Lecture 12

Question 1

Odorant perception

Answer 1

Main olfactory epithelium contains 12 sensory cilia and 1000000 sensory neurons

Olfactory neurons converge

Question 2

Odorant receptors

Answer 2

• members of 7TM-receptor family

> 1000 different odorant receptor genes

Question 3

Odorant perception signalling pathway

Answer 3

[cAMP] peaks in <100 msec

Voltage-gated sodium channels in cell body activated

Trigger action potential

G protein is Golf

Question 4

Photodetection in retina

Answer 4

300nm to 750nm

Question 5

How many rod cells in human retina?

Answer 5

90 x 10^6

1000 discs

Question 6

What occurs when rhodopsin is exposed to light-induced isomerization?

Answer 6

Forms meta-rhodopsin II (activated opsin)

H+ released

Question 7

Light perception signalling pathway

Answer 7

Light -> rhodopsin

Activates transducin

GTP -> GDP

Ga subunit of transducin binds phosphodiesterase

cGMP -> GMP

Closure of cGMP-gated channels hyperpolarises the plasma membrane

Question 8

What does hyperpolarisation of plasma membrane do?

Answer 8

Reduce the rate of neurotransmitter (glutamate) release

Question 9

Calcium-ABA signalling in guard cells

Answer 9

Increase in K+, Cl-, malate2- = increased turgor, guard cell opens

Decrease in K+, Cl-, malate2- = decreased turgor, guard cell close

Question 10

What does ABA induce?

Answer 10

Increased cytosolic calcium ion levels

Ca2+ influx through calcium ion permeable PM channels

Ca2+ release from endomembrane stores

Question 11

What is responsible for Potassium ion influx and efflux in guard cells

Answer 11

KAT1 and GORK

TPK1 transports K+ from vacuole to cytoplasm

Question 12

What is responsible for An- efflux

Answer 12

SLAC1

Question 13

What transports calcium ions into cytoplasm

Answer 13

ICa and TPC1 (from vacuole)