Psyxwar's Biology 3/4 Question Thread

[Scooby]

Fair enough. I got 99 on a prac test for Bio on Homeostasis because I said cAMP for 2nd messenger molecule instead of G-protein

wut...

[Yacoubb]

We already started Unit 4, like before the mid year 'exams'  why are we so ahead.

That's so good (: At least you'll finish earlier + thus enable yourself more time to study for the exam. I'm aiming to finish all of Unit 4 over term 3 because I need to start doing prac exams and notes revision. I'm familiar with Genetics so I guess it shouldn't take me long to finish AOS 1 of Unit 4. I just have to spend a bit more time on Evolution + the application style questions for evolution.

[Yacoubb]

wut...

LOL what?

[zhe0001]

Does this make sense? Have a bio sac coming up, and I want to make sure that the wording is correct so I don't lose any marks.

The possible question: Describe the mode of entry of the pathogen.

My pathogen is the virus, Yellow Fever

My response: Yellow fever is able to enter the human body through a mosquito acting as a vector for the virus

Does it make sense, and does it actually answer the question?

Probably a stupid question, but im really fob, english aint too great.

Thanks!

[simpak]

Hey, I would probably say something a little more specific because that makes it sound like someone could...eat a mosquito!  And then get the virus.
So maybe something along the lines of: 'Mosquito vectors are able to transmit Yellow Fever virus to humans when they bite the human and allow the virus to enter the human bloodstream directly from the mosquito mouthparts'.
The mosquito vector is the way the virus is transmitted but if you're talking about how it enters the body you want to specifically say how it's getting past a barrier - in this case, the mosquito is breaking the skin (barrier) of the human for the virus and the virus enters the bloodstream directly.
Tbqh my sentence was relatively poorly phrased argh my brain is dead, but hopefully you get the gist of what I'm trying to say >.<

[zhe0001]

Hey, I would probably say something a little more specific because that makes it sound like someone could...eat a mosquito!  And then get the virus.
So maybe something along the lines of: 'Mosquito vectors are able to transmit Yellow Fever virus to humans when they bite the human and allow the virus to enter the human bloodstream directly from the mosquito mouthparts'.
The mosquito vector is the way the virus is transmitted but if you're talking about how it enters the body you want to specifically say how it's getting past a barrier - in this case, the mosquito is breaking the skin (barrier) of the human for the virus and the virus enters the bloodstream directly.
Tbqh my sentence was relatively poorly phrased argh my brain is dead, but hopefully you get the gist of what I'm trying to say >.<

Thank you! This is what I was looking for!

Another question, the SAC mentions a report on the 3rd line humoral and cell mediated immunity (worth 12 marks)
Should I only talk about how B and T cells react when they recognise a pathogen, or should I be talking about everything - the maturation of lymphocytes to b and t cells, identifying foreign material with MHC markers and then finally its response to the pathogen?

Thanks!

[simpak]

I'm not sure about maturation (you shouldn't have even learnt much about the development of the cells, unless you just mean activation) but I would definitely talk about clonal selection and think about what kind of response you would expect to a virus.
Obviously a CD8 T cell response is critical and a humoral response would also be useful but only in specific instances - for example, neutralising virions that exist as the virus is passing to new host cells from ones it has already replicated in, to stop viral attachment.
So I think that level of specificity (where you're not just telling your teacher that B cells recognise antigens and then produce antibodies against them, but actually explaining at what stages in the pathogenesis that is helpful) would be good enough to get you most marks.  If you're concerned about the level of detail definitely consult with your teacher - I'm not sure exactly what she/he would expect because I didn't set the task but hopefully this helps out a little?

[psyxwar]

What is a virion exactly? Does it mean the same as "virus"?

[ealam2]

What is a virion exactly? Does it mean the same as "virus"?

essentially yes but it's what they call a virus when it's outside a host cell
 

[alondouek]

Not exactly. A virion is a virus particle: it can be considered as two main parts:

• The capside (external protein layer)
• The nucleic acid 'core'

Essentially, a virion can be thought of as a single (infective) viral particle that is released from a cell to infect other cells of the same type.

[psyxwar]

Thanks. Are T-cell receptors immunoglobulins?

[Yacoubb]

Thanks. Are T-cell receptors immunoglobulins?

No - surface immunoglobulins are found on the outer surface of B-lymphocytes. T-cells have T-cell receptors

[psyxwar]

Thanks.

Is the substrate concentration that causes all the active sites of an enzyme to be occupied the same no matter what the enzyme concentration is? A STAV paper from 2002 seems to suggest so, but this just doesn't make any sense to me. Wouldn't more enzymes mean more active sites, meaning a high concentration of substrate is needed for them to all be occupied?

Also, for the purpose of a control: would something like "to provide a basis of comparison so that changes in the dependent variable can be attributed to the independent variable (and not extraneous variables)" be okay? I see a lot of different answers to this question.

[Yacoubb]

Thanks.

Is the substrate concentration that causes all the active sites of an enzyme to be occupied the same no matter what the enzyme concentration is? A STAV paper from 2002 seems to suggest so, but this just doesn't make any sense to me. Wouldn't more enzymes mean more active sites, meaning a high concentration of substrate is needed for them to all be occupied?

Also, for the purpose of a control: would something like "to provide a basis of comparison so that changes in the dependent variable can be attributed to the independent variable (and not extraneous variables)" be okay? I see a lot of different answers to this question.

1) That doesn't seem right - by increasing the enzyme concentration, and by keeping substrate concentration constant, you'll have more active sites! However, if you increase both, the variability cancels out. In other words, its what the STAV 2002 answer suggests!

2) Thats fine - ensure you do somehow relate it to the context of the question!!

[psyxwar]

1) That doesn't seem right - by increasing the enzyme concentration, and by keeping substrate concentration constant, you'll have more active sites! However, if you increase both, the variability cancels out. In other words, its what the STAV 2002 answer suggests!

Nah it isn't. It suggests that at 80 arbitrary units of concentration of substrate, reaction rate plateaus regardless of what concentration of enzyme you use