Neuron Structure: 

The Neuron is a cell that is responsible for receiving and transmitting information inside of the nervous system.

The Cell Body is composed of 3 major parts that include the Cell body, Dendrites and Axon.

*Image above is from the textbook

The Cell body helps support the cell since it contains genetic information, and helps maintain the structure of the neuron and provides energy to help with the sequence of activities.

Axons are structures that carry impulses from the cell body to the axon terminal

Dendrites receive information from other neurons and bring it to the cell body

Other components of the Neuron include the Myelin Sheath, Schwann cell, Axon terminal, Synaptic knob, Nodes of Ravier and Nucleus.

Myelin Sheath covers the axon of some neurons and helps make neutral impulses work faster

Schwann cell helps protect the neuron by acting as an insulator and this helps prevent electrical impulses from passing through

Axon terminal forms connections with other cells

Synaptic knobs are connections that are formed between the dendrite and terminal of two different neurons

Nodes of Ravier speed up the rate of the signal connection

The Nucleus provides energy to the neuron, allowing it to perform its functions smoothly.

There are 3 types of Neuron Cells: Interneuron, Motor Neuron, and Sensory Neuron

The image above is called the Interneuron. 

The Interneuron is in charge of connecting the Sensory and Motor Neurons so they can exchange information and communicating with the Central Nervous System.

The image above is called the Motor Neuron. 

The Motor Neuron is in charge of relaying signals from the central nervous system to the rest of the body.

The image above is called the Sensory Neuron. 

The Sensory Neuron is in charge of transmitting signals from the outside of your body to the central nervous system.

Neuron Function: 

Action Potential moves along the Axon in multiple stages (Resting Potential, Depolarization, Repolarization and Resting State.

1. Resting Potential: Sodium and Potassium voltage gate channels are both closed. At this state the axon is polarized because the negative and positive ions are equally balanced.

2. Depolarization: The Sodium channels open due to a stimulus causing sodium to rush into the cell and the voltage to increase. Depolarization causes the ions on the axon membrane to be imbalanced. This causes pores on the membrane to also open up and along more charged ions in while the original section is pumping the sodium ions out of the body.

3. Repolarization: The Sodium ions increase until they reach a point of 40 mV when they close and then the potassium voltage channels open. The potassium rushes out of the cell, and it causes the voltage to rapidly decrease.

4. Resting state: Both Sodium and Potassium channels are closed. Sodium potassium exchange pumps moves Sodium out of the cell and Potassium into the cell. This brings them back to normal polarity and resting potential

Synapse Structure:

Down below is an image of Synapse with it’s labelled parts.

Synapse Function: 

The Synapse allows a neuron to pass an electrical signal onto another neuron and this is very important for transferring impulses from one end to another.

This process begins when the nerve impulse reaches the terminal button and it starts releasing Neurotransmitters into the Synapse.  The Neurotransmitters moves into the Synapse and fits into receptors on the dendrites that are located on the opposite side (fits like a lock and key) When the neurotransmitters attach to receptors on the neuron side of the Synapse they produce an excitatory or inhibitory effect. If the neuron side takes in more than one neurotransmitter, it is influenced by the excitatory and inhibitory effect. If the excitatory effects outnumber the inhibitory effects, then it will begin transferring information into the next neuron. In order for the next potential stimulation to occur, neurotransmitters that are not accepted by the receptor sites must be removed from the Synapse. Enzymes will break down the neurotransmitters, which will then be reabsorbed by the terminal buttons and this process will be able to start again.

Protein synthesis is divided into two stages: Translation and Transcription

Down below I will be explaining these processes in more detail.

Differences between mRNA and DNA 

mRNA: 

• Created during the process of Transcription
• Role is to determine the order of amino acids for a Protein
• Known as the “messenger” RNA
• Contains the sugar Ribose
• Made up of the bases Adenine, Guanine, Uracil and Cytosine
• Does not have a double helix shape

DNA: 

• Stores the information for the genes in living organisms
• Constantly making new copies of itself to form new DNA strands
• Contains the sugar Deoxyribose
• Made up of the bases Adenine, Guanine, Cytosine and Thymine
• Created during the DNA replication process
• Located inside the nucleus
• Has a double helix shape

PROCESS OF TRANSCRIPTION: Converting DNA to mRNA

3 stages of Transcription:

1. Unwinding/Unzipping of DNA double helix
2. Complimentary Base pairing
3. Separation of DNA

1. Unwinding/Unzipping of DNA double helix 

A visual model of a DNA double helix structure is shown in the image below.

  The beige hexagon represents Cytosine. Thymine is represented by the yellow hexagon, Guanine by the darker blue polygon, and Adenine by the lighter blue polygon. Every base is linked to a phosphate group (represented by the teal circle) and a deoxyribose sugar (the green Pentagon)

 DNA double helix structure

The dotted lines represent the formation of hydrogen bonds between the base partners (Adenine pairs with Thymine and Cytosine pairs with Guanine)

Transcription occurs in the nucleus and is activated by RNA polymerase. RNA polymerase is an important enzyme that creates a sequence of nucleotides that will be later used to make mRNA (messenger DNA)

The process of Transcription starts when RNA polymerase attaches to the DNA strand and unwinds the double helix structure to form two separate strands of DNA.

                                 Unwinding of the Double Helix

Because nucleotides can only be added from the “5 to 3” direction RNA polymerase will only add nucleotides along one strand because the other strand is anti-parallel and read in the opposite direction.

The strand that RNA polymerase is adding nucleotides too is named the template strand (or the Nonsense strand) because it will be used as a template for complimentary base pairing to form mRNA. The other side of the DNA molecule is known as the “Sense Strand” because its bases are complimentary to the Nonsense strand and the mRNA strand that will be created.

2. Complimentary base pairing 

The picture below on the left side represents the complimentary base pairs that occurs to create an mRNA molecule.

RNA polymerase is represented as the yellow heart.

The picture on the right also represents the process of Complimentary base on the mRNA strand.

                              RNA Complimentary base pairing 

RNA Polymerase is going to form hydrogen bonds between the base partners on the template strand and connect the nucleotides together to form the backbone of the RNA molecule.

Guanine will still pair with Cytosine, but Adenine will pair with Uracil instead of Thymine. The light green polygon represents Uracil.

In the diagram above, each base is bonded to their partner, a phosphate group, and a ribose sugar group (bright red circle), rather than Deoxyribose, as we previously saw in the DNA double helix molecule structure.

Separation of DNA: 

Because DNA is unaffected by transcription, it reforms, and RNA undergoes changes before converting to mRNA and then it transfers to the cytoplasm to begin protein synthesis.

In the picture below we can see that the mRNA strand is being separated from the DNA.

Separation from DNA Strand 

RNA TRANSLATION PROCESS: Process of converting mRNA to a protein

The process of Translation occurs in the Ribosome.

3 stages of Translation: 

1. Initiation:
2. Elongation:
3. Termination

1. Initiation: 

Each set of 3 bases on the mRNA strand is known as a Triplet or Codon and codes for a certain amino acid. For example, the codon AGU codes for the amino acid Serine.

The process of Initiation starts by building the protein by adding one amino acid at a time. The mRNA molecule will attach to a small subunit, and then they will attach together. As the small subunit moves along the mRNA molecule unit, it will find a specific nucleotide sequence on the mRNA strand with the start codon AUG.

In the model below we can see that the codons are highlighted, and the mRNA strand is placed on top of the ribosome (red cut out) and it is reading the START codon of AUG.

               The start codon AUG 

2. Elongation:

The amino acids are brought to the ribosome by molecules called tRNA (transfer RNA) which are represented as the green object in the model below. tRNA molecules have an amino acid at the top and an anti-codon at the bottom. The anti-codon is a set of three bases which are complimentary to the three bases on the mRNA.

The three bases on the mRNA code for the amino acids that the Trna is carrying. Each type of tRNA molecule is specific to a particular triplet on the mRNA it will ensure that it always brings down the correct amino acid.

          Chain of amino acids

Once initiation takes place the charged tRNA molecule is found in the P site of the ribosome. Another tRNA finds the amino acid and then it brings it to the A site. Peptide bonds are formed between these amino acids and then the amino acids detach from the tRNA that is in the P site. Then the molecule from the A site is moved into the P site. Once the A site becomes empty this process repeats itself.

In the image above we can see that the process of elongation causes there to form a chain of amino acids.

The process of Elongation is to ensure that the TRNA’s have now brought the correct amino acids to the ribosome in the correct order so now the ribosome is able to join them together and start building up a chain of amino acids.

3. Termination:

       Chain of amino acids (Primary Structure of Protein)  

This procedure keeps going until a codon lacks a tRNA that matches it in the A-site. It will become a STOP codon as a result, which will stop translation.

As seen in the image above, the entire chain of amino acids will eventually separate from the ribosome and produce a protein.

Model activity questions:

1. A) Our models accurately reflect the process of Protein Synthesis because we were able to show the most important parts that are involved during this process and explain their functions through re-arranging them on a board. The hands-on aspect of this activity helped represent Protein Synthesis more accurately because we were able to show all of the stages, and document the changes made during the various stages. The objects were color-coded to make them easier to distinguish on the model.

B) Our models may have misrepresented this process because they are not as detailed as real-life Protein Synthesis, and we only included the main functions. Also, due to the time and effort required to construct the models, they are not as long or extensive as real-life models and only depict a portion of the actual process.

C) Next time, I think it would be useful to draw a model of Protein Synthesis to help demonstrate the process more accurately because a drawing could make it much more detailed, neat, and include more information. I also believe that using 3D objects rather than 2D objects would be beneficial because it can help show the proportions of the various functions involved and help explain the process more efficiently.

2.  I think that these models are an effective way to engage and educate people about scientific topics since they involve different aspects of learning. These models are useful for hands-on learners because they allow them to build the model while also learning about Protein Synthesis. This model is also beneficial for visual learners because it allows them to visually see where different objects are located, and the different colored coded parts of a model can help them remember the parts of a model and retain the information for a longer period of time.

Resources:

• Class one note (Translation and Transcription PowerPoint notes, Model building activity notes)

  Cited Websites: 

• Study.com, 2022, study.com/academy/lesson/translation-process-location-biology.html. Accessed 22 Oct. 2022.
• “What Is Transcription? – Stages of Transcription, RNA Polymerase.” BYJUS, byjus.com/biology/dna-transcription-mrna/. Accessed 22 Oct.2022