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GENERIC MAGAZINE Volume 4 Issue 2

Topic 2:

CELLS

Are they inside you? Cell Theory SI Measurements Cell Types Membranes S: U

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TABLE OF CONTENTS Cell Theory - How real is it?

An introduction to the three rules of cell theory and the evidence there to back it as well a the contradictions to this commonly taught fact.

SI Units: The Global Standard

We take you through the measurements and an exclusive tutorial on how to use them to determine magnification and actual size.

Is SA:V Ratio the New Black?

Our look at the hottest trend among cells worldwide: the surface area to volume ratio. What is it for?`

How Stem Cells Can Affect You

The origins, the types, the uses, and the controversy surrounding this up and coming science.

Prokaryotes Eukaryotes Membranes Cells Caught Dividing

The new craze called mitosis is sweeping the nation. Learn where to look. Is it right under your nose?


Cornell Stem Cell Project Buchon Lab

Brain Cells

Cornell Stem Cell Project Brain Stem Cells

Human Red Blood Cells

TOUR THE CELL!

Skin Cells


CELL THEORY - Your Questions Answered Mary Grace Bedwell

Many of you readers have been asking recently: What exactly is the Cell Theory. Well, today we have your questions on the matter answered. The following headings are actual questions from our readers, answered just for you. “I heard that there are three rules for the Cell Theory. Can you please explain them to me?” - IBO in New York, NY Hey there, IBO! I most certainly can. Basically, the rules of Cell Theory are as follows: 1. All living things are made of cells. Multicellular organisms have specialized cells to carry out various metabolic functions in the cells. 2. Cells are the smallest units of life. Organelles are able to carry out carious metabolic functions, but are unable to survive alone. 3. Cells come only from other cells. Originally people believed in “spontaneous generation,” but a man named Louis Pasteur disproved that. Cells were found to multiply only by division and to have come from simpler and common ancestors, suggesting that they have always just divided. I hope this helped! “What can you tell me about the evidence for this cell theory?”- Stu in Fairhope, AL Hiya! There are four main scientists whose work is used to back cell theory. The first important guy is Robert Hooke. He was an optics enthusiast, and upon looking at a piece of cork through his microscope, discovered that the wood was divided into what he called cells. The second important figure, known as the father of microbiology, is Anton van Leeuwenhoek, seen to the left. Leeuwenhoek used lenses to look over the cloth he made in his factory and determine its quality. Using his lenses, he discovered what he called animalcules in water. Because of this, he is credited with the actual discovery of cells. Another important figure in proving cell theory is Louis Pasteur. In 1884, people believed that things came randomly from other things (like maggots from meat) by way of spontaneous generation. His experiment involving crook-necked bottle and come boiled broth disproved this idea. You can read all about his experiment over on

Amoeba Mike’s page: SPONTANEOUS GENERATION. The fourth and final gentleman on the list is Robert Remak. This unhappy man was a scientist that discovered cell division upon observing chicken embryos. His results, while fascinating and ground-breaking, were not credited to him, a Jewish scientist. His finding were ignored until they were plagiarized and published in 1858 by a fellow called Rudolf Virchow. “Can you tell me what the limitations of the cell theory are? I may be wrong, but wouldn’t it be more than just a theory if it was 100% unopposed?” - Mark in Summerdale, AL Right you are, Mark! There are four main oppositions to the cell theory. 1. Muscle cells. They’re multi-nucleated and very long, with m i n i m a l division. 2. A m o e b a s . T h e y ’ r e unicellular, but can perform all of the seven functions of life: nutrition, reproduction, movement, growth, response to stimulus, excretion, homeostasis. 3. Fungal Hyphae. They’re very large and multi-nucleated as well, only they have no division into cells. 4.Viruses. They present the biggest issue, as they are only able to reproduce when they are in control of a host cell. So, in a sense, they may not even be considered cells at all. What do you think? Send in your questions to: Mary Grace Bedwell c/o General Magazine 1 General Road New York, New York 12345


The International System of Units and Magnification Mary Grace Bedwell

Basically, every country in the world besides the United States uses a means of measurement know as the International System of Units. This system of units is based off the meter, and can be used to measure a variety of things, just like the system of measurement we use in America, Imperial measurements. However, the SI units are much easier to use because you can easily go from a meter to a kilometer, a nanometer to a kilometer, or anywhere in between simply. Try going from inch to mile that easily! The SI system of measurement is excellent for comparing the sizes of different things we see in science, such as molecules and bacteria. See the chart below for the relative sizes of six things you commonly observe over a microscope, or for more examples of size, check out this website and slide the bar to go through the scale. molecule 1nm

thickness of a membrane 10 nm

viruses 100 nm

bacteria 1μm

organelles up to 10μm

eukaryotic cell up to 100 1μm

When looking at these under a microscope, knowing the actual size of an object is still very important to get a mental picture of what you are looking at. To determine the actual size of an object, divide the measured length of an object by the magnification on your microscope. When looking at a specimen, sometimes the magnification is unknown. If this happens, you can easily find the magnification by dividing the measured length by the length that represents it on the scale bar. That sounds a lot more confusing in words than it actually is, so here’s a look at some examples to help the idea stick.

See how awesome SI Units are? Someone convince America to switch, and our lives will be about 15,000x (see what I did there) easier! Here’s some more looks under the microscope!


How to Make Your Small Surface Area to Volume Ratio Work for You Mary Grace Bedwell

Day after day, we are haunted by the phrase “Size doesn’t matter” and “I’m big son.” Well guess what everybody. I’m here today to tell you that it does, and that being big is overrated. Especially when it comes to your cells. Though society supplies certain ideals, your body’s cells are going a different way this season. They refuse to go along with the way of the modern age, and for that they are commended. Cheers to you, cells. Cheers to you. Their need for a small surface area to volume ratio is incredibly important to your body, and today you are going to learn why. The importance of the surface to volume ratio has got to do completely with the fact that it serves as a limiting factor for the cell and cell size.Many reactions occur within the cell. Substances need to be taken into the cell to fuel these reactions and the wast products of the reactions need to be removed. When the cell increases in size so does its chemical activity. This means that more substances need to be taken in and more need to be removed. The surface area of the cell is vital for this. Surface area affects the rate at which particles can enter and exit the cell, whereas the volume affects the rate at which material are made or used within the cell, hence the chemical activity per unit of time. As the volume of the cell increases so does the surface area however not to the same extent. When the cell gets bigger its surface area to volume ratio gets smaller, as you can see in the four cubes on the right. This surface area to volume ratio is incredibly useful and vital to organisms, so they have to adapt to the changes the ratio causes. Diffusion pathways are shorter, so more efficient - molecules do not have to travel so far to get in or out of the cell, so it takes less time and (if it is active transport) energy. In addition, concentration gradients are easier to generate, which makes diffusion more efficient. Small, warm-blooded mammals lose heat very quickly due to their large surface area to volume ratio. They need to east almost constantly because of this, but that gives them the energy they need. Desert plants would lose their water quickly with flat leaves, so they minimize their ratio in older to conserve water. Some plants even change their metabolism to save water. Cool, right? Still need help? Visit this site to learn more about the surface area to volume ratio.

To learn more about cells and their structure, check out this link and click on “Cell Structure.”


Stem Cells Explained Mary Grace Bedwell

In the world of stem cells, there are a lot of questions regarding what they are, what they do , and how they can affect you. So, let’s dive into this exciting topics with our first question: 1. What are emergent properties? Emergent properties are seen at every level of increasing complexity from the atom to the molecule, to the cell, to the organism to the biosphere. 2. How do stem cells carry out specialized functions? Cells differentiate to carry our specialized functions by expressing some of their genes but other. All of the cells in the body carry the same genes in their nuclei, but cells are different in what they express. The ones not in use are “turned off.”Determining what gene will be expressed is determined by environmental factors around the cells. 3. What do the “-potents”mean? The “potents” referred to here is talking about the terms totipotent, pluripotent, nullipotent, etc. Each one of these words indicated a different division potential of a cell. Once a stem cell has differentiated, it can only make more stem cells of the differentiated cell. The five types of cell differentiation potentials are as follows: - Totipotent cells - Can become any type of cell - Pluripotent cells - Can become any type of cell, excluding embryonic membrane cells - Multipotent cells - Can become a number of different cell types - Unipotent - Can only become one type of cell - Nullipotent - Cannot divide (red blood cells) 4. Where do stem cells come from? Pluripotent cells are found in human embryos that are only a few days old. They have also been developed from fetal tissue (older than 8 weeks of development. There are also cells called induced pluripotent stem cells. “IPSCs are adult cells that have been genetically reprogrammed to an embryonic stem cell–like state by being forced to express genes and factors important for maintaining the defining properties of embryonic stem cells,” says the National Institute of Health. This discovery was released in 2007, but in 2006 mouse IPSCs were tested. You can watch a video about Cryopreservation of these mouse cells here. The NIH went on to say that non-embryonic (including adult and umbilical cord blood) stem

cells have been identified in many organs and tissues. Typically there is a very small number of multipotent stem cells in each tissue, and these cells have a limited capacity for proliferation, thus making it difficult to generate large quantities of these cells in the laboratory. Stem cells are thought to reside in a specific area of each tissue where they may remain quiescent (non-dividing) for many years until they are activated by a normal need for more cells, or by disease or tissue injury. 5. What is a therapeutic use of stem cells? In the treatment of lymphoma, bone marrow is destroyed in chemo- or radio-therapy. Before this aggressive treatment takes place, stem cells are harvested from the bone marrow and stored. These harvested cells can be used to replace the damaged bone marrow, producing healthy blood cells in the recovering patient. Stem cells are also useful in instances other than cancer. Here is an article on how a neurological disease, Multiple Sclerosis, is potentially being treated and/or cured by regrowing myelin sheaths around nerves from bone marrow. 6. What is the debate over stem cells? That is a very loaded question, and if you are really interested, refer to this TIME article. 7. What do stem cells look like?

If you have more questions, check out the NIH’s FAQ page about stem cells here.

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