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BM321: Biomedical Biochemistry > Block B Lecture 1 - Sensing the World > Flashcards

Block B Lecture 1 - Sensing the World Flashcards

1
Q

What are the 3 main senses?

A

Smell
Taste
Vision
(Slide 3)

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2
Q

What pathways do the αs, αi, αq and α12 variations of the alpha subunits of G proteins regulate and what do these lead to?

A

αs - Activation of adenylate cyclase - leading to an increase in cytosolic cAMP leading to cell growth and motility

αi - inactivation of adenylate cyclase - leading to a decrease in cytosolic cAMP - leading to cell motility

αq - activation of phospholipase C beta (PLCß) leading to an increase in intracellular Ca2+ - leading to cell proliferation (division)

α12 - activation of Rho GTPase - which can lead to cancer progression and metastasis

(Slide 4)

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3
Q

Which 2 scientists won the nobel prize in 2004 for “their discoveries of odorant receptors and the organisation of the olfactory system”?

A

Richard Axel and Linda Buck
(Slide 7)

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4
Q

What is the olfactory epithelium?

A

A special piece of tissue located in the upper part of the nasal cavity, responsible for detecting odours and relaying this sensory information to the brain
(Slide 8)

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5
Q

What does the olfactory epithelium include?

A

Exposed olfactory sensory neurons which are highly ciliated
(Slide 8)

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6
Q

Where are olfactory receptors expressed?

A

On cilia
(Slide 8)

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7
Q

How many types of olfactory receptor does any given neuron express?

A

1
(Slide 9)

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8
Q

What is G olf (the olf is meant to be a subscript but I can’t represent that and if I put it together it makes a fucking sport.)?

A

The alpha subunit of the heterotrimeric complex which is linked to Olf receptors, it stimulates adenylate cyclase
(Slide 9)

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9
Q

What happens after G olf stimulates adenylate cyclase?

A

cAMP which adenylate cyclase generates opens cation (positively charged ion) channels, which leads to depolarisation and action potential then propagates into the olfactory bulb in the brain
(Slide 9)

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10
Q

How are neurons arranged in the olfactory bulb in the brain?

A

All neurons expressing one particular olfactory receptor converge on their own discrete area
(Slide 10)

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11
Q

What is “the olfactory code”?

A

The system by which the brain interprets and distinguishes various smells through the activation of specific combinations of olfactory receptors
(Slide 11)

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12
Q

What can the olfactory code result in?

A

Similarly structured ligands eliciting very different smell responses
(Slide 11)

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13
Q

What are 3 examples of the body “having a sense of smell” in parts of the body other than the nose?

A

Answers include:

Odorant receptor hOR 17-4 which has been shown to interact with the floral odour “bourgeonal” and has a role in guiding the sperm to the egg

Receptors present in heart muscle cells are thought to be a metabolic regulator of heart function

Receptors activated in the immune system can promote death of certain types of leukaemia cells

Receptors in the skin increase the regeneration of skin cells and help wounds heal quickly

Receptors in the digestive tract may cause chronic diarrhoea or constipation but may also contribute to better digestion

(Slide 12)

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14
Q

What are the 5 basic types of taste?

A

Sweet
Bitter
Sour
Salty
Umami (savoury taste from some L-amino acids such as MSG)
(Slide 14)

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15
Q

Out of the 5 basic types of taste, which 2 have possible toxins / acidity?

A

Bitter and Sour
(Slide 14)

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16
Q

What receptors deal with each type of taste?

A

Umami - T1R1 + T1R3 dimer
Sweet - T1R2 + T1R3 dimer
Bitter - T2R dimers
Salty - ENaC receptors
Sour - PKD2L1 and CA IV receptors
(Slide 16)

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17
Q

What does taste receptor activation do to a cells membrane?

A

It depolarises it
(Slide 17)

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18
Q

What is a TRPM5?

A

It’s a calcium-activated non-selective cation channel which induces polarisation upon increases in intracellular calcium
(Slide 17)

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19
Q

Do taste responses depend on the taste cell type or the taste receptor type?

A

The taste cell type
(Slide 18)

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20
Q

How did scientists find out that taste responses depend on the taste cell type and not the receptor?

A

Via RASSL (Receptor Activated Solely by a Synthetic Ligand) experiments -

They made a artificial receptor activated by spiradoline (normally tasteless).

The RASSL was artificially expressed in mouse sweet or bitter taste cells, with the mouse reacting differently depending on the cell type.

(Slide 18)

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21
Q

What are 3 examples of smell based diseases?

A

Hyposmia - a reduced ability to detect smells / odours

Anosmia - partial or full loss of smell

Dysosmia - a change in your sense of smell

(Slide 19)

22
Q

What are 2 examples of taste based diseases?

A

Hypogeusia - a reduced ability to taste things

Ageusia - the loss of the ability to taste things
(Slide 19)

23
Q

Where is the optic nerve located?

A

At the very back of the eye
(Slide 22)

24
Q

Where is the retina located?

A

At the back and on the walls of the eye, behind the iris and lens
(Slide 22)

25
Q

Where is the iris located?

A

At the front of the eye, in front of the lens but behind the cornea
(Slide 22)

26
Q

Where is the cornea located?

A

In front of the eye, covering the lens and pupil
(Slide 22)

27
Q

Where is the lens located?

A

In the center of the eye, behind the iris and in front of the vitreous body

(Slide 22)

28
Q

What is the vitreous body?

A

A transparent, gel-like substance that fills the back of the eye, between the lens and the retina

(Slide 22)

29
Q

Where is the pupil located?

A

In the centre of the iris (the coloured part of the eye)
(Slide 22)

30
Q

What kind of receptor is rhodopsin?

A

A GPCR
(Slide 23)

31
Q

What “ligand” activates rhodopsin?

A

The photon
(Slide 23)

32
Q

What is a chromophore?

A

A molecule or chemical group that absorbs light at a specific wavelength and reflects a colour
(Slide 23)

33
Q

What chromophore does rhodopsin contain and where is it located?

A

Retinal, located in the transmembrane domains of rhodopsin
(Slide 23)

34
Q

How does rhodopsin trigger a signal transduction cascade?

A
  1. Light induces the conversion of cis retinal to trans retinal
  2. This induces a conformational change in rhodopsin
  3. This then triggers the heterotrimeric G protein signal transduction cascade

(Slide 23)

35
Q

How does trans retinal get converted back into cis retinal?

A

It dissociates from rhodopsin and undergoes enzymatic recycling to return to its cis form
(Slide 23)

36
Q

Does light polarise or depolarise photoreceptors?

A

It hyperpolarises them
(Slide 24)

37
Q

What does light hyperpolarisation of photoreceptors do?

A

it stops the inhibition of the neighbouring bipolar cell, which enables it to send a signal to the brain
(Slide 24)

38
Q

What do rods deal with?

A

Low light levels, and motion
(Slide 26)

39
Q

What do rods express?

A

Rhodopsin
(Slide 26)

40
Q

What can cons differentiate?

A

Colours and details
(Slide 26)

41
Q

What do cones express?

A

Different kinds of opsin
(Slide 26)

42
Q

What are the 3 different types of cones and what colours and lengths do they deal with?

A

L(Long) cones - red
M (Medium) cones - green
S (Short) cones - blue

(Slide 26)

42
Q

What are 4 diseases of the retina / eye signalling?

A

Night blindness
Age-related macular degeneration
Diabetic retinopathy
Colour blindness
(Slides 27 and 28)

43
Q

What is night blindness caused by?

A

A deficiency in vitamin A - results in a shortage of retinal as vitamin A gets converted into retinal
(Slide 27)

44
Q

What are the 2 types of macular degeneration and what are they caused by?

A

Wet - vasculature leakage problem
Dry (aging related) - thinning of macular and deposition of drusen material
(Slide 27)

45
Q

What are drusen?

A

Yellow-white deposits that are made up of a complex mixture of proteins and fats
(Slide 27)

46
Q

What is diabetic retinopathy and what can it result in?

A

Microvasculature damage in the retina - can lead to loss of vision
(Slide 28)

47
Q

Why is colour blindness more common in makes?

A

As the genes for cones are on the X chromosome and males do not have a second X chromosome to compensate
(Slide 28)

48
Q

What does the OPN4 gene encode?

A

A GPCR opsin called melanopsin located in the retina (also known as OPN4…. the lectures don’t mention OPN4 means both btw :) )
(Slide 29)

49
Q

What cells express melanopsin?

A

Retinal ganglion cells
(Slide 29)

50
Q

What is the purpose of melanopsin?

A

They do not participate in image formation and instead sense light to help the body form a day / night differential - body clock
(Slide 29)

51
Q

Where can retinal ganglion cells signal to?

A

The Suprachiasmatic nucleus (SCN) - located in the brain
(Slide 29)

BM321: Biomedical Biochemistry (10 decks)

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