobin and hemoglobin
heme group
The heme prosthetic group contains one _______ atom in the center
iron (Fe)
oxygen only binds the ________ in the heme
reduced iron (Fe2+)
myoglobin has ______ oxygen binding sites
one
hemoglobin has _____ oxygen binding sites
four
hemoglobin contains ______ polypeptide chains each with a heme capable of binding one O2
four
Positive cooperation
a form of allostery……once one ligand binds it makes it easier for other ligands to bind
The T state of hemoglobin has a _______ affinity for oxygen
LOW
The R state or relaxed state has a _________ affinity for oxygen
HIGH
there are ______ salt bridges in the T state than there are in the R state
more
hemeoglobin consists of ___ alpha dimers and _____ beta dimers
two, two
In the absense of oxygen ______ is out of the heme plane
Fe
myoglobin oxygen binding is _________ which means its hill coefficient is =1
non-cooperative
hemoglobin oxygen binding is _______ which means its hill coefficient is greater than 1
positive-cooperation
homotropic allosteric modifier
when an activator or inhibitor molecule binds to the active site
what is an example of a homotropic allosteric modifier?
oxygen binding to hemoglobin
heterotrophic allosteric modifiers
when an activator or inhibitor molecule DOES NOT bind to the active site…..ligand binding at one site influences ligand binding at a different site
heterotrophic inhibitors stabilize the _____ state of the active site
T (low affinity)
heterotrophic activators stabilize the ______ state of the active site
R (high affinity)
What are the 3 heterotrophic allosteric modifiers of Hemoglobin?
H+, CO2, and 2,3-BPG (they all inhibit O2 binding)
H+ decreases oxygen binding to hemoglobin by stabilizing the hemoglobin ____________ state
low affinity T
CO2 decreases oxygen binding to hemoglobin by stabilizing the hemoglobin ____________ state
low affinity T
What is the Bohr effect?
the effect of pH and CO2 on binding and release of O2 by hemoglobin
2,3-BPG decreases O2 binding to hemoglobin by stabilizing the hemoglobin ____________ state
low affinity T
BPG binds at a site _____ from the O2 binding site
distant
BPG weakens O2 binding to hemoglobin allowing more ______ to be released to the tissues
oxygen
Carbon monoxide at the hemoglobin active site has ________ and _______ effects
non allosteric and allosteric
How does carbon monoxide have non-allosteric effects
carbon dioxide competes with oxygen binding at the active site
How does carbon monoxide have allosteric effects
carbon monoxide bound at the active site increases oxygen binding at the other active site
what are the main types of hemoglobin in adults?
major adult form (Hb A), Hb F, Hb S (sickle cell)
what is sickle cell anemia?
a missense mutation in the beta globin gene…..mutation at position 6…… glu to transfer to val which causes abnormally shaped RBC
What is the underlying reason sickle cell anemia happenss?
in the T conformation, valine 6 on the Hb surface exposes a hydrophobic patch…. forms insoluble fibers on deoxygenation
reversible reactions are controlled by changes in ________
[substrate]
irreversible reactions are _______ regulated
enzyme
flux is defined as the rate at which the ______ material is converted to the ______ of the pathway
starting, products
flux through a pathway is ______ faster than the slowest step
NEVER
The rate limiting step is the _____ step in the pathway
slowest
enzyme regulated steps are usually ______
irreversible
feedback regulation is defined as the
product of the pathway contrrols its synthesis
what is the effect of substrate concentration on enzyme reaction rate?
- when [s] is greater than km, the reaction velocity does NOT change with differences in [s]
- when [s] is smaller than km, the reaction velocity changes in proportion to [s]
Product inhibition occurs when the product of an enzyme is an ______ of that enzyme
inhibitor
feedback inhibition occurs when the product of a metabolic pathway ________
influences its productions
Hexokinase has a _____ km and is inhibited by ______
LOW, its product glucose-6-phosphatase
glucokinase has a ______ km which means that its activity is regulated by the ________
high, concentration of glucose
glucokinase is a _____
glucose sensor
What is allostery
the process by whichc biological macromolecules transmit the effect of binding at one site to another…… also requires a change in conformation
allostery can either result in ________ or _________
activation, inhibition
cooperativity is defined as
binding of a substrate to one active site alters the affinity for substrate at the other active site
positive cooperativity is when substrate binding at one active site ______ affinity for substrate at the other active site
increases
negative cooperativity is when substrate binding at one active site ______ affinity for substrate at the other active site
decreases
homotropic allosteric modifiers
substrates for the active site
heterotrophic allosteric modifiers
DO NOT bind at the active sites, they are NOT substrates
phosphofructokinase-1 incorporates phosphate from ATP into _________ to form ___________
fructose-6-phosphate, fructose-1-6-bisphosphate
PFK-1 is an _________ modifier
allosteric
fructose-6-phosphate is an homotropic allosteric activator of _______
PFK-1
ATP is a substrate and ________ inhibitor of PFK-1
heterotropic
PFK-1 has two ATP binding sites, one is at the _________ and the other is not at the _________ which stabilizes the low affinity T state for F6P
active site
Fructose-2,6-bisphosphate activates _______
PFK-1
F26BP is a heterotrophic _______
activator
phosphorylation/dephosphorylation of serine, threonine or tyrosine residues is caused by the enzymes called ________
kinases
Proteolysis that activate a precursor, called _______, by enzymes called proteases
zymogen or proenzyme
Phosphorylation uses ATP and a protein _______ to transfer a phosphate to the amino acid
kinases
dephosphorylation uses ADP and a protein _________ to add a phosphate to the amino acid
phosphatase
AMP is a heterotropic allosteric _______ of glycogen phosphorylase
activator
The blood clotting cascade is controlled by proteolytic activation of __________
inactive proteases (zymogens)
prothrombin is an inactive protease that is converted to _______ an active protease by factor XA
thrombin
