Saheh's 3/4 question thread

[saheh]

I will undoubtedly have a million questions/confusions regarding bio so i may as well add them to a thread...like everyone else hehe

anyway I'll just start with one...

regarding membranes, specifically ions, one of my sources says ions can't pass through, yet the other says some can...
so how do ions pass through, via their polarity or something..?? also for 'lipid soluble molecules'?
or dont we need to be that specific??

thanks in advance guys

[saheh]

wait I just found it; facilitated diffusion/active transport etcetc
as if i didnt think of that ><




'Explain how the following can affect the ability of a molecule to pass across a cell membrane: a.)size b.)charge c.) solubility (eg lipids)  <<Thats the bit I'm confused on...

[ggxoxo]

a- smaller molecules can diffuse faster than larger molecules (which would need facilitated diffusion; or even active transport at times). This is because smaller molecules can fit easier than larger molecules.

b- charged molecules cannot readily diffuse through molecules because charged ions are polar and plasma membrane is non-polar (like dissolves like; but in this case they aren't the same)

c- lipid soluble (non-polar) molecules (e.g. chloroform) readily pass through plasma membrane (non-polar)- mainly because of that 'like dissolves like' rule

[saheh]

thankyou! i totally get it now

[saheh]

Ok so we had our sac today it was pretty straightforward; sultanas in a sucrose solutions of 0%,2%,5%,10%,20% and 30%
although we don't complete our discussion til next week because of camp

anyway, I've worked out my %change, and it's all over the place :/
we left them for about 40 minutes..
and yeah i expected there to be a stage where it (the osmosis rate) changed because of the sucrose content within the sultana
and this is what i got
0%= 17% + change in weight
2%= 18% + change in weight
5% = 22% + ""   ""
10%= 16% +
20% = 9% +
30% = 15% +
(all gained weight, non lost it ><)

is the discrepancy most likely an error in the 30% jar?? i'd expect it to continue going down.....

any help would be appreciated!! thankyou!

[saheh]

I guess i should try and make this work again instead of spamming the wall lol

What's the difference between Gibberellins and Cytokonins?
Where one promotes cell division, the other stimulates it.. umm?
I was doing a prac exam and a qn asking about Gibberellins was on it,
and yeahh

Thanks guys

[ggxoxo]

I think the best way to view them is that they are BOTH growth promoters.

Gibberellins- stimulates cell division/elongation; stimulate seed germination (i.e. via inducing amylase and protease biosynthesis and mobilising food reserves)

Cytokinin- stimulates lateral bud movement (antagonistic to auxin); slows down senescence; breaks seed dormancy; stimulate cell division (specifically, cytokinises); AND (posibly the major diff b/w the two) cytokinin is involved in TISSUE DIFFERENTIATION (as cytokinin:auxin ratio affects tissue differentiation)

[saheh]

Hey again
Im going away for two weeks and just trying to catch up on my study
I have a sac that im missing out on
its the first for aos2
all i knw is that it's a 'summary report of a plant or animal response to a chemical/physical stimuli'

sooo basically id want to be studying endocrone/nervous system

it wouldnt have anything to do with pathogens and disease no?

Thanks again

[InsaneMcFries]

I doubt it would include disease. It will probably include a fair bit about signalling molecules, how they travel, signal transduction. etc.

I'd prepare for stimulus-response models too.

[saheh]

Thanks!

What sort of sac is it do you know?
Like Prac etc?

[InsaneMcFries]

It'll vary between schools. For instance, my school goes to GTAC and does the prac, and then comes back to school and does a test.

[saheh]

Heeeeeey everyone

I have a question for schoolwork
explain the immune system response , including the third level of defence and the step involved in eliminating it from the body, and any chemicals involved.

how would you go about answering this? would you do cell-mediated, and then how it links to antibody mediated?? with interleukins etc and cytotoxins??

also: What would be the similarities and differences between the second and third level?

And b-cells recognise the antigen right? so would they recognise the one on the antigen/mhc complex of APCs? or just mainly on viruses bacteria?
I know the t-cells bind to the antigen-mhc complex and are activated, but how/what do b-cells bind to/recognise mainly??

thanks!!!!

[saheh]

also guys: adenovirus/retrovirus
was told that retro=rna with viral coat
adeno=dna
??

A tsfx qn says that HIV is caused by a retrovirus (so i think rna) and the qn is
retrovirsus:
a. must produce their own DNA inside host before they can reproduce
b. contain dna with protein coat
c. do not require host cell to reproduce
d. primarily attack bacteria in form of bacteriophages

answer is a, is that because the rna turns into dna in the cell?
i know c and d are wrong..

[InsaneMcFries]

also guys: adenovirus/retrovirus
was told that retro=rna with viral coat
adeno=dna
??

A tsfx qn says that HIV is caused by a retrovirus (so i think rna) and the qn is
retrovirsus:
a. must produce their own DNA inside host before they can reproduce
b. contain dna with protein coat
c. do not require host cell to reproduce
d. primarily attack bacteria in form of bacteriophages

answer is a, is that because the rna turns into dna in the cell?
i know c and d are wrong..

Retroviruses contain RNA and the enzyme "reverse transcriptase" which will catalyse the reaction of RNA to DNA. They DO NOT contain DNA. The easiest way to remember I guess is R for RNA and Retrovirus.

To answer the question, this means they have to convert their RNA to DNA and include it into the host cell's DNA in order to code for its own proteins and reproduce.

[saheh]

hey all

so I know B cells chill out in the lymph nodes after maturing in bone marrow,
and T cells Mature in the thymus after developing in bone marrow,
where do T Cells hang out?
In the lymph nodes? or just floating around everywhere?

thanks!