BIO CH 13

RNA: Ribonucleic acid

consists of a single long chain of nucleotides.

RNA's nucleotides consist of a:

*sugar called ribose ribose c₅ h₁₀ 0₅

*phosphate group deoxyribose c₅ h₁₀ 0₄

*nitrogenous base

RNA's bases are:

*Guanine

*Cytosine

*Adnine

*Uracil (not thymine but uracil has the same bonding shape as thymine)

types of RNA:
*messenger RNA (mRNA)

*carries the DNA message from the nucleus to the ribosome in the cytoplasm

*is a single straight strand of RNA nucleotides
*ribisomal RNA (rRNA)
*makes up part of a ribosome
*transfer RNA (tRNA)
*carries an amino acid to the correct site on the mRNA strand
*has a cloverleaf shape
*the 3 bases found at one end of the tRNA ase called "anticodon" these will bond with 3 complementary bases on the mRNA strand called "codon"

protein synthesis

*the process of making proteins
*the DNA molecule contains all the "directions" for making all the proteins your body needs
*each strand of DNA codes for many different proteins
*there are 2 main steps: transcription & translation.

step 1:
making a copy (transcribing) of the DNA code for the needed protein

*occurs in the nucleus of the cell
*the section of DNA that codes for the needed protein unzips
*RNA polymerase is the enzyme that binds to regions on the DNA called "promoters" (specific DNA base sequences)
*it then begins to unzip the DNA section
*only one of the unzipped strands is used as a template/pattern
*this one strand contains the code for making the needed protein
*RNA nucleotides bond to the DNA strand that codes for the needed protein
*G bonds with C
*U bonds with A
*'T' on DNA will bond with 'A' on RNA
*once the RNA strand is completley made it moves away from the DNA strand
*the RNA strand is "edited" befor tit leaves the nucleus
*introns are the peices that are removed from the RNA strand
*exons are the pieces the are needed and are spliced together once the introns have been removed
*the edited RNA is now called "messenger RNA" and moved out of the nucleus into the cytoplasm

every 3 bases in a row on the RNA strand make up a "coden" each codon codes for a certain amino acids
*there are over 20 different amino acids
*proteins are made of many amino acids bonded together

step 2: translation
the code that mRNA transcribed from DNA now needs to be translated so that the amino acids are arranged in the correct sequence

*occurs in the cytoplasm
*a ribosome attaches to the mRNA strand and moves down the strand until it finds the start codon "AUG"
*as the ribosome moves down the mRNA strand from the start codon tRNA anticodons (bases) bond to the mRNA codons (bases)
*the amino acids that the tRNA's carry bond together
*the bonded amino acid chain (polypeptide chain) breaks away from their tRNA's
*the polypeptide chain will fold into its final shape or bond with other chains to form the protein