Laboratory Exercise #5 Diffusion and Osmosis Diffusion and osmosis are physical
ID: 273671 • Letter: L
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Laboratory Exercise #5 Diffusion and Osmosis Diffusion and osmosis are physical phenomena that impact every living cell. Diffusion is defined as the movement of molecules from an area of higher concentration to an area of lower concentration. Osmosis is the simple diffusion of water. If the barrier separating two solutions is pemeable, diffusion and osmosis will occur until a state of equilibrium is reached. Several factors affect the rate of diffusion. One factor is temperature. As temperature increase rate of molecular movement, thereby increasing the chance of collision between s, diffusion rate increases. This is because an increasing temperature increases the molecules. A second factor infuencing diffusion is molecular size. Generally speaking, smaller molecules diffuse at a faster rate than larger ones In this laboratory exercise we investigate diffusion, osmosis, and the selective permeability of the plasma membrane L Diffusion Through a Selectively Permeable Membrane A cell's success depends on the stability of its internal and external environments. These environments are made up of solutions. A solution consists of two components: the dissolved particles, called the solutes, and the dissolving medium, called the solvent. The most common biological solvent is water The cell membrane represents a boundary between the cell's internal solution and the solution of the external environment. Spaces exist between the various molecules of the cell membrane. These spaces allow small molecules to pass through the membrane easily, but restrict the passage of larger molecules. The ability of the cell membrane to allow some substances to pass through more easily than others is called selective permeability. (Refer to the textbook for a diagram of the cell membrane). The small solutes that pass through the cell membrane move by simple diffusion. Because of diffusion, a cell reaches equilibrium with its external environment Experiment 1 employs dialysis tubing to simulate the selective permeability of the plasma membrane. 5-Explanation / Answer
1. Solute- It is the minor component of the soloution. In this case it is the salt.
Solvent- It is the major component of the soltion. In this case it is the water.
2.Diffusion always increases with an increase in temperature. Diffusion is caused by the movement of atoms or molecules from an area of higher concentration to one of lower concentration. Since heat increases the motion, then diffusion happens faster.
3. A selectively permeable cell membrane is one that allows certain molecules or ions to pass through it by means of active or passive transport.
4. No osmosis will if occur the selectively permeable membrane seperates two isotonic solutions. This is because osmosis requires a concentration gradient to occur, which is not present in this case.
5. NO
6.hypotonic is the one with low concentration, in this case it is with the 10% concentration.
hypertonic is the one with higher concentration, In this case it is the 30% concentration.
the water will move from hypotonic solution to hypertonic solution. Which means it will move towards soluion A.
7. Plasmolysis- If a plant cell is placed in a hypertonic solution, the plant cell loses water and hence turgor pressure by plasmolysis: pressure decreases to the point where the protoplasm of the cell peels away from the cell wall, leaving gaps between the cell wall and the membrane and making the plant cell shrink and crumple. A continued decrease in pressure eventually leads to cytorrhysis – the complete collapse of the cell wall. It is not good for plants.
8.Cytolysis occurs when a cell bursts due to an osmotic imbalance that has caused excess water to move into the cell.
Cytolysis does not occur under normal conditions in plant cells because plant cells have a strong cell wall that contains the osmotic pressure, or turgor pressure, that would otherwise cause cytolysis to occur.
9.A kidney cannot make urine from a concentration of salts of more than 2%. Seawater is made up of approximately 3% salt, so if we drink it to quench our thirst the kidneys have to use existing water from our body in order to dilute the extra salt, which in turn makes us feel even thirstier.
This is due to the osmosis process where the kidneys can only generate urine which is less salty than the water we drink. Consequently, the body tends to urinate more to be able to eliminate the excess of salt but instead of elimination, the result is the formation of more salt as the urine obtained is always less salty than the original. The body would have to expulse more liquid than the amount drunk, which is impossible and that’s why the effect of drinking water from the sea is, paradoxically, dehydration.
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