week 5 Flashcards
clinical manifestations of an allergic reaction:
anaphylaxis
urticaria
angioedema
dermatitis
respiratory allergy
treatment considerations for an allergic reaction:
preparation for anaphylaxis (epi pen)
food diaries
trial avoidance of potential triggers
antihistamines
nasal steroids
allergy shots (immunotherapy)
treatment considerations for an allergic reaction:
preparation for anaphylaxis (epi pen)
food diaries
trial avoidance of potential triggers
antihistamines
nasal steroids
allergy shots (immunotherapy)
describe the appearance of hives:
edematous wheals that blanch with pressure
key treatment for hives:
remove offending agent
types of allergy testing:
RAST serum testing (IgE antibodies)
skin allergy testing
what is angioedema?
a diffuse, non-pitting tense swelling of the dermis and the subcutaneous tissue
what medications are angioedema reactions associated with?
ACE-inhibitors and NSAIDs
what is Celiac disease?
a food insensitivity
an immune reaction to gluten (protein in wheat, barley, and rye)
sx: diarrhea, bloating, gas, fatigue
Tx: remove gluten from diet
what is drug provocation testing?
-administer a medication to a patient in a graduated manner under close observation
-appropriate for patients who are UNLIKELY to be allergic (e.g. “penicillin allergies”)
features common among all signal transduction/intracellular signaling pathways:
- extracellular stimulus (i.e hormone, neurotransmitter, growth factor)
- receptor on cell membrane
- intracellular cell signaling pathway
what are the types of intercellular signals?
autocrine: itself (e.g. T lymphocytes with cytokines)
paracrine: nearby cells (e.g. neuromuscular junction)
endocrine: hormones released into blood stream and stimulates distant locations (e.g. insulin)
juxtacrine: signal binds to neighboring cell receptor, two cells need to be connected (e.g. notch receptor)
basic features of the receptor ligand mediated interactions and signal transduction:
- specificity
- amplification
- modularity
- sensitization and termination
- integration
describe ligand-receptor specificity:
binding of ligand to receptor is mediated by NON-COVALENT interactions
binding brings about a conformational change that alters the activity of the receptor
typically high affinity/specific interaction but the same ligand may bind other isoforms of the receptor or an entirely different receptor with different affinities
how does amplification occur?
enzyme/kinase reactions
what are enzyme/kinase cascades?
- enzymes arranged in a hierarchy in which one enzyme activates many molecules of a second enzyme; amplifications of several orders of magnitude within seconds
- 2nd messengers
what is a second messenger?
intracellular molecule generated in response to extracellular stimuli (1st messenger) that exerts an effect on signaling proteins/enzymes
examples: cAMP, cGMP, phospholipids, calcium
present at low concentration in unstimulated cells, rapidly increase during ligand binding (this increase is TRANSIENT)
describe modularity in terms of ligand binding?
protein receptors = multiple domains that recognize specific binding partners (via domains and motifs)
ensures specific interactions
describe modularity in terms of ligand binding?
protein receptors = multiple domains that recognize specific binding partners (via domains and motifs)
ensures specific interactions
which amino acids do protein kinases phosphorylate?
serine, threonine, and tyrosine
-OH groups
-binding is determined by the AA sequences (domains) surrounding these amino acids
what is the role of phosphatase?
removes phosphate from phosphorylated serine, threonine, or tyrosine
results of phosphorylation:
-alters interactions with other proteins (e.g. act as docking sites)
-oxygen can H bond with the phosphate, these negative charges can repel Asp or Glu, affecting enzyme conformation and activity
-regulation (phosphatase, reverse)
results of phosphorylation:
-alters interactions with other proteins (e.g. act as docking sites)
-oxygen can H bond with the phosphate, these negative charges can repel Asp or Glu, affecting enzyme conformation and activity
-regulation (phosphatase, reverse)
what is receptor desenstization?
receptor signaling is terminated by interacting proteins when the signal is present continuously - uncoupled from the signaling cascade via a protein
receptor down regulated
what is the fate of a desensitized receptor?
receptor internalization/endosome –> lysosome
what is enzyme integration/ “cross talk”?
utilization of the same pathways and enzymes by numerous receptors
instead of having their own pathways
“integration of the response”, “unified response”
converse with each other at several levels
e.g. growth factor receptor (EGF receptor) and epinephrine on a beta adrenergic receptor
describe why micelles are formed:
-forms in a solution of amphipathic molecules that have a larger, more polar head than tail
-head cross section is greater than fatty acid chain (wedged shaped)
-ONE TAIL?
e.g. fatty acids, sodium dodecyl sulfate
-driven by concentration
describe why vesicles are formed:
-small bilayers fuse into a spherical vesicle
-concentration dependent manner
-central aqueous cavity discloses dissolved molecules
what is the clinical importance of vesicles?
useful as artificial carriers of molecules (i.e. drugs)
describe bilayer formation:
-forms when lipids with polar head groups are MORE THAN ONE LIPID TAIL
-cross section: heads are equal to that of side chain
-e.g. phospholipids, sphingolipids
-hydrophilic heads interact with water, FA tails are packed inside
what is an example of a membrane that is mostly lipid?
myelin sheath
aids in signal conduction
name examples of membranes with more protein than lipid composition:
-plasma membranes of bacteria
-membranes of mitochondria and chloroplasts
what is membrane fluidity determined by?
FA composition
melting point
characteristics of FLUID membranes:
-shorter and more unsaturated FA chains
-less interactions of the side chains –> more fluidity
association of fluidity and melting temperature:
more double bonds (unsaturation) - melting temp decreases
increasing length of FA tails - melting temp increases
at higher temps, cells need ____________.
more long, saturated FAs
at lower temperatures, cells need ________.
shorter, more unsaturated FAs
explain the fluid mosaic model:
lipids form a VISCOUS, 2 dimensional solvent in which proteins are inserted and integrated either more or less deeply
proteins can be embedded in or associated with the membrane
characteristics of membrane fusion:
-membranes fuse together w/o exposing the lipids to aqueous environment
-can be spontaneous or protein mediated
e.g. budding of vesicles from Golgi, exo/endocytosis, viral infection, fusion of endosome to lysosome, fusion of sperm and egg, cell division cytokinesis etc.
what are the different types of membrane embedded proteins:
-receptors
-channels, gates, pumps
-enzymes
what are peripheral membrane proteins?
-associate with the polar heads of the membrane
-relatively loose association
-IONIC interactions
-disrupted via high salt or change in pH
what are purified peripheral membrane proteins?
no longer associated with the lipids
what are amphitropic proteins?
-can be conditionally attached to the membrane via COVALENT interaction with lipids or carbs that are attached to the lipids
-allows for biological regulation: attachment vs detachment from lipids
-REVERSIBLE attachment
what are integral membrane proteins?
-span entire membrane
-asymmetry like the membrane (different domains in different compartments)
-tightly associated with the membrane
-hydrophobic stretches interact with hydrophobic membrane regions
-can be removed by detergents
-purified int. membrane proteins still have phospholipids associated with them
monotropic vs polytropic intergral membrane proteins:
monotropic: only reacts with one side, do not span the full membrane
polytropic: span the full membrane
type I IMP:
single transmembrane helix
N terminus is outside
“don’t talk to aNy1 outside”
type II IMP:
single transmembrane helix
N terminus inside
type III IMP:
multiple transmembrane helices in a single polypeptide
type IV IMP:
transmembrane domains of several different polypeptides assemble to form a channel through the membrane
type V IMP:
held to the bilayer via covalently linked proteins
type VI IMPs:
have both transmembrane helices and lipid anchors
what is a hydropathy plot
-used to predict transmembrane domains
-increased hydropathy index – more hydrophobic – transmembrane component
what are the types of passive diffusion?
-simple diffusion via bilayer
-ion channel
-facilitated
what are the types of active diffusion?
primary (ATP)
secondary (coupled to another gradient)
what is the exergonic process of solute movement across a membrane driven by?
driven by increase in entropy
going from ordered to disordered (more microstates, less constraint)
energetically favorable
net movement of solute across a membrane is proportional to ______ but the ______ is the same in both directions.
concentration difference, rate
what x2 factors does membrane potential depend on?
- asymmetric distribution of ions across the membrane
- selective ion channels in the plasma membrane
ion channel structure:
4-5 transmembrane helices with polar core
polar side chains point inwards, towards the pore
hydrophobic side chains point out towards membrane
properties of ion channels:
cation and anion selective
ion selective (e.g. pore loop family: selectivity filter)
example of pore loop filter:
K+ channels
describe the steps of K+ channel selectivity:
- large water filled vestibule allows for K+ hydration
- helix dipole stabilizes K+
- backbone carbonyl oxygens form a cage that fits K+ precisely, replaces waters of hydration spheres
what is an aquaporin?
H2O channel
allows water movement down its gradient
provides for a rapid movement
what are the 3 amino acids that are associated with aquaporin pores?
Arg: electrostatic repulsion
Asn: dipole reorientation
His: size restriction
clinical significance of aquaporins:
roles in urine production and water retention in kidneys
e.g. vasopressin (APQ2-antidiuretic hormone)
APQ2 cells in renal collecting duct
promotes increased reabsorption of water, allows for concentration of urine
defect=decreased water permeability in proximal tubule, increased urine output (polyuria), decreased urine concentrating ability
explain facilitated diffusion:
uses a membrane spanning protein - induces a conformational change
down concentration gradient
does not require energy
for larger molecules such as sugars and AAs
the kinetics of facilitated diffusion are similar to ______.
an enzyme catalyzed reaction
Kt = concentration at which substrate uptake is half maximal
Tmax = transporter-catalyzed uptake is at maximal transport rate (saturated)
overview of secondary active transporters:
- ion moving down its electrochemical gradient
- solute moving from an area of low to high concentration (harnessing energy)
what are the types of primary active transporters?
- P-ATPase
-phosphorylation
-ion transport - F-ATPase
-coupling factor
-H+ transport coupled to ATP hydrolysis/synthesis
-F0/F1 components - V-ATPase
-vacuolar
-H+ transport coupled to ATP hydrolysis
-V0/V1 components - ABC transporters (ATP binding cassette)
-bind and hydrolyze ATP
-for sugars, AAs, ions, peptides, proteins, hydrophobic compounds (e.g. cholesterol, drugs)
equations for facilitated diffusion kinetics:
describe transport rate for simple diffusion:
linear growth
growth directly proportional to concentration gradient
describe the steps of Na+/K+ ATPase:
P-ATPase (dependent on phosphorylation)
- transporter binds 3 Na+ from inside the cell
- phosphorylation favors P-ENZ2
- transporter releases 3 Na+ and binds 2 K+ from the outside
- de-phosphorylation favors ENZ1
- transporter releases 2 K+ to the inside
- transporter resets
describe F-ATPase structure:
2 distinct multisubunits
1) hydrophobic F0 portion embedded in membrane
2) hydrophilic F1 portion protrudes into aqueous space
example of F-ATPase -H+/ATPase:
inner mitochondrial membrane in animals
protons move down their concentration gradient (proton-motive force)
drives ATP synthesis
V-ATPase/H+-ATPase purpose:
vacuolar - ATPase
how cells internalize extracellular material, ligands, and plasma membrane proteins and lipids by endocytosis
proton transport coupled to ATP hydrolysis via rotary mechanism
e.g pumps protons into lysosomes (acidifies them), activates degradative enzymes
describe the structure of a V-ATPase:
V1 peripheral domain - hydrolyzes ATP
V0 intergral domain - proton transport
describe the structure of an ABD transporter:
transmembrane domains span the membrane
nucleotide binding domains (NBD)
what are the steps of ABC transporters:
- substrate binding
- nucleotide binding domain (NBD) dimerization
- rotation of 90 degrees
- ATP hydrolysis
- Pi released first, followed by ADP
what type of transporter is a cystic fibrosis transmembrane conductance regulator (CFTR)?
ABC transporter
Cl- (and also HCO3-) channel
NBD dimerization opens Cl- channel
depends on cAMP, PKA, and ATP (all 3 needed)
steps for CFTR channel opening/closing:
- regulatory domain phosphorylated by PKA (cAMP stimulates PKA), allows ATP to bind (CLOSED)
- ATP binds, allowing for NBD domain dimerization, opening of channel (OPEN)
- hydrolysis of ATP and dephosphorylation (CLOSED)
what mutation in CFTR leads to cystic fibrosis?
mutation of Phe508 in the NBD1 domain
how is CFTR different from typical ABC transporters?
- has a regulatory domain
- acts as an ion channel, not a typical transporter
what type of transporter is GLUT-1?
-passive/facilitated
function of GLUT1 and location:
found in erythrocytes, galactose, and mannose
function: transports glucose across blood brain barrier
substrate: glucose, galactose, and mannose
GLUT 1 deficiency:
GLUT 1 deficiency syndrome (GLUT1DS)
-deprivation of brain glucose
-early onset encephalopathy
-early onset seizures
-delay in development
what type of transporter is Cu2+/ATPase?
primary active transporter
location and function of Cu2+/ATPase:
location: plasma membrane and cytoplasmic vesicles
substrate: Cu2+
function: Cu absorption from the intestine and excretion in the liver
disease in Cu2+ - ATPase:
Wilson’s Disease
excessive deposition of copper in the liver and brain
hepatic failure, acute hepatitis, progressive chronic liver disease
what type of transporter is the Neutral Amino Acid transporter (solute carrier family (SLC)?
secondary active transport
location and function of neutral amino acid transporter:
location: apical brush border of small intestine and kidney proximal tubules
substrates: 10 essential AA (leucine, isoleucine, valine, methionine, phenylalanine,
tryptophan, threonine, and histidine)
function: AA transport
disordered neutral AA transporter:
Hartnup disorder: failure to thrive, photosensitivity, intermittent ataxia, nystagmus and tremor, pellagra (low niacin) like skin changes on face, neck, forearms, and dorsal aspects of hands and legs
what is hypersensitivity?
inappropriate or excessive immune response to exogenous and endogenous (self) antigen
against self - autoimmunity
general characteristics of hypersensitivity diseases:
- involved adaptive immunity
- classified based on the hypersensitivity reaction/the immune effector response
- developments often have a genetic disposition
- clinical presentation depends on mechanism
- imbalance between effector function and control/limiting mechanisms
- mechanisms of tissue injury are the same as defenses against pathogens
-therapy: negate effector molecule, suppress activation and function of immune response
phases of hypersensitivity:
sensitization - generates effector T cell, 1 previous exposure
effector phase - re-exposure to same antigen leading to effector function/tissue injury
** can remain sensitized in the absence of re-exposure due to memory
what are the hypersensitivity class types?
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