Yacoubb's Bio 3+4 Questions

[Yacoubb]

Carbohydrate: C H O
Proteins: C H O N (sometimes Sulfur)
Lipids: C H O
Nucleic Acids: C H O Phosphorus

[Stick]

That isn't entirely correct. Some proteins contain phosphorus and the bases of nucleic acids contain nitrogen.

[Yacoubb]

That isn't entirely correct. Some proteins contain phosphorus and the bases of nucleic acids contain nitrogen.

But that is basically what is 100% required for proteins to be deemed proteins. And I forgot nitrogen in the N-containing bases

[Stick]

But that is basically what is 100% required for proteins to be deemed proteins. And I forgot nitrogen in the N-containing bases

Hmm... All proteins contain carbon, hydrogen, oxygen and nitrogen, some contain phosphorus, but you can distinguish a protein from another type of biomacromolecule with the presence of sulfur.

[Yacoubb]

Proteins must contain Nitrogen, Carbon, Hydrogen and Oxygen. However, they can also contain Sulfur/Phosphorus. Nucleic Acids contain Carbon, Hydrogen, Oxygen, Phosphorus and Nitrogen.

[Shenz0r]

Proteins must contain Nitrogen, Carbon, Hydrogen and Oxygen. However, they can also contain Sulfur/Phosphorus.

Rather than just remembering it like that, it's important to know why.

Whether a protein contains Sulfur/Phosphorus is ultimately dependent on what sort of amino acids are present in the protein's primary structure.

Due to the carboxyl (-COOH) and amine (NH₂) groups, which comprise a part of every amino acid, you definitely have to have nitrogen, carbon, hydrogen and oxygen in proteins.

Amino acids have different R-variable groups, and some will have Sulfur/Phosphorus in these groups (i.e Cysteine) whereas other amino acids don't (i.e Valine). If you have an amino acid which has sulfur/phorphorus in the R-variable group, inevitably you will get a protein molecule which has these elements in it. If you don't have such an amino acid, then you'll just have carbon, nitrogen, oxygen and hydrogen.

[ealam2]

Just a quick question.

Why can't you work out how much of a protein will be present by measuring the amount of mRNA that codes for that particular protein?

[Scooby]

There's no amino acid that contains phosphorus in its R group. Phosphorus can later be added to a protein but doesn't make up any amino acids 

[alondouek]

Just a quick question.

Why can't you work out how much of a protein will be present by measuring the amount of mRNA that codes for that particular protein?

Because the entire mRNA sequence doesn't necessarily code. In unit 4, you'll learn about a process called RNA splicing.

Basically, the DNA template strand isn't copied straight to the mRNA that is read in translation. In a gene, within the coding region, there are 'sub-regions' known as introns and exons. Introns do not code for anything, while exons are coding sequences. The mRNA that is transcribed from the DNA template is known as pre-mRNA, and it contains both intron and exon sequences. However, the process of RNA splicing occurs and the intron regions are removed, and the resulting mRNA strand (which consists only of exon sequences) is capped by a Poly-A (as in AAA repeating) tail. This is the mRNA sequence used in translation.

tl;dr: Technically, not all of the mRNA codes for something. Furthermore, certain codons code for a stop sequence, which is not an amino acid. Hence it would be inefficient to both count the mRNA codons and factor in conditions to account for stop codons.

[ealam2]

There's no amino acid that contains phosphorus in its R group. Phosphorus can later be added to a protein but doesn't make up any amino acids 

So would that be post translational modification? (Thanks by the way for answering.)

[ealam2]

Because the entire mRNA sequence doesn't necessarily code. In unit 4, you'll learn about a process called RNA splicing.

Basically, the DNA template strand isn't copied straight to the mRNA that is read in translation. In a gene, within the coding region, there are 'sub-regions' known as introns and exons. Introns do not code for anything, while exons are coding sequences. The mRNA that is transcribed from the DNA template is known as pre-mRNA, and it contains both intron and exon sequences. However, the process of RNA splicing occurs and the intron regions are removed, and the resulting mRNA strand (which consists only of exon sequences) is capped by a Poly-A (as in AAA repeating) tail. This is the mRNA sequence used in translation.

tl;dr: Technically, not all of the mRNA codes for something. Furthermore, certain codons code for a stop sequence, which is not an amino acid. Hence it would be inefficient to both count the mRNA codons and factor in conditions to account for stop codons.

Okay don't know about any of that but thanks for answering. I should come back to this next time.

[pi]

Okay don't know about any of that but thanks for answering. I should come back to this next time.

You do more on mRNA and all the jazz in Unit 4, so don't be worried

[Daenerys Targaryen]

Just a quick question.

Why can't you work out how much of a protein will be present by measuring the amount of mRNA that codes for that particular protein?

Also because some mRNA are reused; recycled if you like.

[Scooby]

So would that be post translational modification? (Thanks by the way for answering.)

Yeah, that would be considered a post-translational modification. You don't really have to know anything about that though

[hardworker]

Can anyone please help me with these questions from chapter 2 review (Nature of biology book two, fourth edition).

Q5-The folded internal membranes of mitochondria have many stalked particles on their innermost surfaces (figure 2.31). Given the function of mitochondria and where most of the reactions occur, of what advantage might the presence of these particles be for the production of ATP in the organelle?


Q6 In figure 2.31, you may have noted the holes in the folds of the inner membrane of mitochondria. Explain a possible function of these holes