Heffalump .
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I'm doing my Biology Evaluative coursework on thursday, and I just want to make sure all the stuff I say is correct and if not, whats wrong with it, and if I've left anything out please say!
So if I'm investigating how temperature affects the amount of pigment released from the cell surface membrane of the beetroot slices, and measuring this by putting a sample of the water with pigment in it in a calorimeter (assuming there is every limitation and control possible) the:

Independent variable would be: Temperature (degrees Celsius) [edit]
Dependant Variable: (mean) transmission of light (%) [edit]

Control Variables:
Size and shape of beetroot slices/discs
Volume of water in the test tubes
The type of beetroot (all discs must come from the same source of beetroot)
Number of discs in each tubes
Time each of the beetroot discs are heated for
Discs held separately so all are equally exposed to thermal treatment (on a mounted needle)

Limitations:
Inconsistant stirring of slices while submerged in water. Beetroot slices were not stirred in the same way for each, meaning inconsistent rate of pigment leakage. Modification: Standardise timing and method of stirring for each slices.
Insufficient number of values of independent variables e.g.. only at 40,50,60,70,80 degrees Celcius, so lack of results between intervals, meaning you could miss changes so making conclusions about trends are less valid. Modification: Include intermediate temperatures within the range e.g. 45,55,65,75 degrees Celcius.
Insufficient range of independent variables (40-80 degrees) lack of results beyond the range investigated could make it difficult to identify a trend or pattern. Modification: extend the range e.g. 20-80
Discs were handout, so discs will have a different surface area to volume ratio of the slices, so pigment release will differ. Modification: use a mechanical cutter slicer to prepare beetroots
Species of beetroot differ, so the concentration of pigment may differ/vary with age/ species. Modification: take samples all from the same source (same beetroot)
Repeats, if below 4 they are unable to detect anomalous results thus decreasing reliability. Modification: perform at least 4 replicates
If not calorimeter was used, then judging by eye can show lack of consistency in judgement, may lead to less precise, less accurate and less reliable results. Modification: use a calorimeter.

How to improve reliability:
Compare your results with other peoples results, or take a lot of replicates and take the mean of them.

Analysis:
20-45 degrees Celcius, The phospholipids can move around and aren't packed together as tightly- the membrane is partially permeable. As the temperature increases the phospholipids move more because they have more energy- this increases the permeability of the membrane as pigment molecules are able to pass through the membrane. The higher temperature is the more kinetic energy the phospholipids have. This increases movement can disrupt the relatively weak forces holding the different parts of the polypeptide chains together, (like hydrogen bonds etc) and can make holes in the cell membrane inducing leakages, this allows substances that wouldn't normally enter of leave the cell, do so.
Above 45 degrees Celcius: The phospholipid bilayer starts to melt (break down) and the membrane becomes more permeable. Channel proteins and carries proteins denature as their tertiary structure unravels and their binding site changes shape and the membrane is no longer selectively permeable. They can't control what enters or leaves the cell - this increases the permeability of the membrane.
So as the temperature increases the % transmission of light decreases (as higher temperatures have higher pigment leakage therefore lower % transmission)

Okay I know no one is going to read all of this, but I like to get my thoughts down in a structure that makes sense to me, and this might help people who are doing the evaluative as well. If by any chance anyone reads this, it would be SO helpful if you could comment what you think, like if theres anything I should know for my evaluative. If any one has done the paper, is this all I roughly need to know, or have I missed anything out?

EDIT: Also what would be a couple of examples of sources of errors in this experiment?
Thank you!
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Heffalump .
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jaynamodi
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(Original post by Heffalump .)
I'm doing my Biology Evaluative coursework on thursday, and I just want to make sure all the stuff I say is correct and if not, whats wrong with it, and if I've left anything out please say!
So if I'm investigating how temperature affects the amount of pigment released from the cell surface membrane of the beetroot slices, and measuring this by putting a sample of the water with pigment in it in a calorimeter (assuming there is every limitation and control possible) the:

Independent variable would be: (mean) transmission of light (%)

Dependant Variable: Temperature (degrees Celsius)

Control Variables:
Size and shape of beetroot slices/discs
Volume of water in the test tubes
The type of beetroot (all discs must come from the same source of beetroot)
Number of discs in each tubes
Time each of the beetroot discs are heated for
Discs held separately so all are equally exposed to thermal treatment (on a mounted needle)

Limitations:
Inconsistant stirring of slices while submerged in water. Beetroot slices were not stirred in the same way for each, meaning inconsistent rate of pigment leakage. Modification: Standardise timing and method of stirring for each slices.
Insufficient number of values of independent variables e.g.. only at 40,50,60,70,80 degrees Celcius, so lack of results between intervals, meaning you could miss changes so making conclusions about trends are less valid. Modification: Include intermediate temperatures within the range e.g. 45,55,65,75 degrees Celcius.
Insufficient range of independent variables (40-80 degrees) lack of results beyond the range investigated could make it difficult to identify a trend or pattern. Modification: extend the range e.g. 20-80
Discs were handout, so discs will have a different surface area to volume ratio of the slices, so pigment release will differ. Modification: use a mechanical cutter slicer to prepare beetroots
Species of beetroot differ, so the concentration of pigment may differ/vary with age/ species. Modification: take samples all from the same source (same beetroot)
Repeats, if below 4 they are unable to detect anomalous results thus decreasing reliability. Modification: perform at least 4 replicates
If not calorimeter was used, then judging by eye can show lack of consistency in judgement, may lead to less precise, less accurate and less reliable results. Modification: use a calorimeter.

How to improve reliability:
Compare your results with other peoples results, or take a lot of replicates and take the mean of them.

Analysis:
20-45 degrees Celcius, The phospholipids can move around and aren't packed together as tightly- the membrane is partially permeable. As the temperature increases the phospholipids move more because they have more energy- this increases the permeability of the membrane as pigment molecules are able to pass through the membrane. The higher temperature is the more kinetic energy the phospholipids have. This increases movement can disrupt the relatively weak forces holding the different parts of the polypeptide chains together, (like hydrogen bonds etc) and can make holes in the cell membrane inducing leakages, this allows substances that wouldn't normally enter of leave the cell, do so.
Above 45 degrees Celcius: The phospholipid bilayer starts to melt (break down) and the membrane becomes more permeable. Channel proteins and carries proteins denature as their tertiary structure unravels and their binding site changes shape and the membrane is no longer selectively permeable. They can't control what enters or leaves the cell - this increases the permeability of the membrane.
So as the temperature increases the % transmission of light decreases (as higher temperatures have higher pigment leakage therefore lower % transmission)

Okay I know no one is going to read all of this, but I like to get my thoughts down in a structure that makes sense to me, and this might help people who are doing the evaluative as well. If by any chance anyone reads this, it would be SO helpful if you could comment what you think, like if theres anything I should know for my evaluative. If any one has done the paper, is this all I roughly need to know?

Thank you!
I am doing the exact same experiment but you have the independent and dependant variable wrong. The independent is temperature of water as that is what is being changed and the dependant is the conc of pigment being released. I have my quant tomorrow and eval on Friday. Any tips for veal in particular?
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Valyrian
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(Original post by Heffalump .)
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I did the evaluation today for the beetroot experiment, and I'm not going to tell you what's on it but what I can say is that what you have written is perfectly fine, and I would recommend you thinking mainly about limitations and what things could go wrong and how you can tell them on a graph. Good luck
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Heffalump .
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(Original post by jaynamodi)
I am doing the exact same experiment but you have the independent and dependant variable wrong. The independent is temperature of water as that is what is being changed and the dependant is the conc of pigment being released. I have my quant tomorrow and eval on Friday. Any tips for veal in particular?
Oh yeah of course, thank you! I really don't know about tips, like I said, mines tomorrow Just look through limitations of experiments etc like I have is all I can say
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Its good don't worry!!


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Heffalump .
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(Original post by lilypear)
I did the evaluation today for the beetroot experiment, and I'm not going to tell you what's on it but what I can say is that what you have written is perfectly fine, and I would recommend you thinking mainly about limitations and what things could go wrong and how you can tell them on a graph. Good luck
Oh good And okay thank you for the help, I'll have a look at that How you could tell what on a graph? Anomalies? O.o Thanks for the help
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Heffalump .
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Also does anyone have any suggestions on what a source of error would be in this experiment? I'm confused about what a few examples of that would be... thanks
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Valyrian
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(Original post by boodoo)
omg! would u say it was easier than the chemistry evaluative
and how long did it take??

EDIT: + is it anything like this specimen http://www.ocr.org.uk/Images/67662-u...k-specimen.pdf

because the questions look different to the ones we've done in class
I don't take chemistry so I wouldn't know but from what I've heard from friends it was quite tricky.
To be honest the biology evaluative is pretty straight forward except for the last 2 which takes a bit of thinking, so go over your notes and stuff for it!
It took about 30-45 minutes max and we had the option of having 2 hours so we took our time on it!
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Heffalump .
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(Original post by lilypear)
I don't take chemistry so I wouldn't know but from what I've heard from friends it was quite tricky.
To be honest the biology evaluative is pretty straight forward except for the last 2 which takes a bit of thinking, so go over your notes and stuff for it!
It took about 30-45 minutes max and we had the option of having 2 hours so we took our time on it!
Does what I've said originally cover the last two questions? Or do I need extra knowledge on the subject?
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(Original post by Heffalump .)
Does what I've said originally cover the last two questions? Or do I need extra knowledge on the subject?
You've not stated how the beetroot releases betalain and why it increases as temperature goes up. Research that and you're pretty loaded.
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Heffalump .
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(Original post by lilypear)
You've not stated how the beetroot releases betalain and why it increases as temperature goes up. Research that and you're pretty loaded.
Oh yeah, I'll do that now
Thank youu!! I hope you get a good grade on you bio btw
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(Original post by Heffalump .)
Oh yeah, I'll do that now
Thank youu!! I hope you get a good grade on you bio btw
My experiment grade was decent, still an A but hopefully the evaluative will keep it an A
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I have this PSA tomorrow, as I am retaking my AS PSA's. I got 10/10 for the quantitate part for the experiment and want to try and get 18/19 out of 20 on the evaluative. Any tips/ things I definitely need to revise for it?
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this is the prep work I have been given to revise over, have I missed out anything really obvious?

AS PSA PREP EVALUATION


What I am investigating:

How temperature affects the amount of pigment released from the vacuole of the beetroot slices

Independent: temperature – 30%, 45%, 60%, 80%
Dependent: concentration of pigment released
Control:
- Size and shape of beetroot discs
- Volume of water in the test tubes
- All discs from same beetroot
- Same number of discs for each temperature

Background

Beetroot contain the betalin pigment – give the tissue a dark red colour
The pigment, betalin, is contained in the cell vacuole

Why is pigment released?

1. The cell membrane is partially permeable – so some ions and molecules are let in and others are not
2. Increasing the temperature gives molecules more kinetic energy, so they move faster
3. Increasing the temperature also breaks the membrane down because the phospholipds become more fluid/permeable
4. This increased movement of phospholipids and other components makes membranes leaky – which allows substances that would normally not enter or leave the cell do so
5. So at higher temperatures more belatin is released from the cell, since more of it diffuses out of the vacuole
6. Because the cell surface membrane and vacuole are damaged by the heat


Why is more pigment released at higher temperature

Higher temperature increases the rate of diffusion
Because molecules have more kinetic energy – so the rate of random movement increases and so the rate of diffusion increases
So more pigment/belatin is diffused out of the vacuole

Limitations

Beetroot discs are not all the same size

Why it limits:
- Not all being the same size will mean the beetroot discs will vary in thickness
- Thicker cells will have a higher number of cells/vacuoles
- So the thicker cells will have more belatin



Modification:
- Mechanical cutter slice could be used so beetroot slices are all the same size/thickness
- So beetroot slices will have a closer number of cells and vacuoles
- So results will be more accurate

Some of the concentrations of beetroot were intermediates between concentrations we made up

Why it limits:
- Makes it difficult to judge what the concentration is
- Difficult to see by eye
- Leads to inaccurate results
Modification:
- Use a calorimeter
- More accurate way of measuring concentration

No replicates

Why it limits:
- Don’t know anything about realiability – no sense of it
- Results could potentially be anomalies
- Method of experiment is unreliable

Modification:
- Repeat at least 3 times for each temperature
- Results will be more relibale
- Will be able to spot anomalies if there is any

Inconsistent sitrring of beetroot slices

Why it limits:
- Beetroot slices were not stirred in the same way for each temperature
- Some stirred quicker/slower in comparison to other temperatures
- Means there will be an inconsistent rate of pigment leakage
- Increased stirring/moving – increases the rate of diffusion – so more pigment diffused out from vacuole
Modification:
- Standardised timing and method of stirring for each slices
- Electronic stirrer to be used for all temperatures

Insufficient number of values between independent variables

Why it limits:
- Making conclusions about trends are less valid
- Less of an idea of thebig picture
- Ability to spot trends and patterns is limited

Modification:
- Include intermediate temperature
- Eg, 45 – 50 – 55 – 60 – 65 – 70 – 75 – 80 degrees celcius
- Will be able to obtain more valid results
- Since more able to spot trends and patterns


Difference between active transport and facilitated diffusion

Facilitated diffusion:
Definition: Passive process, down a concentration gradient, where where chared, hydrophillic molecules or ions diffuse via channel or carrier proteins
- Small charged particles or larger molecules cannot pass through lipid bilayer
- Carrier and channel proteins allow these substances to pass through the membrane
- Channel proteins = pores in the membrane – often shaped to only allow one ion through. Most of them are also gated – so can be opened or closed
- Carrier proteins – shaped so that a specific molecule can fit into them at the membrane surface – when molecule fits the protein changes shape to allow the molecule through to the other side

Active transport:
- Definition: refers to the movement of molecules or ions across membranes, which uses ATP to drive protein ‘pumps’/carrier proteins within the membrane
- Some carrier proteins = pumps – these proteins are similar to
the ones used in facilitated diffusion

- Similarities in these proteins =
o Shaped in a way that is complementary to the molecule they carry
o They carry larger or charged molecules and ions through the membranes
o These larger or charged molecules and ions cannot pass through the lipid bilayer by diffusion
- Differences:
o They carry specific molecules one way across the membrane – this ensured by shape change of the carrier protein – shape change means that the specific molecule to be transported fits into the carrier protein on one side of the membrane only – when molecule passes through carrier protein this changes the proteins shape so the molecule bing carried leaves and the molecule cannot re-enter
o In carrying molecules across the membrane they use matabolic energy in the form of ATP
o They carry molecules in the opposite direction to the concentration graident
o Carry molecules at a much faster rate the facilated diffusion

Key differences:
- Active transport requires energy, whilst facilitated diffusion is a passive process that requires no energy
- Facilitated uses both carrier and channel proteins, whilst acitve transport just uses carrier proteins
- Differences in carrier proteins – one way for active, use energy in form of ATP for active, opposite direction to concentration for active whilst down a concentration gradient for active, faster rate for active






Why do we rinse the beetroot discs before placing them in the test tubes where the heated water goes?

- To remove excess pigment/belatin on the surface
- We are only interested in the pigment diffusing out from beetroot vacuole due to the temperature
- Excess on the surface because when we cut beetroot into discs the cutting ruptures the cells
- So we are also cutting the vacuoles
- So this causes pigment to be released/diffused out

Control

- Our control = same number of discs for each temperature
- This is our control because if there was different numbers of discs for each temperature the results would be invalid/unreliable/inaccurate because different concentrations of pigment will be diffused out
- The more beetroot discs the more cells/vacuoles there will be – more pigment will be diffused out
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j10ppy
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What grade did you get? Was everything you needed on here?
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username1850327
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i dno about grade but yes everything i needed was on here
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Heffalump .
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(Original post by j10ppy)
What grade did you get? Was everything you needed on here?
I got 39/40 on my coursework, 19/20 being on the beetroot evaluation, everything I put at the top is everything you need, (also look up how pigment leaves the beetroot cell) )
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Cheers baby girl can I suck on your toes now please?
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or your pussy I don't mind
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