LIGAND GATED CHANNELS Flashcards
WHAT IS THE FUNCTION OF SIGNALLING SYSTEMS
RECOGNISE A STIMULUS TRANSFER A STIMULUS INTO A CELL AMPLIFY CYTOPLASMIC SIGNAL MODULATE EFFECTOR SYSTEMS ADAPT THROUGH FEEDBACK
IN MULTI CELLULAR ORGANISMS …………………….. EXPRESSION OF CERTAIN RECEPTORS AND THEIR MOLECULES INVOLVED IN SIGNAL …………………….. ALLOWS CELLS TO RESPOND…………………………. TO PARTICULAR STIMULI
SELECTIVE
TRANSDUCTION
SPECIFIC
WHAT IS THE ROLE OF RECEPTORS
TO DETECT CHEMICAL AND PHYSICAL STIMULI
PHYSICAL INTERACTION BETWEEN STIMULUS AND …………….. PROVIDES………………. TO CHANGE THE STRUCTURE OF THE RECEPTOR IN SUCH A WAY THAT MAY INITIATE ……………………..
RECEPTOR
ENERGY
SIGNALLING
WHAT KIND OF RECEPTOR ARE INVOLVED
MOST ARE EMBEDDED IN THE PLASMA MEMBRANE
SOME CAN BE IC RECEPTORS
SOME ARE TRANSMEMBRANE RECEPTORS
HOW MANY RECEPTOR FAMILIES ARE IN THE MAMMALIAN GENOME
25
HOW MANY GENES CODE FOR ION CHANNELS
400
WHAT TYPES OF GATED ION CHANNELS ARE THERE
LIGAND
VOLTAGE
ION SELECTIVITY OF A PORE IS DEFINED BY WHAT FACTORS
THE SIZE OF THE ‘FILTER’
THE AMINO ACID LINING THE PORE
EVOLUTIONARILY SIMPLE ORGANISMS HAD SIMPLE CHANNELS. OVER ………………….. OF A GENE CODING FOR 2TM DOMAIN CHANNELS GAVE RISE TO A FAMILY OF 2 - …………… TM DOMAINS.
POSITIVE CHARGES IN THE AMINO ACIDS IN TM……. GAVE RISE TO …………………… SENSITIVITY.
DUPLICATION
24
4
VOLTAGE
DESCRIBE THE STRUCTURE OF A Kir CHANNEL
- 2 TM DOMAINS
- NH2 AND COOH TERMNII CYTOPLASM FACING
- EXTRACELLULAR LOOP THAT FOLDS BACK TO FOR THE PORE LINING ION SELECTIVITY FILTER
- 4 OF THESE UNITS COME TOGETHER TO FORM A TETRAMER
- THIS IS THE BASIC STRUCTURE OF MOST ION CHANNELS
IF THE BASIC STRUCTURE OF KIR CHANNEL FUNCTIONS AS NEEDS, WHY ARE THERE OTHER CHANNELS WITH MORE TM DOMAINS
MOST CHANNELS ARE BUILD AROUND THE BASIC STRUCTURE, THE EXTRA DOMAINS IN MORE COMPLEX CHANNELS ARE THE REGULATORY ELEMENTS THAT CONTROL THE OPENING OF CHANNELS AS WELL AS OTHER MORE COMPLEX FEATURES OF VOLTAGE SENSORS ETC
DO ALL CHANNELS EVOLVE FROM THE PRIMORDIAL BACTERIAL K CHANNEL
NO, SOME ARE THOUGHT TO HAVE EVOLVED SEPARATELY
WHAT IS AN EXAMPLE OF A CHANNEL THAT HAS EVOLVED SEPARATELY FROM THE PRIMORDIAL BACTERIAL K CHANNEL
NICOTINIC ACH CHANNELS
GABA CHANNELS
WHAT ARE THE STRUCTURE OF NICOTINIC ACH CHANNELS AND GABA CHANNELS THAT MAKE THEM DIFFERENT FROM THE EVOLUTIONARY PRIMORDIAL BACTERIAL K CHANNEL
THEY ARE PENTAMERIC
THEY HAVE NO P LOOP
SUBUNITS COME TOGETHER TO FORM A …………..
PORE
WHAT IS THE FUNCTION OF A P LOOP
P LOOPS COME TOGETHER TO CREATE A HIGHLY SELECTIVE FILTER/GATE
EXPLAIN THE PROCESS OF A K+ ION MOVING THROUGH A PORE
TO BE SMALL ENOUGH TO FIT INTO THE PORE, K+ MUST LOSE ITS WATER
ITS BINDING GENERATES ENERGY TO OPEN THE CHANNEL
K+ LINE UP TO FIT IN THE PORE CREATING REPULSION WHICH CAUSES FLOW CONDUCTION
THE PORE MUST BE OPEN AT BOTH ENDS
HOW MANY TM DOMAINS DO VOLTAGE GATED K+ CHANNELS HAVE
6
WHAT IS THE STRUCTURE OF A VOLTAGE GATED K+ CHANNEL SUCH AS KV1
- 6 TM DOMAINS
- 4 SUBUNITS
- TM4 IS POSITIVELY CHARGED AND DETECTS POTENTIAL
- ADDITION OF ALPHA AND BETA SUBUNITS FOR REGULATION
- HAS AN INACTIVATION PEPTIDE
LIGAND GATED ION CHANNELS HAVE A …………….. PORE AND ARE …………….. SELECTIVE
LARGER
LESS
WHAT IS THE STRUCTURE OF A LIGAND GATED ION CHANNEL EG CYCLIC NUCLEOTIDE GATED CHANNELS
- 6TM DOMAINS
- EACH SUBUNIT ALSO HAS A CYCLIC NUCLEOTIDE BINDING BINDING DOMAIN
- FOUR SUBUNITS MUST COME TOGETHER TO CREATE THE ION CHANNEL
- THEREFORE THERE ARE 4 NUCLEOTIDE BINDING SITES PER CHANNEL
- AT LEAST 3 MUST BE FILLED FOR THE CHANNEL TO OPEN
IN ION CHANNEL STRUCTURE THE PORE IS USUALLY BETWEEN
S5 AND S6 TMS
WHAT DOES CYCLIC NUCLEOTIDE GATED CHANNELS BINDING DOMAIN DETECTS WHAT
CAMP
GGMP
WHAT IS THE STRUCTURE OF THE P2X RECEPTOR
- 2TM DOMAINS
- TRIMERIC
- GATED BY ATP
- BINDING OF 3 MOLECULES OF ATP CAUSES A CONFORMATIONAL CHANGE TO OPEN THE CHANNEL
WHAT IS THE STRUCTURE OF THE IONOTROPIC GLUTAMATE RECEPTOR
- 4TM DOMAINS
- TETRAMERIC (MADE UP OF A DIMER OF DIMERS)
- EXTENDED EC N TERMINUS WITH A GLUTAMATE BINDING SITE
- HAS A CLAM SHELL CLEFT (WHEN GLUTAMATE BINDS, THE CLEFT CLOSES AND THE PORE OPENS)
WHAT IS AN EXAMPLE OF AN IONOTROPIC GLUTAMATE TYPE LIGAND GATED ION CHANNEL
NMDA RECEPTOR
WHAT IS THE STRUCTURE OF A CYS LOOP LIGAND GATED ION CHANNEL
- 4TM
- NO P LOOP
- PENTAMERIC ASSEMBLY
- AMINO ACIDS LINE THE PORE AND CAN CHANGE SELECTIVITY FROM +VE TO -VE
- TO OPEN THE PROTEINS TWIST
- MUST HAVE TWO ALPHA SUBUNITS WHERE THE LIGAND BINDING SITE IS.
WHAT IS AN EXAMPLE OF A CYS LOOP LIGAND GATED CHANNEL
NICOTINIC ACHR
GABA A
WHAT IS DIFFERENT ABOUT THE CYS LOOP TYPE CHANNELS COMPARED TO OTHER ION CHANNELS
THEY ARE NOT EVOLVED FROM THE THE PRIMORDIAL BACTERIAL K CHANNEL
