AQA BIOL5 ~ 17th June 2013 ~ A2 Biology

It's complementary to the mRNA, not the amino acid. The tRNA with a certain anticodon is 'specific' to the amino acid.


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I understand that.. I mean if for example, if a question asks: whats the codon for the amino acid transported by the tRNA with the anticodon CGG? Would it be CGG or GGC?



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It would be neither of the ones that you mentioned. Instead it would be GCC, given that guanine ia conplementary to cytosine and vice versa

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Sorry thats what I meant GCC* so the amino acid attached to the tRNA is complementary to the tRNA's anticodon, and is also then the original DNA sequence?


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How is everyone revising at this stage? DREADING the essay :'(

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Basically your trna molecule has an anticodon to one end and the amino acid binding site to the other. I wouldnt really say that the anticodon is complimentary to the amino acid as it is in now way bonded to it. You must mean that it is the anticodon of the trna that is complimentary to the codon of mrna. However it is each codon on mrna (and thus anticodon of trna) that corresponds to a given amino acid. You sequencence of organic bases of mrna is complementary to the sequence of organic bases of the strand of dna that forms the template

Okay thanks,.. Making my question in a different way: is simply the anticodon on the trna, the code for the amino acid which it 'carries' ? Sorry for insisting on this...


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Yeah that's a better way to word it


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There are some Na+ channels open, but these are not the voltage-gated ones; these ones are just... there, letting the Na+ do it's thing

The negative charge inside the axon is a result of:
- The sodium-potassium pump actively transporting 2 K+ in for every 3 Na+ out (so there are more positive ions moving out of the axon)
- Negatively charged proteins in the axon
- There are more (NOT voltage-gated) channels for K+ than there are for Na+, so the axon membrane is more permeable to K+. This means that K+ diffuses along the concentration gradient (at a greater rate than Na+ diffuses in) , taking its positivity with it

Hope that makes sense!

Hey there Yes, there Na+ voltage gated ion channels that are open as are K+ voltage gated ion channels. However, there are many more K+ voltage gated ion channels open than Na+ voltage gated ion channels. I believe that at the given point in time, the plasma membrane is approximately 100 times more permeable to K+ ions than Na+ ions. These means that the majority of K+ ions diffuse down a concentration gradient from an area of high concentration (within the interior of the axon) to an area of low concentration (in the surrounding tissue fluid). It is important to note down that this doesn't occur at the point of resting potential (approximately -70mV) but rather when establishing it (i.e. following an action potential). The movement of ions occurs until the electrical and chemical gradient formed across the plasma membrane are balanced, as to ensure that there is no net movement of ions

Hope that helps!

When doing min number of nucleotide base/amino acid calculations does anyone know if we are supposed to take start/stop codons into consideration?

thanks to both of you. I think I'll stick to neither voltage gated channels being open as that was what I was taught, despite the book saying something different. However is it even necessary to mention the word 'voltage' at all?

It's usually just times or divide by three, which is the safest option, but we were told if you did take into consideration the start/stop codes then you'd usually be awarded the mark.

Hey Guys,

http://quizlet.com/11320494/learn/

^^ The above link is something I found really useful, especially to see how well I know the content! Hopefully you guys find it useful too

Hey Guys,

http://quizlet.com/11320494/learn/

^^ The above link is something I found really useful, especially to see how well I know the content! Hopefully you guys find it useful too

Yeah I saw that in one examiner note thing so I think I'll just disregard them




That quiz was great thanks I got mainly little things wrong like acetylcholinesterase instead of cholinesterase and it highlighted how I need to go over gluconeogenesis and stuff :P

Very useful, thanks

Your Welcome guys! From doing this i found out one thing i'm really failing on! SPELLING :| I will try and search for more resources, i like learning it this way cause then you wont really get bored!

I always thought it was Sacromere!!