SAC - 1 Structure and Function of a Phospholipid Membrane

[WhoTookMyUsername]

Good morning all!
I have my first Bio SAC very soon,
its a prac report that aims to use evidence of damage to membranes to draw conclusions about the chemical nature of the cell membrane.

WE place beetroot into 3 solutions (distilled, vinegar and detergent)
People who have done the SAC have had varying results for what and why released the most pigment from the beetroot.

WE leave them in the solution for 30 minutes, how long should we have between observations?

 what causes the colour to appear as the slices are being rinsed

(simply because some cells have been physically severed by a knife? why does water draw out more pigment? Diffusion?)

What 3 other factors (heat is one,) apart from acidity and detergent can affect fuctioning of cell membrane?

What are 3 possible errors with this experiment and what can you classify them as?

Can anyone explain EXACTLY how acid and detergent destroys the cell membrane?

how to we increase quantitaveness?
How do we express results (no graphs???)

Thanks so much!

[WhoTookMyUsername]

! What will happen when beetroot is placed into distilled water? will some pigment leak out via osmosis?

[Truck]

Good morning all!
I have my first Bio SAC very soon,
its a prac report that aims to use evidence of damage to membranes to draw conclusions about the chemical nature of the cell membrane.

WE place beetroot into 3 solutions (distilled, vinegar and detergent)
People who have done the SAC have had varying results for what and why released the most pigment from the beetroot.

WE leave them in the solution for 30 minutes, how long should we have between observations?

 what causes the colour to appear as the slices are being rinsed

(simply because some cells have been physically severed by a knife? why does water draw out more pigment? Diffusion?)

What 3 other factors (heat is one,) apart from acidity and detergent can affect fuctioning of cell membrane?

What are 3 possible errors with this experiment and what can you classify them as?

Can anyone explain EXACTLY how acid and detergent destroys the cell membrane?

how to we increase quantitaveness?
How do we express results (no graphs???)

Thanks so much!

First off, nothing will happen to the beetroot in distilled water because it doesn't destroy the membrane.
We did 15 minutes between observations, but our teacher is just really chilled so maybe you should have 10.
When you slice the beetroot you damage the membrane and the tonoplast of the vacuole, which causes the beetroot pigment to leak out of the cell.
Try something like Heat and, maybe even Alcohols, as a factor.
Figure out the errors yourself during the write up, they should be pretty obvious after you've conducted the experiment - think Random and Systematic.

Vinegar: Vinegar is acidic, which means that it contains more H+ Ions than OH- Ions. The amino acid group in proteins is amphoteric, which means it will gain or lose H+ ions to stabilize a pH solution. Therefore, when placed in a solution of vinegar, the beetroot's proteins will denature as they attempt to stabilize the solution, which ultimately damages the membrane.
Detergent: The detergent emulsifies the fats in the phospholipids, whilst also forming micelles in H2O which tear apart the membrane because they are dipolar.

For quantitativeness, I'm not entirely sure, but I'd assume something like repeating the experiment / using more beetroot slices (5 rather than 3?)

For expressing results, you'd have to draw the cell.

[WhoTookMyUsername]

Thanks a lot

I would have expected the distilled water to have SOME pigment in (as the beetroot has been cut with pigment leaking out of the cut cells)?

[Truck]

Thanks a lot

I would have expected the distilled water to have SOME pigment in (as the beetroot has been cut with pigment leaking out of the cut cells)?

That's true, but the beetroot cells we used had been cut a few hours earlier by the teacher, so everything that could've leaked because of the initial cut already had.

Also fyi, the distilled water has a neutral pH which is why it doesn't do anything to the membrane, just to clarify.

[WhoTookMyUsername]

urgent help needed pls ! Do detergents emulsify (is that the correct term? ) the phospholipids? or does emuslification refer to only non polar substances?

[Truck]

urgent help needed pls ! Do detergents emulsify (is that the correct term? ) the phospholipids? or does emuslification refer to only non polar substances?

Why do I have a feeling you're in my Biology class, when someone in my class doing the rest of the SAC tomorrow just asked me that exact same question lol.

Detergents emulsify the fats in the phospholipids, as far as I am aware .

[shinny]

urgent help needed pls ! Do detergents emulsify (is that the correct term? ) the phospholipids? or does emuslification refer to only non polar substances?

Why do I have a feeling you're in my Biology class, when someone in my class doing the rest of the SAC tomorrow just asked me that exact same question lol.

Detergents emulsify the fats in the phospholipids, as far as I am aware .

For bonus marks, chuck the words surfactant and especially amphiphilic in

[Truck]

urgent help needed pls ! Do detergents emulsify (is that the correct term? ) the phospholipids? or does emuslification refer to only non polar substances?

Why do I have a feeling you're in my Biology class, when someone in my class doing the rest of the SAC tomorrow just asked me that exact same question lol.

Detergents emulsify the fats in the phospholipids, as far as I am aware .

For bonus marks, chuck the words surfactant and especially amphiphilic in

I already did most of the SAC, but my explanation of Detergent's effect on the Bilayer was "The detergent emulsifies the fats in the phospholipids, whilst also forming micelles which are dipolar and thus tear apart the plasma membrane". Do you think that's a full mark answer, or worth changing it around to fit in those technical terms? As I should have time to do so tomorrow (we have a final lesson to finish it off).

[shinny]

Might as well chuck in the reason why the detergent does all of the above; that reason being that they are amphiphilic. So chuck that in, define it, and say that it's the reason why that stuff above actually occurs rather than just saying it does with no justification. Surfactant isn't particularly useful in this case. That refers more to things which change surface tension.

[Truck]

Thanks mate, will do.

[HERculina]

i heard that each biology sac worth 3%. is this true

[Russ]

How many biology sacs do you do?

[Truck]

4 Biology SACs = 1/6 = 17% of the grade.

Therefore 1 SAC = 1/24 = 4.25%.
25 marks per SAC.
Therefore 1 SAC mark = 1/600 = 0.17% of your Study Score.

[HERculina]

i do 11 sacs in total i think