VCE Biology Question Thread

[ErnieTheBirdi]

How is your school assessing this? Are you doing a written report or a poster or something else?

Hey thankyou for answering, um our school is doing a written report not a poster, it consists of 5 paragraphs the notice said

[caqiu]

From 2017 TSFX U3 exam Q6.d:
Streptococcus pneumonia is a bacterial pathogen that infects the lungs. It is inhaled through the airways and reproduces in the lungs. It can cause symptoms such as coughing, fever chest pain and breathlessness.

A number of days after the initial infection, the patient's blood is sampled and they are found to have high levels of antibodies against this antigen. Describe the sequence of events that led to high levels of specific antibodies circulating in the blood.

I wrote - naive B lymphocytes with specific receptors bind to free antigens (toxins) produced by the bacterial pathogen. It is recognised as foreign, phagocytose it and placed it on its MHC-II marker. Selected B cells present it to activated T helper cells. T helper cells releases cytokines causing B cells to undergo proliferation and differentiation in memory cells and plasma cells, that release vast quantities of antibodies into the blood stream.

answer - APC such as macrophages, naïve B-cells or dendritic cells present the antigen to the T-Helper cell in their MHCII markers (1 mark)
T-Helper cell binds to specific naïve B-cell and secretes cytokines, to cause clonal selection of the B-cell to produce many B-plasma cells and B-memory cells (1 mark)
The B-plasma cells produce antibodies which travel in the blood to bind with the antigens on the pathogen and aid in its destruction. (1 mark)

When we talk about the activation of B cells are we suppose to talk about the activation as well?

[sarah15]

How was bipedal motion a driving force for evolution? Was it because of the fact that it freed the hands of H. sapiens for other uses?
Is it correct that bipedalism came before cranial expansion? Why is that?

[Evolio]

From 2017 TSFX U3 exam Q6.d:
Streptococcus pneumonia is a bacterial pathogen that infects the lungs. It is inhaled through the airways and reproduces in the lungs. It can cause symptoms such as coughing, fever chest pain and breathlessness.

A number of days after the initial infection, the patient's blood is sampled and they are found to have high levels of antibodies against this antigen. Describe the sequence of events that led to high levels of specific antibodies circulating in the blood.

I wrote - naive B lymphocytes with specific receptors bind to free antigens (toxins) produced by the bacterial pathogen. It is recognised as foreign, phagocytose it and placed it on its MHC-II marker. Selected B cells present it to activated T helper cells. T helper cells releases cytokines causing B cells to undergo proliferation and differentiation in memory cells and plasma cells, that release vast quantities of antibodies into the blood stream.

answer - APC such as macrophages, naïve B-cells or dendritic cells present the antigen to the T-Helper cell in their MHCII markers (1 mark)
T-Helper cell binds to specific naïve B-cell and secretes cytokines, to cause clonal selection of the B-cell to produce many B-plasma cells and B-memory cells (1 mark)
The B-plasma cells produce antibodies which travel in the blood to bind with the antigens on the pathogen and aid in its destruction. (1 mark)

When we talk about the activation of B cells are we suppose to talk about the activation as well?

Do you mean the activation of B cells to undergo clonal expansion and selection? If so, yes. I usually say that T helper cells activate B cells with cytokines, causing the proliferation.

How was bipedal motion a driving force for evolution? Was it because of the fact that it freed the hands of H. sapiens for other uses?
Is it correct that bipedalism came before cranial expansion? Why is that?

Yes, bipedal locomotion freed the hands allowing Homo species to manipulate objects, allowing them to make tools. They also allowed the human species to be able to stand taller and scan the land for potential predators and food sources. Our teachers also taught us that the bipedal position allowed humans to have a larger surface area, allowing more heat to be expelled out in the form of sweating, especially during hot daylight hours.

I always thought that bipedalism was side by side with cranial expansion. I guess you could look at it this way: Bipedalism, freeing the hands, allowed humans to manipulate objects, increasing their complex thinking skills when making fine tools since they had to calculate where they would strike the stone to make them efficient for killing animals for example. This may have increased the brain size to accommodate the problem solving skills.

Please feel free to correct me if I'm wrong! I just took a stab at it.

[Erutepa]

From 2017 TSFX U3 exam Q6.d:
Streptococcus pneumonia is a bacterial pathogen that infects the lungs. It is inhaled through the airways and reproduces in the lungs. It can cause symptoms such as coughing, fever chest pain and breathlessness.

A number of days after the initial infection, the patient's blood is sampled and they are found to have high levels of antibodies against this antigen. Describe the sequence of events that led to high levels of specific antibodies circulating in the blood.

I wrote - naive B lymphocytes with specific receptors bind to free antigens (toxins) produced by the bacterial pathogen. It is recognised as foreign, phagocytose it and placed it on its MHC-II marker. Selected B cells present it to activated T helper cells. T helper cells releases cytokines causing B cells to undergo proliferation and differentiation in memory cells and plasma cells, that release vast quantities of antibodies into the blood stream.

answer - APC such as macrophages, naïve B-cells or dendritic cells present the antigen to the T-Helper cell in their MHCII markers (1 mark)
T-Helper cell binds to specific naïve B-cell and secretes cytokines, to cause clonal selection of the B-cell to produce many B-plasma cells and B-memory cells (1 mark)
The B-plasma cells produce antibodies which travel in the blood to bind with the antigens on the pathogen and aid in its destruction. (1 mark)

When we talk about the activation of B cells are we suppose to talk about the activation as well?

You are right in saying that B cells require both binding to free antigen and the reception of cytokines from a Th cell in order to be activated, however, I am not sure VCAA care so much about the binding to free antigen part.
I've just looked through the last 10 years or so of VCAA exams and I haven't found any mention of B cells binding to free antigen, but perhaps I am not looking hard enough. So you could probably get away without mentioning it, but I think it's one of those things that I would just write to be safe (assuming the marks of the question justify including it).
Aside from that, make sure you include (as the answer stated) the presentation of the antigen fragments to within the MHC class two markers of APCs to Th cells. Also make sure you clearly specify that the antibodies are produced by the plasma B cells, as in your response it seems like you're saying the antibodies are produced by the memory B cells as well. In addition, antigens aren't always toxins - antigens are really just any foreign substance.

[caqiu]

You are right in saying that B cells require both binding to free antigen and the reception of cytokines from a Th cell in order to be activated, however, I am not sure VCAA care so much about the binding to free antigen part.
I've just looked through the last 10 years or so of VCAA exams and I haven't found any mention of B cells binding to free antigen, but perhaps I am not looking hard enough. So you could probably get away without mentioning it, but I think it's one of those things that I would just write to be safe (assuming the marks of the question justify including it).
Aside from that, make sure you include (as the answer stated) the presentation of the antigen fragments to within the MHC class two markers of APCs to Th cells. Also make sure you clearly specify that the antibodies are produced by the plasma B cells, as in your response it seems like you're saying the antibodies are produced by the memory B cells as well. In addition, antigens aren't always toxins - antigens are really just any foreign substance.

I was suppose to ask, when we talk about the activation of b cells are we suppose to talk about the activation of t helper cells as well, my bad. So we are suppose to include the activation of T helper cells by APCs which then help activate B cells. Or can we simply just state selected, activated T helper cells release cytokines, initiating clonal expansion without talking about how the T helper cells are activated.

[Erutepa]

I was suppose to ask, when we talk about the activation of b cells are we suppose to talk about the activation of t helper cells as well, my bad. So we are suppose to include the activation of T helper cells by APCs which then help activate B cells. Or can we simply just state selected, activated T helper cells release cytokines, initiating clonal expansion without talking about how the T helper cells are activated.

The study design does make specific mention of the role of APCs to transport antigens and questions have appeared in the past (last one was on the 2018 paper) requiring you to know specifically that APCs presenting a specific antigen activate T helper cells causing their subsequently proliferation/increase in numbers. As such, I would recommend including this element within your response.

[BitcoinEagle]

Dear AN,
I was wondering if there is a list somewhere of what has changed in the study design?

[ssillyssnakes]

Dear AN,
I was wondering if there is a list somewhere of what has changed in the study design?

Here's VCAA's document explaining the changes between the previous and current study design

http://www.vcaa.vic.edu.au/Documents/vce/biology/Summary_of_changes_Biology.doc

Hope it helps

[kjistsehrtot]

as stupid as it sounds, can someone describe the concentration gradient (specifically in transport across the plasma membrane) in the simplest way possible to me? like i know what it is, but i really need a solid grasp on what it really means

[Owlbird83]

as stupid as it sounds, can someone describe the concentration gradient (specifically in transport across the plasma membrane) in the simplest way possible to me? like i know what it is, but i really need a solid grasp on what it really means

I don't know if this will help, but the particles want to move so they are spread out, just like people on a train. If there is half the carriage empty, people will spread out roughly evenly throughout. The will not stay cramped together in one half of the carriage if there is a lot of empty space on the other side because people don't like being squished close together if it's not necessary to be --> just like the particles, therefore they will diffuse evenly around the train.
So that means they will move along the concentration gradient towards the empty space and away from the cramped area.

[BitcoinEagle]

I was a bit confused by this question: 2017 Biology Exam VCAA.

Question 25
Scientists are investigating factors that increase the likelihood of developing MS. Recently, the ‘hygiene theory’ has
been considered a possible factor. This theory proposes that, if a child’s environment is overly hygienic and does not
allow sufficient exposure to a wide range of non-self antigens, an overactive immune system will result later in life.
A recent study tested for the presence of antibodies to the bacteria that cause stomach ulcers, Helicobacter pylori, in
the blood of 550 MS patients and 299 healthy people. Both groups of people had the same proportion of each gender
and were of similar age. Exposure to H. pylori usually occurs by the age of two years. The results of the antibody
testing showed that the rate of H. pylori infection was 30% lower in the women with MS than in the healthy women
or healthy men.
The findings of this study are consistent with the suggestion that
A.    monoclonal antibodies could be used to treat MS.
B. males are affected by MS 30% more often than females.
C.    suffering from a stomach ulcer is a common symptom of MS.
D. in females childhood exposure to H. pylori helps to protect against MS.


How would you rule out answers in this situation? 

[Erutepa]

I was a bit confused by this question: 2017 Biology Exam VCAA.

Question 25
Scientists are investigating factors that increase the likelihood of developing MS. Recently, the ‘hygiene theory’ has
been considered a possible factor. This theory proposes that, if a child’s environment is overly hygienic and does not
allow sufficient exposure to a wide range of non-self antigens, an overactive immune system will result later in life.
A recent study tested for the presence of antibodies to the bacteria that cause stomach ulcers, Helicobacter pylori, in
the blood of 550 MS patients and 299 healthy people. Both groups of people had the same proportion of each gender
and were of similar age. Exposure to H. pylori usually occurs by the age of two years. The results of the antibody
testing showed that the rate of H. pylori infection was 30% lower in the women with MS than in the healthy women
or healthy men.
The findings of this study are consistent with the suggestion that
A.    monoclonal antibodies could be used to treat MS.
B. males are affected by MS 30% more often than females.
C.    suffering from a stomach ulcer is a common symptom of MS.
D. in females childhood exposure to H. pylori helps to protect against MS.


How would you rule out answers in this situation? 

A is incorrect as the results really don't indicate or suggest a causative agent of MS. since we have no real indicated cause, we have no reason to suspect monoclonal antibodies as a treatment.

B is incorrect as no data is given of males. We quite simply don't know the relative proportion of males and females who suffer from MS.

C is incorrect as the results show that MS is associated with lower levels of H. pylori infection, and since H. pylori causes stomach ulcers, MS would be associated with a lower incidence of stomach ulcers.

This leaves D as correct since the results show that women with H.pylori infections have a lower incidence of MS. Thus, it can be suggested than being exposed to H. pylori as a child, may protect females from developing MS.

These kinds of questions can seem confusing because your own knowledge may lead you to believe that multiple suggestions are correct, however it is important to remember that you must answer this question using the information provided in the stem.

Hope this is clear, but feel free to ask for further clarification.

as stupid as it sounds, can someone describe the concentration gradient (specifically in transport across the plasma membrane) in the simplest way possible to me? like i know what it is, but i really need a solid grasp on what it really means

In addition to owlbirds nice and clear response, I will just add that the concentration gradient refers to the movement of particles across different concentrations. If a substance is moving from a high concentration to a low concentration (known as diffusion) it is said to be moving down the concentration gradient. If a substance is moving from a low concentration to a higher concentration gradient (as inactive transport) it is said to be moving up the concentration gradient.

[PhoenixxFire]

I was suppose to ask, when we talk about the activation of b cells are we suppose to talk about the activation of t helper cells as well, my bad. So we are suppose to include the activation of T helper cells by APCs which then help activate B cells. Or can we simply just state selected, activated T helper cells release cytokines, initiating clonal expansion without talking about how the T helper cells are activated.

This question was a bit open to interpretation because it asked about the production of antibodies, rather than the humoral response, so it is plausible that they wouldn't care about how Th cells are activated, as it's not the focus of the question. However, VCAA will pretty much always want you to talk about the activation of Th cells when talking about humoral immunity, so if you get any question about it it's definitely safest to include it, even if the question is only asking about B cells.

Hey thankyou for answering, um our school is doing a written report not a poster, it consists of 5 paragraphs the notice said

That makes it a bit hard (a lot of schools do a poster). There are examples of those sorts of reports around, but not any at a high school level that I know of, so they won't really be any help to you. Do you have a rubric or guide of some sort on how to write it? (or will you be getting one?) I can probably give you some recommendations on how to structure it and what sort of stuff to include if you do, although I can't help with anything about your topic specifically because it's a SAC.

[Comet striker]

Yo can someone answer this doubt?:
if PCR amplifies a DNA sample, why would gel electrophoresis normally used after PCR? PCR would produce the same size fragments at each cycle no?
thnx