Protein Synthesis

Proteins synthesis is the process of using the information stored in DNA to make proteins. It generally happens in two steps: Transcription and Translation. As a reminder...

Proteins are made of Amino Acids
- Ribosomes combine amino acids into chains called polypeptides.
- Polypeptides are combined in the Golgi Apparatus to make full proteins.
Proteins determine your traits
- Proteins have very specific shapes, some shapes reflect/absorb light differently and create different colors
- Some proteins regulate how the body works. Insulin is a protein that regulates blood sugar; there are proteins in the brain that affect how we learn and respond to stimuli.
DNA stores the information to make all of your proteins, but it doesn't leave the nucleus...but RNA can.
- A gene is a section of DNA that codes for 1 polypeptide/protein/trait
  - a gene can be 100s to 1000s of base pairs long
- Each chromosome in your cells holds on average about 1000 genes (21-25,000 genes in the genome spread out over 23 unique chromosomes)

Transcription

Just as a script is the written-out form of a play or movie, Transcription is the process of writing out the recipe for a protein.

RNA Polymerase, an enzyme, opens DNA at a specific gene and begins to read.
- As it reads, it copies the information into mRNA (m=messenger)
The messenger RNA leaves the nucleus and travels to a ribosome.
- Sometimes, before it leaves the nucleus, it is altered or modified by other enzymes or RNA to make a slightly different protein.

Translation

Translation is the process of reading RNA and combining amino acids in a chain. Think of translation as converting the language of DNA/RNA into the language of proteins. DNA is made of nucleotides with specific bases (ACTG), proteins are made of specific amino acids.

mRNA travels to the ribosome where it is scanned through the middle kind of like a credit card.
- The ribosome reads the mRNA 3 bases at a time in segments called codons.
  - AUG - start codon
  - GUA - Valine (1of 20 amino acids coded for by 60 different combinations of A,U,G, and C)
  - UGA - stop codon (also UAG and UAA)
  - Search the web for "Codon Table" for more specifics
tRNA molecules are floating in the cytoplasm nearby.
- they have 3 bases (anticodon) at one end of the molecule and a specific amino acid attached at the other end.
As each codon passes through the ribosome, the complementary tRNA enters the ribosome and drops off its amino acid.
rRNA (ribosomal) helps to connect each amino acid together making a chain (polypeptide)