Category Archives: Grade 12

Diffusion in Agar Cubes

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What determines the efficiency of diffusion throughout the model “cells”?

The smaller the cells, the more efficient diffusion will be.

1. In terms of maximizing diffusion, what was the most effective size cube that you tested?

It was the smallest cube, that was 1 centimeter cubed, that had maximized the diffusion.

2.   Why was that size most effective at maximizing diffusion?  What are the important factors that affect how materials diffuse into cells or tissues?

The most effective was the smallest cube because it had a very small amount of volume which allowed the diffusion to be easily carried out all throughout the cube itself. Furthermore, it had a large surface area to volume ratio which allows diffusion to be the most effective. Additionally, temperature, concentration, type of material, size of the cell, and polarity are all factors that affect how materials diffuse into cells or tissues.

3. If a large surface area is helpful to cells, why do cells not grow to be very large?

A cell does not grow because if it did then the volume would get much larger which would result in a decrease in the surface area to volume ratio. A decrease in the ratio would result in a less effective diffusion and would take much longer for the process of diffusion to occur. In addition, there is less cell membrane for substance to diffuse through, meaning that the center of the cell is not receiving its necessary substances.

4.   You have three cubes, A, B, and C.  They have surface to volume ratios of 3:1, 5:2, and    4:1 respectively.  Which of these cubes is going to be the most effective at maximizing diffusion, how do you know this?

The most effective will be the 4:1 ratio, cube C, because, as stated above, the larger ratios are the ones that with hold the most maximization for diffusion. The smaller the cell (bigger the ration) the more adequate it is to have substances moving in and out of it.

5.   How does your body adapt surface area-to-volume ratios to help exchange gases?

Our bodies have larger organs that have a large surface area, meaning that it also has a large surface area : volume ratio. To have the good ratio we must have respiratory organs, such as lungs to have that gas exchange (oxygen in – carbon dioxide out).

6.   Why can’t certain cells, like bacteria, get to be the size of a small fish?

They cannot grow because once size increases the surface area: volume ration gets smaller. They cannot become larger because if that happens then the cell will no longer be efficient enough to bring enough nutrients and other things from the outside to the inside of the cell. Diffusion would not be able to occur throughout the whole cell.

7.   What are the advantages of large organisms being multicellular?

To begin multicellular organisms, have multiple different types of cells, while unicellular only cell. The multicellular organisms have special cells that deal with more difficult and understanding cells. Additionally, they have specific tasked organ systems such as the digestive, cardiovascular and respiratory systems. In order to survive it is crucial that these processes are done.

Pipe Cleaner DNA

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  1. Explain the structure of DNA – use the terms nucleotides, antiparallel strands, and complimentary base pairing.

The structure of a DNA is a long polymer that is made out of many nucleotide monomers. It has two backbones that have a sugar and phosphate bonded pattern. The two backbones are not identical, as the sugar phosphate bond are opposite form each other, also known as antiparallel strands (1-phosphate-sugar-phosphate  2-sugar-phosphate-sugar). Furthermore, the bases are always paired with the same partner (purine-pyrimidine) à Adenine & Thymine; Guanine & Cytosine.

 

  1. How does this activity help model the structure of DNA? What changes could we make to improve the accuracy of this model? Be detailed and constructive.

This model helps show the structure of the DNA through the colored bases, that helps recognize their partnered base. Also, it shows the sugar phosphate antiparallel strands, as shown through the black beads. In addition, the twist in the DNA stricture is easily achieved by the bending capability of the pipe cleaners. The model could be improved if the bonds in the middle were shorter, thus to making the twist look a little messy. When we bent the DNA structure the long bonds would not stay straight thus twisting and bending as well, which is not how the DNA structure should look.

 

3. When does DNA replication occur?

   It occurs before cell division.

 

4. Name and describe the 3 steps involved in DNA replication. Why does the process occur differently on the “leading” and “lagging” strands?

-Unwinding & unzipping- DNA helix-case                                                                                                        – Complimentary base pairing- DNA polymeras                                                                                                                                                                                      – Joining of adjacent nucleotide- DNA ligase

The process occurs differently for the leading and lagging strands because they are built differently. The leading strand is built from the 3’ end to the 5’ end, which is the strand that has the sugar at the top of the strand. However, the lagging strand is built oppositely with 5’ at top and 3’ at bottom. DNA polymerase works in small segments, reading the strand backwards.         ** DNA polymerase is responsible for H-bonding new nucleotides to the strand, it can only read DNA in one direction. From 3’ end to 5’ end.**

 

5.  The model today wasn’t a great fit for the process we were exploring. What did you       do to model the complimentary base pairing and joining of adjacent nucleotides steps of DNA replication. In what ways was this activity well suited to showing this process? In what ways was it inaccurate?

We attached the (little white pipe cleaner) nucleotides to half of the parent DNA (backbone with unpaired nucleotides) to form a daughter DNA. For the leading strand we had to attach from top (3’) to bottom (5’). Though for the lagging we had to build backwards form bottom to top.

It was inaccurate because technically the DNA backbone is not one long strand of sugar phosphates (represented by blue pipe cleaner). It is supposed to be phosphates and sugars bonded together molecule by molecule as each nucleotide is paired. Furthermore, due to the fact that we created the model by hand, it is impossible to accurately replicate the parent DNA, since in reality they are exact copies of one another. For example, the length of our nucleotides and the length of their hydrogen bonds were not all the same which created a relatively uneven model. However, it was accurate because it gave us a good visual to show the same sequence DNA that was split to form same sequence daughter DNA. It also, gave a good visual to show the attachment of the lagging and leading strands.

 

 

6. How is mRNA different than DNA?

The difference between mRNA and DNA is that m RNA has 1 backbone, while DNA has 2 backbones. Additionally, mRNA is built with RNA polymerase (superhero), while DNA is built with DNA polymerase & DNA Ligase. Furthermore, mRNA carries DNA’s message and information, while DNA doesn’t carry any RNA information or messages.

7. Describe the process of transcription.

Transcription starts with the RNA polymerase who binds to a sequence of DNA called the promoter. Which is found near the beginning of a gene. It then separates the two strands of DNA apart. Then, one DNA strand acts as a template for RNA polymerase. As it reads the template it creates an RNA molecule out of complimentary nucleotides. The RNA molecule that is created holds the same information as the non-template DNA though, instead of Thymine it uses Uracil. Finally, sequences called terminators signal that the RNA is complete. Once it is complete, it is released form the DNA polymerase.

8. How did today’s activity do a good job of modelling the process of RNA transcription? In what ways was our model inaccurate?

It was a good way of modelling the process of RNA transcription because it showed how the RNA molecule that is created matches the ‘non-template’ DNA strand. It also shows very well how the Thymine is changed to Uracil on the RNA molecule. In addition, it shows how the DNA Splits apart by RNA polymerase and then rejoins back together very well also. Finally, due to the fact that it was easily moveable it was very simple to show how the DNA ‘unwinds’ before it gets separated.

The model was inaccurate because it was difficult to truly show how it creates its complimentary bases.

9. Describe the process of translation: initiation, elongation and termination.

Is when the code that is carried by mRNA is transformed into a polypeptide. First step is initiation, which is when mRNA binds to the small ribosome subunit. The two ribosome subunits then bind together, reads the start codon. The second step is elongation, which is when ribosome moves along mRNA reading each codon, bringing in the complimentary tRNA and building amino acid chain. Finally the third step is termination, which is when a ribosome reads a stop codon, no complimentary tRNA for a stop codon. This makes the ribosome release mRNA, tRNA and polypeptide strand.

10. How did today’s activity do a good job of modelling the process of translation? In what ways was our model inaccurate?

This model was accurate because it showed how the ribosomes move along and the process of elongation. However, it was inaccurate because we were ‘moving’ the tRNA while the mRNA should have been the one ‘moving’. (was away for the beginning of lab due to arm therefore it made it more difficult to understand the model).

 

vocabulaire 1.2

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Effleure (page 34): Verbe effleurer ; De toucher quelque chose très doucement et plutôt des fois n’apporte pas de l’attention à l’action, inaperçu ; ” J’ai essayé de marcher dans la foule et avait effleurer contre plusieurs personnes. ”

Nuque (page 34): Nom féminin ;  le derrière du cou ; ” J’ai oublié de mettre de la crème solaire sur ma nuque, alors je l’ai brûler.”

Hissé (page 34): Verbe hisser ; s’élever à côté de quelqu’un ou quelque chose ; “Barry s’est hissé à coté de Cindy, qui était assis sur la trampoline.”

Quai (page 35): Nom masculin ; le trottoir à côté du l’eau ;  “J’ai couru jusqu’à la fin du quai où j’ai sauté dans l’eau ”

Fautif (page 35):  Adjectif ; coupable / responsable ; ” John est fautif car il a pris tous les bonbons quand il n’était pas supposé ”

Erré (page 36): Verbe intransitif ; marcher autour sans objectif ; “Quand Ella attendait pour sa mère dans le magasin elle erré autour des allées.”

Faubourg (page 37): Nom masculin ; un quartier d’une ville ; “Je vis dans un bon faubourg de Seattle, il a plein de grandes maisons.”

Balayait (page 38): Verbe balayer ; action de nettoyer quelque chose avec un balai ; “Austen balayait la céréale qu’il a renverser sur la plancher.”

Banlieue (page 39): Nom féminin ; les régions habiter qui sont placé jusqu’au extérieure des villes ; “Rachel vie à New Westminster ce qui est une banlieue proche à Vancouver.”

Songeurs (page 40): Adjectif ; d’être absorbé dans une pensée ; “J’étais songeurs après que j’ai finis la livre de mystère.”

“Should students learn about world religion in school?”

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The world today is being controlled by an overwhelming ignorance that can be killed with knowledge and education. By educating our young we can fulfill the lack of knowledge and understanding that is bread from racism surrounding fellow religions. It will also contradict the racist ideologies that this generation is being introduced to. A child is not born racist, they a taught. It is extremely heartbreaking that such a new generation is being influenced by racism. Though, with the help of education from our schools we can teach the children how wonderful and unique each race/culture is. Furthermore, by doing so it will make them open-minded and respectful towards others, specifically minorities. Being taught, even the smallest bit, about different religions is such a great opportunity to be introduced to something entirely new. Due to this, it will make you open your mind to accept and appreciate the culture of the world. Many people, especially the young, are easy targets at being embarrassed towards their own culture because of all the ignorance that surrounds them. However, if the religions not as known to the western world are being taught, it will reassure and teach the young that you should not be ashamed of your culture and who you are. Moreover, it will create an unprejudiced environment that will influence all parties for the better. To be able to live, for the most part in an ignorant free world we must conduct change within our lives. To do so we must inculcate the many beautiful differences to our developing generation. Teaching to accept and respect can create a new wave of people that will be willing to take a stand against the bigotry. Not only would they be learning to stand-up but they will also be learning to have courage and to fight for the right thing. Implying the concept of having multiple religions in the world is one thing but to have people to act upon it is a whole new lesson they will be introduced to. The purpose of education upon this subject is not only to create an unbiased world but one that aspires to celebrate differences and courtesy.