Throughout this unit, there were a variety of topics some of which I found to be fairly straightforward, and some which I found difficult. Coming fresh off of the macromolecules unit, I found it helpful to see some of the ways in which carbohydrates, lipids, and proteins are found in cells. Carbohydrates are found in chains around the cell membrane, the cell membrane is made up of phospholipids. Channel proteins as well as proteins made by ribosomes that are found inside the cell.
We also discussed the different parts of a cell; we likened the cell to a factory. There are many organelles that have very specialized jobs: the nucleus holds the DNA that contains instructions for all the cell's activities; the mitochondria are the "powerhouses" and carry out cellular respiration; the ribosomes do protein-synthesis; the ER packages and completes protein-making...etc. I found this topic to be one of my strengths because the different functions of how each organelle works is easy to remember by comparing it to a job in a factory; such as comparing the Golgi Apparatus to a UPS.
We also studied how the cell membrane is selectively permeable, and only some substances can pass through. I felt as though diffusion was definitely one of my strengths: understanding how particles move from a high concentration to a low concentration until equilibrium is reached, at which point particles move back and forth in every direction. I feel as if I have a grasp on the differences between osmosis, diffusion, and facilitated diffusion. Active transport requires energy to be put in from the cell, whereas passive transport does not.
Photosynthesis and respiration were very detailed and went far beyond what I had learnt in the past about them, and in this unit we learnt a lot more about the chemistry behind the basic reactions. Photosynthesis was difficult to understand at first, but with more drawings and with reading the information from multiple sources, I began to grasp it. Inside the mesophyll cells, inside the chloroplasts, photosynthesis occurs. The "photo" part of the reaction happens in the thylakoids of the granum, and the "synthesis" part happens in the stroma of the chloroplast. I feel that I still do not have a full understanding of cellular respiration, although I basically understand that it takes place in the mitochondria and that the three stages are glycolysis, the Krebs cycle, and the electron transport chain. I think with more practice and more re-reading of the topic, I will be able to strengthen this weak area.
From this unit, I learnt that drawing diagrams (and color coding them) is extremely helpful and is great for really understanding the information. I learnt how to properly focus a microscope and reinforced the do's and don't's of how to use it. I learnt more about the structure and function of cells as well. I want to learn more in the future about the chemistry behind the Krebs Cycle and the Calvin Cycle. I wonder how the first scientists even imagined that cells could exist, and I think it is fascinating how they designed the microscopes. In order to study, I am going to re-draw the diagrams and look at unlabeled diagrams to try and name all the parts.
Friday, October 16, 2015
Wednesday, October 7, 2015
Egg Diffusion Lab
In this lab we wanted to further explore how diffusion works, and we wanted to find out how and why a cell's internal environment changes when its external environment changes? We first took two eggs and soaked them in vinegar for 24-48 hours. After this amount of time, the calcium carbonate shell had been dissolved by the acetic acid. After washing and recording the mass and circumference of the eggs, one egg was placed in deionized water and the other was placed in sugar water. We let the eggs sit for 24-48 hours, and then recorded the new circumference and mass.
When the sugar concentration of the solution increased, the mass and circumference of the egg decreased, and the egg began to look shriveled up. The mass of the egg in sugar water decreased on average by 47.25% and the circumference decreased on average by 22.94%. In the egg that was placed in deionized water, the sugar in the macromolecules were the solute inside of the egg and water was the solvent outside. From a desire to reach equilibrium, the solvent wanted to move by diffusion from a low concentration of solute (outside cell) to a high concentration of solute (inside cell). Therefore, the cell gained water and grew. This is an example of a hypertonic solution.
It is desirable for cells to have an equal concentration of solute and solvent inside and outside of the cell. The cell membrane is semi-permeable and does not allow for the solute to leave the cell or enter the cell. The conditions of the cell are only changed by the movement of solvent. This is an example of passive diffusion. The cell expanded when put in vinegar, it shrunk when put in sugar water, and it grew when put in water.
In class we have learned about molecules which move from a high concentration to low concentration when there is an unequal concentration of solute or solvent.
Since cells grow when they are put in water, fresh vegetables in markets will be sprinkled with water to keep them fresh and help them to not shrivel up. Salt is sometimes sprinkled on roads to melt ice because since salt is a solute, the ice (which is water and is a solvent) the solvent will move outside and in order for it to do this it must melt. However, if the salt is sprinkled along the roadside where there are plants, the plants will die. This is because the plant cells will shrink when exposed to too much salt, and when they shrink, they will not function as well.
I would like to see the effect of putting salt on plants in action and other such experiments that illustrate cells shrinking due to too much solvent. Also, I would like to know if the shriveled up egg was placed back in deionized water, how long would it take to be revived?
When the sugar concentration of the solution increased, the mass and circumference of the egg decreased, and the egg began to look shriveled up. The mass of the egg in sugar water decreased on average by 47.25% and the circumference decreased on average by 22.94%. In the egg that was placed in deionized water, the sugar in the macromolecules were the solute inside of the egg and water was the solvent outside. From a desire to reach equilibrium, the solvent wanted to move by diffusion from a low concentration of solute (outside cell) to a high concentration of solute (inside cell). Therefore, the cell gained water and grew. This is an example of a hypertonic solution.
It is desirable for cells to have an equal concentration of solute and solvent inside and outside of the cell. The cell membrane is semi-permeable and does not allow for the solute to leave the cell or enter the cell. The conditions of the cell are only changed by the movement of solvent. This is an example of passive diffusion. The cell expanded when put in vinegar, it shrunk when put in sugar water, and it grew when put in water.
In class we have learned about molecules which move from a high concentration to low concentration when there is an unequal concentration of solute or solvent.
Since cells grow when they are put in water, fresh vegetables in markets will be sprinkled with water to keep them fresh and help them to not shrivel up. Salt is sometimes sprinkled on roads to melt ice because since salt is a solute, the ice (which is water and is a solvent) the solvent will move outside and in order for it to do this it must melt. However, if the salt is sprinkled along the roadside where there are plants, the plants will die. This is because the plant cells will shrink when exposed to too much salt, and when they shrink, they will not function as well.
I would like to see the effect of putting salt on plants in action and other such experiments that illustrate cells shrinking due to too much solvent. Also, I would like to know if the shriveled up egg was placed back in deionized water, how long would it take to be revived?
Data Table for Eggs in Deionized and Sugar Water
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| Top: Egg that was placed in sugar water Bottom: Egg that was placed in deionized water |
Friday, October 2, 2015
Egg Macromolecules Lab
The egg membrane tested positive for having polysaccharides, lipids, and proteins. When the test tube that contained egg membrane was tested for proteins, and sodium hydroxide with copper sulfate was added, it turned from blue to purple, and we knew that proteins were present. It is logical that proteins would be found in the egg membrane because transfer proteins are used to transport substances back and forth through the cell.
The egg white tested positive for all four macromolecules: monosaccharides, polysaccharides, lipids, and proteins. We added benedicts solution, iodine, Sudan III, and sodium hydroxide mixed with copper sulfate, to see if monosaccharides, polysaccharides, lipids, or proteins respectively, were present. The test tube with benedicts turned from blue to green to orange, the test tube with iodine turned from brown to black, the test tube with Sudan III turned from red to orange. Monosaccharides, polysaccharides, and lipids are needed in the egg white for proper growth and development of the chick (if the egg was fertilized).
The egg yolk tested positive for proteins and lipids. The test tube which had Sudan III added turned from brown to black, which showed that lipids were present. The egg yolk is the actual cell, and lipids were sure to be found in the membrane.
While our hypothesis was supported by our data, there could have been errors due to how much chemical was added into each test tube, and how each part of the egg was separated and put into its own test tube. We might have added too much or too little of each chemical to each sample due to errors in how big each drop was. If one test tube had more chemical than another, it would affect if the egg tested positive for that molecule, or what color it turned. It was also difficult to isolate the egg membrane, and I believe there was still egg white mixed into the test tube when we tested the membrane. Due to these errors, in future experiments I would recommend that we use an instrument to cut the membrane and measure how much chemical we add before we add it.
This lab was done to demonstrate our understanding of where macromolecules are found in the cell. From this lab, I learned firsthand how phospholipids are found in the membrane, as well as transport proteins and carbohydrate chains (polysaccharides). Based on my experience in this lab, I better understand where the different macromolecules are found.
The egg white tested positive for all four macromolecules: monosaccharides, polysaccharides, lipids, and proteins. We added benedicts solution, iodine, Sudan III, and sodium hydroxide mixed with copper sulfate, to see if monosaccharides, polysaccharides, lipids, or proteins respectively, were present. The test tube with benedicts turned from blue to green to orange, the test tube with iodine turned from brown to black, the test tube with Sudan III turned from red to orange. Monosaccharides, polysaccharides, and lipids are needed in the egg white for proper growth and development of the chick (if the egg was fertilized).
The egg yolk tested positive for proteins and lipids. The test tube which had Sudan III added turned from brown to black, which showed that lipids were present. The egg yolk is the actual cell, and lipids were sure to be found in the membrane.
While our hypothesis was supported by our data, there could have been errors due to how much chemical was added into each test tube, and how each part of the egg was separated and put into its own test tube. We might have added too much or too little of each chemical to each sample due to errors in how big each drop was. If one test tube had more chemical than another, it would affect if the egg tested positive for that molecule, or what color it turned. It was also difficult to isolate the egg membrane, and I believe there was still egg white mixed into the test tube when we tested the membrane. Due to these errors, in future experiments I would recommend that we use an instrument to cut the membrane and measure how much chemical we add before we add it.
This lab was done to demonstrate our understanding of where macromolecules are found in the cell. From this lab, I learned firsthand how phospholipids are found in the membrane, as well as transport proteins and carbohydrate chains (polysaccharides). Based on my experience in this lab, I better understand where the different macromolecules are found.
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