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March 28, 2024, 11:36:08 pm

Author Topic: VCE Biology Question Thread  (Read 3570485 times)  Share 

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darkz

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Re: VCE Biology Question Thread
« Reply #10005 on: March 23, 2018, 05:58:13 pm »
+1
thanks darkdzn,

last question,
would anyone be able to explain what I should talk about in the results section of my prac. I have a table and a graph, just unsure what to write. Like do I just regurgitate what is in the table and graph and explain in my conclusion?

thanks

Hey,
I’m pretty sure that in the results section you only have your table/graph. The area where you actually discuss them would be within your discussion. That’s where you’d talk about the effect of the independent variable on the dependent variable and always give specific references to values from your data and also discuss experimental design/errors/improvements etcetera
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bach34

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Re: VCE Biology Question Thread
« Reply #10006 on: March 26, 2018, 06:15:10 pm »
0
Hey can anyone please clarify if two drops of dilute salt solution (0.17 M sodium chloride) is isotonic and if two drops of strong salt solution (2 M sodium chloride) is hypertonic? Thanks!!

darkz

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Re: VCE Biology Question Thread
« Reply #10007 on: March 26, 2018, 06:19:14 pm »
+4
Hey can anyone please clarify if two drops of dilute salt solution (0.17 M sodium chloride) is isotonic and if two drops of strong salt solution (2 M sodium chloride) is hypertonic? Thanks!!

Hey,
I don't think that there is any really way to confirm the above since isotonic means that there is no net movement of water across a semi-permiable membrane etc. So you'd need to compare the sodium chloride concentration inside the "cell" or whatever you've got inside a semi-permiable membrane
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #10008 on: March 26, 2018, 06:20:52 pm »
+2
Hey can anyone please clarify if two drops of dilute salt solution (0.17 M sodium chloride) is isotonic and if two drops of strong salt solution (2 M sodium chloride) is hypertonic? Thanks!!
It depends what you are comparing it to - Hypotonic/isotonic/hypertonic are comparative terms, used for comparing the solute concentrations of two solutions, we can't tell you whether that is correct without knowing what the other solution is (i'm assuming potato or beetroot or something like that?)

Edit: Beaten to it again haha (good job darkdzn ;D)
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bach34

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Re: VCE Biology Question Thread
« Reply #10009 on: March 26, 2018, 06:52:12 pm »
0
It depends what you are comparing it to - Hypotonic/isotonic/hypertonic are comparative terms, used for comparing the solute concentrations of two solutions, we can't tell you whether that is correct without knowing what the other solution is (i'm assuming potato or beetroot or something like that?)

Edit: Beaten to it again haha (good job darkdzn ;D)

Its rhubarb cells if that helps

bach34

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Re: VCE Biology Question Thread
« Reply #10010 on: March 26, 2018, 06:55:22 pm »
0
Hey,
I don't think that there is any really way to confirm the above since isotonic means that there is no net movement of water across a semi-permiable membrane etc. So you'd need to compare the sodium chloride concentration inside the "cell" or whatever you've got inside a semi-permiable membrane

All i am asked to do, is draw and describe what happens to the water movement and pressures when a rhubarb cell is placed in two drops of distilled water (A)  two drops of dilute salt solution (0.17 M sodium chloride) (B)  and two drops of strong salt solution (2 M sodium chloride).
 (C)
I wrote, that:
(A) = Distilled water has a lower solute conc. outside the cell, as compared to the cell fluid which has a higher solute conc. Thus, this rhubarb cell was placed in a hypotonic solution. As a result, the rhubarb cells take up water molecules and so the cells start to swell (cells become turgid), as osmosis is occurring. However, the cell wall of rhubarb cells prevent it from bursting. Pressure inside the cell also increases until the pressure inside is equal to the pressure outside.

(B) = A dilute salt solution has equal solute concentrations on both the inside and outside of the cell. Therefore, there is no net osmotic movement of water.

(C) = A strong salt solution has a higher solute concentration outside the cell then inside. Thus, this rhubarb cell is placed in a hypertonic solution. As a result, the osmotic pressure will cause the water to move out of the cell through the cell membrane. Rhubarb cell becomes flaccid and plasmolysis occurs as the cell shrinks and moves away from the cell wall.

I am not sure if this is even correct? Please help, thanks

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #10011 on: March 26, 2018, 07:18:26 pm »
+3
Yep, your answers are correct - For a task like this where you are given 3 salt concentrations and are not given the cells solute concentration you can normally assume that the middle value will be isotonic. I've edited your answers a bit to give you an idea of how you should approach them - the way you wrote these are correct but they could be more specific and concise - it's something you will get better at as the year goes on.

(A) = Distilled water has a lower solute concentration (0M). outside the cell, as compared to the whereas cell fluid which has a higher solute concentration. Thus Meaning, this rhubarb cell was placed in a hypotonic solution. As a result, the rhubarb cells take up water molecules via osmosis and so the cells start to swell (cells become turgid), as osmosis is occurring. However, the cell wall of rhubarb cells prevent it from bursting. Pressure inside the cell also increases until the pressure inside is equal to the pressure outside

(B) = The 0.17M salt solution A dilute salt solution has equal solute concentrations to the solute concentration inside the cell, they are isotonic. on both the inside and outside of the cell. Therefore, there is no net osmotic movement of water.

(C) = The 2M salt solution is hypertonic to the solute concentration inside of the cell. A strong salt solution has a higher solute concentration outside the cell then inside. Thus, this rhubarb cell is placed in a hypertonic solution. As a result, the osmotic pressure will cause the water to move out of the cell through the cell membrane. Rhubarb cell becomes flaccid and plasmolysis occurs as the cell shrinks and moves away from the cell wall.

I am being super nitpicky here – Unless you’re teacher is super harsh, I expect that you would get full marks for your answers. The most important things that I have changed here is that you must be specific with your answers – especially for the end of year exam, if you are given specific values but don’t use them, you will lose marks. Most of the other things I changed are just for the sake making your answer more precise – not particularly important for homework, but in a sac/exam it will save you a lot of time. You should also avoid shortening words like conc. (meaning concentration) unless it is said like that in the question. Some words can be shortened (like Endoplasmic Reticulum to ER, because that is common in biology, but I would avoid shortening non bio-specific words.

I'm being super harsh, so don't worry too much but saying:
A strong salt solution has a higher solute concentration outside the cell then inside.
Doesn't make it particularly clear, for all I know both sides of the semi-permeable membrane are salt solutions. It implies that the strong salt solution is on both sides of the cell, which is not correct.
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bach34

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Re: VCE Biology Question Thread
« Reply #10012 on: March 26, 2018, 07:27:54 pm »
0
Wow, thankyou so much PhoenixxFire

I was also wondering for part (2) of the question, What did you observe after washing the rhubarb in the strong salt solution in distilled water? (Full sentence, 1 mark) (assuming i couldn't conduct the experiment)

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #10013 on: March 26, 2018, 07:33:26 pm »
+1
Wow, thankyou so much PhoenixxFire

I was also wondering for part (2) of the question, What did you observe after washing the rhubarb in the strong salt solution in distilled water? (Full sentence, 1 mark) (assuming i couldn't conduct the experiment)
You really just need to think about the process of what is happening, the strong salt solution will cause the rhubarb cell to shrink - there is otherwise nothing wrong with it aside from the missing water, placing it in a distilled solution will cause water to go back into the cell - returning it to normal. I'll leave it up to you to word that in a way that is appropriate for the question.
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bach34

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Re: VCE Biology Question Thread
« Reply #10014 on: March 26, 2018, 07:47:21 pm »
0
You really just need to think about the process of what is happening, the strong salt solution will cause the rhubarb cell to shrink - there is otherwise nothing wrong with it aside from the missing water, placing it in a distilled solution will cause water to go back into the cell - returning it to normal. I'll leave it up to you to word that in a way that is appropriate for the question.

Yup thanks heaps i was in the right track

PopcornTime

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Re: VCE Biology Question Thread
« Reply #10015 on: March 30, 2018, 05:08:16 pm »
0
For the materials section of a scientific report is it 1x or x1?

For example, is it:
1x measuring cylinder
or
x1 measuring cylinder

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #10016 on: March 30, 2018, 05:11:41 pm »
+1
For the materials section of a scientific report is it 1x or x1?

For example, is it:
1x measuring cylinder
or
x1 measuring cylinder
I normally write 1 X measuring cylinder but it doesn’t really matter so long as your teacher understands what you mean.
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Sine

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Re: VCE Biology Question Thread
« Reply #10017 on: March 30, 2018, 05:13:04 pm »
0
For the materials section of a scientific report is it 1x or x1?

For example, is it:
1x measuring cylinder
or
x1 measuring cylinder
1 x is what most people do but it shouldn't be too much of a problem

EDIT: beaten by PF

Mr West

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Re: VCE Biology Question Thread
« Reply #10018 on: March 30, 2018, 07:52:19 pm »
0
Hey everyone!

I constructed a few resources quite some time ago after the VCE Biology year came to an end, so I thought, why not share them here for everyone to peruse and better themselves with

thanks heaps!

this will help a lot of people, including myself :)

PopcornTime

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Re: VCE Biology Question Thread
« Reply #10019 on: April 01, 2018, 09:54:28 pm »
0
Just have a couple of questions about the EPI:

1. In the results section, what can I comment on without doing too much explanation?

2. Where can I justify the use of oxygen gas production as a suitable dependent variable?

3. How can I comment on whether the investigation generated useful results?

4. How can I effectively comment on the meaning/significance of results obtained?

Thanks.