MAY13 Biology HL TZ2 paper 1 paper 2

[Johanna St]

Yeah the answer to the last question was embryo... that is under the section were it discusses which substances pass from mother to embryo and from embryo to mother. So I am probably wrong on that question, but I must say the wording left the question open to too many interpretations, maybe the IBO will decide to make both answers right in the end ;D

[Megan Dimmick]

Did anyone do Q6 in Section B? I was unsure what they were looking for when they asked to outline how and where plants store energy. I talked about source cells, sink cells, phloem vessel, and converting glucose into starch.

For DNA replication I was debating between C and D ( I don't remember why I discarded answers A and B) but I chose C ( the one with 3-5 and anti parallel strand) mainly because of the term "antiparallel". I also chose the neurotransmitter at synapses because when an action potential is generated, Na goes in and K goes out, but they don't do it simultaneously, and the answers said that they either both diffused in or both diffused out. Did anyone answer Q40 in paper 1? I chose embryo, but I thought none of the answers were correct because HCG is secreted by blastocyst and then placenta. I thought a blastocyst is different from an embryo.

For the first question in paper 1, what did the error bars signify? I said that at 20 the range is the greatest.

I did question 6 and that's what I wrote for the plants storing energy, asked my teacher and she said that should get us the 4 marks as you couldn't really go into too much detail.

Question 40 was really confusing as I thought none of them were right so I guessed But I cant remember what, and for the first question on paper one it was the range is greatest at 20

[timmotytimmoty]

Question nr 40 the answer is EMBRYO, it was on past papers guys What's the answer for DNA replication? Is it adding nucleotide to the last phosphate? because any other answer seems to be incorrect.

[lilianna009]

Question nr 40 the answer is EMBRYO, it was on past papers guys What's the answer for DNA replication? Is it adding nucleotide to the last phosphate? because any other answer seems to be incorrect.

Yup, exactly, I thought so ;].

About the DNA for me it was the answer with adding phosphate. Cause if it goes in 5'-3' direction than how possibly could you have a free phosphate to which a nucleoside binds? For me it's that the phosphate binds to C3, covalent bonds form blah blah. But maybe I'm just making things up .

[madame_lexie]

What was the answer for the genetics pedigree chart question in paper 1? I couldn't work it out - I guessed it's dominant allele.

Even the question about the flies and the deviation from the expected 9:3:3:1 ratio, I didn't know the answer - I chose crossing over but I think it's wrong. I suck at genetics

[lovingbub]

For Paper 1:

-genetics question: the only sensible choices are autosomal dominant and sex linked recessive. Sex linked recessive is impossible because two affected parent have unaffected daughter. Answer is autosomal dominant.

-depolarization question: the question asks about the INITIATION of an impulse, which is caused by sodium (and sodium only) entering the neuron. The mechanism which causes this is neurotransmitter (from the pre-synaptic neuron).

-replication question: to get it right you have to understand the concept of 5' to 3'. The 5' is the phosphate end while the 3' is the ribose end. Therefore nucleotides only assemble themselves by sticking the phosphate to the ribose of the previous one. So the answer is B.

I am pretty sure of these answers. Hope this helps (and don't beat yourself up for just messing up one MC or two. You answered most of them correctly:D)

[Szczebrzeszyn]

I agree with lovingbub's explanations.

Does anyone know what was the answer to the genetics question (the one with flies) about why the genotype ratio was different than expected?

[Hens48]

Pretty sure it was 'crossing' over, that's what I put and what the text books seem to (albeit loosely) suggest.

[kinguncaged1]

For Paper 1:

-depolarization question: the question asks about the INITIATION of an impulse, which is caused by sodium (and sodium only) entering the neuron. The mechanism which causes this is neurotransmitter (from the pre-synaptic neuron).

So in your opinion the answer was the one which involved aceytlcholine?

[Bernardo Silva]

Paper 1? I didn't think it was too bad but after talking to friends and seeing your answers, I probably got a couple wrong. It's okay though, I still think I did well. Nothing overly complicated other than one genetics question where all answers seemed wrong.

Paper 2? I loved that they included so much genetics. I find genetics really easy so those marks were a given. Section B wasn't as nice for me. I did 7 and 8, even though I didn't study the placenta in depth. I skimmed the study guide the night before the exam, expecting it not to show up. I still think it went pretty well. Wrote lots, data questions were pretty easy compared to stuff I had seen in past papers.

Paper 3? It's as if the examiners who made the paper knew exactly what I had studied and what I hadn't. All questions were a godsend, pretty much. I think it went really well. Our options were Further Human Physiology (H) and Neurobiology and Behavior (E).

Overall, it went pretty damn well. Hoping for a 6 if not a 7. That would rock.

[Rafie Izwan]

i did very well in paper 1 and paper 2 section A.. Section B i did pretty good for both question i picked but am screwed at the last question at C..