Test 3: 46 and 47 Flashcards by jillian Bastidas

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?

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

Mutation in the rhodopsin gene causing retinal degeneration

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___ are the largest family of transmembrane receptors

G protein coupled receptors (GPCRs)

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Half of GPCR are devoted to ___

sensory transduction

G protein coupled receptors

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GPCRs help with ___

sensory transduction, neural, physiological and cardiovascular functions

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GPCR pathway overview

GPCR (7-TMR: 7 alpha helical)

Trimeric G protein

Cyclic nucleotides

membrane channels

membrane signals

gene regulation

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the __ subunit of G proteins binds to GTP

alpha

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explain how light gets to brain

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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Two types of photoreceptor cells?

rod and cones

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___ are photoreceptor cells that help with night vision.

Rods

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___ are photoreceptor cells that help with day vision.

cones

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Which photoreceptor cells detect color?

cones

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rod cells

about 100 million per retina

Very sensitive to light

Vision in dim light (night vision)

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cone cells

about 3 million per retina

Less sensitive to light

Vision in bright light, detect color

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

True

100 million rods, 3 million cones

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the outer segment of a rod cell are filled with

membrane discs

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

rhodopsin

N terminal faces outward of cell

C terminal faces toward nucleus

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

11 cis retinal

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where does 11 cis retinal come from

carrots

Beta carotone → all trans retinal

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what does light do to 11 cis retinal

changes from 11 cis retinal

all trans retinal

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rhodopsin + light=

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unusual properties of 11 cis retinal

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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visual pathway in a nut shell

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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amplification step of light

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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**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”.**

glutamate

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.

hyperpolarized glutamate

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

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

what cause Na channels to close when light hits rods?

**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**

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

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

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

cGMP

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

gamma subunit of PDE

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

arrestin

how to stop rhodopsin from interacting with transucin

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

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

11-cis retinal rhodopsin

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

Phosducin

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

beta gamma alpha

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

phosphorylated lower

Mutation in the rhodopsin gene causing retinal degeneration called \_\_\_

**retinitis pigmentosa**

treatment for retinal degeneration

Vitamin A Omega3 fatty acids Retinal cell transplants Growth factors Retinal prosthetic devices that detect light Gene Therapy

Achromatopsia treatment:

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

when light hits rhodopsin what happens first?

11 cis retinal is converted to 11 trans retinal

what is the role of arrestin in the visual pathway

it binds to phosphorylated rhodopsin

In the visual pathway, what is the tole of recoverin

to active guanylate cyclase

where is 11 cis retinal derived from

vit A

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

to increase SA to allow more space for rhodopsin

what protein domain usually interacts with membranes

FYVE domain

what is a main function of scaffold proteins

to efficiently link kinases in a signaling pathway

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

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

They specifically target the growth of normal endothelial cells

which of the following expresses multiple different sensory receptors per cell? rod cone olfactory receptor gustatory receptor sensitivity training

gustatory receptor

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

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

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

once every 500 years

three cone receptors

blue 455 green 530 red 625

why is color blindness more common in males?

red and green sit on X chromosome

what are some species differences of color perception?

olfactory epithelium (pseudostratified) **olfactory cells** stretch into the basal membrane and at the other end have **olfactory vesicles** **sustentacular cells-** microvilli

olfactory vesicle have ___ to increase surface area

cilia

Insect pheromones can be detected at a few molecules \_\_\_

per animal

Some airborne odorants are detected at parts per \_\_\_

trillion

how many categories of smells?

13 ## Footnote Genetics suggests hundreds or more receptors. **Fruity, Amines, Herbaceous, Organic Acids, Minty, Sulphydryl Compounds, Floral, Methoxy Pyrazines, Putrid, Alkyl Pyrazines, Aromates, Stereoisomers and Aldehydes**

People with ___ cannot detect particular categories of odor molecules.

anosmias

biochemistry of olfaction

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

difference between vision and smell biochemistry

Cell Surface Receptors 2. Trimeric G Proteins **Golf for Olfaction** **Transducin for Vision** 3. Cyclic Nucleotides **Adenylate Cyclase and cAMP for Olfaction (make cAMP)** **Phosphodiesterase and cGMP for Vision (breakdown cGMP)** 4. Membrane Channels **Open for Olfaction (depolarization)** **Close for Vision (hyperpolarization)** 5. Nerve Impulse 6. Deactivation of Biochemical Pathway 7. Clearing of Odorant Molecule

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

allele, (mom or dad not both) receptor gene

how to deactivate smell

slow suppression: neural fast suppression: biochemical: **phosphorylation** of **Golf** and binding of **arrestin** to receptor cytochrome P450 helps clear odorants

\_\_\_ helps clear odorants from smell receptors

cytochrome P450

why is olfactory system so sensitive

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

5 types of taste

sweet salty bitter sour umami(mono-sodium glutamate)

Gustatory system has ___ receptors

50-80

how does gustatory system work

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

g protein of taste system

gusducin

g protein of sight system

transducin

in vision c\_\_\_ turns into \_\_\_ while in taste c\_\_\_ turns into \_\_\_ in smell ___ turns to \_\_\_

cGMP → GMP cAMP → AMP AMP → cAMP

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

multiple one

GPCR can effect

**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**

Test 3: 46 and 47 Flashcards

(76 cards)