Yacoubb's Bio 3+4 Questions

[psyxwar]

Would it be accurate to say that natural killer cells induce apoptosis in viral-infected cells??

I'm not sure if that's all they can do (I doubt it), but they definitely are able to induce apoptosis.

https://en.wikipedia.org/wiki/Granzyme

[Yacoubb]

I'm doing some revision of the plasma membrane, and movement across the plasma membrane, and I'd just like to see if my expression for the functions of the components of the plasma membrane are accurate.

Phospholipid Bi-layer:
- The hydrophilic phosphate heads and the hydrophobic fatty acid tails allow the movement of selectively small, uncharged and/or lipid-soluble substances into and out of the cell.

Protein Channel:
- Allow the movement of selective, non-lipid soluble substances into and out of a cell.

Cholestrol - found only in animal plasma membranes:
- Provides more stability and flexibility to the plasma membrane
- Reduces the fluidity of the plasma membrane at normal range temperatures to provide stability to the plasma membrane.
- Increases the fluidity of the plasma membrane

[Bad Student]

I'm doing some revision of the plasma membrane, and movement across the plasma membrane, and I'd just like to see if my expression for the functions of the components of the plasma membrane are accurate.

Phospholipid Bi-layer:
- The hydrophilic phosphate heads and the hydrophobic fatty acid tails selectively allow the movement of small, uncharged and/or lipid-soluble substances into and out of the cell (I believe the nuclear membrane and vacuolar membrane and some other organelles also have phospholipid bilayer membranes..

Protein Channel:
- Selectively allow the movement of non-lipid soluble substances into and out of a cell.

I think it sounds slightly better if you put the "selectively" in those places.

Cholestrol - found only in animal plasma membranes:
- Provides more stability and flexibility to the plasma membrane more stability and flexibility than what?
- Reduces the fluidity of the plasma membrane at normal range temperatures to provide stability to the plasma membrane.
- Increases the fluidity of the plasma membrane

[Yacoubb]

I'm doing some revision of the plasma membrane, and movement across the plasma membrane, and I'd just like to see if my expression for the functions of the components of the plasma membrane are accurate.

Phospholipid Bi-layer:
- The hydrophilic phosphate heads and the hydrophobic fatty acid tails selectively allow the movement of small, uncharged and/or lipid-soluble substances into and out of the cell (I believe the nuclear membrane and vacuolar membrane and some other organelles also have phospholipid bilayer membranes.. [Good point]~!!

Protein Channel:
- Selectively allow the movement of non-lipid soluble substances into and out of a cell.

I think it sounds slightly better if you put the "selectively" in those places.

Cholestrol - found only in animal plasma membranes:
- Provides more stability and flexibility to the plasma membrane more stability and flexibility than what? (It just provides MORE flexbility and stability... not more than anything else).
- Reduces the fluidity of the plasma membrane at normal range temperatures to provide stability to the plasma membrane.
- Increases the fluidity of the plasma membrane

Thanks!

[Bad Student]

It provides more stability and flexibility than a plasma membrane without cholesterol but phrasing it in this way sounds clumsy.

[Yacoubb]

It provides more stability and flexibility than a plasma membrane without cholesterol but phrasing it in this way sounds clumsy.

The assessment report has written that one of the functions of cholestrol is to provide more stability and flexibility!

[Bad Student]

Then I guess that's good enough. I'm just really careful about this stuff because my school marks the SACs very harshly.

[Yacoubb]

Then I guess that's good enough. I'm just really careful about this stuff because my school marks the SACs very harshly.

Haha yeah same! I lost a mark because I said 'Test Tube A and B will have similar enzymatic activity rates', but I wasn't test tube specific and thus lost the mark. I learnt my lesson haha!

[Yacoubb]

HI

I was doing a practice paper and came across this question:

A series of experiments was carried out with rattlesnakes to determine the major receptors involved in their rapid accurate strikes to catch their food (mice, rats, etc). The following results were obtained.

• Experiment 1 - snake in bright light with dead mouse - no strike
• Experiment 2 - snake in dark with dead mouse pulled quickly along - no strike
• Experiment 3 - blindfolded snake in dark with live mouse - rapid, accurate strike

The results suggest rattlesnakes detect their prey using:
a) chemoreceptors
b) mechanoreceptors
c) photoreceptors
d) thermoreceptors

The answer was in fact D, however I chose B. Could someone explain this question to me and how the answer is in fact D?

Thanks![/list]

[Smiley_]

can you please explain to me how you got your answer?

[Russ]

if the answer is B, why didn't the snake strike in scenario 2?
Go down the list and eliminate each option as it becomes impossible. A is plausible. B would mean the snake would strike at any movement, not just a live mouse moving. C would mean the snake would not strike in scenario 3. D is plausible.

Comparing A and D, I prefer D since it has a rationale that seems based in science (live mouse is warm and snake can detect this) rather than conjecture (somehow the snake can detect chemicals from a live mouse that are not present on a dead mouse)

[Bad Student]

We can rule out photoreceptors because the snake was blindfolded and in the dark so it would not have been able to see.

We can rule out chemoreceptors because both the dead mouse and the live mouse would have had a scent.

We can also rule out mechanoreceptors because the snake didn't strike the dead mouse which was being pulled along.

The only other difference between each each of the experimental groups is whether the mouse is alive or dead. Since mice are mammals, they will emit body heat when they are alive. Therefore, thermoreceptors is the best option.

[alondouek]

HI

I was doing a practice paper and came across this question:

A series of experiments was carried out with rattlesnakes to determine the major receptors involved in their rapid accurate strikes to catch their food (mice, rats, etc). The following results were obtained.

• Experiment 1 - snake in bright light with dead mouse - no strike
• Experiment 2 - snake in dark with dead mouse pulled quickly along - no strike
• Experiment 3 - blindfolded snake in dark with live mouse - rapid, accurate strike

The results suggest rattlesnakes detect their prey using:
a) chemoreceptors
b) mechanoreceptors
c) photoreceptors
d) thermoreceptors

The answer was in fact D, however I chose B. Could someone explain this question to me and how the answer is in fact D?

Thanks!

Right, lets start off by eliminating what we can. The changes to stimuli don't seem to have any relation to chemoreceptors, so we can get rid of A. Mechanoreceptors respond to pressure or physical distortion, so we can eliminate B as the stimuli don't relate to 'touch'.

C can be eliminated as experiments 1 and 2 demonstrate that light is not a factor in striking.

D is correct as the strike occurs when the mouse is living (i.e. producing thermal energy).

These sort of questions are easy marks in the exam, because it's really just comprehension![/list]

[Yacoubb]

Right, lets start off by eliminating what we can. The changes to stimuli don't seem to have any relation to chemoreceptors, so we can get rid of A. Mechanoreceptors respond to pressure or physical distortion, so we can eliminate B as the stimuli don't relate to 'touch'.

C can be eliminated as experiments 1 and 2 demonstrate that light is not a factor in striking.

D is correct as the strike occurs when the mouse is living (i.e. producing thermal energy).

These sort of questions are easy marks in the exam, because it's really just comprehension![/list]

Thanks. Are we required to know about any specialised receptors for the VCAA exam? (i.e. about mechano/chem/thermo/photoreceptors)? I know them basically in terms of their functions, but not a LOT about them...

[alondouek]

Doubt it. Generally, if they ask a question about a specific receptor, they'll give a couple of paragraphs background first (and the questions will likely be quite straightforward or more comprehension based).

You could certainly do some light wider reading if you wanted; maybe start with the wiki pages and follow some links?