Psyxwar's Biology 3/4 Question Thread

[Shenz0r]

thats about all you need for carbs (thanks Shenz0r!) you wont ever need to know the chemical structure of any carb, but you should know the 'golden ratio'!
 C(1):H(2):0(1)

It won't have to be an exact ratio, but close to it. This is because every time there's a condensation reaction, you lose one H₂O molecule.

For example:
Glucose is C₆H₁₂O₆
Maltose/Sucrose will be C₁₂H₂₂O₁₁
A trisaccharide of 3 glucose molecules will be C₁₈H₃₂O₁₆

[psyxwar]

It would be good help knowing the monosaccharides, disaccharides, and polysaccharides that VCAA use most often.

Monosaccharides:
Glucose
Fructose
Galactose

Disaccharides:
Maltose (multiple Glucoses)
Lactose (from Galactose)
Sucrose (Fructose + Glucose)

Polysaccharides:
Glycogen (very branched, used as short-term energy storage in animals. Might help to ask yourself: Why does the amount of branching make it a good source of energy in the short-term?)
Starch (not very branched, used as energy-storage in plants. So, why do plants use a polysaccharide that's not really branched?)
Cellulose (used as structural support in plants)

EDIT: You won't need to know what the monosaccharides and disaccharides actually look like. But you should know the structure of the polysaccharides.

Yup thanks. I know about that ratio and the dehydration reactions too, so that shouldn't be an issue.

Does the branched nature of glycogen make it easier to breakdown via hydrolysis (hence it can be broken down more easily -> faster access to energy). I'm not sure about starch though -- is it because its spirally nature means that it isn't soluble in water, and consequently won't affect the osmotic action of cells? Or am I completely off here?

and that it happens in the rough endoplasmic reticulum (never write ER... EVER) and the golgi complex/body/apparatus

Yeah sound advice. I'm always incredibly conscious of writing shorthand in exams though, so hopefully I'll be fine.

[Stick]

Yes, your reasoning for glycogen and starch are correct.

[psyxwar]

Is mRNA transcribed off the antisense strand of DNA? The TSFX notes here seem to suggest otherwise, but the sense strand of DNA runs 5' to 3' and so does the mRNA strand... Therefore, for this to be the case, wouldn't it have been formed from RNA nucleotides complementary pairing with the antisense strand?

[Scooby]

Yep, RNA polymerase transcribes the template (antisense) strand of the DNA molecule. I think this mistake in the TSFX notes has come up a few times 

[psyxwar]

Yep, RNA polymerase transcribes the template (antisense) strand of the DNA molecule. I think this mistake in the TSFX notes has come up a few times 

Thanks. Haha you'd think they'd have fixed it by now...

[Scooby]

Thanks. Haha you'd think they'd have fixed it by now...

Yeah, it's a pretty common mistake though. I'd probably stick to calling them the template and coding strands

[psyxwar]

If say a cell membrane is placed in an environment that is of an extreme pH and consequently, the proteins denature. What are the implications of this? For example, if a channel protein denatures, what happens to it, and what affect does it have on transport?

[Scooby]

If say a cell membrane is placed in an environment that is of an extreme pH and consequently, the proteins denature. What are the implications of this? For example, if a channel protein denatures, what happens to it, and what affect does it have on transport?

If you put a cell into an extremely basic or acidic solution, it's going to die. If we look specifically at proteins in the cell membrane - yeah, they're going to denature. As a result they won't be able to transport substances across the cell membrane

[psyxwar]

^Thanks.

Would this suffice as a definition for bulk transport? Bulk Transport refers to the vesicular transport of large substances into or out of a cell through the cell membrane.

[TheAntiSocialist]

In what case is active transport used?

Is it used often by our cells?

Observation: Isn't it possible for those solutes to MOVE OUT of the cell by diffusion?

This has puzzled me for some time...did ask some people...but since I'm thick I didn't get what they were saying

[Snorlax]

In what case is active transport used?

Is it used often by our cells?

Observation: Isn't it possible for those solutes to MOVE OUT of the cell by diffusion?

This has puzzled me for some time...did ask some people...but since I'm thick I didn't get what they were saying

Active transport is used when transporting is going against a concentration gradient. (Requiring energy, hence 'active')
Yes they do move out of a cell with the means of protein channels (carrier and channel). However, If the molecule being transported is too large it will be transported by the means of endo/Exocytosis.
That's the jist of it all. Hope that helps

[psyxwar]

Active transport is used when transporting is going against a concentration gradient. (Requiring energy, hence 'active')
Yes they do move out of a cell with the means of protein channels (carrier and channel). However, If the molecule being transported is too large it will be transported by the means of endo/Exocytosis.
That's the jist of it all. Hope that helps

Yeah that's right, but do channel proteins facilitate active transport at all? I was under the impression that just provided a hydrophilic tunnel for substances to diffuse through along the concentration gradient.

[Bad Student]

In what case is active transport used?

Is it used often by our cells?

Observation: Isn't it possible for those solutes to MOVE OUT of the cell by diffusion?

This has puzzled me for some time...did ask some people...but since I'm thick I didn't get what they were saying

It's possible for those solutes to move out of the cell by diffusion when the concentration of the solute inside the cell is higher than the concentration of the solute outside the cell.

If the concentration of the solute outside the cell is higher than the concentration of the solute inside the cell, then the solute must be transported via active transport, usually with an ion channel.

[Bad Student]

Yeah that's right, but do channel proteins facilitate active transport at all? I was under the impression that just provided a hydrophilic tunnel for substances to diffuse through along the concentration gradient.

I think channel proteins are for facilitated diffusion and ion channels are for active transport.