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July 09, 2025, 06:13:56 am

Author Topic: Biology Unit 3 Questions Megathread  (Read 114198 times)  Share 

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WhoTookMyUsername

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Re: Biology Questions Megathread
« Reply #150 on: February 23, 2011, 06:53:36 pm »
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Can someone pls explain (possibly from a chemistry POV) why a substance such as glycogen or starch and only be hydrolysed at the end molecules? I know it has something to do with free OH groups, but am still confused

so if you have

monosaccharide - monosaccharide - monosaccharide etc...

do the "taken up" OH groups in the middle somehow prevent hydrolysis (HOW exacltly  ) thanks

Russ

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Re: Biology Questions Megathread
« Reply #151 on: February 23, 2011, 06:54:49 pm »
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do the "taken up" OH groups in the middle somehow prevent hydrolysis (HOW exacltly ;) ) thanks

If someone else wants to try and attempt to explain this to a year 11 chemistry level, they can, but at this point I think you're better served by just accepting it and not worrying.

WhoTookMyUsername

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Re: Biology Questions Megathread
« Reply #152 on: February 23, 2011, 06:56:36 pm »
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okay maybe not from a year 11 chemistry level. i think there was a simple explanation that i forgot :S

Something about simply a reason why Hydrolysis needs 1 free bond to work?

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Re: Biology Questions Megathread
« Reply #153 on: February 23, 2011, 07:49:26 pm »
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People I need help please!!! ASAP!!! My class is doing a SAC on osmosis right now and we are testing potato cylinders. Now we are putting the potato cylinders in different sucrose concentrations. Our control is potato cylinder in distlled water. However apparently it is not a 'true' or 'valid' control. why is that? Please reply ASAP!

Well first you've got to define what a control group is. Simplest way to put it is a group which isn't exposed to the intervention that is being put in place. In this case, that intervention is the sucrose solution, and you're measuring the effect of this solution on the mass of the resultant cylinders. The control which is needed to verify that the cylinders aren't just changing their mass spontaneously or due to a factor other than the osmosis that's expected to occur is to have a potato which is given no solution at all. If the mass of a potato without the solution did change, then obviously there's something else going on here other than just the osmosis and that'd invalidate all your results. So pretty much, that's the ideal control. The 0% sucrose solution doesn't really work because distilled water itself is hypotonic to the potato cells, so obviously that's going to create some weight change.
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HERculina

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Re: Biology Questions Megathread
« Reply #154 on: February 23, 2011, 09:44:13 pm »
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hm im confused  :buck2:
 it says in my workbook that glycogen is more highly branched and water-soluble than starch cause it has more alpha-1,6 glycosidic links than alpha -1,4 ones.

Glycogen is more soluble than starch (even though they both have 1,6 glycosidic links and alpha -1,4 ones) because starch exists in general as an alpha helix while glycogen is a more highly branched and random structure. In the alpha-helical conformation there are less exposed -OH (hydroxide) groups to the solution making the starch less hydrophilic than the glycogen. As there are less OH groups available to from hydrogen bonds with the polar water molecules, that is why starch is less soluble.

It is due to this 'extra' branching that glycogen has that enables it to be more soluble.

Hope that helps. :)


(this specific stuff will never come up in the exam btw)

oooooo but does this mean that its fully water-soluble? i thought that all polysaccharides were insoluble in water?

Out of curiosity, what is everyone's classes up to? We just started membranes today, would you say that we're behind? :/
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pi

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Re: Biology Questions Megathread
« Reply #155 on: February 24, 2011, 04:34:53 pm »
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No. we're still halfway through chapter 1 :S (though our teacher was on camp for first week)

MHS rarely finishes the bio course (any teacher)

a/b

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Re: Biology Questions Megathread
« Reply #156 on: February 24, 2011, 05:28:46 pm »
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Hey guys, can someone explain the events that take place in apoptosis in simple terms? NOB is confusing me -.- and how would you explain caspases? Thanks in advance :)
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Russ

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Re: Biology Questions Megathread
« Reply #157 on: February 24, 2011, 07:10:32 pm »
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Caspases are just a particular family of proteases, responsible for breaking down the internal structure of the cell during cell death/destruction.

In apoptosis, the cell receives a signal to self destruct or fails to suppress such a signal. This leads to activation of the relevant enzymes and destruction of the cell organelles. "blebbing" occurs, where the cell membrane forms random invaginations/bulges and apoptotic bodies are released (similar to vesicles). Eventually the cell membrane begins to lose its integrity and molecules can leak from the cell.

TrueLight

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Re: Biology Questions Megathread
« Reply #158 on: February 24, 2011, 07:12:44 pm »
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this video is pretty awesome (as usual by wehi lol)

please dont remember all these steps lol

http://www.youtube.com/watch?v=9KTDz-ZisZ0
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a/b

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Re: Biology Questions Megathread
« Reply #159 on: February 24, 2011, 09:04:19 pm »
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Caspases are just a particular family of proteases, responsible for breaking down the internal structure of the cell during cell death/destruction.

In apoptosis, the cell receives a signal to self destruct or fails to suppress such a signal. This leads to activation of the relevant enzymes and destruction of the cell organelles. "blebbing" occurs, where the cell membrane forms random invaginations/bulges and apoptotic bodies are released (similar to vesicles). Eventually the cell membrane begins to lose its integrity and molecules can leak from the cell.

Thanks! That was a lot easier to understand :)
this video is pretty awesome (as usual by wehi lol)

please dont remember all these steps lol

http://www.youtube.com/watch?v=9KTDz-ZisZ0

LOL ! That was actually unnerving haha, the background music and stuff, but thanks guys, helped a lot.
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Arju94

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Re: Biology Questions Megathread
« Reply #160 on: February 24, 2011, 10:03:58 pm »
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Heya Guys

Whats the difference between Peripheral Proteins and Integral Proteins, and what are examples of each

pi

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Re: Biology Questions Megathread
« Reply #161 on: February 25, 2011, 05:02:01 pm »
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Heya Guys

Whats the difference between Peripheral Proteins and Integral Proteins, and what are examples of each

Both are associated with the cell plasma membrane. Peripheral proteins (eg G-proteins) are attached to the membrane temporarily, whilst integral proteins (eg Insulin receptor) are attached to it permanently. Peripheral proteins can actually attach themselves to integral proteins.   
« Last Edit: February 25, 2011, 05:09:33 pm by Rohitpi »

WhoTookMyUsername

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Re: Biology Questions Megathread
« Reply #162 on: February 27, 2011, 08:46:45 am »
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Can triglycerides etc. (not phospholipids) form micelles? They still have a hydrophillic head (glycerol)? If not why not?

Russ

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Re: Biology Questions Megathread
« Reply #163 on: February 27, 2011, 09:21:29 am »
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iirc, yes they can

dooodyo

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Re: Biology Questions Megathread
« Reply #164 on: February 27, 2011, 11:58:27 am »
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haha nice  ;D

That would probably look weird though with the
3 fatty acid tails and all.  :P