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10

Indeed, bacteria are susceptible to osmotic stress from being in pure water. They are also susceptible to starvation in such an environment. However, wild bacteria tend to have many mechanisms that protect against this and allow them to survive in spite of being exposed to water. Note, also, that freshwater can serve as a habitat for many species of ...


9

Great question, for which still no definite answer is known despite ~100 years of research. A simple physical basis for the wrinkling however seems unlikely as glabrous skin without sweat glands does not wrinkle, and as wrinkling requires the activity of specific nerves. Moreover plausible evolutionary ideas, which used to be popular, such an anticipated ...


8

The reason why the cell would shrink more in CaCl2 solution is because it has a higher van't Hoff factor i.e. total number of dissociated ionic species per solute molecule (it is 2 for NaCl whereas it is 3 for CaCl2). (Nonionic solutes do not dissociate and will therefore have a van't Hoff factor of 1) Osmotic pressure (and other colligative properties) ...


5

Short answer, yes. The fresh water concentration inside saltwater fish is higher than the surrounding sea water, and the salt concentration inside the fish is lower. This means that fresh water continuously flows out of the fish through their gills via osmosis. To combat this loss of fresh water, fish must constantly be drinking sea water to replenish the ...


5

The bag will swell. Diffusion results in molecules moving down their concentration gradient. In the set-up described only glucose and water are able to diffuse. Glucose is at the same concentration inside and out so there will be no changes in glucose concentration. Water will move into the bag because it is effectively at a lower concentration (more ...


5

This paper is a compelling example of an effect of osmotic pressure on enzyme function. Restriction enzymes are normally very selective in the base sequences of sites at which they cut DNA, but in some conditions they show cutting at off-target sites, called "star activity." "Star activity" increased for some restriction enzymes almost linearly with osmotic ...


5

Great question, the answer has to do with the definition of osmotic pressure and the difference between this pressure and "hydrostatic pressure" which is the water pressure you are thinking of. Here is the definition of "osmotic pressure" given by Google: the pressure that would have to be applied to a pure solvent to prevent it from passing into a given ...


5

Fluid movements across capillary wall is determined by 2 main factors. Hydrostatic Pressure (Blood Pressure) - tends to push fluid out of the blood vessel Osmotic Pressure - Tends to pull fluid back into the blood vessels mainly due to the presence of plasma proteins. (especially albumin) Important points you should know Hydrostatic pressure or blood ...


4

Comparative physiology of body fluid regulation in vertebrates Cells are not passive components that always return to osmotic equilibrium. Through hormonal, cell signaling, and the number of pores for ion and water exchange marine animals can maintain osmoregulation in various aquatic environments. In land mammals osmoregulation is more passive since it is ...


3

No, the chloride cells in the gills rely on the relationship between chloride and sodium to remove salts out of the body against the gradient. Switching the environment to sugar would cause the chloride cells to not be able to maintain ionic regulation. See the below link for basic info on chloride cells: https://en.m.wikipedia.org/wiki/Chloride_cell


3

Normally, epithelial cells of mucous membranes express a chloride ion channel that allows movement of Cl- down its electrochemical gradient and out of the cell. This increase in extracellular electrolytes draws water out of the cells by osmosis, hydrating the mucus. In cystic fibrosis, this protein is defective, most commonly caused by misfolding and ...


3

What is "Osmotic Pressure"? Consider the following system -1 : Fig.1: Left container: Pure water (Solvent). Right container: Solution of glucose (solute) in water (solvent); separated with a semi-permeable membrane. In this system; as we know, water (solute) will flow from left container (Lower concentration of solute) to the right (higher ...


3

I think you've got the solutions the wrong way round and that you should be applying the pressure on the non-pure solution, not the pure solution. Pure water is drawn in through the membrane so you have to put pressure on the non-pure solution to keep it out. Which textbook are you using? See the following quote from Voet et al. 5th ed. p. 30 and figure from ...


3

The LD 50 listed on the wikipedia page you link to is 90 mL/kg, which would be about 6 liters for a 68 kg (150 lb) person. This is consistent with at least one report, where someone died from drinking 7 liters of water in 1.5 hours. The mechanism by which water kills people is by lowering the amount of ions (chiefly sodium) in the blood. A condition called ...


3

You're correct that tonicity needs two solutions to define. Osmolarity (or osmotic concentration) is the measure of solute concentration, defined as the number of osmoles of solute per litre (L) of solution (Osm/L). Tonicity, on the other hand, refers to the relative concentration of two solutions separated by a semipermeable membrane. The difference is ...


3

Osmosis works across every cell membrane along a concentration gradient as its a physico-chemical principle. Water can cross the membrane (or cell wall), while the substance dissolved in it (for example salts) can not. Because eukaryotic cells only have a cell membrane, they will burst eventually, while bacteria (and also plant cells) have a more rigid cell ...


2

Since posting, I did some more research using background refs from the intro (who knew?). The trick seems to be that when protons are pumped out, the cell regenerates them from water in order to maintain pH. So the solute concentration DOES increase inside the cell with more Na/H transport.


2

Osmotic pressure: pressure applied by a solution to prevent the inward flow of water across a semi-permeable membrane. Osmotic potential: the potential of water molecules to move from a hypotonic solution to a hypertonic solution across a semi-permeable membrane. Osmotic pressure can be calculated using the following formula: $$Π = iMRT$$ where $Π$ is ...


2

Bulk flow and osmosis are different; I'm guessing your text might be talking about using osmosis to drive bulk flow, but they are occurring at different stages. For example, if you get your water from a water tower, your house's water pressure is driven by gravity. However, the water tower could be filled by an electric pump. You could say your water ...


2

I think you have the conceptual understanding down, but my guess is that the textbook is not representing the situation quite correctly. Based on the phrasing of the statement, I can imagine they are describing one of two situations: Imagine a dropping a cell in to a solution of 0.5 M urea with no other solutes. Urea will diffuse across RBC membranes due ...


1

In addition to killing microorganisms, the salt may provide a better environment for some 'beneficial' organisms, and a less beneficial environment for other 'problem' organisms. For instance, in production of kimchi and sauerkraut, salt encourages lactofermentation to the detriment of more harmful bacteria and fungi.


1

It doesn't As long as liquid water is present osmosis will never stop, the closest you can get is a point at which it happens at equal rates in both directions, called equilibrium. Plant cells will help you understand as osmosis will create immense internal pressure as water enters the cell even though the cell cannot expand thanks to the cell wall. the ...


1

Maybe this passage is referring to this experiment? The key missing from your description is that each potato is placed in water. When the cells are intact (unboiled), this causes water to flow into and out of the cells via osmosis: into the cells from the tray of water, and out from the cells into the salt. Once the cells are destroyed via boiling, there ...


1

INTRODUCTION: The basic process by which opening of stomata takes place is by endosmosis.Endosmosis causes an increase in turgidity in the guard cells thereby causing its opening. The closing of stomata is achieved by exosmosis which makes the guard cells flaccid. HOW DO THE REGULATION TAKES PLACE IN PLANTS: If you read the theory proposed by Levitt from ...


1

Peptidoglycan is formed by the linkage of molecules of NAM ( N-acetylmuramic acid) and NAG (N-acetylglucosamine) into a polysaccharide structure. Many of these structures are then formed into a lattice by crossbridges of polypeptides. In gram + bacterial cell walls many layers of this lattice are stacked up forming a rigid structure, that is external to ...


1

As you said, distilled water is completly out of minerals/ions. The principle of diffusion is that reagents diffuse from high-concentrated to low concentrated places to reach an equilibrium. So normally, ions from the erythrocytes would diffuse into the plasma to reach that equilibrium. However, it is quite difficult for ions to pass the cell membrane which ...


1

The phenomena that you are describing, where bread, which is a porous material, similar to a sponge, absorbs water, is the absorption of water by capillary action. As @Joel mentioned, osmosis is specifically the flow of a fluid across a semipermeable membrane, such as the plasma membrane of a cell or dialysis tubing, that occurs in such a way as to cause a ...


1

The force driving osmosis exists in any system with an imbalance of solute molecules across a semipermeable membrane. Think of a concentration gradient as an electrical potential, where high concentration is negative charge and low concentration is positive charge. In the case of electricity, its the magnetic force which causes the interactions leading to ...


1

The most popular theory is the ‘hydraulic limitation hypothesis’ (Ryan & Yoder, 1997), which suggests that as trees grow taller, it becomes more difficult to supply water to their leaves. This hydraulic limitation results in reduced transpiration and less photo-synthesis, causing reduced growth. It is known that in larger/taller trees water supply is ...


1

But when does exactly osmosis occurs instead of diffusion? These processes are not mutually exclusive. Both can happen simultaneously. Their rates depend on different parameters such as permeability of the membrane towards water and the solutes. A semi-permeable membrane has different permeability for different molecules. There are cases when one of these ...


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