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Cell Bio > Osmotic Stress > Flashcards

Osmotic Stress Flashcards

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1
Q

What is osmosis

A

The spontaneous diffusion of water molecules across a semipermeable membrane from a solution of lower solute concentration to one of higher solute concentration

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2
Q

What is the hydrostatic pressure

A

Osmotic pressure between solutions use van Hoff equation to determine the solution B to prevent water flow pie = RT (Cb-Ca)

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3
Q

What does osmotic pressure depend on

A

The total number of all solute moelcules not just concentration which can be ions or non ison

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4
Q

Does 1 mol of glucose have the same osmotic pressure as 0.5 NaCl

A

Yes because NaCl dissasociates into 0.5 Na and 0.5 Cl

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5
Q

What determines the volume of an individual cell

A

The movement of water across the plasma membrane

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6
Q

What is istonic

A

Solution causes neither shrinking nor swelling of cells

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7
Q

What is hypertonic vs hypotonic

A

Hypertonic is the concentration of solute is higher than in the cyrosl as water moves out
Hypoton the concentration of solutres is lower thatn cytsol as water moves in

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8
Q

What is the concentration of Na Cl and K

A

Na Cl are higher outside than inside the cell and K is higher inside

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9
Q

What do the low concentrations of Na Cl

A

Balance the high intracellular concentration of organic compounds equalizing the osmotic pressure and preventing the net influx of water

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10
Q

How is water mediated

A

Transmembrane protiens called aquaportins

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11
Q

What was the frog oocyte experiment

A

Resistant to pont water impermable to water
Control oocyte remained unchanged under hypotonic conditions
If injected with aquaporins they become sensitive to hypotonic solution
Aquaporins specifically increase the permability of biomembranes to water

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12
Q

How many transmebranes are there

A

Each subunit contaisn six transmembrane alpha helicas connected by 2 hyrdophillic loops (Asp)

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13
Q

Why is it specefic to water binding

A

0.28nm in diameter so only slightly larger than the diameter of a water molecule forms hydrogen bonds with channel-lining hydrophilic amino acids so block passage of ions

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14
Q

How many genes in human express protiens for aquaporin

A

11

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15
Q

What happens if you inactivting mutations in the aquaporin 2 gene

A

Causes diabetes insipidus a kidney diease marked by excretion of large volumes of dilute urine due to inability of certain kidney cells to resorb water form the urine

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16
Q

What is the osmotic concertation measured in

A

Osmoles that corresponds to the total molar concentration of solute particles both molecules and ions

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17
Q

What is osmolality

A

The solution is the number of osmoles per kg solvent usually expressed in millosmoles

18
Q

Is hypersomotic conditions in animal tissues unusual

A

NO lymphoid and hepatic tissues are hyperosmolar and kidney so animal cells have systems that allow them to be adapted to hypertonic conditions

19
Q

What is osmotic shock or osmotic stress

A

Sudden change in the solute concentration around a cell causing a rapid change in the movement of water across its cell membrane in cel lvolume

20
Q

What is an immediate cellular response

A

Takes place within seconds and involves changes in the intracellular concentrations of ions such as K NA and CL

21
Q

What are some other immediate responses

A

Cytoskelton reorganization
activation of integrinis
Receptro tyrosine kinases
various channles and transporters

22
Q

What is the most common osmotic stress

A

Hypertonic conditions

23
Q

What is TonEBP

A

Specefic transcrption factors that are releated to signal transduction networks leading to synthesis of organic molecules

24
Q

What is one of the immediate responses to hyperosmotic stress

Do with the skelton

A

Remodling actin cytoskelton induces hyperoniciinty and accumulation of F-actin and reduces stress fibers in the cytoplasm that helps cells to resist increased osmotic pressure

25
Q

What does the activation of TonEBP require

A

Nuclear redistribution, dimerization and phosphorylation

26
Q

What is the TonEBP pathway

A

Binds to the TonE enhancer elements and stimulate transcrption of osmoprotective genes (SMIT) (AR) (BGT1) allowing cells to adapt to the high osmolaity by accumulating intracellular non-ionic organic osmolytes or compatible solutes

27
Q

What compounds are induced

A

Inositol
Sorbitol
Betaine
Taurine
Glycerphosphocloine
Glycerol
non tocix and allow cells to adapt to high osmolality reducing intracellular ionic strength which would be more dangerous as ions

28
Q

What else TOnEBP stimulate

A

Transcrption of genes encoding HSP70 and AqB2 and UTA which help to cope and prevent cell death

29
Q

What are the domains of TonEBP

A

Consists of at least 7 domains two transactivation domains DNA binding domain RHD dimerization domain and three doamine to nuclear transport (NES, AED, NLS)

30
Q

Why is NFAT5 different from other NFATS

A

Lacks docking sites for calcineurin and thus the calcimum calcineurin signaling cascade is dispensable for its activating

31
Q

What is NFATS5

A

Transcrpition regulator of the cellular response to hypertonic stress since its sevelral domains are senestive to hypertonian leading to TonEVP activation adn translocation to the nucleus

32
Q

How TonEBP activated

A

First pos-translational modifications of TonEVP including phosphorylation possibly sumolyation (nuclear localization)
Second interaction with other regulatory molecules such as RNA helicase A, Pls and ROS

33
Q

How does TonEBP dimerize

A

Inhibiton of RHA binding to RHD which unblocks dimerization domain and allows TonEBP dimerization

34
Q

When is TonEBP active

A

Isotonic conditions based on expression of its target genes

35
Q

What is bidriectional regulation

A

TonEBP activity and nuclear localzation increase with ambient toncitis is lowered whereas it increases when ambient tonicity is elevated

36
Q

Where is TonEBP is different condtions

A

Cytoplasma-Hypotonic
Both_ Isotonic
Nucleus- Hypertonic

37
Q

How does the dimer work with TonEBP

A

Complete circle around DNA interacating RHD-C and two RHR-N domains
One binds to the consensus tonicity-responsive enhancer wile the other binds the nonconsensus seqeunce

38
Q

What are the two different modes of TonEBP

A
  1. Nuclear redistribution of available TonEBP
  2. Increase in the abudncae of TonEBP in mRNA
39
Q

What happens if long term to hypertonic stress

A

Takes more time they express the sufficient basal elvels to mediate response to hypertonic stress

40
Q

What does the TonEBP expression in other tissues that are normally not exposed to hypertonic environment

A

A general safety system that protects agains pathologic hypertonicity

Cell Bio (13 decks)

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