Monthly Archives: August 2011

Do You Suffer From Decision Fatigue?

a. Decision fatigue:

Decision fatigue is when you get very tired from making so many decisions that you start making poor ones. The more choices you have to make, the harder they become and then you start looking for easy way outs, leading to poor choices such as recklessness or acting impulsive instead of thinking through the consequences of the decision.

Ego depletion:

Ego depletion is a term used to explain one’s will power or self-control. When they have to use their self- control, it makes it harder to control themselves later on. For example, if someone were told not to eat chocolate, because they are controlling themselves at that time, they would be weaker if they were asked to do something else later on.

b. I think that the most interesting example was about glucose. Our bodies and brains get energy from glucose which is the sugar found in many sweets and foods. When experiments using lemonade mixed with sugar or diet sweetener was used, they realized that it tasted the same as glucose but didn’t have the same effect on the brain. This meant that people were able to have more self-control, which improved decision-making. Through this experiment, skeptics and researchers found out why glucose was able to cause ego depletion. When glucose is low in the body, the brain works on some parts and doesn’t on other parts. This can cause irrational and quick decision making instead of paying attention to the long-term consequences of a decision. This is the reason why dieting is hard test of self-control. Dieters need a lot of self-control not to eat and as they resist certain foods, it takes out their willpower, but to regain their willpower, they need glucose and need to eat, which makes dieting such a hard task. This is an interesting example because it is easily relatable.

c. This relates to economics because all businessmen and economists have to constantly make decisions. Each day companies and people need to come up with ideas on how they are going to make a profit, which is their main goal. As they make more decisions, it could be possible that they suffer from ego depletion or decision fatigue, which could cause loss to the company. However, if they are careful about the choices they make and are always aware of the long-term consequences, their company could be very successful.

d. In the past year, I have tried to go on diets but realize that they never work for me. Every time I use self control to resist eating something, the more tired I get and the less I am able to make decisions and think straight. When this happens, it can cause decision fatigue and the decisions I make can be very silly because I am too tired to make up my mind. Also, after dieting, I am no longer able to have willpower against the food I wasn’t able to eat before which causes ego depletion. The same goes for shopping. If I have shopped for a very long time, by the end of the day, I can’t make any more decisions and my judgment starts to become worse and worse. Through this article, I think that I have learned to use my self-control to a certain point. I should use it when necessary, but should not push myself too much so I can still make good decisions.


2.3 Eukaryotic Cells

Eukaryotic cells are much more complicated internally than prokaryotic cells. Examples of eukaryotic cells include those in humans and animals. Each organelle has a specific structure and function. While prokaryotic cells do not have a nucleus, eukaryotic cells do. The nuclear membrane is double and has pores. Uncoiled chromosomes are inside and are called chromatic. The nucleus stores most of the genetic material and it is where DNA is replicated and transcribed, and where mRNA is changed before it is sent to the cytoplasm. The rough endoplasmic reticulum has flattened membrane sacs called cisterna and out of these cisternae, ribosomes are attached. The rER synthesizes protein for secretion and once the protein is synthesized by the ribosomes of the rER, they pass in the cisternae and are then carried by vesicles, which are small membrane sacs. They are then moved to the Golgi apparatus. The Golgi apparatus also contains cisternae. However they are not as long, are curved, and do not have ribosomes attached but do have many vesicles close by. The Golgi apparatus processes proteins that have been brought in vesicles from the rER and most of these proteins are then carried to the plasma membrane for secretion through vesicles. Lysosomes have a single membrane and are formed from Golgi vesicles. They contain high concentrations of protein and contain digestive enzymes, which can be sued to break down the food ingested in vesicles or to break down the organelles in the cell or the whole cell.  Mitochondria have a double membrane with the inner membrane forming structures called the matrix. The shape is usually spherical or ovoid. They produce ATP for the cell by aerobic cell respiration. Fat digested here can be used as a energy source for the cell. Lastly, free ribosomes appear as dark granules in the cytoplasm and do not have a membrane surrounding them. They are the same size as the ribosomes that are attached to the rER and synthesize protein then release them into the cytoplasm as enzymes. Ribosomes are constructed in the nucleolus of the nucleus.

There are many similarities and differences between prokaryotic and eukaryotic cells. While both have DNA, prokaryotic cells contain a naked loop of DNA in the nucleiod of the cytoplasm while eukaryotic cells have chromosomes that consist of DNA associated with the protein in the nuclear envelope of the nucleus. While eukaryotic cells have mitochondria, prokaryotic cells do not. Also, the ribosmes are smaller in prokaryotic cells. Laslty, prokaryotic cells have few or none internal membranes while eukaryotic cells have many such as the endoplasmic reticulum, Golgi apparatus, and lysosomes.

Chapter 1 Questions

1ai. The cell is a eukaryotic vell because it has a nucleus with naked DNA in it.

1aii. It is part of a root tip because there is a cell wall present and human cells do not have cell walls.

1aiii. It is in the phase of interphase because we are not able to see the chromosomes yet.

1bi. 2500= 4 cm/actual size

actual size= 0.0016 cm

1bii. 2500= image size/ 5 µm

image size= 12500 µm

1c. If this cell was kept in a concentrated salt solution, water from the cell would leave because of osmosis, which would cause the plasma membrane to break down.

2a. I- mitochondria

II- nucleus

III- lysosome

2b. magnification= 0.5 cm/1.5 µm

magnification= 5 mm/ 1.5 µm

magnification= 5000 µm/ 1.5 um

magnification= 3333.333 x

1c. 3333.333 x = image size/ 10 µm

image size= 33333.333 µm

1d. 3333.333 x = 0.3 cm/ actual size

3333.333 x = 3 mm/ actual size

3333.333 x = 3000 µm/ actual size

actual size= 0.900 µm

3a. magnification= 2.1 cm/ 0.6 mm

magnification= 21 mm/ 0.6 mm

magnification= 35 x

magnification= image size/ actual size

35 x = 0.6 cm/ actual size

35 x = 6 mm/ actual size

35 x = 6000 µm/ actual size

actual size= 171. 429 µm

3b. 180 x= 3.3 cm/ actual size

actual size= 0.0183 cm

3c. Bryopsis pennata is not an animal but a plant because it has a vacuole, chroloplasts, and a cell wall which are only found in plant cells not animal cells.

3d. According to the cell theory, this plant can’t be multicellular because it is multinuclient. It could be acellular if it is not considered a cell or it could be unicellular.

3e. One advantage of this is that the fluid can easily move around the plant. However a disadvantage is that because it is interconnected, if one area fails, the whole thing will break apart.

3f. If the Bryopsis pennata is transferred from sea water to fresh water, osmosis could occur. This is because the plant is used to water with salt, but if it is exposed to fresh water, there would be more water which would cause more water to enter the cell and osmosis to occur, destroying the cell.

2.2 Prokaryotic Cells

From the 1950s, using electron microscopes cell structures could be studied in detail. Prokaryotes were the first organism to ever evolve on Earth. They have the simplest cell structure because they are unicellular and are mostly small in size and they divide in two by a process known as binary fission. Bacteria are examples of prokaryotes. These cells can be found anywhere from on our skin to the soil and the water we drink. Prokaryotes have many organelles. Firstly, the have the cell wall that protects the cell and maintains its shape. The cell wall is also composed of peptidoglycan and prevents the cell from bursting. Pushed up against the inside of the cell wall is the plasma membrane. The plasma membrane is somewhat permeable and is a thick layer composed of mostly phospholipids. It controls what substances enter and exit the cell and can also pump substances in or out by active transport. The plasma membrane produces ATP by aerobic cell respiration. The cytoplasm is fluid that fills the space inside the plasma membrane. It consists of water with many dissolved substances and contains many enzymes as well as ribosomes. It does not consist of any membrane- bound organelles. Also, it carries out the chemical reactions of metabolism, mentioned on the previous readings as one of the six functions unicellular organisms carry out themselves. Ribosomes are small granular structures, smaller than those of eukaryotic cells. Ribosomes synthesize proteinsm and are 70s. Lastly, the region of cytoplasm that contains the genetic material is the nucleoid. It is a DNA molecule that is circular and is not associated with proteins. The nucleoid contains fewer ribosome and protein in it, therefore less stained than the rest of the cytoplasm. The amount of DNA in nucleiod’s of prokaryotes is less than the amount in eukaryotes. Outside of the cell, prokaryotes have pili and flagella. Pili are protein filaments that come out of the cell wall. It can be pulled in or pushed out by a ratchet mechanism and is used for cells to join and form aggregations of cells. It is used when two cells are exchanging DNA, a process known as conjugation.  Lastly, flagella are also structures protruding from the cell wall. They are solid and inflexible, unlike eukaryote flagella. It has a corkscrew shape and the base in fixed in the cell wall. It allows the cell to move from areas to another and rotate using energy. Some cells also have capsules that protect the cell and help it attach to other cells and surfaces.

2.1 Cell Theory- 2

Surface area to volume ratios in cells are very important for the chemical reactions in cells, known as metabolism, to continue. For metabolism to occur, the cell must absorb substances that are used in the reaction and remove waste products. The movement in and out of the cell is done through the plasma membrane and the rate at which this is done depends on the surface area. This ratio is important for two reasons, firstly for the size of the cell and secondly for controlling the heat in cells both of which were mentioned in the previous reading. If cells are too big, this ratio would be too small which would mean that substances will not enter the cell or leave the cell fast enough and waste will gather up in these cells. Also, the cells may overheat because the metabolism will produce heat faster than what is lost on the surface of the cell.

Some unicellular organisms live together in colonies where many cells area attached to the surface and area co-operating but are not fused together to form a single cell. Multicelluar organisms consist of a single mass of cells fused together. These cells do not carry out all the functions in their life as unicellular organisms do but are instead specialized for a specific function. This is known as differentiation, cells developing differently to perform different functions. The cell only uses some of the genes in the nucleus but not all. In science, a gene that is being used is known as a gene being expressed, meaning that the gene is functioning and the information in it is used to make protein or some other gene product.

DBQ: gene expression in thyroid tumor cells

In an investigation of thyroid tumors, the relative level of expression from 1139 genes in the tumors was shown through 13 cancer patients.

  1. Eight patients had benign tumors while five had malignant tumors.
  2. The malignant tumor genes have more white bands and orange bands than the benign patients. This means that malignant patients show both more increased gene expression and decreased expression, indicating that there is more activity occurring on the malignant side than the benign side.
  3. This research into gene expression can be useful for many reasons. It can be very useful for other cancer tumors. With this research, scientists can see what indicate increased gene expression and decreased gene expression. This information can then be used in other areas of the body to research other tumors.
  4. The reasons for the differences in gene expression between malignant and benign cells is the age and gender of the individual. As you age, your cells develop and therefore you can have differences in how your genes are expressed compared to younger people. Also, depending on your gender, you may have different functions and cells.

Stem cells are cells that can self- renew by cell division and differentiate. At an early stage, the human embryo consists of stem cells that slowly start to differentiate in particular ways. Once they are dedicated in a particular way, the cell can divide six more times but all the cells produced differentiate in the same way and are no longer considered stem cells for that reason. However, in humans there are still a few cells that are stem cells for instance bone marrow, skin, and liver and these tissues have a considerable powers of regeneration and repair. The stem cells in our brain kidney and hear however allow limited repair.

Stem cells have interested many because of its potential to repair tissue and treat many degenerative conditions. In some diseases such as Parkinson, multiple sclerosis and strokes, neurons and other cells in the nervous system are loss and though this is still being experimented, there is a potential to use stem cells to replace these lost cells. Adult stem cells and embryonic stem cells both have advantages and disadvantages. Though it is harder to obtain adult cells, in adult cells, embryos do not need to be destroyed but are destroyed for embryonic stem cells to be obtained. Adult cells are compatible with tissues of the adult so no rejection issues occur as they do in embryonic cells because the tissue is genetically different from patients receiving it. Also, adult cells have fewer chances of malignant tumors developing. On the other hand, embryonic stem cells have an almost unlimited growth potential and less chance of genetic damage than adult stem cells. Also they have a greater capacity to differentiate than adult cells. Another issue with using embryonic cells is the ethics of it. The Islam do not think this is morally wrong because they believe that human life is possible later in the development of the embryo and the Roman Catholic argue that if no life is destroyed in the process, the Roman Catholic tradition would not be opposed to such reason. However, if the embryos are considered human, they should not be destroyed for research.

Scientists are now researching therapeutic uses of stem cells. One example is by transplanting pancreas tissue from donors, juvenile-onset diabetes can be treated, however the supply of this tissue is inadequate. If a reliable method that stimulates embryonic stem cells to become insulin- secreting cells is created, more patients with this diabetes can be treated. Another therapeutic use of stem cells in for injured spinal cords. Inured spinal cords of experimental animals have be transplanted with stem cells, and this has causes some mobility to occur. However, side effects have also occurred to the animals. The most successful therapeutic use involves bone marrow transplants. The cells used are hematopoietic stem cells also known as HS cells. They are found in the bone marrow and divide continually to produce cells that differentiate as red or white blood cells. HS cells have huge growth potential and with just 100 of these cells, a mouse’s blood system can be completely replaced. HS cells are also used in blood disorders such as leukemia, SCIED, multiple myeloma and lymphoma. Lastly, the placenta and umbilical cord of a baby can be used as a source of stem cells. After childbirth, blood can be taken from the umbilical cord and collected. This blood contains many hematopoietic stem cells that can divide and differentiate into any type of blood cell. There are also risks associated with using stem cells. Stem ells can form tumors called teratocarcinomas. This is when rapid cell division occurs and up to 30 types of tissues is formed by cell differentiation.

As mentioned in the previous posts, one of the expectations to the cell theory are extracellular matrices, one example bring plant cell walls. Cellulose micro fibrils are gathered in the cell then put around the cell through the plasma membrane to add thickness to the cell wall. As the plant cell grows, the wall becomes thinner so more cellulose has to be added to keep it thick. Also, the cell wall allows the plant to stay upright by preventing water from entering and causing pressure to build up in the cell.

Cells in tissues work together and stick together therefore needing some form of communication. In multicelluar animals, cells are connected to each other directly and also he extracellular matrix surrounding al cells, the EMC. The EMC molecules influence shape, orientation and polarity, movement, metabolism, and differentiation of cells. Different tissues of the body use different amounts of EMC. Bones and cartilages contain more EMC than cells. There are two forms of EMC, interstitial matrix and basement membrane. Interstitial matrix is a three-dimensional gel that surrounds cells and fill spaces. Basement membrane is a mesh like sheet formed at the base of epithelial tissues and an extraordinary cellular organizer. Basement membranes also stimulate differentiation in particular cell types.

Multicellular cells show emergent properties because of the interaction occurring between cells. This means that the whole is greater than the sum of its parts. For example, consciousness is a property that emerges because of the interaction between nerve cells in the brain.

Cell Theory 1

Cells are the smallest form of life and are controlled by a single nucleus, surrounded by a plasma membrane and consist of cytoplasm. They are known as the building blocks of life. Humans have about 100 trillion cells in many different sizes.  There are types of organisms that contain one cell and others that contain many more. Unicellular organisms have to perform their own functions of life such as metabolism (chemical reactions inside the cell), response/sensitivity (reacting to changes in the environment), homeostasis (controlling circumstances inside the cell), growth (size of cell getting larger), reproduction (producing offspring), and nutrition (acquiring food for energy and materials for growth). Multicellular cells do not have to perform their own functions but are instead specialized in a specific function allowing them to perform that function efficiently. Because of this, cells in multicellular organisms develop differently, known as differentiation. Also, multicelluar organisms show emergent properties because of the interaction between cells therefore the whole organism is more than the sum of its parts. An example of unicellular organism is a bacterium and examples of multicellular organisms are humans or animals.

After the discovery of cells in 1665, the cell theory was developed. Firstly, the cell theory states that living organisms consist of cells. However, there are times when this idea does not seem fit, for example in multinucleint cells and extracellular matrices. Multinucleint cells are when cells have more than one nucleus. Example of multinucleint cells includes the muscle fibre which makes up the skeletal muscle and fungal hyphae. Muscle fibres are much larger than most cells and consist of hundreds of nuclei. The cytoplasm does not split but there are several nuclei that make the cell to work better. In muscle fibers, mitosis (the act of creating new nuclei) is preformed without cytokinesis (when the cytoplasm divides). Also, many fungi consist of thread-like structures known as hyphae and in some species it contains many nuclei without dividing walls between them. An example of an extracellular matrix is our bones. Bones contain more extracellular material, material outside of the cell membrane, than cells. This means that when things are made within the cell, they are put around the cell and are connected to other cells this way. However, besides these cases, all living things are composed of cells. Secondly, cells are the smallest unit of life. When cells are taken from organisms, they survive a long time but the smaller parts of the organisms do not which shows that cells seem to be the smallest units of life able to survive. Lastly, cells come from pre-existing cells. Past experiments in biology have shown that spontaneous generation of life is impossible. This poses the question of where the first cells come from. However, life in the past was different from today because today we have oxygen whereas in those days we did not. These days, cells can only be formed from division.

Plants and animals are also made up of cells. Animal cells and plant cells are similar in many ways. They both consist of a nucleus and have cytoplasm around it that is enclosed by a plasma membrane. However they are also different. Firstly, plant cells have a cell wall while animal cells have cell membranes. Cell walls are needed for the plant cell to maintain its shape (unless the plant cell grows) and also prevent extra water from entering using osmosis, which is a passage that allows water to go from regions of high concentration to low concentrations through semi- permeable membranes. This is another example of extracellular matrices because the cell wall in made in the cell then put around it and connected to other cell walls. Secondly, plant cells have large permanent vacuoles surrounded by a vacuole membrane. These vacuoles allow the plant cells to grow rapidly by absorbing mineral ions and water. Animal cells on the other hand have vesicles which are small fluid filled sacs in the cytoplasm. Lastly, plant cells contain chloroplasts in the cytoplasm. These chloroplasts are green because of the chlorophyll and they make food for the cell and give it energy. Animal cells do not have chloroplasts and instead use the food made by other organisms.

Cells do not grow forever but instead grow to their maximum size then start to divide. The reason for this is because cells have surface area to volume ratios and this ratio becomes smaller every time the size of something is increased. The rate at which materials enter or exit the cell depends on the surface area and the rate at which materials are used or produced depends on the volume. So if the cell becomes too large, the cell would start developing problems as the ratio would be very small. It would not be able to take in essential materials or emit waste substances quickly enough. The same is true for heat. Cells that create heat may not be able to lose it quickly enough if they grow large.

Cells are impossible to look at with the naked eye so sometimes organisms and other things are magnified to appear larger than they actually are for diagrams and such. This is known as magnification. Because there are larger, it is important to know the actual size and this can be calculated using the formula size of image/ size of specimen. This formula can also be used to calculate the size of the specimen if the magnification and size of the image are given. A scale bar is a line that is added to a micrograph or drawing to show the actual size of the structure. For example if there is a picture of a DNA molecule that is 1 nanometer, a 1 nanometer scale bar would be used to show the size of the 1 nanometer molecule. This way, one can use the scale bar to find out the actual size of the image and the magnification used. Many of the S.I. units are different from each other so it is important to know that one millimeter is a thousand times smaller than one meter, one micrometer is a thousand times smaller than one millimeter, and one nanometer is a thousand times smaller than one micrometer. By knowing this, it is easy to convert these units into other units to find out the magnification and size of specimens.