LECTURE 31 Flashcards
CHECK ON LEARNING
enzymes are considered _____?
catalysts
enzymes do this to spontaneous reactions?
accelerate
what do enzymes do to the transitional state so that the reaction can occur?
lowering the energy state
how do spontaneous reactions occur more rapidly?
increase substrate
decrease product energy
how do enzymes accelerate the reactions?
by stabilizing the transitional state with van der waals, electrostatic and hydrogen bonds decreasing the activation energy
bring substrate molecules into close proximity with each other
what is total activity in reference to enzyme activity?
specific activity x amt
how is the specific activity of enzymes measured?
international units
how does activity get changed for an enzyme?
change amount of enzyme present
change specific activity of existing enzyme molecules via feedback inhibition, regulatory proteins, enzyme phosphorylation, proteolytic activation
what is a common example of regulatory proteins?
calmodulin
name the two examples of enzyme phosphorylation?
kinases
phosphorylation
what is the significance of K1? K2 and K3?
KI is a measure of the rate of formation of ES
causes ES to disappear
what is the measure of affinity? what is this known as?
the rate of disappearance of ES (K2+K3) and divided by the rate of formation of ES (K1)
michaelis constant
what does low Km mean?
low Km means high affinity
high affinity means what kind of Km?
low Km
low affinity means what kind of Km?
high km
Km is the substrate concentration that produces what type of velocity?
half maximal velocity
how is enzyme kinematics graphed?
double reciprocal or lineweaver burke plot
how do high and low affinity enzymes look on a double reciprocal plot?
Vmax is the same for each, high affinity enzyme has a lower Km so -1/km will be a larger negative number
this type of inhibitor competes for binding at the active site?
how is affinity and Km affected?
competitive inhibitor
affinity is decreased and km is increased
this type of inhibitor binds at sites other than the active site, so they don’t change affinity for substrate, what happens to the rate of the reaction of Vmax?
decrease Vmax
what is needed to help facilitate enzyme catalyzed reactions?
cofactors or coenzymes, i.e. vitamins
what is the job of the cells?
sense
survive
respond
reproduce
any response by a cell is a change in what?
total activity
total activity=specific activity x amount
what does signaling mean for a cell? what are the examples?
information is being transferred from one place to another and that it brings about a response
direct electrical communication
chemical signals
t/f, chemical signals are faster than electrical signals?
f, slower than electrical
what are the three examples of chemical signals, name any subclasses?
neurotransmitters
hormones like polypeptides (insulin, somatotropin, IGF-1, FSH) and steroids (cortisol, estradiol, aldosterone)
local signals like paracrine (NGF, histamine, PGs, Kinins) and autocrine (adenosine)
what is the response like for the polypeptides and steroids?
faster onset
short acting
slow onset
long acting
these hormones alter the specific activity primarily, faster onset, shorter duration response
polypeptides (insulin, somatotropin, IGF-1, FSH)
these hormones alter gene expressions primarily, so slower onset and longer duration response
steroids (cortisol, estradiol, aldosterone)
these local signals are released by one cell and affect neighboring cells. Onset and duration varies
paracrine (NGF, histamine, PGs, Kinins)
these local signals affect the behavior of the cell that released them; fast onset and duration varies
autocrine (adenosine)
what type of hormone are the hydrophilic signals?
polypeptide hormones
T/F, lipophilic signals are polypeptide hormones? how are these signals associated with total activity?
steroid hormones
total activity=specific activity (hydrophilic signals) x amount (lipophilic signals)
what are examples of paracrine?
histamine
PGs
Thromboxanes
Leukotrienes
aka “eicosanoids”
which of the eicosanoids are being constantly released? what are the eicosanoids made from?
PGs
arachidonic acid cleaved from membrane phospholipids by phospholipase A2 stimulated by:
epinephrine
bradykinin
thrombin
angiotensin II
so we know eicosanoids come from arachidonate, what are the enzymes used to make them?
lipooxygenase to produce HPETE to produce LTs
cyclooxygenase to produce PGG then peroxidase to produce PGH, both activities fall under the same enyzme (PG synthase) then on to PGs and TBs (via thromboxane synthase)
what is cyclooxgenase inhibited by?
aspirin, ibuprofen and indomethacin
what do thromboxanes promote?
vasoconstriction and platelet aggregation
what do prostaglandins promote?
platelet aggregation
what do leukotrienes promote?
bronchoconstriction and vascular permeability
what inactivates PGs responses?
15-hydroxyprostaglandin DHase (metabolizes eicosanoids) and cyclo oxygenase (destroys self)
