A plant whose cells are in a hypertonic solution will appear droopy because there is a loss of turgor pressure in each cell. When the concentration of water is the same in the cell and the solute the cell is said to be isotonic and is at equilibrium. There is no net movement of water across the membrane. (Biology Department, 2010). Surface area to volume ratio has a direct effect on the amount of water (as well as nutrients and waste) that can diffuse through the plasma membrane.
In mammals this forms a circulatory system of arteries, capillaries and veins. In flowering plants, transport is not circulatory and occurs in microscopic xylem and phloem. Both transport systems use water as the basis for transport since it is a good solvent, has a high specific heat capacity, is not too viscous and is unreactive (inert). Both animals and plants have more than one type of tissue which is specialised to make transport an efficient process. The vessels and tracheids in xylem are made up of dead, lignified cells.
Diffusion is the tendency of molecules of a substance to diffuse from where it is more concentrated to where it is less concentrated. In general a substance will diffuse down its concentration gradient until concentrations on either side of the membrane is at equilibrium. This metabolic process is called passive transport because it is a spontaneous process and therefore the cell does not expend any energy to make it happen (Campbell. 1993). The diffusion of water across a selectively permeable membrane is known as a special case of passive transport called osmosis (Campbell.
Water potential is a measure of the amount of free kinetic energy of water molecules in a solution. Osmosis is described as the movement of water molecules from a higher water potential to a lower water potential across a selectively permeable membrane. The solute potential of a cell or solution lowers the amount of free kinetic energy that the water molecules possess ie. Lowers the water potential. As the concentration of sucrose solution increased the solute potential of the solution also became more negative.
Title: Water Potential and Osmosis Aim: To determine the solute potential of plant cells Discussion: The aim of this lab was to determine and observe how six different solutions of varying sucrose concentration affected the epidermis of an onion in terms of the solute potential. Onions are made up of 89% water and 8% to 9% soluble sugars, the rest is minerals, fats, proteins, and sulphur compounds. The solute potential (ψs) is the reduction in the water potential of the solution in the cell due the presence of particles dissolved in the solution. The presence of solutes in water causes the solute potential to decrease and it reduces the free energy of water. This is so because water molecules will tend to bind to the solutes rather than moving freely and away from the solution.
Microorganisms are classified by their optimum growth temperature. Microorganisms can be classified as psychrophiles, mesophiles, thermophiles, and hyperthermophiles, and each classification has its own set of special characteristics. If a microbes cell is in a solution in which the concentration of solutes is higher than that found in the cell, cellular water passes through the cytoplasmic membrane in the direction of the high solute concentration. During the loss of water, the cytoplasmic membrane collapses away from the cell wall, which is called plasmolysis. Extreme halophiles (sometimes called obligate halophiles) are organisms
The cell is able to do this because it is selectively permeable. This means that some things can pass through the pores in the cell membrane, and that something is water. This potato cell will try to equalize the concentrations by taking in water. As the water is taken in, the concentration slowly dilutes. In this particular solution, both the potato cell and the solution will never be equal because salt cannot be moved through the cell membrane.
It is important for an IV solution to have salts in it so the water and solute can be equal to create an isotonic environment. If there wasn’t, there would either be a hypotonic causing the cell to burst, or there would be hypertonic causing the cell to shrink. We created models of living cells by using dialysis tubing. The dialysis tube represented the cell membrane to act as selectively permeable to water and some solutes. We observed different solutes (NaCl, Ovalbumin, Glucose, Sucrose, and Water) in the dialysis tubing.
Dialysis Lab Background: Dialysis works on the principles of the diffusion of solutes and ultrafiltration of fluid across a semi-permeable membrane. Diffusion is a property of substances in water; substances in water tend to move from an area of high concentration to an area of low concentration. Blood flows by one side of a semi-permeable membrane, and a dialysate, or special dialysis fluid, flows by the opposite side. A semipermeable membrane is a thin layer of material that contains holes of various sizes, or pores. Smaller solutes and fluid pass through the membrane, but the membrane blocks the passage of larger substances (for example, red blood cells, large proteins).
Osmolarity involves the movement of water across a cell membrane which is osmosis, this movement of water can be hypertonic; a higher concentration of a solute inside the cell which means the cell loses mass, hypotonic; a lower solute concentration inside the cell than outside which means the cell gains mass, or isotonic; a solute concentration the same as the outside of the cell which means there is no net movement of water. In a hypertonic solution in a cell water will leave the cell in order to balance the solute concentration making the cell shrink, in a hypotonic solution however water will enter the cell to balance the concentration. In an isotonic solution water will not move since both sides are equal in concentration. b. Purpose-The purpose of this lab was to determine the osmolarity of plant cells by using potato cores as the cells and sugar as the solute. c. Hypothesis-My hypothesis was that if the amount of solute increases then the then potato core’s weight decreases.