Agar+Cells+Report

 16 Feb Exploration 4B- Agar cells

Table 1- Rate of Conductivity mS over period of 2 min 1 || 0.9 || 1.01 || 1.01 || 1.03 || 1.03 || 1.05 || 1.07 || 1.09 || 1.11 || 1.11 || 1.13 || 1.16 <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.15 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">8 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.30 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.73 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.40 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.54 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.63 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.72 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.76 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.78 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.85 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.90 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.98 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">2.02 || <span style="background: yellow; font-family: "Arial","sans-serif"; font-size: 10.0pt; mso-highlight: yellow;">2.06 <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">64 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">0.26 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.05 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.22 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.46 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.43 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.58 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.67 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.76 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.86 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.94 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">2.11 || <span style="background: yellow; font-family: "Arial","sans-serif"; font-size: 10.0pt; mso-highlight: yellow;">2.68 <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">2.22 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">*Note: Highlighted portion indicates highest rate of conductivity change. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Table 2- Comparison of rate of conductivity change for different surface area to volume ratios <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">2 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">24 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">8 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">3 : 1 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1.16 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">8 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">1 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">48 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">8 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">6 : 1 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">2.06 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">64 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">0.5 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">96 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">8 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">12 : 1 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">2.68 || <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Ensure that the agar cubes were of the size needed <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Ensure that the volume of water is exactly 200cm (through reading at eye level) <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Same person was used to stir the water so that results will be more consistent <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">The smaller the length, the greater the number of pieces obtained, thus, the greater the surface area. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Salt is made of sodium and chloride ions. When salt dissolves, the bonds between the ions weaken, and the ions become free to move. As the ions are small enough, they will diffuse through the semi-permeable agar cube into the surrounding water. The conductivity sensor then monitors the total concentration of ions in a solution. Hence, if the rate of conductivity change is higher, then there’s a higher concentration of ions in the solution, implying that the rate of diffusion is higher. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> For the biggest piece of agar, the rate of conductivity change is 1.16, for the medium sized piece of agar, the rate of conductivity change is 2.06 while the smallest sized piece of agar has the highest rate of conductivity change of 2.68. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> This thus shows that the greater the surface area of the agar, the higher the rate of conductivity change. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> This is because a smaller piece of agar has a larger amount of surface area compared to its volume so there will be a larger surface area for the sodium chloride to be exposed to the water and diffuse out. A larger piece of agar, however, has a smaller amount of surface area in relative to its size so lesser sodium chloride ion diffuses out, into the solution. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> From the Table 2, as the surface area: volume ratio increases, the rate of conductivity change increases as well, meaning that diffusion is more efficient. Hence, the agar with the largest surface area: volume ratio has the most efficient rate of diffusion and vice versa. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt; mso-bidi-language: X-NONE; mso-fareast-language: #0400;">In the previous experiment, the agars were cut into 3 different shapes, triangle, rectangle and trapezium. The total surface area for each agar was calculated. Following that, the agars were soaked in an acid that will turn the agar pink. The time was measured for each agar to turn completely pink. This experiment was not as accurate because it was quite hard to tell when it was fully pink. However, the data logger used in this experiment is able to calculate the conductivity change and rate of diffusion is obtained more accurately. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt; mso-bidi-language: X-NONE; mso-fareast-language: #0400;"> <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt; mso-bidi-language: X-NONE; mso-fareast-language: #0400;"> Small organisms, with simple shapes like an earthworm has a large surface area: volume ratio and can easily accomplish the exchange and get all the oxygen and nutrients it needs by simple diffusion. This also means that things can also diffuse out of its body faster. For example, smaller animals tend to have higher metabolic rates. Because of their large surface area relative to volume, small animals lose heat at much higher rates than large animals, and therefore must produce more heat to offset the effects of thermal conductance. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> Larger organisms, like a tiger, have a much smaller surface area: volume ratio, so it cannot accomplish all the exchange it needs by simple diffusion. Because it is important for cells to have a large surface area: volume ratio, larger organisms exhibit different modifications to compensate for changes in the surface area to volume ratio associated with size differences. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> Internal transport systems are developed in plants and animals for actively moving materials throughout the organism, thus enabling them to circumvent the limits imposed by passive diffusion. Many organisms developed structures to increase their surface area e.g. leaves on trees, microvilli on the lining of the small intestine, root hairs and capillaries and the convoluted walls of arteries. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> For example, a tiger needs special respiratory organs such as lungs taking in sufficient oxygen for the entire body and removing carbon dioxide. Since large amounts of exchange of gases take place in the lungs, it contains millions of sacs (alveoli) which allow oxygen to diffuse into the bloodstream, by maximizing the large surface area into a small space. With a greater surface area, the rate of diffusion is increased. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> **<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Question 7: ** **<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Once a cell grows to a certain size it becomes too large for the complete diffusion of needed substances throughout its cytoplasm. As a cell grows, is the surface area of the cell membrane as efficient relative to the volume of the cell? ** <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> · <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">A cell is a metabolic compartment where a multitude of chemical reactions occur. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> · <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">The reactions increase along with the volume of metabolic volume within a cell (i.e. The larger the volume the larger the number of reactions.). · <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">All raw materials necessary for metabolism can enter the cell only through its cell membrane. · <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">The greater the surface area, the larger the amount of raw materials that can enter at the same time. · <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Each unit of volume requires a specific amount of surface area to supply its metabolism with raw materials. · <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">The amount of surface area available to each unit of volume varies with the size of a cell. A s a cell grows, its surface area: volume ratio decreases. · <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">At some point in its growth its surface area: volume ratio becomes so small that its surface area is too small to supply its raw materials to its volume. · <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Hence, the cell cannot get larger. <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> <span style="font-family: Arial,sans-serif;"> · //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Surface to Volume // //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">[] // · //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Surface Area to Volume Ratio // //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">[] // · //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">How Surface Area to Volume Ratio Limits Cell Size // //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">[] // · //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">The Problem of Size // //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">[] // · //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Cells // //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">[] // · //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">SIZES OF ORGANISMS: THE SURFACE AREA: VOLUME RATIO // <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;"> //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">[] // · //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">How Surface Area / Volume Ratio Affects The Rate Of Diffusion In Substrates And How This Relates To The Size And Shape Of Living Organisms // //<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">[] //
 * __<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Results: __**
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">No. of pieces of agar cells ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">0s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">10s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">20s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">30s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">40s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">50s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">60s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">70s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">80s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">90s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">100s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">110s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">120s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">120s ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">No. of pieces of agar cells ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Length (cm) ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Surface area (cm3) ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Volume (cm3) ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Surface area to volume ratio ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Rate of conductivity change ** ||
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Rate of conductivity change ** ||
 * __<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Discussion Questions: __**
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Question 1: **
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">What precautions did you take in this experiment? **
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Question 2, 3 and 8: **
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">What can you infer from the results above? **
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">What do the graphs reveal to you about the rate of diffusion and the surface area of the agar? **
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Examine the agar cells below and work out the surface area: volume ratio of each cell. Which is the most efficient and which is the least? **
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Question 5: **
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">Compare this experiment with the one you did in Lower Secondary where the coloured agars were soaked in acid. Which do you think is more accurate? **
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt; mso-bidi-language: X-NONE; mso-fareast-language: #0400;">Question 6: **
 * <span style="font-family: "Arial","sans-serif"; font-size: 10.0pt; mso-bidi-language: X-NONE; mso-fareast-language: #0400;">How do you relate this to the shape of simple (e.g. earthworm) to complex (e.g. tiger) living organisms? **
 * __<span style="font-family: "Arial","sans-serif"; font-size: 10.0pt;">References: __**