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March 29, 2024, 07:03:34 am

Author Topic: VCE Biology Question Thread  (Read 3570901 times)  Share 

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darkz

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Re: VCE Biology Question Thread
« Reply #9960 on: March 17, 2018, 02:08:44 pm »
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Are cofactors a requirement for certain enzymes, or do they simply increase the rate of a reaction?
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9961 on: March 17, 2018, 03:03:40 pm »
+2
Are cofactors a requirement for certain enzymes, or do they simply increase the rate of a reaction?
Technically the enzymes themselves are not required but obviously the reaction would be extremely slow without them.

So yes cofactors are required, the reaction could happen without them but not at any useful rate.
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peachxmh

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Re: VCE Biology Question Thread
« Reply #9962 on: March 17, 2018, 07:53:39 pm »
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Could someone please outline how substrate concentration can become a limiting factor?

I wrote that as the concentration of substrate increases, so do the enzyme substrate complexes created, which increases the reaction rate until the concentration of substrate is too high and the active sites are saturated with substrate (assuming that the number of enzymes stays the same), at which point substrate concentration no longer has an effect on reaction rate. However, when I got my test back, the feedback said that my answer corresponded to how enzyme concentration can become a limiting factor instead of how substrate concentration can become a limiting factor.

I asked my teacher about this but he couldn't tell me why I was marked down as another teacher had marked the test. Would love some help!

Another more general question I have is about key terms/keywords. I was also marked down for not including specific keywords in my answers and I was wondering if anyone had any advice for knowing how to identify keywords to include in answers?

Thanks in advance :)
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darkz

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Re: VCE Biology Question Thread
« Reply #9963 on: March 17, 2018, 07:58:13 pm »
+4
Could someone please outline how substrate concentration can become a limiting factor?

I wrote that as the concentration of substrate increases, so do the enzyme substrate complexes created, which increases the reaction rate until the concentration of substrate is too high and the active sites are saturated with substrate (assuming that the number of enzymes stays the same), at which point substrate concentration no longer has an effect on reaction rate. However, when I got my test back, the feedback said that my answer corresponded to how enzyme concentration can become a limiting factor instead of how substrate concentration can become a limiting factor.

I asked my teacher about this but he couldn't tell me why I was marked down as another teacher had marked the test. Would love some help!

Another more general question I have is about key terms/keywords. I was also marked down for not including specific keywords in my answers and I was wondering if anyone had any advice for knowing how to identify keywords to include in answers?

Thanks in advance :)

Well since you lost the mark for that, then we can safely assume that your teacher has considered enzyme concentration to be infinite, and thus decreasing the substrate will decrease the rate of reaction while increasing will increase the reaction indefinitely. Or at least, that's what I think your teacher is trying to say
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9964 on: March 17, 2018, 08:22:48 pm »
+1
When talking about a limiting factor we assume all other variables are infinite. It is the limiting factor because there is the least of it. You described having increasing substrate, which leaves enzyme concentration as the limiting factor.

Substrate becomes the limiting factor when it is what is slowing the reaction down, if there is only a few bits of substrate in a cell, there is less chance of them bumping into an enzyme, so reactions will occur slower, it is the limiting factor. If you then increase substrate concentrations there will be more substrate floating around, therefore they will bump into enzymes more frequently, thus speeding up the reaction.


As for key terms, I just made sure to name processes. Normally the names of processes are what you need to include. For example, don’t say a protein was packaged into a vesicle and travelled to the membrane where it was released, just say a protein left the cell via exocytosis. (Obviously this doesn’t apply if the question is ‘describe how a protein leaves a cell’)
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randomnobody69420

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Re: VCE Biology Question Thread
« Reply #9965 on: March 17, 2018, 08:27:21 pm »
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Does the independent variable in an experiment ALWAYS have to be on the horizontal axis? For example: let's say your measuring the rate of photosynthesis of a plant over time when exposed to different amounts of light. Can you put rate of photosynthesis on y axis, time on x axis and use different colored lines to indicate different amounts of light? Is there a better way to do this, cause I can't think of any other way you can graph 3 variables.

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9966 on: March 17, 2018, 08:45:05 pm »
+1
Does the independent variable in an experiment ALWAYS have to be on the horizontal axis? For example: let's say your measuring the rate of photosynthesis of a plant over time when exposed to different amounts of light. Can you put rate of photosynthesis on y axis, time on x axis and use different colored lines to indicate different amounts of light? Is there a better way to do this, cause I can't think of any other way you can graph 3 variables.
Hey, no the IV does not always have to be on the x axis. Rate of photosynthesis is your DV and that is on the Y axis so that’s correct.

I pulled out my prac on light colour that I did last year and I had put reaction rate on the y axis, time on the x axis and represented the different colours with different lines so you should be fine to do this for light intensity - I would check with your teacher though because they’re the one who is going to be marking it.

Your other option is to ignore time altogether (although this depends on how you are measuring the rate of reaction), the rate of reaction shouldn’t change much over time (although the amount of reaction will) so you could just use the average rate and put that on your y axis and then put light intensity on your x axis.

It would look something like this
In reverse though
« Last Edit: March 17, 2018, 08:54:27 pm by PhoenixxFire »
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Bell9565

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Re: VCE Biology Question Thread
« Reply #9967 on: March 18, 2018, 12:20:14 am »
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Does the independent variable in an experiment ALWAYS have to be on the horizontal axis? For example: let's say your measuring the rate of photosynthesis of a plant over time when exposed to different amounts of light. Can you put rate of photosynthesis on y axis, time on x axis and use different colored lines to indicate different amounts of light? Is there a better way to do this, cause I can't think of any other way you can graph 3 variables.
As PhoenixxFire said it depends on your school and teacher but we were always told in all my sciences (chem, biol, psych and general) & in further (known as response and explanatory variables but in essence the same thing) that the IV is on the X axis and Y axis is always DV. We would have been marked incorrect if we were to make a graph the other way around.
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9968 on: March 18, 2018, 12:29:28 am »
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As PhoenixxFire said it depends on your school and teacher but we were always told in all my sciences (chem, biol, psych and general) & in further (known as response and explanatory variables but in essence the same thing) that the IV is on the X axis and Y axis is always DV. We would have been marked incorrect if we were to make a graph the other way around.
Yeah that’s what I was always told too, I think it’s ok though because the DV is still on the y axis, the iv is just inside the graph instead of on the x axis.
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Mr West

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Re: VCE Biology Question Thread
« Reply #9969 on: March 18, 2018, 10:34:39 am »
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Hey everyone,

can someone please explain to me the difference between intercellular, intracellular and extracellular

thanks

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9970 on: March 18, 2018, 10:41:27 am »
+2
Hey everyone,

can someone please explain to me the difference between intercellular, intracellular and extracellular

thanks
Intracellular: Inside the cell

Intercellular and extracellular can be used to mean the same thing but are slightly different.

Intercellular: Between cells.

Extracellular: Outside of cells (but still in the body).

Extracellular is normally used for things that have access to general body fluid, whereas intercellular is limited to a few specific cells. e.g. interneurons are intercellular messaging molecules whereas hormones are extracellular messaging molecules. Extracellular and intracellular are the terms you will use the most - intercellular is normally only used when talking about signalling.
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peachxmh

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Re: VCE Biology Question Thread
« Reply #9971 on: March 18, 2018, 12:35:59 pm »
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When talking about a limiting factor we assume all other variables are infinite. It is the limiting factor because there is the least of it. You described having increasing substrate, which leaves enzyme concentration as the limiting factor.

Substrate becomes the limiting factor when it is what is slowing the reaction down, if there is only a few bits of substrate in a cell, there is less chance of them bumping into an enzyme, so reactions will occur slower, it is the limiting factor. If you then increase substrate concentrations there will be more substrate floating around, therefore they will bump into enzymes more frequently, thus speeding up the reaction.


As for key terms, I just made sure to name processes. Normally the names of processes are what you need to include. For example, don’t say a protein was packaged into a vesicle and travelled to the membrane where it was released, just say a protein left the cell via exocytosis. (Obviously this doesn’t apply if the question is ‘describe how a protein leaves a cell’)

So would you recommend also talking about how eventually as you increase the substrate concentration, the active sites become saturated with substrates and substrate no longer becomes a limiting factor? Or is that irrelevant to the question?
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FabAsianZung

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Re: VCE Biology Question Thread
« Reply #9972 on: March 18, 2018, 12:37:56 pm »
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In an experiment. What do you takes notes of?

Thanks in advance :)
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darkz

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Re: VCE Biology Question Thread
« Reply #9973 on: March 18, 2018, 12:40:00 pm »
+4
In an experiment. What do you takes notes of?

Thanks in advance :)

Here's a list of the things you should know of about the experiment
- Variables, independent, dependent, controlled
- Experimental Errors
- Experimental Improvements
- Interpretation of your data and how your dependent/independent variables link with each other
- Background information that affects the experiment/ aim of experiment
« Last Edit: March 18, 2018, 12:43:50 pm by darkdzn »
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darkz

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Re: VCE Biology Question Thread
« Reply #9974 on: March 18, 2018, 12:42:45 pm »
+2
So would you recommend also talking about how eventually as you increase the substrate concentration, the active sites become saturated with substrates and substrate no longer becomes a limiting factor? Or is that irrelevant to the question?

You don't need to talk about the active sites becoming saturated, because as PhoenixxFire said, when considering substrate as a limiting factor, we assume everything else is infinite. So the active sites will never become saturated, as there is an infinite supply of enzyme.
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