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June 18, 2019, 06:38:41 am

Author Topic: VCE Biology: mtDNA’s Question Bonanza!  (Read 991 times)  Share 

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mtDNA

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VCE Biology: mtDNA’s Question Bonanza!
« on: April 28, 2019, 12:46:28 pm »
+20
Hey there, welcome to my integrated questions thread! With this thread, integrated questions will be posted from biology Tutesmart tutors on a weekly basis for you to answer. By the end of the week, high scoring solutions will be posted for review. Without further ado, let’s get started!

Integrated Question 1: Decapitated Fingers


While Reginald was cutting some onions for dinner, he accidently slipped and cut his finger off. When he called 000, the paramedics told him to avoid washing the decapitated appendage with distilled water.

a)   [Units 1-4] Explain why the paramedics instruct Reginald to avoid washing his decapitated finger with distilled water (2 marks)


Instead, the paramedics tell Reginald to place the appendage in an air-locked bag surrounded in an ice bath.

b)   [Units 3/4] Explain why the paramedics instruct Reginald to place the appendage in an air-locked bag surrounded in an ice bath (3 marks)

c)   [Units 1-4] Suggest what type of solution medical professions may use to clean the decapitated appendage at hospital (1 mark)
« Last Edit: May 13, 2019, 12:49:35 pm by mtDNA »


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ssillyssnakes

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #1 on: April 29, 2019, 03:29:13 pm »
+8
I'm totally guessing for most of these and I'm excited to see what the actual answers are because I have found these questions quite tough, honestly.

a)   Explain why the paramedics instruct Reginald to avoid washing his decapitated finger with distilled water (2 marks)

If Reginald placed his severed finger in distilled water, his cells would be exposed to the water and in a hypotonic solution, with a higher concentration of water outside of the cells than inside. This would result in osmosis into the cell, and may lead to hemolysis of the cells and could hinder the reattachment of his finger

For the other two I don't really know. I'm excited to learn though
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Ash Grey

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #2 on: May 01, 2019, 09:44:09 pm »
+6
These questions are very interesting and different, but pretty hard, so I'm just going to try and guess these answers.

b)   Explain why the paramedics instruct Reginald to place the appendage in an airlocked bag surrounded in an ice bath (3 marks)
The paramedics instruct Reginald to place the appendage in an airlocked bag so as to avoid any contact with air, which may cause infections due to bacteria present in air. The airlocked bag is also so as to ensure that there is no difference in the movement of substances in and out of the cell, when surrounded in ice bath. The ice bath would help in reducing inflammation caused by necrosis due to the decapitation of the finger.

c)   Suggest what type of solution medical professions may use to clean the decapitated appendage at hospital (1 mark)
An isotonic solution with a similar concentration with the appendage

mtDNA

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #3 on: May 05, 2019, 12:29:32 pm »
+11
Hey hey - Attached are the solutions for the first integrated solution!

Below are my comments for ssillyssnakes and Ash Grey - great stuff guys!

I'm totally guessing for most of these and I'm excited to see what the actual answers are because I have found these questions quite tough, honestly.

a)   Explain why the paramedics instruct Reginald to avoid washing his decapitated finger with distilled water (2 marks)

If Reginald placed his severed finger in distilled water, his cells would be exposed to the water and in a hypotonic solution, with a higher concentration of water outside of the cells than inside. This would result in osmosis into the cell, and may lead to hemolysis of the cells and could hinder the reattachment of his finger

For the other two I don't really know. I'm excited to learn though


I love the enthusiasm! So with part a, you are absolutely on the sauce - the hypotonic solution will cause cytolysis, causing the cells to die (and therefore cannot be recovered). I would definitely give you 2/2, particularly given you mentioned the key terms (osmosis, hypotonic, and cytolysis/haemolysis).

These questions are very interesting and different, but pretty hard, so I'm just going to try and guess these answers.

b)   Explain why the paramedics instruct Reginald to place the appendage in an airlocked bag surrounded in an ice bath (3 marks)
The paramedics instruct Reginald to place the appendage in an airlocked bag so as to avoid any contact with air, which may cause infections due to bacteria present in air. The airlocked bag is also so as to ensure that there is no difference in the movement of substances in and out of the cell, when surrounded in ice bath. The ice bath would help in reducing inflammation caused by necrosis due to the decapitation of the finger.

c)   Suggest what type of solution medical professions may use to clean the decapitated appendage at hospital (1 mark)
An isotonic solution with a similar concentration with the appendage

Great stuff with your answers! For part b, I would give you 2/3. This is because “the airlock bag is also ... to ensure that there is no difference in the movement of substances in and out of the cell, when surrounded in ice bath” isn’t quite true - the low temperature and low oxygen concentration would reduce movement, but would not stop movement completely (I know this is being pretty pedantic, but VCAA examiners are like Roz from Monster’s Inc). Also note that your other points are valid, despite them being different to the suggest solutions  8) . Finally, you’re definitely correct with part c!

I can’t wait to see all your responses for the future integrated questions!



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mtDNA

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #4 on: May 05, 2019, 01:12:25 pm »
+9
Integrated Question 2: Connexin 26 & Deafness


Michael, a biomedical researcher, was interested in observing the cellular and molecular basis of congenital deafness. In his research, Michael identified the GJB2 gene located on chromosome 13 which is responsible for synthesising the connexin 26 protein.


a.   [Units 3/4] Identify the subunit of proteins (1 mark).

Connexin proteins form the subunits of connexons; two connexons then combine to form certain channel proteins called gap junctions that permit the movement of particular substances between adjoining cells. The size of the gap junction and the types of particles that move through it are determined by the particular connexin proteins that make up the channel.

b.   [Units 1-4] Identify the properties of substances that move through channel proteins (2 marks).

A diagram showing the arrangement of connexins in the plasma membrane is shown below.


c.   [Units 1-4] Using your knowledge of the chemical properties of the plasma membrane, determine the chemical nature of the interior and exterior surfaces of connexin protein (2 marks).

d.   [Units 1-4] Explain how the difference in chemical nature of the interior and exterior surfaces of connexin proteins aid its role in transporting substances across the membrane (2 marks).

Gap junctions made from connexin 26 are predominantly found in cells of the inner ear and are particularly important for the transport of vital substances between these cells to ensure their survival. In the case of congenital deafness, a common cause of this hearing loss is due to mutations in the GJB2 gene which codes for the connexin 26 protein.

With his research, Michael discovered that the most common mutation in many populations, particularly in people of northern European descent, deletes a C-G base pair at position 35 in the GJB2 gene.

e.   [Units 3/4] Suggest how this mutations in the GJB2 gene results in deafness of newborn children (3 marks).

Good Luck!
« Last Edit: May 13, 2019, 12:51:09 pm by mtDNA »


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mtDNA

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #5 on: May 12, 2019, 11:27:44 pm »
+7
Yes that's right, Christmas has come early: welcome to your third integrated question!

Just a bit of an update before we get started: the solutions to 'Integrated Question 2: Connexin 26 & Deafness' will only be posted next Sunday once there is a response. I understand these question present some difficulty, but that’s the point! If you’re unsure, have a crack and you’ll learn something new  8) . Therefore, I encourage you to try answer both Integrated questions 2 and 3 this week - now let’s get started!

Integrated Question 3: The Case of Acidosis


Carbonic acid creates a buffer system for blood pH in order to keep pH levels within a narrow and controlled range. The following reaction illustrates the mechanism of this buffer system.


In this equilibrium reaction, increases in reactants drive the reaction towards the products. For instance, if CO2 levels increase, then the reaction will drive the forward direction to increase the level of carbonic acid, and ultimately bicarbonate and hydrogen ions.

The presence of bicarbonate and hydrogen ions result in a more acidic environment. When blood plasma gets too acidic, the condition ‘acidosis’ results.

a.   [Units 1/2] Identify the name describing an environment maintained within a narrow and controlled range (1 mark).

Haemoglobin, a quaternary structured protein found in red blood cells, are responsible for the uptake of four oxygen molecules (O2). The amount of uptake, known as the percentage saturation (%), is dependent on the partial pressure of O2 (mmHg) as shown in the graph below. (Note: partial pressure of O2 is equivalent to the concentration of O2).


The partial pressure of O2 in the lung alveoli is approximately 100 mmHg, while it is approximately 40 mmHg in the blood. A decrease in saturation (%) indicates the removal of O2; for example, from collecting oxygen in the lungs and removing them for delivery to cells in body tissue.

b.   [Units 1-4] Outline the approximate percentage of oxygen delivered to body tissues when the pCO2 in blood plasma is 80 mmHg (1 mark).

c.   [Units 1-4] Using the information regarding the reaction and graph above, describe the effect - known as the bohr effect - of an increase in CO2 in the blood plasma (2 marks).

d.   [Units 1-4] Explain why the bohr effect is beneficial to metabolically active tissues (3 marks).

e.   [Units 3/4] If there was an excessive increase of CO2 whereby acidosis was induced, explain how the individual would be impacted on the molecular level. In your response, include a potential symptom of this disease (3 marks).

Good Luck!
« Last Edit: May 13, 2019, 12:52:08 pm by mtDNA »


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Erutepa

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #6 on: May 13, 2019, 09:22:04 pm »
+7
Integrated Question 2: Connexin 26 & Deafness


Michael, a biomedical researcher, was interested in observing the cellular and molecular basis of congenital deafness. In his research, Michael identified the GJB2 gene located on chromosome 13 which is responsible for synthesising the connexin 26 protein.


a.   [Units 3/4] Identify the subunit of proteins (1 mark).
Amino acids
Quote
Connexin proteins form the subunits of connexons; two connexons then combine to form certain channel proteins called gap junctions that permit the movement of particular substances between adjoining cells. The size of the gap junction and the types of particles that move through it are determined by the particular connexin proteins that make up the channel.

b.   [Units 1-4] Identify the properties of substances that move through channel proteins (2 marks).

Substances that move through channel proteins are too large to move across the membrane unfacilitated and are polar
Quote
A diagram showing the arrangement of connexins in the plasma membrane is shown below.


c.   [Units 1-4] Using your knowledge of the chemical properties of the plasma membrane, determine the chemical nature of the interior and exterior surfaces of connexin protein (2 marks).
Since the interior of the plasma membrane is hydrophobic in nature, the exterior surface of the connexin protein would be similarly hydrophobic, while the interior would thus then be hydrophilic in chemical nature.
Quote
d.   [Units 1-4] Explain how the difference in chemical nature of the interior and exterior surfaces of connexin proteins aid its role in transporting substances across the membrane (2 marks).
The hydrophobic nature of the exterior surface enables the incorporation of the connexin protein within the plasma membrane while the hydrophilic nature of the interior surface facilitates its interaction with polar molecules. Thus the chemical nature of both surfaces enables its role in facilitating the movement of polar molecules across the plasma membrane.
Quote
Gap junctions made from connexin 26 are predominantly found in cells of the inner ear and are particularly important for the transport of vital substances between these cells to ensure their survival. In the case of congenital deafness, a common cause of this hearing loss is due to mutations in the GJB2 gene which codes for the connexin 26 protein.

With his research, Michael discovered that the most common mutation in many populations, particularly in people of northern European descent, deletes a C-G base pair at position 35 in the GJB2 gene.

e.   [Units 3/4] Suggest how this mutations in the GJB2 gene results in deafness of newborn children (3 marks).
This single base deletion mutation causes a frameshift which subsequently alters the reading frame of the GJB2 gene downstream of this mutation. As such, the gene possesses a sequence of different DNA triplet codes which transcribe to give a sequence of different mRNA codons compared to the mRNA sequence of the functional gene. This means that the translated protein will be composed of a different amino acid sequence, and may even be truncated if the frameshift mutation results in an early stop codon. This alteration in the primary structure of the connexin 26 protein thus affects the functional 3D conformation of the protein and therefore will alter its function to transport vital substances within the inner ear, pertaining to the deafness of newborn children who possess this GJB2 mutant gene.
« Last Edit: May 13, 2019, 09:52:10 pm by Erutepa »
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enociz

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #7 on: May 13, 2019, 11:00:09 pm »
+5
Hey, just taking a crack at these. I'm loving how out there they are.

Integrated Question 2: Connexin 26 & Deafness

a.   [Units 3/4] Identify the subunit of proteins (1 mark).

Amino acids.

b.   [Units 1-4] Identify the properties of substances that move through channel proteins (2 marks).

Small, charged or polar substances such as potassium ions.

c.   [Units 1-4] Using your knowledge of the chemical properties of the plasma membrane, determine the chemical nature of the interior and exterior surfaces of connexin protein (2 marks).

The plasma membrane is made up of phospholipids arranged in a bilayer, with the hydrophilic heads facing the aqueous cytoplasm and extracellular matrix, while the hydrophobic tails face inwards to each other.
Given this, it is likely that the connexin proteins have a similar nature, with a hydrophobic exterior surface, and a hydrophilic interior surface. This would mean that the hydrophobic side chains of these amino acids that make up the protein's exterior surface can interact with the fatty acid chains of phospholipids, allowing the protein to be embedded in the membrane.

d.   [Units 1-4] Explain how the difference in chemical nature of the interior and exterior surfaces of connexin proteins aid its role in transporting substances across the membrane (2 marks).

The connexin proteins would have a hydrophobic exterior surface and hydrophilic interior surface. This would allow the interior surface to form a channel.
Since the amino acids making up the channel's surface are hydrophilic, they will interact with polar and charged molecules, allowing them to pass through the channel that the interior surface has created, moving in or out of the cell.

e.   [Units 3/4] Suggest how this mutations in the GJB2 gene results in deafness of newborn children (3 marks).

This mutation affects the pre-mRNA that is transcribed in the nucleus, changing every nucleotide from position 35 onwards. After this molecule undergoes  post-transcriptional modification, it will be translated at the ribosome.
During translation, the codon involving the base pair at position 35 will be changed since that base pair has been deleted and so the next takes its place. This will mean that all amino acids added to the polypeptide chain, including that and the ones that follow, will be different from the ones required to form the connexin 26 protein.
Therefore, the connexin 26 protein will not be produced, meaning the membranes of the cells in the ear will not have the gap junctions formed by connexsomes, and therefore will not survive. This leads to a lack of these cells in the ears, and thereby, deafness in newborns.

SmartWorker

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #8 on: May 15, 2019, 12:16:37 pm »
+4
Yes that's right, Christmas has come early: welcome to your third integrated question!

Just a bit of an update before we get started: the solutions to 'Integrated Question 2: Connexin 26 & Deafness' will only be posted next Sunday once there is a response. I understand these question present some difficulty, but that’s the point! If you’re unsure, have a crack and you’ll learn something new  8) . Therefore, I encourage you to try answer both Integrated questions 2 and 3 this week - now let’s get started!

Integrated Question 3: The Case of Acidosis


Carbonic acid creates a buffer system for blood pH in order to keep pH levels within a narrow and controlled range. The following reaction illustrates the mechanism of this buffer system.


In this equilibrium reaction, increases in reactants drive the reaction towards the products. For instance, if CO2 levels increase, then the reaction will drive the forward direction to increase the level of carbonic acid, and ultimately bicarbonate and hydrogen ions.

The presence of bicarbonate and hydrogen ions result in a more acidic environment. When blood plasma gets too acidic, the condition ‘acidosis’ results.

a.   [Units 1/2] Identify the name describing an environment maintained within a narrow and controlled range (1 mark).

Haemoglobin, a quaternary structured protein found in red blood cells, are responsible for the uptake of four oxygen molecules (O2). The amount of uptake, known as the percentage saturation (%), is dependent on the partial pressure of O2 (mmHg) as shown in the graph below. (Note: partial pressure of O2 is equivalent to the concentration of O2).


The partial pressure of O2 in the lung alveoli is approximately 100 mmHg, while it is approximately 40 mmHg in the blood. A decrease in saturation (%) indicates the removal of O2; for example, from collecting oxygen in the lungs and removing them for delivery to cells in body tissue.

b.   [Units 1-4] Outline the approximate percentage of oxygen delivered to body tissues when the pCO2 in blood plasma is 80 mmHg (1 mark).

c.   [Units 1-4] Using the information regarding the reaction and graph above, describe the effect - known as the bohr effect - of an increase in CO2 in the blood plasma (2 marks).

d.   [Units 1-4] Explain why the bohr effect is beneficial to metabolically active tissues (3 marks).

e.   [Units 3/4] If there was an excessive increase of CO2 whereby acidosis was induced, explain how the individual would be impacted on the molecular level. In your response, include a potential symptom of this disease (3 marks).

Good Luck!

Just a note I am currently doing unit 1/2 bio.

a. Homeostasis.

b. 80%.

Do we use the PCO¬2 80 graph?

c. An increase in CO2 concentration in blood plasma results in a higher saturation of oxygen in
Haemoglobin.

d. Increased CO2 concentration results in a balanced increased in oxygen concentration. Hence, metabolically active tissues are able to rid of CO2 waste product and absorb the O2 essential.

e. -   Acidosis induces abnormalities in the release of hormones and their functions
-   Acidosis could cause impaired growth among infants and children
-   A symptom of this disease is fast breathing. This is due to inefficient expelling of CO2 and requires faster breathing in order to maintain the homeostasis of CO2 concentration in the body.


Thank You for the questions.  :) :) :) :) :) Please check my expression .

 :)

Joseph T

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #9 on: May 18, 2019, 08:08:52 pm »
+2
First time doing this...hope it's formatted right

Units 1-4] Explain why the paramedics instruct Reginald to avoid washing his decapitated finger with distilled water (2 marks)

As adding distilled water will result in a hypotonic solution outside the blood cells, this could result in the cells in the decapitated finger to lyse and burst.


b)   [Units 3/4] Explain why the paramedics instruct Reginald to place the appendage in an air-locked bag surrounded in an ice bath (3 marks)

Temp affect the rate at which enzymes works, which in this case would be breaking down the finger. A decrease in temperature results in the enzymes working slower as substrates collide less with enzymes and therefore slowing down the decay of the finger.


c)   [Units 1-4] Suggest what type of solution medical professions may use to clean the decapitated appendage at hospital (1 mark)

Alcohol? Can someone explain this one thx

mtDNA

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #10 on: May 19, 2019, 11:50:38 am »
+3
Integrated Question 2 Feedback
solutions are attached below

Erutepa
a) 1/1
b) 1/2 - remember that charged particles also need to use channel proteins to get through the membrane. Another note, you can try make your response more concise by simply listing the two properties: large and hydrophilic; charged molecules.
c) 2/2
d) 2/2
e) 3/3 - you correctly identified the effect of the mutation on the primary structure, the effect of the changed primary structure on the tertiary structure, and finally how this changed conformation would impact the ability for the connexin protein to form gap junctions and ultimately lead to impeded transport across these cells.

Overall this is an awesome effort, so well done!  ;D

Enociz
a) 1/1
b) 1/2 - this is being a bit pedantic, but be careful about your expression: “Small, charged or polar substances such as potassium ions” implies that either small OR charged OR polar substances move through channel proteins. Although this is true for charged molecules such as ions, this isn’t always the case for ’small’ since plenty of small hydrophobic molecules can travel through phospholipids such as oxygen, and ‘polar’ since water can enter through simple diffusion. Therefore, you need to be more specific by writing 'large and hydrophilic; charged'
c) 2/2 - you got the marks for mentioning the interior was hydrophilic and the exterior was hydrophobic. However, note that your explanation wasn’t quite right (though it’s not a big issue here given this was not an ‘explain’ question), so I would recommend you read Erutepa’s response.
d) 1/2 - you got a mark for mentioning how the hydrophilic interior enables the channel protein to interact with polar and charged molecules; however you needed to be more specific with your reasoning for the hydrophobic exterior. Here, being hydrophobic enables the protein to be incorporated into the phospholipid bilayer (which I understand you were trying to say this, but it needed to be more explicit).
e) 1/3 - you few points here: firstly, “this mutation affects the pre-mRNA ... it will be translated at the ribosome” is irrelevant to the question and can be omitted. Secondly, “all amino acids added to the polypeptide chain ... will be different from the ones required to form the connexin 26 protein” is correct, though the key term I was looking for was primary structure (first mark). Continuing on with this, the changed primary structure will ultimately change the tertiary structure of the connexins (second mark) which would impede their ability to form connexons and therefore channel proteins. Instead of this, you mentioned “connexin 26 protein will not be produced”, which is not necessarily the case, so just be a bit cautious with your statements (examiners can be picky  :-\ ). Finally, You mentioned the result would lead to cell death which is where you got the mark - great stuff Enociz!

As always, I can’t wait to see more of your responses in future!


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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #11 on: May 19, 2019, 12:22:36 pm »
+6
Integrated Question 3 Feedback
solutions are attached below

SmartWorker
a) 1/1
b) 0/1 - you will need to use the pCO2 graph. When calculating the delivery of oxygen, you should note the percentage difference of saturation from the lung alveoli to the body tissue. Therefore, the lung alveoli saturation is approximately 90% while the body tissue saturation is approximately 50%. Therefore, the amount of oxygen delivered would be 90 (oxygen absorbed in lungs) - 50 (oxygen remaining on haemoglobin after delivery to the body tissue) = approximately 40% delivered. Figures between 30-50% would be acceptable.
c) 0/2 - As you can see from the graph, the higher concentration of CO2 (e.g. pCO2 = 80) has a lower saturation level of oxygen than lower concentrations of CO2 (e.g. pCO2 = 20). Therefore, haemoglobin actually has a lower binding affinity for oxygen when pCO2 increases.
d) 1/3 - you got a mark for mentioning the bohr effect ables greater oxygen delivery to metabolically active tissue, but it should also be mentioned that metabolically active tissue would increase CO2, in turn decreasing pH and reducing the binding affinity of haemoglobin to oxygen, therefore allowing the greater deliver of oxygen. 
e) 1/3 - you correctly identified two symptoms (increasing breathing rate and stunted growth), but you also needed to explain the effect of acidosis on a molecular scale. In this way, your discussion should have pertained to the effect of pH on proteins, particularly haemoglobin in this particular context.

Overall, a great effort  :D

@Joesph T, note that the solutions to the first integrated question have been posted above, so feel free to compare your solutions to those ones I prepared early.

As always, keep up the effort guys, I’m loving it  8)
« Last Edit: May 19, 2019, 12:29:53 pm by mtDNA »


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mtDNA

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Re: VCE Biology: mtDNA’s Question Bonanza!
« Reply #12 on: May 19, 2019, 04:20:53 pm »
+3
Integrated Question 4: #healthy #newyearsresolution #clean #cleaneating


Some bacteria have protein appendages, known as fimbriae, which enable their attachment and adhesion to their host cells. In doing so, they enable a close interaction which the host, allowing certain strains of bacteria to enter the intracellular environment of the host and cause disease. The interaction of fimbriae is shown below.


a.   [Unit 1-4] Identify Molecule X (1 mark)

b.   [Unit 3/4] Identify the method of transport bacteria would use to move into the cell (1 mark)

c.   [Unit 3/4] Suggest how fimbriae confer a selective advantage for bacteria (2 marks)

Sam and Ella decided to have chicken sushi for dinner. When preparing for dinner, Sam wondered why, for centuries, humans have always cooked meat. He then proposed to create some raw chicken sushi rather than going to the effort of putting it in the oven. Ella argued that he would definitely regret eating raw chicken sushi.

d.   [Unit 3/4] Explain why the chicken should be cooked instead of being eaten raw? (2 marks)

e.   [Unit 3/4] Suggest why humans can eat raw salmon but not raw chicken? (1 mark)

Good Luck!
Integrated Question 5 will be posted in a fortnight, so feel free to have a go at this question and previous questions before then!
« Last Edit: May 19, 2019, 06:46:34 pm by mtDNA »


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