smell taste and vision

Question 1

how does taste perception work

Answer 1

chemicals in foods are detected by taste buds:
5 elementary taste qualities:

BITTER
SWEET
UMAMI

SWEET
SOUR

Question 2

how do taste buds control the concentration at which diff chemicals are sensed

Answer 2

THRESHOLD CONCENTRATIONS - evolutionary mechanism developed to ensure that the body takes up enough substances for life but avoid dangerous ones

EG: we need 120g of glucose daily for the body - hence the taste buds only sense glucose at HIGH saturaitons - to promote the intake

EG: sour (acidic) and bitter substances can be bad for the body homeostasis so the receptors sense them at low concentrations mM

Question 3

3 diff cells in taste perception

Answer 3

TYPE 1: taste supporting cells. Contain ectoATPases for ATP clearance and regulate ion balance

TYPE 2: contain transmembrane receptors for umami, bitter and salty

TYPE 3: contain channels for NT depol to taste sweet and sour

Question 4

umami taste is associated with

Answer 4

glutamate receptors

Question 5

Signal transduction of taste

Answer 5

1. Chemicals sensed and bind to receptors
2. change in membrane polarisation
3. Ca2+ released and internalised
4. this binds with SNARE complex to allow fusion of presynaptic vesicle to membrane
5. release of NTs that induce their effect

Question 6

what are sweeteners

Answer 6

mimic sugar by binding to diff regions of the sugar receptors

hence the body percives them as sugars

Question 7

what is the main NT for taste

Answer 7

ATP!!!! - acts solely as a NT and not an energetic compound

-controls multiple cells (both autocrine and paracrine) for multiple types of flavors

ATP CLEARING: necessary to remove the NT from the area to maintain a high velocity of taste perception - this is done with the ectoATPases present on type 1 cells

Question 8

what are the conditions that an odorant must satisfy

Answer 8

small molecule
hydrophobic
volatile

Question 9

structure and location of olfactory neurons

Answer 9

-location on olfactory epithelium in upper nasal chamber, axons protrude through cribriform plate

-soma with nuc
-aoxn for transfer of info
-CILIA: non mobile bcos they lack the motor proteins - act as receptors to perceive chemical signals and allow NT release

Question 10

what is a SOS point about odorant/receptor recognition in olfaction

Answer 10

FLEXIBLE ASSOCIATION:
neither odorant nor receptor are rigid: many odorants can bind in diff way to receptors and diff receptors can bind to multiple diff odorants

ADVANTAGE: almost infinite combination of smells can be picked up that allows us to better interact and have awareness of out encironment

Question 11

olfactory signal transduction

Answer 11

TAKES PLACE WITHIN THE OLFACTORY CILIA:
1. g protein coupled
2. Ca2+ activation
3. NT release

TERMINATION OF THE SIGNAL: with the removal of calcium (usually by SERCA)

Question 12

cells and molecules involved in vision

Answer 12

CELLS: in retina
1. cones: colour perception
2. rods: perception of light intensity

KEY MOLECULE: 11 cis retinal and is produced by vitA.

RETINAL IS CONTAINED WITHIN:
-opsin in cones
-rhodopsin in rods