Rishi's Biology Thread

[grannysmith]

1) they stay around longer; neurotransmitters are rapidly broken down/absorbed after binding to a post synaptic neuron, to prevent over stimulation; generally affect gene expression
2) hormones are secreted by endocrine cells into the internal environment and exert an effect on target cells with specific receptors, whereas pheromones are secreted by exocrine cells into the external environment and exert an effect on organisms of the same species

[Rishi97]

1) Describe the steps involved in forming a functional enzyme comprising two polypeptide chains
2) What is the significance of the anti-parallel nature of DNA?

Thanks heaps

[nhmn0301]

1) Describe the steps involved in forming a functional enzyme comprising two polypeptide chains
2) What is the significance of the anti-parallel nature of DNA?

Thanks heaps

1) enzymes can have tertiary or quaternary structure. If an enzyme is composed of 1 polypeptide chain, it's tertiary. If an enzyme is composed of 2 polypeptide chains, it's quaternary. So basically, 2 polypeptide comes and aggregates, stabilising the structure by Hydrogen bond etc. (I only know this much details about the process ).
2) Cause you are doing Chem 3/4, you probably remember that the phosphate is bonded to the 5' Carbon whilst the nitrogenous base is bonded to the 1' Carbon. On a piece of paper, try and draw 2 single DNA strands from 5' -> 3'. If you draw it this way, do you see that it's impossible for the nitrogenous base to "face" each other and create H-bond between them? Hence, this is why you need anti-parallel structure (this is not examinable in Bio but probably in Chem )

[Yacoubb]

1) Describe the steps involved in forming a functional enzyme comprising two polypeptide chains
2) What is the significance of the anti-parallel nature of DNA?

Thanks heaps

1. This is a question that if asked on an exam, would probably be broken up into a, b, c, etc. You'd probably be asked to explain the synthesis of individual polypeptide chains, and how these two polypeptide chains then join together in a particular manner, to form an overall 3-D shape to the enzyme with an active site of a specific conformation (as you know, specifically complementary to the shape of the specific substrate in which it binds to). So, I'd say in VERY summarised terms:
1. Each polypeptide chain comprising the enzyme are synthesised via the protein-synthesis pathway (i.e. transcription and translation).
2. The polypeptide chains are joined together in a specific manner by (not 100% sure, but I think) covalent (peptide) bonds.
3. The protein molecule adopts an overall 3D shape with an active site of a specific conformation specifically complementary to the shape of the substrate in which it joins to.

2. If this was ever asked, it would be a suggest question because this isn't really examinable in the Biology syllabus. The nitrogenous bases chemically bond to their corresponding, complementary base by hydrogen bonds, which ultimately connects the two strands of polynucleotides together to form DNA. By having two anti-parallel strands of DNA, the bases are able to face each other in a manner that the bases can chemically bond together, and thus allow the DNA molecule be double-stranded. Again, knowing this in Chem is probably important, but it's not assessed in Biology to this degree.

[nhmn0301]

1. This is a question that if asked on an exam, would probably be broken up into a, b, c, etc. You'd probably be asked to explain the synthesis of individual polypeptide chains, and how these two polypeptide chains then join together in a particular manner, to form an overall 3-D shape to the enzyme with an active site of a specific conformation (as you know, specifically complementary to the shape of the specific substrate in which it binds to). So, I'd say in VERY summarised terms:
1. Each polypeptide chain comprising the enzyme are synthesised via the protein-synthesis pathway (i.e. transcription and translation).
2. The polypeptide chains are joined together in a specific manner by (not 100% sure, but I think) covalent (peptide) bonds.
3. The protein molecule adopts an overall 3D shape with an active site of a specific conformation specifically complementary to the shape of the substrate in which it joins to.

2. If this was ever asked, it would be a suggest question because this isn't really examinable in the Biology syllabus. The nitrogenous bases chemically bond to their corresponding, complementary base by hydrogen bonds, which ultimately connects the two strands of polynucleotides together to form DNA. By having two anti-parallel strands of DNA, the bases are able to face each other in a manner that the bases can chemically bond together, and thus allow the DNA molecule be double-stranded. Again, knowing this in Chem is probably important, but it's not assessed in Biology to this degree.

Hi Yacoubb, I'm pretty sure there's no peptide bond in the Quaternary structure here. It is maintained by the same type of bonds in Tertiary . But again, we will not turn this into a Chemistry thread!

[Yacoubb]

Hi Yacoubb, I'm pretty sure there's no peptide bond in the Quaternary structure here. It is maintained by the same type of bonds in Tertiary . But again, we will not turn this into a Chemistry thread!

Yeah I was doing an exam once for Biology, and it asked what type of bond it was, and the answer said covalent bond. I just assumed it was peptide given it was a protein. But yeah, this isn't knowledge needed for Biology

[Rishi97]

During DNA Replication:
A) Messenger RNA (mRNA) is produced
B) reverse transcriptase enzymes play an important role
C) bonds between phosphate and sugar molecules break
D) each of the DNA strands acts as a template strand

I thought the answer was A but I was wrong so could someone please explain why
Thanks

[grannysmith]

The answer should be D. mRNA is produced during protein synthesis (transcription).

[dankfrank420]

During DNA Replication:
A) Messenger RNA (mRNA) is produced
B) reverse transcriptase enzymes play an important role
C) bonds between phosphate and sugar molecules break
D) each of the DNA strands acts as a template strand

I thought the answer was A but I was wrong so could someone please explain why
Thanks

A is incorrect, as mRNA is produced in transcription

B is incorrect, as reverse transcriptase is an enzyme that helps a DNA strand be "reverse transcripted" from a pre-existing RNA strand.

C is incorrect, as the breaking of phosphate and sugar bonds indicates the breaking down of a nucleotide, which does not occur in DNA replication

By process of elimination, D is correct.

[Rishi97]

A is incorrect, as mRNA is produced in transcription

B is incorrect, as reverse transcriptase is an enzyme that helps a DNA strand be "reverse transcripted" from a pre-existing RNA strand.

C is incorrect, as the breaking of phosphate and sugar bonds indicates the breaking down of a nucleotide, which does not occur in DNA replication

By process of elimination, D is correct.

Thanks dankfrank that makes soo much more sense now

[Rishi97]

-What are the two ways meiosis produces variation?

Thanks

[Scooby]

-What are the two ways meiosis produces variation?

Thanks

- Genetic recombination in prophase I
- Independent assortment in metaphase I and to a lesser extent metaphase II

[Rishi97]

- Genetic recombination in prophase I
- Independent assortment in metaphase I and to a lesser extent metaphase II

Thanks Scooby
By genetic recombination, you mean 'crossing over' right?

[Reus]

Thanks Scooby
By genetic recombination, you mean 'crossing over' right?

Exactly that 

[Rishi97]

Describe 2 features of restriction enzymes that vary in the way they cut DNA