Reflection Topic Cell as Unit of Life

8/3/2019 Reflection Topic Cell as Unit of Life

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Name : Mohamad Arif Bin Nasaruddin

Matrix number : D20091035123

Lecturer : Dr Shakinaz Bt Desa

Reflection for Class One (Biology 2 TBU3032)

Biology 2 is a subject in a major course of AT16 (Science Education). As a student of AT16, I already set in my mind that I must score with flying colours for that subject in thissemester. Dr. Shakinaz Desa is my lecture for Biology 2 subject. Last Tuesday, Biology classwas held in Tadahan Utara 6 of Universiti Pendidikan Sultan Idris. Our class start at 5.00 P.Mand end about 7.00 P.M. My friends and I came a little bit late for that class. Well, its better late than never. But we will try to come early for that class later. Okay, l ets go straight to thepoint. Dr Shakinaz already gave the task to us to write an article or essay as a reflection for

the class one. This is my reflection base on what I got from that class and my point of view.

The first topic for TBU 3032 is How Cell Reproduce. For me as a ex-student of Biological Science in Perak Matriculation Collage, I already learn this topic before. Then Ithought that this class will be boring and lame. Yeah, people like always get bored easilywhen keep doing the same thing repeatly. But I was wrong. This class is okay and help me toenhance my understanding for this topic. The class begin with Read and Tell session. Theperson in charge is Azuita. She explains about what we are going to learn at that evening.From her reading, she is really able to describe about Cell cycle, begin with Interphase and MPhase( Mitotic Phase).

Next, its a time for Dr. Shakinaz to handle the class. The first thing that she did is sheasked about the mind map. She wanted us to rose the mind map and shown it to the class.Then, she asks about the task that she gave in the class a week before. Everybody show whatthey had drawn. Dr Shakinz asked us to improve the way of making mind map and we canget inspired by other friends ideas. Then, Dr Shakinaz starts her explanation about this topicby describing Chromosome. Chromosome is a genetics unit that carry heredity information orDNA molecule. So, it is an important thing for human to pass the genetics information fromone generation to other generation. Chromosome locate in the nucleus of cell and it is beensurrounded by nuclear envelope. When we pull the chromosome out from nucleus it lookslike a rope. The chromosome made up of double helix strand of DNA. It is also associatedwith Histone protein. Histone protein is a molecule that involve in a coiling process of chromosome. This molecule made up of positive charge of amino acids. The chromosomeinvolved in the process of Mitosis.

After that Dr Shakinaz ask the class about the cell cycle. From that class I know thatCell Cycle is a series of events from one cell division to next. It starts when new daughter cellis form as a result of Mitosis process and cytokinesis process. It will end when the cell divide.In other word cell cycle is a series of event of a complete life of diploid cell. In Cell cycle,there are two major phases that take place in order for cell to divide. First phase is Interphasephase and the second phase is M phase or Miotic phase. Interphase is the longest phase in the


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cell cycle while on the other hand Mitotic phase is shortest phase cell cycle. In Interphasethere are three major stages involved. The first stage is G1 stage. Second stage is S phase.And the third stage is G2 phase. In general, Interphase is a stage for cell to get ready for celldivision. Okay let get a clear look for Interphase. G1 is an interval of cell growth before the

cell undergoes DNA replication. During this stage several event take place in cell. All cellularcontain in cell are duplicate except for chromosome. As are result, the number of organellesin cell increase and the volume of cytoplasm for cell also increase. The chromosome areinvisible (It is called as chromatin), nucleus bound by a membrane and nucleoli clearlyvisible with proper staining. That is why this stage can be described as a growing phase forcell by me (just to enhance my understanding).

After G1 phase, the cell will undergo the S phase. S is representing synthesis. Duringthis phase the DNA of cell will replicate and the chromosome will duplicate. So, thechromosome will have two identical chromatid (one chromatid and another one is called

sister chromatid) that joint at centromere but the chromosome is not distinctly visible. At thisstage, there will be two DNA molecules per one chromosome. Beside that the synthesis of protein also starts. Next phase is G2 phase. This is last phase in Interphase but it is shorterthan G1 phase. During this phase, the cell double check for duplicate chromosome and therepairing process will be done if there is anything wrong with it. The cell mass will increase,energy storage for cell will increase (due to the increase in the number of mitochondria), thereplication of centriole take place, the synthesis of tubulin protein start, and the chromosomewill start to condenses and coil. The cell will ready for Mitosis.

Then Dr Shakinaz tells us about M phase or Mitotic phase. Some of us already knom

thas Mitotic phase is the phase where the division of nucleus (karyokineisis) take place andfollowed by cytoplasm division (cytokinesis). Nuclear division (karyokinesis) refer toMitosis. The Mitosis can be define is the division of nucleus of cell into two geneticallyidentical of daughter nuclei. Dr Shakinaz stress to us that there are four stages in Mitosis. Thestages are Prophase, Metaphase, Anaphase and Telophase. Then she explains to us about allevents that occur during Mitosis. First stage is Prophase. During this stage the chromosome isreally clearly visible. It is condenses and highly coiled. The centriole will migrate to oppositepole of cell, nuclear membrane will breaks, nucleolus will degenered, aster will form frommicrotubule, and mitotic spindle will begin to form. Next stage in Mitosis is Metaphase.

During Metaphase, the chromosome will align at the Metaphase plate that is an equator of cell. The chromosome will attach to the spindle fiber at the centromere. Each chromosome iscomposed of two chromatids.

Third stage in Mitosis is Anaphase. During Anaphase the centromere will split due tothe progressive removal of tubulin protein. On the other hand, the spindle fiber that thecentromere of chromosome attaches to it will shorten due to action of some enzyme. As thefibers shorten, they pull the chromatids apart (mean that the chromatid and its sisterchromatid separate) and towards opposite ends of the dividing cell. The centromeres leadwith the arms of the chromosomes trailing behind. A complete set of chromatids migrates to

opposite sides of the cell by this process. While some fibers shorten, other microtubles of thespindle not attached to the chromosomes increase in length and size of the cell just prior to


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cytokensis. The last but not least stage in Mitosis is Telophase. In Telophase, thechromosome already reached at the centriole at each pole. There are two clusters of chromosomes, that decondense (the chromose will become invisible again). The nuclearenvelopes will appears again due to the fuse of new membrane. The nucleolus also will

reappear. In the other hand the spindle fiber will completely degenerate. This is the sign thatthe Mitosis is over. What can I can say about Mitosis is all about the division of nucleus of cell that will maintain the chromosome numbers of cell.

Another event in M phase/ Mitotic phase is cytokinesis. Cytokinesis is the division of cytoplasm of the cell. It is a process whereby the cytoplasm of a single cell is divided to formtwo daughter cells. It is occur for both plant cell and animal cell but there are a bit differentbetween each other. In animal cell the cytokinesis occur by the formation of the cleavagefurrow. A ring of actin microfilaments associated with plasma membrane encircles the cell inequatorial region. The actin filament will contract and form the cleavage furrow. This

cleavage furrow will deepens gradually. As a result, the cytoplasm will separate into twodaughter cells. For plate cell the cytokinesis occur by the formation of the cell plate. Cellplate is form from the vesicles that have fused from Golgi apparatus, an organelle in cell.Microtubules appear to guide the movement of the Vesicles to the centre of the cell and thesebecome more peripheral as the new wall grows. As the cell plate elongate and fuse with thecell wall of the cell. This will form new cell wall and middle lamella of the cell and separatethe cell into two daughter cells. There are gaps in the Cell Plate. These becomePlasmodesmata and connect the cytoplasm of both new cells. The cleavage furrow cannotform in the plant cell because it is surrounded by a rigid cell wall.

When the cell is divide to new to daughter cells it is indicate that the cell has alreadycomplete its life cycle or cell cycle. Then Dr Shakinaz explains about the mechanism thatcontrols the cell cycle. There is several check point in the several phase in cell cycle. Sheshows to us an animanition about this subtopic. That animation states that they are threechecks point in cell cycle. The checks point are G1 check point, G2 check point and M check point. These check point will control the cell division. I am wondering how its control thedivision of the cell. At the end of the call I ask Dr about it. Dr explains too me that there areseveral enzyme reaction that occur at each check point. This enzyme controls the cell cycle.What will happen if the cell division is uncontrolled? Dr Shakinaz tells that the cell will

divide continuously and unstop. This will cause cancer and we need to go to the hospital inorder to remove some cell in our body. That is why the cell cycle must be control. Then oneof our classmates asks is it the cell division is a cycle process. She answers that the celldivision is a cycle process but there are a little gap.

Next session is a talent time by first group. But there is some technical problem. So, itwill be postponed to next class, I guess so. Then Dr Shakinaz explains about the differencesbetween the cell division of plant cell and animal cell. She explains about how to explain thedifferences between them by using high level of thinking method. I think I understood what itall about. But I am not confident that I can use it during examination. It is quite tough for me.

For animal cell the division of the cell involve the present of centriole, cytokinesis occurs byfurrowing and cleavage of the cytoplasm and the cell division occur to the cell throughout the


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body. In other hand, the cell division in plant cell do not involve the centriole, the cytokinesisoccur by the formation of the cell plate, and cell division mainly occur in the Meristem cell.The Mitosis also have some significant. It help cell to growth, replace dead tissue andmaintains the number of chromosomes in cell. Next, Dr Shakinaz shows to us several

diagrams that represent several stages in Mitosis. She asks us to guess which stage in Mitosisthat representing the diagram. We answer it almost all correct. Then just before the class endshe gave to us some question to answer within ten minute. All questions are about the topicthat we just learnt in the class. After 10 minute period, we check the answer. Then weexchange the answer paper with each other. I got 12 correct over 13 questions. I think that Ihave good understanding about this topic. From the question I know that during Anaphaseand and Telophase there are a double number of chromosomes in the cell. I never notice thisbefore this. This question can also help me to enhance my understanding. Our class end about7 PM.

Last but not least, I want to give some constructive comments and suggestion for you,Dr Shakinaz in order to ensure that your class will be great for next time. Overall I think youdid a good job for our class. Two thumbs up for you Dr Shakinaz. Your power point isinteresting and clear. We do not have any problem with that. We can jot down note from yourpower point easily. Besides that your explanation is brief and almost perfect. That is reallygood in order to help some of us that do not learn this topic before especially to physicalstudent. You help to turn the complicated thing to simple thing. Then you also show to us alot of diagram or picture about this topic. This method can help us to remember informationof this topic quickly and last longer in our mind. Yes, the theory of physiology state that likethat. You also show to us some video or an animation that related to this topic (Cell cycle,Mitosis and etc). This is really helpful to us. First it can avoid us from get bored in the class.For me the time for this class (5.00 PM 7.00 PM) is not really a suitable time for learnt. Soby doing that it, you can make us want to stay focus in class. In addition, you alwayscommunicate with us during the class session. It can prevent us from being sleepy in class.Thats all that I can comments.

For suggestion, I think you should share some tips to us about some tips that is reallyuseful for us during examination of this paper. You can give us a way to tackle the question,method on how to answer the question and how to give a good answer sheet regarding the

question in this subject. As you know that, some of us in this class never learnt Biologybefore. So they are zero for content in Biology subject. So, by doing that you can help they tounderstand Biology more efficiently. Before this they must thing that biology is all aboutremembering facts. But this opinition for me is not 100% true. Biology is not like that. Thisfirst thing that we must able to do is to understand the concept of Biology. Then it will helpus to remember facts easily. If we just remember the facts in Biology without understandingit first, we will find that Biology is a killer subject or a complicate subject. That is mysuggestion. It is depend on you whether you to consider it or not. Okay that is all myreflections for class one. Thank you Dr Shakinaz.

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Reflection Topic Cell as Unit of Life