Biology SL/HL help

[Sandwich]

The unit given to you is in macrometers, you measure how many centimeters that 1 macrometer scale bar is. Say its 4 cm.

Every 4 cm of that picture is 1 macrometer in reality.

13.2/4= 3.3 macrometers is the actual length of the cell.

magnification= measured size / actual size.

measured size= 13.2*1000= 13200 macrometers

magnification= 13200/ 3.3 = 4000

The picture is 4000 times the actual size.

Please check if this is correct.

A micrometre is actually a millionth of a metre, so by my reckoning you should multiply 13.2 by ten thousand rather than one thousand to convert from cm to micrometres. I think! I'm not that fab at these conversions.

Anyway, Masochist: did you plug in the correct measurement for the '4cm' that Maha invented in her answer? I'm assuming 4cm was a guess!

[Mahuta ♥]

It is a guess, and I think I got the scale wrong..

so 10000 micrometers is 1 cm..yeah?

[lobsta]

hey guys i have a question about Biology HL, i only just started studying , and since paper 1 and 2 is on monday and 3 on tuesday, i was wondering is 1 day enough to study the options? is it possible for me to just study the options the day before the exam? I am probably going to pick ecology and conservation as 1 option, i dont know about the 2nd one though... which one is the easiest? seems like perhaps 'neurobilogy and behavior' and 'ecology and conservation' to me... anyone can help?

[ABC123456]

hey guys i have a question about Biology HL, i only just started studying , and since paper 1 and 2 is on monday and 3 on tuesday, i was wondering is 1 day enough to study the options? is it possible for me to just study the options the day before the exam? I am probably going to pick ecology and conservation as 1 option, i dont know about the 2nd one though... which one is the easiest? seems like perhaps 'neurobilogy and behavior' and 'ecology and conservation' to me... anyone can help?

I'm picking Neurobiology and Behavior since I took Psychology and my Psychology teacher went over the biological aspect in more detail than my biology teacher(who was of no help anyway) and I'm also thinking of doing Evolution. The teacher who retired last year knew his stuff a whole lot more, and he told us not to do Ecology because many students think it is fairly easy when they answer the first few questions, but it gets a lot harder. I don't know though, that was his viewpoint. I also have this question then. I'm picking Neurobiology and if I have time I might try and study 2 more options just in case one isn't ideal, but what is another option that is good to do?

[lobsta]

Yea my bio teacher who was also no help got pregnant this year, meaning we didnt do any bio this year. Hence, it was all up to us, which in my case I even forgot how to spell biology. Just started studying today, and aiming for a 3 or at best a 4. I dont know about those option things... but everyone recomends me that neurobiology and ecology... I dont think i will have time for a 3rd... so i guess ill just have to stick with those 2 options and hope they are good. Do you know if its possible to study options in 1 night? i looked at the textbook and it isnt too long, 15 pages each option and seems managable. Since i didnt study alot, i am thinking of doing at best 20/40 in paper 1, try to do my best and just improvize in paper 2 and study on monday after paper 1 and 2 for paper 3 and try to do something there as well... my IA was also 33/45 so i hope with these grades i can manage to get a 3 or if something magically happens and i do good, perhaps a 4...

[Mahuta ♥]

You are taking Biology HL, you should have chosen option H.

I found option H very easy.

If you are good at memorizing things, then consider option F and Neurology one.

And no, one day is not enough for options..give it another day or a half.

[102jon]

You are taking Biology HL, you should have chosen option H.

I found option H very easy.

If you are good at memorizing things, then consider option F and Neurology one.

And no, one day is not enough for options..give it another day or a half.

Would you be able to explain the digestion and liver stuff in a little detail? I have not studied that stuff yet, but as far as the rest of Option H goes i am fairly ready. Thank you.

[Mahuta ♥]

Give me specific points on the syllabus so that I can explain them.

I can't just explain the whole digestion and the whole liver, that would take like a whole page, lol.

[CommeDesEnfants]

Is the descending limb of the loop of Henle permeable to ions? One of my sources says yes, some say slightly and one says not at all.

[Sandwich]

The descending loop is permeable to H2O and the ascending loop is permeable to Na+. It's part of how the concentration gradient is built up in the medulla of the kidney so H2O can be extracted in the collecting duct via the Aquaporin 2 channels when ADH is around.

[pomoni]

*TOPIC 8 (8.1.4/8.2.5)---Kreb's Cycle and Calvin's cycle.*

Mahuta...do you know anything about Kreb's Cycle/Calvin Cycle??

Oh my god yes! One of my favorites.

It would help if you have the diagrams infront of you now.

Krebs Cycle:

• After the link reaction, you have acytelcoA, a 2 Carbon molecule with the coA enzyme.
  
• The Cycle starts with a 4carbon.
  
• The 2carbon is added to it so: 2+4=6 we get a 6 carbon molecule.
  
• The 6 carbon is changed into 5 carbon. Therefore, we must reduce the carbon number by removing CO₂, so CO₂ is lost. Everytime a CO₂ is lost, a H₂ is lost as well. So you have the NAD⁺ + H₂----> NADH⁺ + H⁺.
  
• The 5 carbon is changed into 4carbon by the exact same process, CO₂ and NADH⁺ + H⁺ formed.
  
• The 4 carbon formed isnt the same as the one we started with, so to get it back to the first one, we remove 2H_2. One is taken by the NAD⁺ and the other by FAD.
  
• ATP is formed as well in this process.
  
• So to sum up the krebs cylce produces the following: 1 ATP, 1 FADH₂, 3NADH⁺ + H⁺, 2CO₂
  

Calvin's Cycle:

• Calvin Cycle is the independent reaction part of photosynthesis.
  
• We start with a 5 carbon sugar called Ribulose Bisphosphate but you can call it RuBP.
  
• RuBP chnages to 2 molecules of 6 carbon, so a CO₂ is added.
  
• The 6 carbon compound(organic acid) is called Glycerate 3-phosphate(a 6 carbon with 3 phosphates).
  
• This is done by RUBISCO ENZYME.
  
• Glycerate 3-phosphate is turned into a carbohydrate called triose phosphate (by reduction = addition of Hydrogen).
  
• This happens by removing 2 phosphates, hence, 2ATP--->2ADP + P.
  
• Also, 2 hydrogens are ADDED, so 2NADPH----> 2NADP^+_.
  
• You have 6 molecules of triose phosphate formed. 5 of which are regenerated into RuBP. One molecule is used to form glucose phosphate to use for biomass, storage..etc..etc.
  

The whole purpose of the Calvin's Cycle is to convert CO₂ to a carbohydrate. This how we get glucose as a product of photosynthesis. This is also why we say plants generate their own nutrition.

If there's any part you want clarified dont hesitate to ask me, because I dont feel I made it that clear.

I read this old post and I still don't really understand the Calvin cycle. Are we supposed to memorize all the steps? Or is it enough if we know thhe roles of Rubisco and RUBP?

[Mahuta ♥]

You are suppose to know all the steps because they can ask you in an 8 mark question describe the light independent reaction.

Put the cycle diagram in front of you and take it step by step you will see that I just explained the steps of the cycle.

Like I said there, if there is a certain point you don't understand, ask.

[pomoni]

"•We start with a 5 carbon sugar called Ribulose Bisphosphate but you can call it RuBP.

•RuBP chnages to 2 molecules of 6 carbon, so a CO2 is added."

I don't understand this. The RuBP has 5 carbon right? So when one carbon is added, you end up with 6 carbon. But then how can it be TWO molecules of 6 carbon?

(Sorry if this sounds too stupid )

"•Glycerate 3-phosphate is turned into a carbohydrate called triose phosphate (by reduction = addition of Hydrogen).

•This happens by removing 2 phosphates, hence, 2ATP--->2ADP + P.

•Also, 2 hydrogens are ADDED, so 2NADPH----> 2NADP+."

So basically, are we reducing the GP and the NADPH to be able to turn GP into a triose phosphate?

Thanks alot

[Mahuta ♥]

"•We start with a 5 carbon sugar called Ribulose Bisphosphate but you can call it RuBP.

•RuBP chnages to 2 molecules of 6 carbon, so a CO2 is added."

I don't understand this. The RuBP has 5 carbon right? So when one carbon is added, you end up with 6 carbon. But then how can it be TWO molecules of 6 carbon?

(Sorry if this sounds too stupid )

Nope it doesn't sound stupid, lol.

I am sure I meant something then, but re-reading it, it's not that clear, maybe I was describing two molecules at the same time.. , or I meant 2 3carbon molecules.

But yeah 5 carbon sugar..you add a CO2 it become a 6 carbon sugar.

"•Glycerate 3-phosphate is turned into a carbohydrate called triose phosphate (by reduction = addition of Hydrogen).

•This happens by removing 2 phosphates, hence, 2ATP--->2ADP + P.

•Also, 2 hydrogens are ADDED, so 2NADPH----> 2NADP+."

Yes, exactly.

[pomoni]

Okay I have one more question: in topic 7.4.3 it says "state that translation consists of initiation, elongation, translocation and termination" but the book doesn't even mention the name "translocation". Can you please explain to me what that is? o.O

Thanks in advance. =D

[Mahuta ♥]

Honestly, we weren't told that part and I wasn't bothered to look it up, because I have not seen it anywhere. Whenever the question says "describe the process of translation" the markscheme only mentions the 3 steps mentioned in the book.

So, I am afraid I don't know the answer to that.

But I can refer you to this:

Translocation

[pomoni]

The link isn't working o.O weirdo lebanese connection

anyways if you say they don't put it in the markscheme then whatever it's fine!

Thanksssss again =)

[sweetnsimple786]

If it's in the syllabus, it might just show up.. here's the site

http://www.molecular-plant-biotechnology.info/genetic-translation/eukaryotic-translation.htm

Good luck!

[soadquake981]

Translocation is when the growing polypeptide moves through the ribosome so that another amino acid can be added to it. It occurs after each amino acid is added.

[lobsta]

Hey guys i have some calculation questions , I am trying to predict what i might get for bio... So: If i get a 33/45 for my IA, 15/40 for paper 1, 30/72 for paper 2 and 10/40 for paper 3 , you guys think i will get a 3. I calculated it with the 2009 boundaries and it comes up something like 45, i know that is enough for a 3, perhaps even a 4, but i just cant be sure