Biology SL/HL help

[sweetnsimple786]

As far as I know, we need to know that exons are the translated parts and introns are the highly repetitive parts that are cut out, so they aren't translated. I imagine new advances might have a lot more to say on this, but where the syllabus is concerned, that's the core.

[Mahuta ♥]

Hey,

I apologize for the late reply,

you don't exactly have to know all the details about gene structure but to make it easier:

You have a

A)coding region: The coding region is the exons' part because the exons are what code for the proteins.

B)non coding region: The non coding region includes 2 parts:

1- Transcribed but not translated: which include the INTRONS, STOP and START codons...etc.

2- Non transcribed: which include all the rest.

The introns are called junk DNA because they have no indentified use till now and they are removed from the premature mRNA to form the mRNA which is translated to synthetise the polypeptide.

I hope this makes sense.

edit:

Regarding the previous question:

As the picture shows, the first Phosphate is linked to the 5th carbon of the sugar, the 2nd to the 1st, 3rd to the 2nd.

[Pima]

Since no one seemed to be offering help in biology, I am.

If anyone needs help with any topic in Biology, that is Higher and Standard Level. Including the following options:

• Cells and Energy (for SL, which is aHL topic)
  
• Microbes and Biotechnology
  
• Further Human Physiology
  

I'm here to help. I enjoy Biology *bio-freak yes*

This doesnt take much of my time and I'm doing it willingly.

Hey.

I have to design an experiment on microbes or energy, but I have no idea what I could do.

Can you help me?

[Mahuta ♥]

It does clearly say I can't give IA design help. It's what you get marks for. Come up with an idea design it, and if you're uncertain about anything relating to concepts you need for the experiment, I can help you.

[bLub]

Hey Mahuta,

I know you're more the medical-replyer, but maybe you know the following, too:

In the syllabus it says:

Explain how the abiotic factors light, temperature, wind and humidity affect the rate of transpiration in a typical terrestrial plant

I don't really get the wind-bit. Found some explanations on the internet but they just confused me. Any idea? Thanks!!

[sweetnsimple786]

She'll probably be able to explain this better, but think about the pulling of water up a plant's xylem. The way I think about it is that the presence and the increase in intensity of wind allows for the evaporation of more water because it can take the moist, humid air around the plant and displace it with less humid air. Water evaporates now due to the physical factor of the wind and because of the decrease in humidity, so more water is pulled up [cohesion + adhesion] and the process continues. Does that make any sense?

[Mahuta ♥]

Hey, I apologize once again for the late reply, but I am in for good now.

Ok the wind part:

The stomata on the leaf, its like a small pit. Condensed water gathers there, which explain the effect of humidity on the transpiration rate.

If it's windy around or 'outside' the pit, then simply the wind will blow away the condensed water gathered in the pit. In these factors, use your simple common sense.

So basically, you have condensed water particles, the wind will come and it will blow it way. Hence emptying the pit, and then it will be filled again by the cohesion-adhesion Sweetnsimple had explained for you.

[HanoBee]

hey guys, i just have one question. in the bio SL exam, do we get a question asking us to design an experiment in papers 2 or 3? cuz i heard its just for the higher levels but im not sure

[Sandwich]

hey guys, i just have one question. in the bio SL exam, do we get a question asking us to design an experiment in papers 2 or 3? cuz i heard its just for the higher levels but im not sure

Neither at SL nor HL are you expected to design an experiment in the exam

[HanoBee]

hey guys, i just have one question. in the bio SL exam, do we get a question asking us to design an experiment in papers 2 or 3? cuz i heard its just for the higher levels but im not sure

Neither at SL nor HL are you expected to design an experiment in the exam

are you sure? because I think in the HL mock exam paper 2 or 3 they got a question about designing an experiment (material, procedure, variables), but not too detailed, im not really sure what the requirements were but it was something like that. im not sure if you're taking the IBID biology book but i was thinking about maybe the experiments mentioned about measuring the rate of photosynthesis on pages 49 and 50, part of the "Chemistry of Life" topic.

thanks!

Edited April 22, 2010 by Mahuta ♥
Please make sure you don't use text speak on the fourm- thanks :)- Maha

[Sandwich]

You may have been given that for your mocks by your teachers, but although you're expected to be able to analyse an experiment, you're never asked to design one outside of your Internal Assessments/Coursework. Basically if it's not in the syllabus, the IB don't do it, and experimental design is definitely not a component of the exam syllabus. If you're revising for your Biology exams this year (May 2010) I'd seriously encourage you to just go through the syllabus point by point and treat that as your Biology Bible if you're not already. It is the be-all and end-all of what you need to know and be able to do, and the best possible way to get top marks. Doing more than what it states is not necessary

[masochist]

I'm not really sure how to deduce which one is the limiting factor for each of these? Can some one explain that to me? Thank you!

[masochist]

I'm a little bit not too sure about this area of photosynthesis: the following is my understanding of it - can you tell me whether or not it is correct?

Non cyclic:

It begins with photosystem II being hit by photons, exciting electrons to a high energy state. As it goes through the carriers in the thylakoid membrane the energy state of the electron gradually drops while it pumps protons into the lumen. When the electron reaches photosystem I it is once again excited to a higher energy level and it continues in the same way until it reaches ATP synthase, helping to form ATP and then finally it reaches NADP+ and helps form NADPH.

Cyclic:

When light is not the limiting factor, NADPH accumulates in the stroma and there is a shortage of NADP+. Therefore photosystem I absorbs light - e gets excited - energy state drops while going through the carriers and reaches a carrier between photosystem II and photosystem I then goes back to photosystem one (essentially does that whole thing with the proton gradient/atp formation but no NADPH formation).

Was that all accurate?

If so I have a question: why do the electrons in cyclic photophosphorylation NOT go through photosystem II? And why can't the electrons in non cyclic photophosphorylation be initially excited in photosystem I?

[Sandwich]

Okay directly comparing 1 and 2, you can see they have the same CO2 concentration with only temperature different. The one with the lower temperature drops at 260ish and the one with the higher temperature at 500ish. Clearly if you increased the temperature of 2, you would see it match up to 1. Therefore temperature is the limiting factor, because the other one obviously has enough CO2 to keep photosynthesising without stopping and the only reason for this would have to be that the temperature is greater.

3 and 4 both stop at the same level, despite one having a greater temperature than the other. Obviously the factor which limits them must be shared for them to do this, so the answer is CO2, which they both have the same concentration of. Even increasing the temperature doesn't allow them to photosynthesise more because they've both run out of available CO2 to increase the rate.

I may be having a stupid moment here, but I'm not 100% how you can tell whether 1 is due to CO2 or temperature. Hrm!

[Mahuta ♥]

I'd say it's due to CO2, there are two lines at 30degrees, they both have the 'plateau' part, one is more flat than the other. Also, the only difference between the two is the CO2 level.

Rate of photosynthesis is favored by temperature 30degrees and 0.15% CO2 (1). If we say that the temperature is the limiting factor, we should take a look at the 30degrees and 0.035%CO2, the difference between that and the first one is not as big as the one between 1 and 3.

To simplify: difference between 1 and 3 is much bigger than the difference between 1 and 2.

This is the logic I would use to deduce what's the limiting factor in 1.

Hope that makes sense.

Cyclic phosphorylation occurs when you have shortage of NADP+. Electrons start from P1 and move along the transport chain. The reason it doesn't get to P2 is because the final acceptor (NADP+) is not available. The plant needs to produce energy which is accomplished by going over and over past P1 as it pumps H+.

That's all you need to know for IB.

[skyhs0168]

Can you give me some tips how can I prepare for biology SL final exams?

I just started today to prepare, i didnt study anything before because i was preparing for maths and business.

I need to get grade 4 or 5.

Thank you.

[Mahuta ♥]

bio is not something you can study DURING IB exams.

However, since it's too late to start blaming I am going to tell you what everybody says:

1- Go through the syllabus and make sure you understand every single point of it.

2- Practice pastpapers, like ALOT.

3- Use your studyguide and NOT the textbook, it's too late for that.

4- If you're a notes person, make notes as you go through the syllabus, I tend to always make sure I have something simple and summarized before the exam instead of taking the whol studyguide with me.

5- For paper 1, make sure you know the objective 1 points on the syllabus.

6- For papers 2 and 3, go through the rest, trust me, sticking to the syllabus is the best thing you can do now, you have no time.

Do not aim for a 4 or 5 because you're likely to get lower, do as I just said, and you WILL get the 5 or even more.

If you do not understand a point on the syllabus, do not ignore, ask for it to be explained, it it may be the one point keeping you away from a 4 or a 5!

[lobsta]

Hi, I have biology HL and I only started studying. As you can see I have very limited time like only a few days to study and a lot to memorize. I am aiming for a 3 but I doubt I can even get that after looking at some past papers. Paper 2 is like death, I don't even understand what the question asks... I am having very bad time. For my internal assesment, I guess it effects %24 of the general grade, and i got 33/45 from it. How much will this effect my grade? Is it hard to get a 3 in Biology HL? I am really confused and scared

[pomoni]

Well I'm sure you must've been at least studying throughout the 2 years of your IB DP... go over all your notes and see animations (I find those very helpful) and tackling paper 2 questions is not this hard. It's also a skill you acquire throughout the 2 years. You just look at the info given and relate it to the studied concepts.

And if you dedicate all the coming days to studying biology then you can manage to have at least most of the concepts in your head. Just try and give your best!

[Sandwich]

To repeat what's been said above: go through the syllabus point by point and memorise it. That's all you can do! Don't bother with past papers, it's more important to know stuff than to identify the little bits you don't know at this point in time. Point by point, with a study guide/textbook. Get somebody to test you as frequently as possible. HL Bio isn't hard, it's just a lot to remember.