Biology help

OP

Original post by Supermanxxxxxx

Would you suggest writing your own notes or just learning some pre written ones and doing past papers

Posted from TSR Mobile

Whichever works best for you tbh, I've always made my own notes because I did history and geography GCSE and the only way to remember all the data was to write it all out in one place, and then when I did well in my GCSEs I attributed it to making good notes, so I've made them ever since. You definitely have enough time at GCSE/A-level, and it's also good to personalise your notes to you, but there's nothing wrong with using other people's notes, I've been making my own notes at uni as well as using an older year's notes (because there's not enough time to make all your notes yourself) and I'm getting on fine doing that. Again, whichever works best for you

Reply 62

OP

Original post by Toile

No problem, I think sending your notes would be a better idea because I'm stuck on the topic in general rather than little parts. So if you could send me your notes I will greatly appreciate it :smile:

Okay, how would you like me to send them? Also, just bear in mind they're not very clear (I have very small handwriting), so I'll try and take some clearer photos

Reply 63

OP

Original post by PlayerBB

Are anabolic steroids: synthetic testosterone-like hormones ?

Also, when steroid hormone-receptor complex enters the nucleus, and acts as a transcription factor binding to the DNA, does it switch particular genes on which are related to produce the needed enzymes and at the same time, does it switch some genes off ? Also how these needed enzymes cause muscles to get stronger and bigger ?

Posted from TSR Mobile

So my knowledge on this anabolic steroids is pretty rubbish, but I'll do my best. First of all, that is the correct definition of what an anabolic steroid is. In terms of how they work, it's complicated haha, just look at this and see for yourself
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2439524/ I'm not sure whether you need to know the details for your course? When I did gene regulation last year, all we had to know was that a steroid hormone enters the cell and binds to a receptor on a transcription factor, this causes an inhibitor to leave the TF and the TF then enters the nucleus and binds to a gene, either up-regulating or down-regulating the level of transcription of that gene. Basically TF's can either switch genes on or switch them off. But yh, from what I've read, it doesn't seem like the mechanism of action is as simple as "it switches on genes which make more protein". Sorry I couldn't be of more help! If I learn more about this I'll let you know

Reply 64

Original post by AortaStudyMore

So my knowledge on this anabolic steroids is pretty rubbish, but I'll do my best. First of all, that is the correct definition of what an anabolic steroid is. In terms of how they work, it's complicated haha, just look at this and see for yourself
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2439524/ I'm not sure whether you need to know the details for your course? When I did gene regulation last year, all we had to know was that a steroid hormone enters the cell and binds to a receptor on a transcription factor, this causes an inhibitor to leave the TF and the TF then enters the nucleus and binds to a gene, either up-regulating or down-regulating the level of transcription of that gene. Basically TF's can either switch genes on or switch them off. But yh, from what I've read, it doesn't seem like the mechanism of action is as simple as "it switches on genes which make more protein". Sorry I couldn't be of more help! If I learn more about this I'll let you know

Thank you so much, you've really helped, I was kinda confused :h:

and yeah you're right, we're not told to know those details, I was just curious but i guess curiosity kills sometimes haha

Reply 65

OP

Original post by PlayerBB

Thank you so much, you've really helped, I was kinda confused :h:

and yeah you're right, we're not told to know those details, I was just curious but i guess curiosity kills sometimes haha

Haha no problem, I was the same last year, I felt like there were so many gaps in my knowledge, unfortunately in cases like this you just have to accept you don't know. Another example is the menstrual cycle, last year we were just told that oestrogen goes from having a negative feedback effect on LH to a positive feedback effect without any explanation of why, so I asked my endocrinology professor this year about it and even he didn't know! This is what is rubbish about science sometimes, so much isn't fully understood

Reply 66

Original post by AortaStudyMore

Haha no problem, I was the same last year, I felt like there were so many gaps in my knowledge, unfortunately in cases like this you just have to accept you don't know. Another example is the menstrual cycle, last year we were just told that oestrogen goes from having a negative feedback effect on LH to a positive feedback effect without any explanation of why, so I asked my endocrinology professor this year about it and even he didn't know! This is what is rubbish about science sometimes, so much isn't fully understood

Yeah!! Like it really sucks like okay this happens but how? so this is the question i keep asking myself while studying biology and chemistry, however, when I reach details about a process I'll be like okay thanks god it's not in the syllabus.

Indeed! There is many gaps and processes which aren't fully understood, but like I feel the more I know about science, the more I discover I basically don't know nothing like there is so many things happening that I didn't even think about. And yeah it sucks when you're like I want to know how it turns to a positive feedback but yet there is no explanation why!

Reply 67

sububzi

Hey there

It's my literal dream to study medicine in Imperial like omgsjfdhalds it would be amazing. I'm currently in year 12 and am about to take my AS exams?
What would be your biggest tips to getting into Imperial? Also, HOW do you stay motivated to revise and work. I stopped revising after lunch and it's making me feel absolutely **** negl D:
Essentially how can I become you since your goals to me rn lol without sounding creepy :P

Reply 68

OP

Original post by sububzi

Hey there

It's my literal dream to study medicine in Imperial like omgsjfdhalds it would be amazing. I'm currently in year 12 and am about to take my AS exams?
What would be your biggest tips to getting into Imperial? Also, HOW do you stay motivated to revise and work. I stopped revising after lunch and it's making me feel absolutely **** negl D:
Essentially how can I become you since your goals to me rn lol without sounding creepy :P

I know what you mean, staying motivated is hard, especially in year 12 when you have nothing really to aim for. The trick is to find something that motivates you, and in this case it looks like the thing that would motivate you is thinking that if you get good grades you stand a chance of getting into imperial. For me (and this will sound quite bad), the thing that motivated me was thinking that the more I revise, the cleverer I will be compared to other people. I loved the idea of helping people (and still do, hence this forum) so I revised loads so that I could teach other people. And it worked, I ran revision sessions for lower years when I was in year 13, and I also tutored some people in my year. I also had good competition from my best friend, we were always trying to do better than eachother, and when he revised I had to revise, so it helps to have a hard working intelligent friend too.

There aren't really any tips specific to imperial yet, you only really start worrying about that in year 13. For now, just go about sorting out work experience (in hospitals or GP surgeries) and getting volunteering experience. Also, try boost your extracurricular activities if you haven't already got loads, I took up various sports in prep for applying to medical school, and I enjoyed them so much I now do them at uni haha. I also did quite a lot of academic stuff ("supercurricular") such as running science clubs, doing dissections, reading journals on cancer, writing essays (albeit on physics) etc. You probably already know this, but a standard medicine application will have work experience, volunteering, something which shows you can work in a team, something which shows you can communicate and something which shows you can relax. The trick is to find relatively unique ways of showing those skills, that is what will make you stand out.

When it comes to it, if you want to get into imperial, then you will need to ace the BMAT (get atleast above the cutoff which I believe are high 4's in the first 2 sections and 2.5B or something in the essay) and then ace the interview. But come back to me when you get that far (which you will!). In the mean time, go about doing a general medicine application, because it's still early days, I didn't decide where to go until like 2 days before I sent my application. Also, I know you're set on imperial, but with medicine, you got to take what you're given, I didn't actually want to go to imperial, I wanted to go to either bristol or birmingham, but I got rejected by both post-interview! So yh, the best thing you can be doing right now is doing everything possible to boost your application, year 12 is make-or-break year, make the most of it, I did all my work experience, extracurricular stuff etc etc in year 12 (and continued a lot of it into year 13), it has to be done in year 12 because you write your PS this summer. Also, don't forget to nail those exams, 3 or 4 A's are needed for imperial realistically! And don't worry about not being motivated, it happens to everyone, I've done no revision for my exams yet :s-smilie:

I can't remember how much I did over easter, but I think it was just note taking. You'll be fine, if there's anything else, then let me know.

Reply 69

Hey, I am really confused about sth, when the action potential occurs in the membrane of nerve fibre, does it occur in parts or all at once because in the book they're saying "the potential difference in the membrane adjacent to the first action potential changes and a second potential is initiated" so does it mean like more than one action potential occur at different parts of the same membrane at the same time ?

Also when Sodium ion channels open and depolarisation occurs then finally action potential, how does these events lead to the nerve impulse to pass ?

I am really really confused so I would appreciate any help!!!!

Posted from TSR Mobile

Reply 70

OP

Original post by PlayerBB

Hey, I am really confused about sth, when the action potential occurs in the membrane of nerve fibre, does it occur in parts or all at once because in the book they're saying "the potential difference in the membrane adjacent to the first action potential changes and a second potential is initiated" so does it mean like more than one action potential occur at different parts of the same membrane at the same time ?

Also when Sodium ion channels open and depolarisation occurs then finally action potential, how does these events lead to the nerve impulse to pass ?

I am really really confused so I would appreciate any help!!!!

Posted from TSR Mobile

Okay so the best way to think of a nerve impulse is to think of it as a mexican wave. Just imagine each sodium ion channel is a person in a football stadium, each person stands up when the person before them has stood up, this is similar to sodium channels on a neurone. Let me explain, voltage gated sodium ion channels open when the membrane potential (which is essentially just the difference in charge between the inside of the cell and the outside) reaches a certain value. The first channels are opened by some stimulus (eg from a receptor or from another neurone), the membrane depolarises as a result.

Now this is the tricky bit (and also the answer to your question I hope). Imagine a neurone membrane which is polarised, the outside is more negative than the inside, and the voltage gated sodium and potassium channels are CLOSED. A stimulus comes a long and opens the voltage gated sodium channels, and sodium enters the cell, reversing the membrane potential. Now you have a region inside the cell which is positive relative to the outside. Imagine the action potential is moving from left to right. To the right of this depolarised region, you still have a polarised region, i.e. the outside is positive relative to the inside. What you have created here are "localised currents". Basically, on the outside, you have a negative region with a positive region to the right, and on the inside of the cell you have a positive region with a negative region on the right. These regions have these charges because of the ions, and as we know, opposite charges attract, so what happens is, the positive ions begin moving towards the negative region on the outside (i.e. they begin to move left) and on the inside, the positive ions move right, towards the negative region on the inside of the cell. Now, this has now made the positive regions more negative and the negative regions more positive. If we just focus on the region to the right of the depolarised region, the outside of the cell has been made more negative because of these localised currents, and the inside of the cell has been made more positive. The result of this is that the membrane potential is now more positive, and this then stimulates sodium channels to open, and this causes some sodium to enter the cell, which makes the membrane potential even more positive, and eventually a threshold will be reached where there is a massive influx of sodium. This then continues a long the whole length of the neurone.

This is in an unmyelinated neurone btw, in a myelinated one, the same thing happens, except these localised currents arise between adjacent "nodes of Ranvier", essentially, the action potential hops a long the neurone instead of walking a long it like in an unmyelinated neurone.

Now there is a lot of information there, and I'm worried it may have confused you more, but honestly, don't worry about it, because I'm 99% sure they won't ask you a question on it. They key thing to remember here is that adjacent depolarised regions of the neurone stimulate the adjacent polarised regions to depolarise, and in myelinated neurones, there are large gaps between the depolarised and polarised regions, which allows the action potential to skip a long the surface, thus increasing the nerve impulse speed.

Reply 71

OP

Original post by PlayerBB

Hey, I am really confused about sth, when the action potential occurs in the membrane of nerve fibre, does it occur in parts or all at once because in the book they're saying "the potential difference in the membrane adjacent to the first action potential changes and a second potential is initiated" so does it mean like more than one action potential occur at different parts of the same membrane at the same time ?

Also when Sodium ion channels open and depolarisation occurs then finally action potential, how does these events lead to the nerve impulse to pass ?

I am really really confused so I would appreciate any help!!!!

Posted from TSR Mobile

http://highered.mheducation.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

Here you go, give this a watch, it doesn't explain it in as much detail as I did, but it's probably better for understanding movement of an action potential in the level of detail you will need for your exams!

Reply 72

Original post by AortaStudyMore

Okay so the best way to think of a nerve impulse is to think of it as a mexican wave. Just imagine each sodium ion channel is a person in a football stadium, each person stands up when the person before them has stood up, this is similar to sodium channels on a neurone. Let me explain, voltage gated sodium ion channels open when the membrane potential (which is essentially just the difference in charge between the inside of the cell and the outside) reaches a certain value. The first channels are opened by some stimulus (eg from a receptor or from another neurone), the membrane depolarises as a result.

Now this is the tricky bit (and also the answer to your question I hope). Imagine a neurone membrane which is polarised, the outside is more negative than the inside, and the voltage gated sodium and potassium channels are CLOSED. A stimulus comes a long and opens the voltage gated sodium channels, and sodium enters the cell, reversing the membrane potential. Now you have a region inside the cell which is positive relative to the outside. Imagine the action potential is moving from left to right. To the right of this depolarised region, you still have a polarised region, i.e. the outside is positive relative to the inside. What you have created here are "localised currents". Basically, on the outside, you have a negative region with a positive region to the right, and on the inside of the cell you have a positive region with a negative region on the right. These regions have these charges because of the ions, and as we know, opposite charges attract, so what happens is, the positive ions begin moving towards the negative region on the outside (i.e. they begin to move left) and on the inside, the positive ions move right, towards the negative region on the inside of the cell. Now, this has now made the positive regions more negative and the negative regions more positive. If we just focus on the region to the right of the depolarised region, the outside of the cell has been made more negative because of these localised currents, and the inside of the cell has been made more positive. The result of this is that the membrane potential is now more positive, and this then stimulates sodium channels to open, and this causes some sodium to enter the cell, which makes the membrane potential even more positive, and eventually a threshold will be reached where there is a massive influx of sodium. This then continues a long the whole length of the neurone.

This is in an unmyelinated neurone btw, in a myelinated one, the same thing happens, except these localised currents arise between adjacent "nodes of Ranvier", essentially, the action potential hops a long the neurone instead of walking a long it like in an unmyelinated neurone.

Now there is a lot of information there, and I'm worried it may have confused you more, but honestly, don't worry about it, because I'm 99% sure they won't ask you a question on it. They key thing to remember here is that adjacent depolarised regions of the neurone stimulate the adjacent polarised regions to depolarise, and in myelinated neurones, there are large gaps between the depolarised and polarised regions, which allows the action potential to skip a long the surface, thus increasing the nerve impulse speed.

Thank you so FREAKING much for your detailed explanation, you have literally saved me!!!! Your explanation was much clearer than the book and I really believe like I get now what's going on, I think I was just turning around circles!!!!

Thank you again, and the information you gave me, even though you're 99% sure won't be asked but It has really cleared my head around what's going on which will able me to answer any of the questions that may come

I really appreciate your detailed explanation!! :biggrin:

Reply 73

Original post by AortaStudyMore

http://highered.mheducation.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

Here you go, give this a watch, it doesn't explain it in as much detail as I did, but it's probably better for understanding movement of an action potential in the level of detail you will need for your exams!

Thank you, I will definitely have a look at it!! :biggrin:

Reply 74

dyezrawna

3

Hey,I've got a quick question. I've just finished unit 4 and 5 for AQA A2 Biology, and now I'm going to start past papers. Do you think doing each past paper from 2010 onwards and memorising the mark schemes is a good trick? I've also printed off every single past paper question for each topic

Reply 75

username1133132

15

Original post by dyezrawna

Hey,I've got a quick question. I've just finished unit 4 and 5 for AQA A2 Biology, and now I'm going to start past papers. Do you think doing each past paper from 2010 onwards and memorising the mark schemes is a good trick? I've also printed off every single past paper question for each topic

Although I know it works for some, I would recommend you first go through past paper..
Highlight all questions you got wrong write them down and then write the mark scheme answer and try your best to understand it.. If you don't, get out your notes/revision guide and try to find the answer. The main thing is understanding. well done for getting A2 content revision done! :smile:

Reply 76

OP