Biology Unit 3 Questions Megathread

[Russ]

pfft they arent all Y shaped lol

haha, I was going to say this but I figured it didn't actually matter

[dooodyo]

Hmmm I would say that not all polysaccharides play a role in structural support,
infact in both heinemann and NOB only cellulose is mentioned, other than that I would say
they obviously are energy storage molecules. And in reference to Bazza's initial question
" two functions of monosaccharide" the first one i said before was obviously right, but maybe
another one could be building blocks for larger molecules such as polysaccharide (even though
this pertains more to disaccharide).

[pi]

pfft they arent all Y shaped lol

Shows how much I knew about Unit 3 bio...

[WhoTookMyUsername]

IgM, IgA

How are they shaped, are the individual molecules still Y shaped, just that their is multiple bodies that form a *ring* almost?

[shinny]

IgM, IgA

How are they shaped, are the individual molecules still Y shaped, just that their is multiple bodies that form a *ring* almost?

Yeh, the individual antibody proteins are all Y-shaped. However they form complexes (IgG, IgA, IgM, IgE, IgD i.e. 'GAMED') of which G, E and D are monomers, A is a dimer and M is a pentamer. See here for an illustration.

[pi]

IgM


IgA



Wow, I never knew that...




EDIT: Beaten by better pics by shinny

[TrueLight]

yep all the antibodies are in monomeric form when they are membrane bound but those two polymerize when secreted to form those structures^

pfft they arent all Y shaped lol

Shows how much I knew about Unit 3 bio...

no it doesnt mean that its probably that your teacher didn't think it was important for you to know as Russ said

[Russ]

Incidentally, IgD seems to be the useless sibling of the Ig family and I've never seen it used

[Russ]

Which ones? Most/all of them have been answered

[WhoTookMyUsername]

1 ) Do things like penicillin also prevent cell wall synthesis in plants? (are the enzymes they block common ?)

2 ) Are all poisons non - competitive inhibitors ? (poison must have permanent bond???)

3 ) Is Cysteine very common in proteins ? ( is it in most ? douchy said that i think )

4 ) IS a better defintion of a Organic compound Carbon and Hydrogen or Carbon containing excluding carbonides etc...

5 ) Are things like Oxygen Gas molecules ? (according to douchy must have more than one different element covalently bonded ) if not, what are they called

6 ) Does water soluble refer to the complete breakdown of the molecular compound / molecule structure (e.g. NaCl -> Na + Cl) and/or the tendency for substances to seperate into individual, unconnected parts in water (e.g. full glucose molecule). Does it depend on Ionic / Covalent bonds?

7 ) Does cell membrane refer to the outermost membrane of a cell, and plasma membrane as also to membrane bound organelle?
8 ) NOB says some enzymes work by lock and key and others by induced fit, biozone states Induced fit is the current model, which is correct?



What are the two major functions of monosaccharides:
1) Immediate energy source
2) ? ( monomer of polysaccharides? )

Still not 100% certain on these ones

[TrueLight]

Incidentally, IgD seems to be the useless sibling of the Ig family and I've never seen it used

{warning: vce students, you do not need to know any of this below}

heh yeah not much is known about it compared to the others although heres some of them i found in one journal article

'used as marker of B-cell maturation'
'The importance of its function in the immune responses is considered enigmatic due to the fact that IgD-deficient mice have an intact immune development and a relatively normal humoral immune response to a variety of T-cell-dependent and -independent antigens.'
'mIgD can recognize and bind antigens through its variable region with same specificity and avidity as mIgM. Such bindings through mIgD can lead to activation and/or clonal deletion or anergy of B-cells in vivo.'
'Similarly, an antibody that cross-links mIgD(anti-IgD) can also elicit a pronounced and complex immune response through activation of B-cells in vitro and in vivo.'
'It can also modulate both T-helper (Th) cell-dependent and-independent polyclonal antibody responses in vivo.'
and the study also found that
'In summary,our study provided an evidence-based rationale for the therapeutic use of anti-IgD as a new method of selective depletion of mature B cells that can also induce immune tolerance through the augmentation of regulatory B-and T-cell populations, and possibly by promoting an anti-inflammatory Th2-biased response.'
so i guess there is a therapeutic use for using antibodies to target IgD

[TrueLight]

Bazza16
 1) already answered by Russ on page 3. no its specific to bacterial cell wall synthesis, plants do not have peptidoglycan in their cell wall

3) do you need to know that? i dunno but disulfide bonds form between side groups of cysteine residues and disulfide bonds give stability and strength to a protein, one example of this is a protein like IgG.
this is what wikipedia says
"In secreted proteins that do not spend time in the cytoplasm, disulfide bonds between cysteine residues help to maintain the protein's tertiary structure. "
"The disulfide bonds are extremely rare in cytosolic proteins, since the cytosol is generally a reducing environment."

7) interchangable like if your talking about eukaryotic cells, the one surrounding the entire cell i would use either, although cell membrane seems so generic lol but yeah if its the membrane surrounding organelles just say plasma membrane.

i would know both but enzymes do have some leeway they arent like stone, so they can move to some little degree.

[WhoTookMyUsername]

How is the cytosol a reducing environment and how does it affect disuplhide bonds? (adding back the Hydrongen?)

[TrueLight]

all i know is that in an increasingly reducing environment, the disulfide bonds will break down

wiki to the rescue...
"The oxidation and reduction of protein disulfide bonds in vitro also generally occurs via thiol-disulfide exchange reactions. Typically, the thiolate of a redox reagent such as glutathione or dithiothreitol attacks the disulfide bond on a protein forming a mixed disulfide bond between the protein and the reagent. This mixed disulfide bond when attacked by another thiolate from the reagent, leaves the cysteine oxidised. In effect, the disulfide bond is transferred from the protein to the reagent in two steps, both thiol-disulfide exchange reactions."
"In eukaryotic cells, in general, disulfide bonds are formed in the lumen of the RER (rough endoplasmic reticulum) but not in the cytosol. This is due to the oxidative environment of the ER and the reducing environment of the cytosol (see glutathione). Thus disulfide bonds are mostly found in secretory proteins, lysosomal proteins, and the exoplasmic domains of membrane proteins."

http://en.wikipedia.org/wiki/Disulfide_bond

go learn some chemistry...na but seriously i dont think you need to know this

[shinny]

If you're asking questions for VCE Bio which are pushing the limits of Me, Russ and Truelight, you know you're going too far Besides that, a lot of those questions in your last list have already been answered. If you want another explanation, expand on what you don't understand so we can give a proper explanation which corrects any misunderstandings. Right now I don't really know what to say without simply repeating what's already been said.