Agar Cube Lab Report

Cells and molecules in the environment are constantly moving and changing, for cells to function properly there is a need for equilibrium to be met. The size of the cell and the solution outside of the cell affects the rate of diffusion and osmosis in the cell. Cells are constantly trying to reach an equilibrium with the molecules and substances around it, which is why there are such terms as: hypertonic, hypotonic and isotonic. The procedures allowed testing of whether or not surface area or volume increased diffusion and how different substance control diffusion. Cells are constantly moving to reach equilibrium through diffusion and osmosis.

Two variables that affect the rate of diffusion are the MWCO membrane and the solute concentration. Increasing the membrane size and solute concentration will also increase the average diffusion rate. Decreasing the membrane size and solute concentration will reduce diffusion rates and can even prevent all diffusion.

All organisms need to exchange particles such as food, waste, gas and heat with their surroundings. there are two different types of ways in which substances can enter or/and leave a cell. these ways are called Passive and Active. with in these there are different processes for example, in passive process there are diffusion, facilitated diffusion and osmosis and in the active process there is molecule and particle. in this assignment I am going to discuss all of these processes starting with diffusion.

7. Explain how incubation plant tissues in a series of dilutions of sucrose can give an

1. Understand the importance of diffusion to cellular metabolism and the how it constraints the evolution of cell/body size and shape

A major determinant of diffusion in a biological system is membrane permeability. Small, uncharged molecules pass through cellular membranes easily, while most and/or charged molecules cannot pass through the membrane. The movement of water across a selectively permeable membrane, like the plasma membrane

The difference is that along with large molecules, living cells prevent molecules with positive charges and solubility. This is not representing in dialysis tubing, and is only found in living cells because the tubing is only based on molecular size (98). When referring the rate of diffusion, the concentration gradient influences the diffusion rate, based on the factors of temperature. The ability for molecules diffuse from high to low concentrations primarily depends on the concentration gradient between the two areas.(96-99). My hypothesis for the study is that in the hypotonic, hypertonic, and isotonic solutions, the direction and rate of osmosis will determine based on the concentration inside the dialysis tubing. My prediction is that if the solution is hypotonic the results will decrease, if the solution is hypertonic the results will increase and if the solution is isotonic the solution will vary and or remain constant.

▪ Surface area to volume ratios and the ability of cells to get nutrients in and waste products out of the cell

The following hypothesis was made in regard to effect of the concentration gradient on the rate of diffusion: The higher the concentration gradient, the faster the rate of diffusion.

In order to assimilate diffusion through a permeable membrane potassium permanganate and methylene blue were used in experiment. The objective was to compare the rates at which the liquid compound of different molecular weight diffused through agar. This was achieved by obtaining agar in a petri dish with two wells to hold the liquid compounds. The rate was measured by time and diameter distance diffused. This process was observed for 60 minutes at 15 minute intervals.

A cell needs to perform diffusion in order to survive. Substances, including water, ions, and molecules that are required for cellular activities, can enter and leave cells by a passive process such as diffusion. Diffusion is random movement of molecules in a net direction from a region of higher concentration to a region of lower concentration order to reach equilibrium. Diffusion does not require any energy input. Diffusion is needed for basic cell functions - for example, in humans, cells obtain oxygen via diffusion from the alveoli of the lungs into the blood and in plants water

Diffusion is an automated process by where the levels of oxygen, water and carbon dioxide pass over a ‘semi-permeable membrane’ between the walls of the cells and blood vessels to create a level environment. This membrane only allows these three elements to pass whilst retaining other elements such as blood cells, hence semi-permeable. The high concentration on one side of the cells transfers through this membrane until the level is equal on both sides.

The next experiment was to test diffusion in agar solution. A petri dish with a layer of solidified agar had four holes punched in it using a No. 5 cork borer. Three holes were punched in a triangle shape with the fourth hole directly in the middle. There should be 15 mm between each outside hole and the middle hole. The three outside holes were filled with one drop each of potassium bromide, potassium Terri cyanide, and sodium chloride. The middle hole was filled with a drop of silver nitrate. It is very important to make sure that none of the holes overflow. After each has been filled allow to sit for an hour and observe the results.

Cell diffusion is a type of passive cell transport. In diffusion, molecules move from areas of high concentration to areas of low concentration in order to decrease the concentration gradient. Difffusion from areas of low concentration to areas of high concentration is not energetically favorable

The process of diffusion occurs in and out of a cell when molecules travel from areas of higher