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March 29, 2024, 12:28:11 am

Author Topic: VCE Biology Question Thread  (Read 3570530 times)  Share 

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nerdmmb

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Re: VCE Biology Question Thread
« Reply #615 on: February 15, 2014, 11:08:29 am »
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Can someone pleeease help me with this..

I get confused between independent and dependent variables.

Say in an osmosis experiment involving potato pieces in a salt water concentration,
what is the independent variable and what is the dependent variable?
Is it true to say that a controlled experiment can have many dependent variables but only one independent variable?

If I were to observe what would happen to potato pieces in three beakers (A, B and C). (Note beaker A contains dilute water, beaker B contains 2.5% salt and beaker C contains 5% salt), what would be a good hypothesis for this?

Thanks!!  ;D

nhmn0301

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Re: VCE Biology Question Thread
« Reply #616 on: February 15, 2014, 12:27:01 pm »
+1
Can someone pleeease help me with this..

I get confused between independent and dependent variables.

Say in an osmosis experiment involving potato pieces in a salt water concentration,
what is the independent variable and what is the dependent variable?
Is it true to say that a controlled experiment can have many dependent variables but only one independent variable?

If I were to observe what would happen to potato pieces in three beakers (A, B and C). (Note beaker A contains dilute water, beaker B contains 2.5% salt and beaker C contains 5% salt), what would be a good hypothesis for this?

Thanks!!  ;D
In an experiment, for eg the potato experiment, in order to get the diluted and concentrated solution, you must add salt to each beaker, hence, you can change the concentration of salt whatever you want, you can add more, you can add less, it's all up to you. Hence, we call the concentration of salt the INDEPENDENT VARIABLE. Since the external environment will determine the net movement of wAter in or out of the potatoes cells, we call the net movement of water the DEPENDENT VARIABLE since it is caused by the concentration of substrate outside. In practice, it is actually really hard to make sure that all the other variables constant and ONLY the independent and dependent variables that change,hence, we have to minimize as much as possible the changes in all other variables except independent and dependent variables.
A good hypothesis is all about making a measurable and observable hypothesis, you have to be specific about your quantities. Hypothesis is usually an " If....then..." statement.  Hence, my possible hypothesis for this is, " If the concentration of salt on the external environment changes in an addition of 2.5% then, there will be a net movement of water from the potato cells to the external environment (a hypertonic environment) by osmosis effect, hence, there will be a decrease in mass of the potato due to the loss of water content"
Hope this helps.
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alchemy

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Re: VCE Biology Question Thread
« Reply #617 on: February 15, 2014, 12:32:40 pm »
+1
Can someone pleeease help me with this..

I get confused between independent and dependent variables.

Say in an osmosis experiment involving potato pieces in a salt water concentration,
what is the independent variable and what is the dependent variable?
Is it true to say that a controlled experiment can have many dependent variables but only one independent variable?

If I were to observe what would happen to potato pieces in three beakers (A, B and C). (Note beaker A contains dilute water, beaker B contains 2.5% salt and beaker C contains 5% salt), what would be a good hypothesis for this?

Thanks!!  ;D

Hey, I had the same prac  :D

I mentioned that the independent variable was the salt concentration and the dependent variable was the mass of the potato tuber cells (if you used the 'weighing method'). Yes, there can be more than 1 dependent variable in an experiment but, for this experiment, you should only be investigating one DV. For example, in another experiment, if you were investigating the effect of catalase on hydrogen peroxide, the dependent variable could be the height of oxygen bubbles and/or the number of oxygen bubbles that formed when catalase was reacted with hydrogen peroxide. However, you will most likely only measure and compare the height of oxygen bubbles as it's much more difficult to count the number that form. So, my point is: even though there may be more than one DV, you only mention how many you tested (mostly likely 1 or 2). Also, it's important to know that the whole purpose of control variables is to know that your independent variables don't act in isolation (so you know that there isn't any other factor affecting them during the experiment).
« Last Edit: February 15, 2014, 12:36:18 pm by alchemy »

nerdmmb

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Re: VCE Biology Question Thread
« Reply #618 on: February 15, 2014, 12:38:28 pm »
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Thanks heaps nhmn0301 and alchemy!

And do you know roughly how long schools give for students to write up their experimental reports? I have a sac coming up this week :(

alchemy

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Re: VCE Biology Question Thread
« Reply #619 on: February 15, 2014, 01:00:34 pm »
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Thanks heaps nhmn0301 and alchemy!

And do you know roughly how long schools give for students to write up their experimental reports? I have a sac coming up this week :(

We didn't have to write up a prac report; only answer questions regarding the prac. It was 45 mins for us.

Chang Feng

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Re: VCE Biology Question Thread
« Reply #620 on: February 15, 2014, 05:10:35 pm »
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Just curious why does ADP have to add another free phosphate molecule before it can brake of the terminal phosphate to release energy. Why isn't ADP capable of also breaking of its terminal phosphate??

vox nihili

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Re: VCE Biology Question Thread
« Reply #621 on: February 15, 2014, 05:18:56 pm »
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Just curious why does ADP have to add another free phosphate molecule before it can brake of the terminal phosphate to release energy. Why isn't ADP capable of also breaking of its terminal phosphate??

It technically could, and in some reactions it does. It's just that ATP is better set up to do it. I can't exactly explain why, because it'd require higher level chemistry than I'll ever know, but it'll have to do with ATP—>ADP just being an easier pathway to cycle through, and give the biggest energy yield as well. It's also probably because AMP is also a nucleotide, so ADP—>AMP levels wouldn't be able to regulated as well as ATP/ADP :)
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Chang Feng

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Re: VCE Biology Question Thread
« Reply #622 on: February 15, 2014, 06:32:07 pm »
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Thanks. Sorry another question. Isn't it that only carrier protein can be used in active transport and not channel protein??  And for endocytosis can large, non-lipid soluble molecules pass through and why (cause isn't it still repelled by the lipid membrane of plasma membrane. Thanks- got confused with my knowledge when had a question regarding this.

vox nihili

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Re: VCE Biology Question Thread
« Reply #623 on: February 15, 2014, 06:36:35 pm »
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Thanks. Sorry another question. Isn't it that only carrier protein can be used in active transport and not channel protein??  And for endocytosis can large, non-lipid soluble molecules pass through and why (cause isn't it still repelled by the lipid membrane of plasma membrane. Thanks- got confused with my knowledge when had a question regarding this.

Yep, only carriers.
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nerdmmb

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Re: VCE Biology Question Thread
« Reply #624 on: February 15, 2014, 06:42:11 pm »
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Yep, only carriers.

Can carrier proteins also be used for passive carrier mediated transport for specific molecules?

vox nihili

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Re: VCE Biology Question Thread
« Reply #625 on: February 15, 2014, 06:54:12 pm »
+1
Can carrier proteins also be used for passive carrier mediated transport for specific molecules?

Carrier proteins play a role in facilitated diffusion, yep.
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madhatter117

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Re: VCE Biology Question Thread
« Reply #626 on: February 15, 2014, 08:55:34 pm »
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Hey I was wondering if someone could answer my questions?
I was wondering if anyone could explain a simplified version of protein synthesis? The way my teacher has taught it really confused me...
Also is anyone able to explain/define signal transduction??
Thanks heaps! :)

nerdmmb

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Re: VCE Biology Question Thread
« Reply #627 on: February 15, 2014, 09:07:20 pm »
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Hey I was wondering if someone could answer my questions?
I was wondering if anyone could explain a simplified version of protein synthesis? The way my teacher has taught it really confused me...
Also is anyone able to explain/define signal transduction??
Thanks heaps! :)

RNA polymerase transcribes the template strand of a DNA molecule in the nucleus. mRNA takes this strand from the nucleus to the ribosome for translation. tRNA transports amino acids that corresponds with each 3 nitrogen bases on the mRNA strand. Once another tRNA approaches the ribosome, a peptide bond is formed between the amino acids. Once all the amino acids have been assembled (in other words, once the nitrogen bases have been translated), a stop codon is attached to stop any more amino acids from being assembled.
The ribosome then frees the mRNA stand which is broken down in the cytoplasm.
Ta-da you have a polypeptide chain :)

Note: the amino acids are found in the cytosol.

Please correct me if I'm wrong.

vox nihili

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Re: VCE Biology Question Thread
« Reply #628 on: February 15, 2014, 10:44:52 pm »
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RNA polymerase transcribes the template strand of a DNA molecule in the nucleus. mRNA takes this strand from the nucleus to the ribosome for translation. tRNA transports amino acids that corresponds with each 3 nitrogen bases on the mRNA strand. Once another tRNA approaches the ribosome, a peptide bond is formed between the amino acids. Once all the amino acids have been assembled (in other words, once the nitrogen bases have been translated), a stop codon is attached to stop any more amino acids from being assembled.
The ribosome then frees the mRNA stand which is broken down in the cytoplasm.
Ta-da you have a polypeptide chain :)

Note: the amino acids are found in the cytosol.

Please correct me if I'm wrong.

For someone in Unit 3, this is very good  :D
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nerdmmb

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Re: VCE Biology Question Thread
« Reply #629 on: February 15, 2014, 11:42:29 pm »
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For someone in Unit 3, this is very good  :D

Thank-you :D