Category Archives: Grade 12

Diffusion in Agar Cubes

Posted on by under Bio 12, Grade 12

After our diffusion lab and letting each cube soak in our sodium hydroxide, then cutting them open, the smallest cube (1cm) was the most effective in terms of maximizing diffusion due to the entire cube (and even the inside) was fully pink.

The smallest cube had the greatest surface area to volume, therefore it being the most effective in maximizing diffusion. Having a greater surface area to volume ration basically allows a solution to fully surround the cube and enter more of the volume it holds as it enters through the larger surface area. Other important factors that can also affect how materials diffuse into cells or tissues are:

  • the concentration
  • the pressure
  • the temperature
  • the nature of material/thickness
  • the ratio of the surface area to volume.

Although surface area is helpful to cells, cells do not grow to be very large because this would increase the volume size, resulting in a smaller surface area to volume ration. This means that it will be harder, and less effective, for  maximizing diffusion in order to allow things like nutrients, resources, water, etc to pass through the cell membrane.

With three cubes, A, B, and C with surface to volume rations of 3:1, 5:2, and 4:1 respectively, the most effective at maximizing would be cube C due to it’s larger surface area, yet smaller volume. This essentially means that there is more surface area for materials to pass through, yet less “insides” that it will penetrate, making it easy for everything inside the cell to be effected by the material.

Our body adapts to surface area to volume to help exchange gases by having differently shaped cells. For example, having nerve cells be thin and long. Also, there will be folds in the membrane.

Certain cells, like bacteria, cannot become the size of a small fish because if the cell grows to be this size, the surface : volume ratios start to become smaller, and less efficient in the process of diffusion. The cell won’t function properly because it is not fully absorbing the materials trying to penetrate it. Also, the cell will divide in order to prevent this loss of functionality and wouldn’t be able to reach this size.

One of the advantages of large organisms being multicellular is that their diffusion rate is much higher, helping the larger number of functions that exist in large organisms. This higher rate of diffusion allows for better efficiency as an organism, including its systems within and its processes in general.

Protein Synthesis – Transcription and Translation

Posted on by under Bio 12, Grade 12

Protein Synthesis is the process in which cells make proteins, with the help of RNA, DNA and amino acids. It happens through stages which are: transcription and translation.

Transcription: process by which the building instructions spelled out by DNA is transferred to mRNA

Translation: process by which the code carried by mRNA is converted into a polypeptide

How is mRNA different than DNA?

  • DNA contains deoxyribose, while mRNA contains ribose
  • DNA is double stranded, mRNA is single stranded
  • They have different functions: DNA is responsible for storing and transferring genetic information, and mRNA acts like a messenger between DNA and ribosomes to make proteins
  • base pairing is different: DNA’s bases are thymine, cytosine, adenine and guanine while mRNA’s bases are uracil, cytosine, adenine, and guanine
  • DNA is longer/bigger than mRNA: DNA has 85 million nucleotide pairs, whereas mRNA has only around 1000 nucleotide pairs

Describe the process of transcription:

  • Unwinding and unzipping of DNA
    • the DNA molecule unwinds until it is the shape of a flat ladder
    • DNA helicase starts to break h-bonds between complementary base pairings within DNA molecule
  • Complementary base pairings:
    • one strand of the DNA molecule is used as a template to produce a mRNA strand
    • RNA polymerase is responsible for h-bonding existing RNA nucleotides to the template DNA strand and joining the adjacent nucleotides
  • Separation from DNA
    • once the entire gene has been transcribed onto the mRNA strand, this strand will separate from the DNA strand and transport itself out of the nucleus to deliver DNA’s message

How does this activity do a good job of modelling the process of RNA transcription? In what ways was our model inaccurate?

  • This model was able to show us the basic process of RNA transcription, step by step
  • It showed us how RNA and DNA:
    • have unique bases (uracil and thymine), by having different coloured beads
    • have a different number of backbones: RNA had one pipe cleaner as the backbone, whereas DNA had two
    • completely replicated each other’s complementary base pairings, showing how transcription works
  • It was slightly inaccurate because
    • the model didn’t show the differing sizes between the DNA molecule and RNA molecule, as we used the same sized pipe cleaners
    • we couldn’t quite see the exact process that the enzymes go through when producing certain stages
    • the model didn’t show the existing nucleotides only attaching to the complementary bases before the backbone being bonded together on the RNA strand

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

  • Initiation
    • mRNA is held by a ribosome with a “P” site and a “A” site
    • once the “P” site reads a START codon (AUG), the matching tRNA will bring in a corresponding amino acid to the start
  • Elongation
    • the initiation process continues, as the amino acid chain grows with every new codon being read
    • the “A” site will read the next mRNA codon and bring in the next corresponding matching tRNA
    • the amino acid changes from the tRNA in the “P” site will be transferred to the tRNA in the “A’ site
  • Termination
    • once the codon reads as the STOP codon, as there is no tRNA for a STOP codon, the amino acid change will stop growing
    • the ribosome will let go of the mRNA and the tRNA will let go of the polypeptide

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

  • It was able to show us:
    • how the translation process is dependant on mRNA codons (Start and stop)
    • the ribosome can accommodate two tRNA’s at once
    • amino acids attach and become a long chain to form a polypeptide
  • It was inaccurate in showing:
    • the reality of the ribosome having two sites (our model showed the ribosome as one unit)
    • how translation will happen at multiple places along a mRNA strand, ours only shown it happening at one location

DNA and Protein Synthesis

Posted on by under Bio 12, Grade 12

single strand of DNA molecule sugar-phosphate backbone, with nucleotides ready to hydrogen bond to their complimentary base pairings

The structure of DNA is made up of two polynucleotide anti parallel strands that are shaped into a double helix with phosphate-sugar backbones on the outside and complimentary base pairings on the inside. These base pairings, (nucleotides), are hydrogen bonded together, connecting the two strands into one DNA molecule. The bases, pyrimidines and purines, bond to each other depending on their complimentary base. Adenine always h-bonds to thymine, while cytosine always bonds to guanines

 

DNA molecule twisted to model true double-helix shape

DNA molecule

This activity helps model the structure of DNA by clearly showing the basic structure of having 2 sugar-phosphate backbones, and showing the complimentary bases bond to each other depending on which base they are. The changes we could’ve made to improve the accuracy of this model would have to be ensuring the sizes and proportions of the materials match. The model didn’t perfectly illustrate exactly how a DNA molecule would be formed, as the white pipe cleaners weren’t all the same size, therefore not creating a “consistent” bond. Also, H-bonding is a lot more complicated than just two hooks latching onto each other, which is what the model shows. The spacing of the beads (representing the bases) and the white pipe cleaners from each other were not consistent nor equally distanced. To improve this, we could treat the model with more detail and try harder to equally space and place all materials.

DNA replication occurs before a cell divides.

  1. Unwinding

The two strands that make up DNA “unzip” – the h-bonds (which are very weak) between the complimentary bases break. The enzyme HELICASE causes this to happen.

  1. Complimentary base pairing

New nucleotides, which are always present in the nucleus, fit into place with their complimentary base pairing. The enzyme POLYMERASE causes this to happen and is present.

  1. Joining

The complimentary base pairings all join together to form new strands, therefore new DNA molecules. This step is caused by the enzyme DNA LIGASE

This process may occur differently on the “leading” and lagging” strands because when the sugar is at the top of the strand, the parent strand is read by the DNA polymerase from the 3’ end towards the 5’ end replicates normally, but when it is the opposite (Lagging strand), the complimentary strand will need to be built by DNA polymerase in short segments moving backwards from the “replication fork”

To model the complimentary base pairing and joining of adjacent nucleotides steps of DNA replication, I used 2 new strands of blue pipe cleaners (representing the sugar phosphate backbones) lined with the replicated opposite side of bases with the beads, therefore making it able for unzipping strands to find a new strand to hydrogen bond with to form a new, replicated DNA molecule. This activity was well suited to showing this process by clearly displaying the way that the molecule unzips with the help of the enzyme polymerase. The model shows how one molecule turns into two complete copies because of this unwinding. It was inaccurate in the way it showed the hydrogen bonding and exactly where the original sugar phosphate backbone ended up and how a new one forms in a real DNA replication. Also, the true double helix shape of the molecule wasn’t possible to be kept during the model of the process since the natural shape of pipe cleaners are parallel. The complexity of the work of the enzymes weren’t able to be shown due to the simplicity of the model, yet the detailedness of the true process. Lastly, this model didn’t show that the parent DNA molecule stays in tact during this replication process

 

Journalism in Verse

Posted on by under English 12, Grade 12

Image result for flowers in a dead field

Swept away.

 

His hateful words have crawled into the ears of those passing by

Reputation of the land of the free, now crushed to pieces

His shadow covers the country,

only letting those who he chooses, see the sun

 

Those who care to care, raise their fists

They shout into the streets

They sing into the wind,

hoping something high above will sweep him away

 

Although he made the innocent cower

The afraid, terrified

He propelled the strong to become stronger

In division, he united those against him

 

Now, the wind has taken him away

His voice still echoes in the mountains

They will never quite fade, his footprints in the grass

But the seeds planted by the new, will cover it with sunflowers.

 

The article

Introductory writing assignment

Posted on by under English 12, Grade 12

The Power of the Media 

Image result for activism

What stories, videos, content (either print or visual) on the internet inspires you, scares you, makes you think, makes you angry, makes you want to read/watch more? Share some examples.

Being exposed to so many media outlets, I’ve definitely felt many different feelings while reading or watching content. With today’s political climate, so many controversial posts flood my timeline and I can’t help but consume it and react. Politically, I am quite progressive and agree with the left side of the argument so seeing the situation in the United States has evoked emotions of  fear and anger. Even just watching videos of the President speak on sensitive subjects during his speeches or rallies makes me feel sick to my stomach. I can’t help but watch this type of media because I am a very curious person who craves information. This motivation has even ended up with me having sleepless nights watching more and more. On the other hand, I have also really been inspired by the internet. Personally I feel most inspired when I read an article or watch a short video about people standing up for what they believe in. Specifically young people because it makes me believe that I could do something like that. For example, the young girl, Greta Thunberg, and her “Friday’s for Future” campaign. I was so intrigued by her maturity and passion that I attended one of the events in Vancouver.

If you could interview any one person in the world, who would it be and why? (please don’t make, ‘because they’re rich’ your answer)

I would want to interview Ruth Bader Ginsberg. She is such an educated and experienced woman who has surpassed so many boundaries given to woman, especially back when she was just starting. She used to be a lawyer, which is a career I’m considering. I would ask her so many questions about her experiences, her opinions, and her advice for a young woman wanting to study a subject that she has committed her entire life to. I think it would be so interesting to hear her perspective on the political situation and see if I could take anything from her to use in my own day to day life to live by.

What are you passionate about? What do you ‘stand for’? How do you express your passion? Does your online activity support your passion, values and interests? How so?

A topic that I feel very passionate about is the wellbeing of others and also the environment. As a young person, I will be the generation living upon the Earth for many years to come, whereas those in power making decisions about whether or not to put money into environmental friendly methods won’t be. Also, a fire in my chests starts when I see stories circulating about the maltreatment of humans around the world. Whether it be in my own country, or across the world. I am someone who is very empathetic so my passion is basically to help others and my environment thrive to the best that they can be. I would say that my online activity does support my interests in these fields as I follow a lot of activism accounts that share new stories and perspectives of what’s going on around the world. I often repost and share posts on my main accounts to spread the word and raise awareness about issues that I find interesting and important.

What does knowledge mean to you?

To define knowledge for me personally would be the ability to adapt to the world around you. I believe that to be an all-around intelligent being, you need to be capable to see more than just the facts. Our world is changing with every day, so we need to change with it or you would get left behind. To be knowledgeable, you would need to understand the importance of staying on top of updating and learning more and more as time goes by. Also, soft and hard skills are essential to knowledge. These two components work together to form a human who is open-minded to other’s opinions and, eager to learn and absorb more information from those around them.

Do you believe that people in a democracy should have some knowledge of current events?

I absolutely believe that people in a democracy should have some knowledge of current events. If not, I feel like it is not really a democracy. The government would have too much power and the public wouldn’t know the full truth of everything going on behind closed doors. It is key in a progressive society to have different views and opinions on the countries events, and that’s what journalism does. It gives important information to the citizens, providing free speech and positive or negative feedback. How would the citizens know if who they voted for is following through with their promises? How else would the public be aware that there is an issue in their society.

 

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