Biology Unit 3 Questions Megathread

[Russ]

afaik, water diffuses through the membrane but also must use channels (presumably aquaporins) to achieve the measured rate of osmosis.

Naive T lymphocytes differentiate into Helper/Cytotoxic cells in the Lymph Nodes (technically in the thymus I guess but they acquire their actual effector function in the lymph nodes). They're usually activated by interaction with Dendritic Cells and subsequent stimulation by cytokines.

Macrophages can act to activate them but it's much less common

[TrueLight]

CD4+ T cells (Helper T cell)
CD8+ T cells (CTL)

well yea naive CD4+ T cells, CD8+ T cells get activated and differentiate into effector CTL's or Th lymphocytes in the periphery (doesn't have to be lymph nodes, its in the peripheral lymphoid organs like spleen) but yes what Russ said DC's are the cells that initiation the primary adaptive immune response. But the cytokines produced by the DC's or macrophages does help to activate the T cells (like IL-2) and certain cytokines can help to differentiate T helper cells into certain types of Th cells (ie: Th1, Th2, Th17 etc) for example IL-12 produced by DC's or macrophages help to turn CD4+T cell into Th1 phenotype.

[WhoTookMyUsername]

After excercise, should amount of CO2 exhaled increase or decrease? we just did a praac where everyone got CO2 exhaled decreases after excercise, should i try and validatet this, or say it's wrong and attribute it to an error?

[ariawuu]

After excercise, should amount of CO2 exhaled increase or decrease? we just did a praac where everyone got CO2 exhaled decreases after excercise, should i try and validatet this, or say it's wrong and attribute it to an error?

sounds like a PE question haha, im guessing its decrease.. simply because there is limited time to convert oxygen to co2, hence small amounts of co2 is exhaled? but i recommend you msg lexitu

[Kaille]

i'm getting annoying but i got another question.

I am having trouble finding a solid description on the process of cell mediated immunity, there seems to be some discrepancies between text books such as heinemann and other texts. heinemann says that a naive t cell will recognise an antigen on the mhc 1 marker on the antigen displaying cell. the t cell will then develop and proliferate into t cytotoxic cells and t helper cells. The t helper cells then release cytokines (interleukin-1) to activate natural killer cells. Cytotoxic cells and natural killer cells then directly kill virus infected cell. Other texts say that a t helper cell recognises the antigen, rather than a naive t cell.

Which is correct?

[lexitu]

After excercise, should amount of CO2 exhaled increase or decrease? we just did a praac where everyone got CO2 exhaled decreases after excercise, should i try and validatet this, or say it's wrong and attribute it to an error?

sounds like a PE question haha, im guessing its decrease.. simply because there is limited time to convert oxygen to co2, hence small amounts of co2 is exhaled? but i recommend you msg lexitu

Just about to leave for work, will answer this later - short answer it will decrease gradually.

[scocliffe09]

i'm getting annoying but i got another question.

I am having trouble finding a solid description on the process of cell mediated immunity, there seems to be some discrepancies between text books such as heinemann and other texts. heinemann says that a naive t cell will recognise an antigen on the mhc 1 marker on the antigen displaying cell. the t cell will then develop and proliferate into t cytotoxic cells and t helper cells. The t helper cells then release cytokines (interleukin-1) to activate natural killer cells. Cytotoxic cells and natural killer cells then directly kill virus infected cell. Other texts say that a t helper cell recognises the antigen, rather than a naive t cell.

Which is correct?

Our uni lecturer taught that naive T cells are activated by antigens, which causes them to specialise and proliferate.

[WhoTookMyUsername]

After excercise, should amount of CO2 exhaled increase or decrease? we just did a praac where everyone got CO2 exhaled decreases after excercise, should i try and validatet this, or say it's wrong and attribute it to an error?

sounds like a PE question haha, im guessing its decrease.. simply because there is limited time to convert oxygen to co2, hence small amounts of co2 is exhaled? but i recommend you msg lexitu

Just about to leave for work, will answer this later - short answer it will decrease gradually.

YES! that's what my results / class results show I'm excited ! Woudl love if you could do this by tomorow, as that's when my sac is to be finished

[Russ]

@CO2, if lexitu is going to answer it in depth then I won't bother, but from a purely biochemical standpoint I presume it's related to decreased ATP production from the TCA cycle (and thus reduced CO2 production)

i'm getting annoying but i got another question.

I am having trouble finding a solid description on the process of cell mediated immunity, there seems to be some discrepancies between text books such as heinemann and other texts. heinemann says that a naive t cell will recognise an antigen on the mhc 1 marker on the antigen displaying cell. the t cell will then develop and proliferate into t cytotoxic cells and t helper cells. The t helper cells then release cytokines (interleukin-1) to activate natural killer cells. Cytotoxic cells and natural killer cells then directly kill virus infected cell. Other texts say that a t helper cell recognises the antigen, rather than a naive t cell.

Which is correct?

A naive T cell will recognise an antigen on MHC (MHC1=CD4, MHC2=CD8). This will cause proliferation and differentiation. CD4 cells will become T helper (Th) cells and CD8 cells will become cytotoxic T lymphocytes (CTLs).

Th cells will produce multiple cytokines, some of which will activate NK cells. NK cells do not absolutely require activation, they can have effects without T cell help. CTLs and NK cells will then target intracellular pathogens (NK cells are predominantly for antiviral functions, CTLs can target all many of intracellular pathogens).

The confusion may stem from the fact that a naive T cell can be either a Th cell or a CTL. By the time they reach the periphery and encounter Ag, they've already determined whether or not they will become Th or CTLs. As such, sometimes people say "naive cells encounter Ag" and sometimes they say "T Helper cells encouter Ag".

Our uni lecturer taught that naive T cells are activated by antigens, which causes them to specialise and proliferate.

fwiw, Ag signalling isn't enough for specialisation, they need cytokine stimulation as well

[Kaille]

i'm getting annoying but i got another question.

I am having trouble finding a solid description on the process of cell mediated immunity, there seems to be some discrepancies between text books such as heinemann and other texts. heinemann says that a naive t cell will recognise an antigen on the mhc 1 marker on the antigen displaying cell. the t cell will then develop and proliferate into t cytotoxic cells and t helper cells. The t helper cells then release cytokines (interleukin-1) to activate natural killer cells. Cytotoxic cells and natural killer cells then directly kill virus infected cell. Other texts say that a t helper cell recognises the antigen, rather than a naive t cell.

Which is correct?

A naive T cell will recognise an antigen on MHC (MHC1=CD4, MHC2=CD8). This will cause proliferation and differentiation. CD4 cells will become T helper (Th) cells and CD8 cells will become cytotoxic T lymphocytes (CTLs).

Th cells will produce multiple cytokines, some of which will activate NK cells. NK cells do not absolutely require activation, they can have effects without T cell help. CTLs and NK cells will then target intracellular pathogens (NK cells are predominantly for antiviral functions, CTLs can target all many of intracellular pathogens).

The confusion may stem from the fact that a naive T cell can be either a Th cell or a CTL. By the time they reach the periphery and encounter Ag, they've already determined whether or not they will become Th or CTLs. As such, sometimes people say "naive cells encounter Ag" and sometimes they say "T Helper cells encouter Ag".

Our uni lecturer taught that naive T cells are activated by antigens, which causes them to specialise and proliferate.

fwiw, Ag signalling isn't enough for specialisation, they need cytokine stimulation as well

Oh i see, so i could say either the t helper cell or naive t cell? thanks for the help.

[TrueLight]

T cells during development in the thymus already develop into CD4+ (helper) or CD8+ (cytotoxic) T cells... so that is already determined by the time they are in circulation

when they are exit the thymus and enter circulation they are all naive since they have not encountereed their antigen... once they encounter their antigen and are activated they become effector CD4+ T cells or effector CD8+ T cells
this may help you depending how much you know the terms already  http://vce.atarnotes.com/forum/index.php/topic,25843.0.html

[WhoTookMyUsername]

True light if you kjnow the answer to my question, could you please ask it ? I'm  not sure what time Lexitu gets baclk and i realy need an answer tonight

Thanks!

[Russ]

Simplest explanation I can think of is that anaerobic respiration will be producing lactic acid, which has the unfortunate side effect of being an acid. That means it'll dump protons and drop the physiological pH. CO2 will be consumed by the body to buffer against this via hydrogen carbonate (H2CO3) production.

[WhoTookMyUsername]

how does h2cO3 buffer against acids? thought it could only buffer basic solutions

[WhoTookMyUsername]

As H2Co3 splits into

HCO3 + H, this would raise the acidity of the blood???

or does the body have some way of ridding the protons, so HCO3 can acept other hydrogen ?