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21 fall: Biochem > Test 3: 46 and 47 > Flashcards

Test 3: 46 and 47 Flashcards

1
Q

Your patient suffers from excessive thirst and is excreting large volumes of dilute urine. Plasma osmolarity is increased, but urine osmolarity is decreased. What is the problem and what is the cause?

A

Your patient suffers from nephrogenic diabetes Insipidus, an improper response of the kidney to ADH, leading to a decrease in
the ability of the kidney to concentrate the urine by removing free water. This is caused by mutations in the vasopressin V2 receptor

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2
Q

Your patient suffers from retinitis pigmentosa. What is the problem and what is the cause?

A

Mutation in the rhodopsin gene causing retinal degeneration

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3
Q

___ are the largest family of transmembrane receptors

A

G protein coupled receptors (GPCRs)

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4
Q

Half of GPCR are devoted to ___

A

sensory transduction

G protein coupled receptors

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5
Q

GPCRs help with ___

A

sensory transduction, neural, physiological and cardiovascular functions

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6
Q

GPCR pathway overview

A

GPCR (7-TMR: 7 alpha helical)

Trimeric G protein

Cyclic nucleotides

membrane channels

membrane signals

gene regulation

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7
Q

the __ subunit of G proteins binds to GTP

A

alpha

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8
Q

explain how light gets to brain

A

light interacts with photoreceptors in the back of the eye that are imbedded in a pigment epithelium

those photoreceptors interact with bipolar cells which interact with ganglion cells that form together to form the optic nerve

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9
Q

Two types of photoreceptor cells?

A

rod and cones

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10
Q

___ are photoreceptor cells that help with night vision.

A

Rods

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11
Q

___ are photoreceptor cells that help with day vision.

A

cones

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12
Q

Which photoreceptor cells detect color?

A

cones

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13
Q

rod cells

A

about 100 million per retina

Very sensitive to light

Vision in dim light (night vision)

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14
Q

cone cells

A

about 3 million per retina

Less sensitive to light

Vision in bright light, detect color

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15
Q

there are more rod cells than cone cells in the eye. True or False

A

True

100 million rods, 3 million cones

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16
Q

the outer segment of a rod cell are filled with

A

membrane discs

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17
Q

What is the light receptor that sits on the membrane disc of rod cells?

A

rhodopsin

N terminal faces outward of cell

C terminal faces toward nucleus

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18
Q

what is the name of the protein that sits inside rhodopsin?

A

11 cis retinal

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19
Q

where does 11 cis retinal come from

A

carrots

Beta carotone → all trans retinal

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20
Q

what does light do to 11 cis retinal

A

changes from 11 cis retinal

to

all trans retinal

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21
Q

rhodopsin + light=

A
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22
Q

unusual properties of 11 cis retinal

A

stability- when in dark very stable in cis form

sensitivity- if hit by photon of light will quickly flip from cis to trans form

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23
Q

visual pathway in a nut shell

A

rhodopsin +light→ activated rhodopsin

activated R will activate transducin to bind to GTP instead of GDP

active transducin will activated PDE (phosphodiesterase)

PDE will make cGMP to GMP

decrease in cGMP will cause channels to close which membrane hyperpolarization which will cause signal to travel across neuron to brain saying “we saw the light!”

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24
Q

amplification step of light

A

1 rhodopsin can activate 500 transducin

activated PDE can cleave cGMP to GMP at 4200 GMP per second = very fast drop of cGMP in the cell

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25
Q

In the dark, sodium flow into the cell through the channels yielding a depolarized rod cell membrane. At the synaptic terminal ___ is released to signal bipolar nerve cells causing a “dark current”.

A

glutamate

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26
Q

In light, the rod membrane channels close yielding a ___ membrane. This leads to less ___ released at the synaptic terminal and a reduction in signal to the bipolar nerve cells. This indicates light has been detected.

A

hyperpolarized

glutamate

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27
Q

A decrease in glutamate released at the synaptic terminal indicates ___ has been detected

A

light

decrease in cGMP = Na+ channels close, no Na into cell= hyperpolarization of membrane =less glutamate released

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28
Q

what cause Na channels to close when light hits rods?

A

cGMP decreases

light activated Rhodopsin which binds to transducin, this causes transducin to let go of GDP and bind to GTP. alpha subunit of activated transducin then leaves and binds to gamma subunit of PDE. This activates PDE to change cGMP to GMP= decreased cGMP in cell = Na+ channels close, no Na into cell= hyperpolarization of membrane =less glutamate released

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29
Q

when light hits cell, Na and Ca are not brought into cell because channel is closed. This decrease in calcium leads to ___

A

activation of guanylate cyclase, which leads to synthesis of cGMP, which leads to opening of Ca, Na channels in cell

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30
Q

Low Calcium in cell after light hits: activates guanylate cyclase. ___ increases.

A

cGMP

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31
Q

GTPase of transducin: Transducin goes from GTP to GDP state, releases ___. So PDE and Transducin are inactivated.

A

gamma subunit of PDE

32
Q

Rhodopsin: Phosphorylated by rhodopsin kinase and interacts with ___ to stop signal to transducin.

A

arrestin

33
Q

how to stop rhodopsin from interacting with transucin

A

Phosphorylated by rhodopsin kinase and interacts with arrestin to stop signal to transducin.

34
Q

Rhodopsin internalized: convert 11-trans to ___ , remove phosphates on rhodopsin, and recycle ___ to cell surface.

A

11-cis retinal

rhodopsin

35
Q

___: in light it binds to transducin beta gamma subunits. This keeps transducin alpha active longer: keeps pathway activated

A

Phosducin

36
Q

Phosducin: in light it binds to transducin ___ subunits. This keeps transducin __ active longer: keeps pathway activated

A

beta gamma

alpha

37
Q

Phosducin: in dark is ___ and no longer binds transducin beta-gamma subunits. Reduces transducin activity and keeps pathway in ___ activity.

A

phosphorylated

lower

38
Q

Mutation in the rhodopsin gene causing retinal degeneration called ___

A

retinitis pigmentosa

39
Q

treatment for retinal degeneration

A

Vitamin A

Omega3 fatty acids

Retinal cell transplants

Growth factors

Retinal prosthetic devices that detect light

Gene Therapy

40
Q

Achromatopsia

treatment:

A

can only see in dark and black and white, no colors; daylight vision impaired

gene therapy

41
Q

when light hits rhodopsin what happens first?

A

11 cis retinal is converted to 11 trans retinal

42
Q

what is the role of arrestin in the visual pathway

A

it binds to phosphorylated rhodopsin

43
Q

In the visual pathway, what is the tole of recoverin

A

to active guanylate cyclase

44
Q

where is 11 cis retinal derived from

A

vit A

45
Q

what is a major function of the membrane discs in the outer segment of rod cells?

A

to increase SA to allow more space for rhodopsin

46
Q
A
47
Q

what protein domain usually interacts with membranes

A

FYVE domain

48
Q

what is a main function of scaffold proteins

A

to efficiently link kinases in a signaling pathway

49
Q

most growth factors exert their function in what stage of the cell cycle?

A

G1

50
Q

Why are anti-angiogenic drugs believed to be potentially useful for anti cancer therapy?

A

They specifically target the growth of normal endothelial cells

51
Q

which of the following expresses multiple different sensory receptors per cell?

rod

cone

olfactory receptor

gustatory receptor

sensitivity training

A

gustatory receptor

52
Q

what is red-green the most common form of color blindness?

A

the red and green receptor genes lie near each other and often undergo recombination

53
Q

in the dark, how often does 11 cis retinal spontaneously change to 11 trans retinal?

A

once every 500 years

54
Q

three cone receptors

A

blue 455

green 530

red 625

55
Q

why is color blindness more common in males?

A

red and green sit on X chromosome

56
Q

what are some species differences of color perception?

A
57
Q
A

olfactory epithelium (pseudostratified)

olfactory cells stretch into the basal membrane and at the other end have olfactory vesicles

sustentacular cells- microvilli

58
Q

olfactory vesicle have ___ to increase surface area

A

cilia

59
Q

Insect pheromones can be detected at a few molecules ___

A

per animal

60
Q

Some airborne odorants are detected at parts per ___

A

trillion

61
Q

how many categories of smells?

A

13

Genetics suggests hundreds or more receptors.

Fruity, Amines, Herbaceous, Organic Acids, Minty, Sulphydryl Compounds, Floral, Methoxy Pyrazines, Putrid, Alkyl Pyrazines, Aromates, Stereoisomers and Aldehydes

62
Q

People with ___ cannot detect particular categories of odor molecules.

A

anosmias

63
Q

biochemistry of olfaction

A
  1. Cell Surface Receptors
  2. Trimeric G Proteins- Golf for Olfaction
  3. Cyclic Nucleotides Adenylate Cyclase and cAMP (make more cAMP)
  4. Membrane Channels open
  5. Nerve Impulse
  6. Deactivation of Biochemical Pathway
  7. Clearing of Odorant Molecule
64
Q

difference between vision and smell biochemistry

A

Cell Surface Receptors

  1. Trimeric G Proteins

Golf for Olfaction

Transducin for Vision

  1. Cyclic Nucleotides

Adenylate Cyclase and cAMP for Olfaction (make cAMP)

Phosphodiesterase and cGMP for Vision (breakdown cGMP)

  1. Membrane Channels

Open for Olfaction (depolarization)

Close for Vision (hyperpolarization)

  1. Nerve Impulse
  2. Deactivation of Biochemical Pathway
  3. Clearing of Odorant Molecule
65
Q

Olfactory Receptors are expressed from only one ___ ,and only one ___ per receptor cell.

A

allele, (mom or dad not both)

receptor gene

66
Q

how to deactivate smell

A

slow suppression: neural

fast suppression: biochemical: phosphorylation of Golf and binding of arrestin to receptor

cytochrome P450 helps clear odorants

67
Q

___ helps clear odorants from smell receptors

A

cytochrome P450

68
Q

why is olfactory system so sensitive

A
  1. Air-Water Partition
  2. High Surface Area due to Olfactory Cilia
  3. High Density of Receptor Proteins in the Membrane
  4. Biochemical Amplification
  5. Neural Processing
69
Q

5 types of taste

A

sweet

salty

bitter

sour

umami(mono-sodium glutamate)

70
Q

Gustatory system has ___ receptors

A

50-80

71
Q

how does gustatory system work

A
  1. Gusducin(g protein): binds GTP or GDP
  2. Activates PDE: cleaves cAMP to AMP
  3. Closes sodium membrane channel
72
Q

g protein of taste system

A

gusducin

73
Q

g protein of sight system

A

transducin

74
Q

in vision c___ turns into ___

while in taste c___ turns into ___

in smell ___ turns to ___

A

cGMP → GMP

cAMP → AMP

AMP → cAMP

75
Q

in taste ___ receptor can be expressed in each cell, this is different from sight and smell with ___ receptor per each cell

A

multiple

one

76
Q

GPCR can effect

A

Vision

Olfactory

Gustatory

Neurotransmission: Behavior, serotonin, dopamine, GABA, glutamate

Immunity: Chemokine receoptors

Autonomic nervous system: Blood pressure, heart rate, digestion

Homeostasis: Water balance

Growth and Metastasis

21 fall: Biochem (44 decks)

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