This is all one question so you know :(. Please provide justifications for answe

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This is all one question so you know :(.

Please provide justifications for answers so I can learn. Extra detail is very helpful. My teacher is not helpful, so please help. Thank you so much.

Question 5 Part 16 pts Apoptosis is an important cellular process where cells within an organism undergo controlled cell death A. What is one example of how controlled cell death is used by organisms? [2 pts] B. Contrast apoptosis with necrosis. What is necrosis and why might an organism benefit from apoptosis instead of necrosis? [2 pts] C. One of the first steps in apoptosis often involves breaking down the mitochondrial membrane. Explain how this leads rapidly to cell death. [2 pts]

Explanation / Answer

Ans a. The apoptosis is the programmed cell death that includes the death or destruction of those c ells which are non functional or have spent their life span for the purpose they were originated.

The example is tadpole tail is induced to undergo apoptosis when a tadpole is converted to adult frog. In the sequential and programmed way the tail is lost as a result of metamorphosis. The process includes the activation of caspases in an ordered fashion leading to the release of apoptotic factors that lead to the death of cells.

B. Apoptosis is a very well regulated programmed cell death that has been triggered by normal and healthy processes in body; contrary to this the necrosis is the dying of healthy cells due to some injury or external factors like disease or infections.

Apoptosis is a repair or healing mechanism to the body, which is always in benefit of the body as a defense mechanism while necrosis is harmful and abnormal. Usually there are no external symptoms in apoptosis, while symptoms like inflammation, redness, tissue death etc. can been seen in case of necrosis.

Organism is benefitted with apoptosis only while the necrosis is always detrimental because the process of apoptosis includes the process (Membrane blebbing, shrinkage of cell, nuclear collapse), apoptopic body formation followed by engulfment by white blood cells. While the necrosis involves membrane disruption, hypoxia, ATP depletion, metabolic collapse, cell swelling and rupture causing inflammation. This is why necrosis is due to disease or infection and is harmful.

c. The disruption of mitochondrial membrane leads to the release of cytochrome, and proteins from the intermembrane space of mitochondria. This activates the intrinsic pathway of the apoptosis in which second mitochondria-derived activator of caspases are released that binds to the apoptosis inhibiting protein and hence allow the apoptosis to occur.

cytochrome c is binds with Apoptotic protease activating factor and ATP, that activates the pro-caspase-9 and bind with it to form apoptosome. This complex then cleaves pro-caspase to its active form of caspase-9, activates caspase-3 in a cascade form and apoptosis is successful.

2. A. The changes in chromosome occur during each phase of cell cycle is as follows:

Prophase: In this stage the chromosomes start to condense in compact structure, and the mitotic spindle starts to pull together outside nucleus.

Pro metaphase: After the condensation in prophase the chromosomes starts to attach to spindle microtubules through kinetochores. The nuclear envelope also breaks down in prometaphase.

Metaphase: The kinetochore attaches to the opposite pole while the chromosome align themselves on the metaphase plate in middle of spindle fibres.

Anaphase: The chromatids of the chromosomes starts to detach and separated from each other followed by shortening of kinetochore and microtubules and the spindle poles move apart.

Telophase: Chromosomes in segregated form get covered with formation of nuclear envelope. Contractile ring begins to assemble.

B. In a cell

Chromosome no. in diploid = 24

In the beginning of mitosis: the chromosome no. will be 24 because the mitosis generates identical copies of parent cells with same no. of chromosomes as originally.

However the no. of chromatids was 48 because chromosome have two chromatids.

C. In a normal human cells the 46 no. of genomes will be present before mitosis occurs because they have 46 no. of chromosomes.

D. Microtubule filaments are the cytoskeletal elements that is involved in the mitosis as they hold the chromatids together.

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