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Biology SL/HL help


Mahuta ♥

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1- Why are cells so small?

2- In Prokaryotes, is the cell wall the most outer layer or the next outer layer?

3- why do prokaryotes divide by binary fission? What is binary fisson?

Well i hope my explanations aren't rusty because it's been a year since i did cells and i tend to forget :blink:

For the 1st question: cells are small because they need the large SA and volume so as to help with the cells absorption and excretion of certain substances. it needs to maintain a small structure so that absorption and excretion can take place and when a cell grows large in size, it divides to form smaller cells so as to maintain the size of the cell. If a cell was not small then it would take time for body processes to take place and the body will not function efficiently. You can check out this site which i found useful: http://morningsidemicro.wikidot.com/why-cells-are-so-small

The 2nd question: the cell wall is the outer layer in prokaryotes followed by the plasma membrane.

the 3rd question: i'm not sure but this is what i found on the net: In biology, fission is the carp of a body, population, or species into parts and the regeneration of those parts into separate individuals.Binary fission, or prokaryotic fission, is a form of asexual reproduction and cell division used by all prokaryotes, some protozoa, and some organelles within eukaryotic organisms. This process results in the reproduction of a living prokaryotic cell by division into two parts that each have the potential to grow to the size of the original cell.

Mitosis and cytokinesis are not the same as binary fission. To be specific, binary fission cannot be divided into prophase, metaphase, anaphase, and telophase because prokaryotes have no nucleus and no centromeres. The ability of some multicellular animals, such as echinoderms and flatworms, to regenerate two whole organisms after having been cut in half, is also not the same as binary fission. Neither is vegetative reproduction of plants.

^^ from wikipedia but basically, prokaryotes are very different from eukaryotes in terms of structure and the organelles they contain so the types of division will defer since they're not like eukaryotes. I hope that made sense :/ i'm not at explaining through typing but i can explain verbally :blink: I hope that helped and did not confuse you more.

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Guest KAPOWW!!

'because a chemical communication called synapse occurs between these neurones' Seriously WHOA! this is what my text book says, this IS wrong right? if so, this there a thread where I could post this. Pearson Biology HL(textbook)

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Hello! Would really appreciate help on these Q's:

1- Why are cells so small?

2- In Prokaryotes, is the cell wall the most outer layer or the next outer layer?

3- why do prokaryotes divide by binary fission? What is binary fisson?

Would be happy to get some help on this, my teacher just went through it and i didnt get her explanation, thanks!:-)

I have only a comment on what Kim said, the outer most layer isn't the cell membrane. It is a sugar based material called Capsule, the capsule has mainly two functios:1- Adherence 2- Protection.

And for the third question, you don't need to know why or how. The assesment stament says the following: 'State that prokaryotic cells divide by binary fission " and state means to give names without expalination.

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1- Why are cells so small?

2- In Prokaryotes, is the cell wall the most outer layer or the next outer layer?

3- why do prokaryotes divide by binary fission? What is binary fisson?

Well i hope my explanations aren't rusty because it's been a year since i did cells and i tend to forget :blink:

For the 1st question: cells are small because they need the large SA and volume so as to help with the cells absorption and excretion of certain substances. it needs to maintain a small structure so that absorption and excretion can take place and when a cell grows large in size, it divides to form smaller cells so as to maintain the size of the cell. If a cell was not small then it would take time for body processes to take place and the body will not function efficiently. You can check out this site which i found useful: http://morningsidemicro.wikidot.com/why-cells-are-so-small

The 2nd question: the cell wall is the outer layer in prokaryotes followed by the plasma membrane.

the 3rd question: i'm not sure but this is what i found on the net: In biology, fission is the carp of a body, population, or species into parts and the regeneration of those parts into separate

individuals.Binary fission, or prokaryotic fission, is a form of asexual reproduction and cell division used by all prokaryotes, some protozoa, and some organelles within eukaryotic organisms. This process results in the reproduction of a living prokaryotic cell by division into two parts that each have the potential to grow to the size of the original cell.

Mitosis and cytokinesis are not the same as binary fission. To be specific, binary fission cannot be divided into prophase, metaphase, anaphase, and telophase because prokaryotes have no nucleus and no centromeres. The ability of some multicellular animals, such as echinoderms and flatworms, to regenerate two whole organisms after having been cut in half, is also not the same as binary fission. Neither is vegetative reproduction of plants.

^^ from wikipedia but basically, prokaryotes are very different from eukaryotes in terms of structure and the organelles they contain so the types of division will defer since they're not like eukaryotes. I hope that made sense :/ i'm not at explaining through typing but i can explain verbally :blink: I hope that helped and did not confuse you more.

Thankyou! I understand it better know, and no you did not confuse me at all :-)!

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So I've read that the calvin cycle takes place in the stroma of the chloroplast since it contains a lot more enzymes, substrates etc. than the cytosol. Unfortunately I cannot find any "back up" for this online and apart from checking if this very statement is true, I'd also like to know if it is the same case regarding the matrix of the mitochondria.

Thanks,

Matt :)

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Hello! Would really appreciate help on these Q's:

1- Why are cells so small?

2- In Prokaryotes, is the cell wall the most outer layer or the next outer layer?

3- why do prokaryotes divide by binary fission? What is binary fisson?

Would be happy to get some help on this, my teacher just went through it and i didnt get her explanation, thanks!:-)

1. Because they are? I really don't know what kind of answer you're looking for here...

2. Prokaryotes can have 3 layers. Cell Membrane->Cell Wall->Capsule (in order from inside to outside)

3. I think it's because of how much they don't have in them. They just split the nucleoid region and then split the cytoplasm. Why it's binary fission is because it doesn't involve the centromeres and all that good stuff like mitosis does. In general it's just the division of prokaryotes that is tons simpler than mitosis XD

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Hello! Would really appreciate help on these Q's:

1- Why are cells so small?

2- In Prokaryotes, is the cell wall the most outer layer or the next outer layer?

3- why do prokaryotes divide by binary fission? What is binary fisson?

Would be happy to get some help on this, my teacher just went through it and i didnt get her explanation, thanks!:-)

1. Because they are? I really don't know what kind of answer you're looking for here...

2. Prokaryotes can have 3 layers. Cell Membrane->Cell Wall->Capsule (in order from inside to outside)

3. I think it's because of how much they don't have in them. They just split the nucleoid region and then split the cytoplasm. Why it's binary fission is because it doesn't involve the centromeres and all that good stuff like mitosis does. In general it's just the division of prokaryotes that is tons simpler than mitosis XD

1. Since the surface area/volume ratio limits it. This is due to the fact that cells have their own metabolism (that's obvious for you i hope :D) and if the volume increases, the metabolism rate increases as well and it would be all perfect except for the fact that the substrates for the metabolism reactions diffuse through the plasma membrane of the cell. Now, the surface area of the plasma membrane increases as the cell grows but not as fast as the cell's volume which means that the surface area/volume ratio shrinks as the cell grows. There comes a moment when the surface area of the cell is too small for the diffusion of the substrates to occur fast enough. This is also a case with heat since the larger the cell the more heat it produces, and when the cell grows, the heat must be disposed of faster and faster so there comes a moment when the disposal is too slow and overheating may take place.

3. The more interesting fact about binary fission is that i think a Z ring splits the cell, similarly to the plant cell division.

Hope I helped ;)

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I have only a comment on what Kim said, the outer most layer isn't the cell membrane. It is a sugar based material called Capsule, the capsule has mainly two functios:1- Adherence 2- Protection.

oh well at school that's what they taught us so that's what i thought too sorry

So I've read that the calvin cycle takes place in the stroma of the chloroplast since it contains a lot more enzymes, substrates etc. than the cytosol. Unfortunately I cannot find any "back up" for this online and apart from checking if this very statement is true, I'd also like to know if it is the same case regarding the matrix of the mitochondria.

Thanks,

Matt

well for the krebs cycle, yes i think it's the same because the enzymes in the mitochondria remove hyrogen and carbon dioxide from the pyruvate. The product of this oxidative decarboxylation is an acetyl group which is accepted by CoA to form acetyl CoA. After that reactions continue to happen in the matrix of the mitochondria until ATP is formed. You should use the IB study guide by Andrew Allot, it's very useful :)

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  • 2 weeks later...

Hi,

I really need to find the acfor scale. Does anyone know how? I've been surfing the web for the last 2 hours and haven't found anything. It is a scale for measuring the abundance of a given species on a particular amount of space. I would really appreciate it if someone could help me, thank you so much :)

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  • 2 weeks later...

[quote name=iBsita :)' timestamp='1315267644' post='130387]

I am soooo lost right now! Can someone explain Bio IA's? My Bio teacher sucks and simply told us to go home and create a lab! But where do I start?? 0_o

Biology IAs are very open-ended in that you can create a lab about practically anything you want. In my Biology SL class, for the first IA my teacher let us design any lab we wanted, the only condition being that it had to do with hermit crabs (random, I know). For the second IA, he required us to incorporate photosynthesis or cellular respiration (or both) into it. The task seems simple, but it is often the more open-ended assignments that are more difficult because you have no idea what you're doing. Good luck! =]

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The syllabus says:

"Draw and labes a diagram of the digestive system showing mouth, oesophagus, stomach, small intestines, large intestines, anus, liver, pancreas and gall bladder. Diagram should show interconnections between these structures"

So there isn't a specific diagram you have to draw, as long as it's a diagram showing all those structures. So something like the picture below would do, just draw the ones in the list above:

image8KP.JPG

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Hi! :D

Could anyone please paste a link or a picture of the digestive system? I mean the one we are required to draw on the exam.

Thanks :)

http://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Digestive_system_diagram_edit.svg/340px-Digestive_system_diagram_edit.svg.png

You do not have to be able to draw all the structures in the image.

"The diagram should show the mouth, esophagus,

stomach, small intestine, large intestine, anus, liver,

pancreas and gall bladder. The diagram should

clearly show the interconnections between these

structures." - Syllabus

EDIT: Too late... :)

Edited by Sammie Backman
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  • 3 weeks later...
Guest -Guns of Steel-

Guys I'm really frustrated, because I'm pretty sure I'm right but my Bio teacher thinks I'm wrong in doing this:

IN the attached Image, you can that the table shows temperature readings for each subject against time. Isn't that bloody well ;Time Vs Temperature for all subjects' but she wants me to write 'Temperature and various subjects'-which I think its not: informative about the table and childish.. :/

Secondly the graph is plotted is in the second attachment, she thinks it should be the same skeleton of dependant on x and independant on y. Well I'm ignoring that, since the graph perfectly well demonstrates the changes and it take a 5 year old to see that the temperature is increasing as time passes. Besides that I hate working hard, yes its tough to make these graphs, and then having my work f*cking cancelled out

I wrote this:

'Though some anomalous readings show variance within 1oC like Subject 8 and some showed extreme variance like subject 1, 7 and 15 with temperature differences more than 3.20 oC'

She wants this:

"Subject 1,7,8 and 15 showed anomalous readings." WTF seriously, is it necessary to speak bad english to be a good at labs!! :o

post-63670-0-50211500-1319250865_thumb.j

post-63670-0-01031500-1319251125_thumb.j

Edited by -Guns of Steel-
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I've never really seen a graph where the dependent variable was on the x axis, heck I've only ever seen one graph where time is the y axis but that was for physics...

Sentence structure seems irrelevant, they both convey the same message...but being more precise in your writing gets the message across much clearer. She basically took your almost 2 line sentence and cut it down to less than half a line, makes things easier for the reader/grader and honestly you want the grader to be able to understand what you say perfectly.

Also if you really want to bring up the 1oC and 3.2oC anomalies you would need to explain how those possibly happened and what they could possibly mean. If you put it the way your teacher suggested you would simply say they were anomalies and could simply conclude them as insignificant error.

And...I personally think both graph/chart titles (your teachers suggestion and yours) are not at all specific enough. The chart has "bicep temperature" which is good, but then you jut have "time" which tells us nothing. Were the people just standing in a hot room so their temperature went up? Time they had their bicep contracted? Time sitting in a cold room? Etc...and yes I know somewhere towards the beginning you say exactly what they are doing and how you are measuring but it's all about precision in lab writing and the titles of the graph and chart aren't very precise.

Oh, you need some uncertainties in there too :o

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  • 1 month later...

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