Untitled Quiz

Study Notes

Proteins are composed of amino acids.
There are 20 different amino acids.
Different proteins are made by combining these 20 amino acids in different combinations.
Amino acids come from the food we eat.
Proteins we eat are broken down into individual amino acids and then rearranged into new proteins.
Proteins are manufactured by ribosomes.

Transcription - DNA → RNA - Translation - RNA → Protein (Chain of amino acids)

Transcription is the process of copying a complementary single strand of mRNA from part of the DNA in the nucleus.
RNA polymerase is an enzyme that unwinds the DNA strand and reads one strand of DNA bases to make the RNA strand.
mRNA leaves the nucleus, and the DNA strands coil back up.
RNA polymerase I transcribes rRNA.
RNA polymerase II transcribes mRNA.
RNA polymerase III transcribes tRNA.
If DNA is TACCAGTTT, mRNA will be AUGGUCAAA.

mRNA editing: involves cutting and splicing mRNA before it leaves the nucleus.
Introns are "junk DNA" that doesn't code for proteins and are cut out.
Exons are "good DNA" that codes for proteins. They stay and are expressed.
Introns are removed, and exons are spliced together.
**Edited mRNA is sent out of the nucleus to the ribosome. **
The exons can be spliced together in different sequences to produce different mRNA's = different proteins.

Translation is the process of translating mRNA codons into a protein (amino acid chain).
It takes place on ribosomes in the cytoplasm.

Every 3 bases on mRNA represents a code for an amino acid = codon.
Amino acids are abbreviated most times by using the first 3 letters of the amino acid’s name: Met = methionine, Leu = leucine.

Edited mRNA attaches to a ribosome.
As each codon of the mRNA molecule moves through the ribosome, the tRNA brings the proper amino acid to the ribosome.
The anticodon on tRNA is complementary to the mRNA codon.
The amino acids are joined together by chemical bonds called peptide bonds to build an amino acid chain called a "polypeptide".

A series of three adjacent bases in an mRNA molecule codes for a specific amino acid—called a codon.
Each tRNA has 3 nucleotides that are complementary to the codon in mRNA.
Each tRNA codes for a different amino acid.

Start codons are found at the beginning of a protein.
There is only one start codon: AUG (methionine)
Stop codons are found at the end of a protein (end of a polypeptide chain).
Three stop codons that do not code for any amino acid, therefore making the process stop: UAA, UAG, UGA.

As the ribosome moves along the mRNA, more tRNA molecules deliver their amino acids.
The amino acids are linked together by peptide bonds, forming a growing polypeptide chain.
As the ribosome reaches a stop codon, the polypeptide chain is released.

The cell uses the DNA "master plan" to prepare RNA "blueprints."
The DNA molecule remains within the safety of the nucleus, while RNA molecules go to the protein-building sites in the cytoplasm—the ribosomes.