Okay, so that is our catabolic reaction. We broke down glucose, usually in the presence of oxygen. We got between 30 and 32 ATP.
What are we going to use those ATP for? We're going to use those ATP to produce big biomolecules that can include big DNA molecules, that can include big proteins. So we need to make the nucleotides to make DNA and RNA, and then we need to assemble the nucleotides together to form DNA or RNA.
We need to make the amino acids, and then we need to assemble the amino acids together to form a protein. All of those are anabolic reactions. They require ATP that came from cellular respiration, and they start with small molecules, and the small molecules, when we add the energy of ATP, are built up into bigger molecules.
So we're going to focus on, as our example, protein synthesis. So there are two important steps in protein synthesis, transcription and translation. And we could say a lot more than we're going to about transcription and translation.
And we're going to reach back into our genetics lab just a little bit here. So transcription is where we start with the gene in the nucleus, a sequence of nucleotides in DNA, and we use those nucleotides as a template. to make a messenger RNA molecule.
A messenger RNA molecule is a polymer. It's not DNA, it's RNA instead. So the sugar in the nucleotides is ribose, not deoxyribose, and instead of the base thymine, we are using the base uracil.
But other than that, RNA and DNA are similar molecules. The messenger RNA is only, is a lot shorter than the big DNA molecule that's part of a chromosome. It's just enough nucleotides to specify how to assemble amino acids to build one particular protein.
So one gene is used as a template. One segment of this bigger chromosome, of this big giant DNA molecule, one segment is used as a template to make the messenger RNA molecule. And that segment of DNA is the gene, and then the messenger RNA molecule is like an expendable version of the gene. that can leave the safe nucleus and go out into the cytoplasm where it will ultimately be broken down and destroyed but before that happens it can be read by a ribosome and used to make a protein that's so transcription is where we make a molecule of messenger RNA using a DNA template that happens in the nucleus then the messenger RNA molecule leaves the nucleus goes into the cytoplasm and bind is bound by a ribosome and the ribosome uses the messenger RNA the sequence of nucleotides in the messenger RNA as instructions for which amino acids to assemble to make a protein and then the protein can do just about anything the cell needs it to do depending on what protein it is. So I think of it as a transcription is you're going you're staying within the same language but you're making another copy you're staying within the language of nucleotides.
L-A-N-G-U-A language of nucleic acids or nucleotides, right? Like you transcribe a book or something or a report, like you've got your rough draft with all your scribbles and eraser marks and then you're going to transcribe that into your final version that you're going to turn in here. staying, you're going from English to English, right, you're staying in the same language, you're just transcribing it into a different form, or maybe you're typing it up, that would be transcription.
You're staying with the language of nucleic acids, we're just going from DNA to RNA, transcription. Translation, we're changing languages, we're going from the language of nucleic acids to the language of proteins. So instead of a polymer of nucleotides, we're going to have a polymer of amino acids. So we use the messenger RNA. to determine which amino acids we link together to form a protein.
So it's like we're translating from one language to another. That's where translation comes from. We're going from the language of nucleotides to the language.
of amino acids.