RNARNA

Differences between RNA and DNA ?Differences between RNA and DNA ?

RNA vs DNARNA vs DNA

Strand.Strand. Pentose sugar.Pentose sugar. Base pair.Base pair. Fx.Fx.

RNA properties:RNA properties:

RNA = nucleotide bases RNA = nucleotide bases + 5 carbon sugar + 5 carbon sugar (ribose instead of (ribose instead of deoxyribose) + deoxyribose) + phosphate phosphate

RNA has 4 types of RNA has 4 types of nucleotide bases: A, C, nucleotide bases: A, C, G, U (U replaces T) G, U (U replaces T)

RNA is usually a single RNA is usually a single strand, not a helix strand, not a helix

RNARNA

nucleotide bases + 5 carbon sugar nucleotide bases + 5 carbon sugar (ribose instead of deoxyribose) + (ribose instead of deoxyribose) + phosphate phosphate

RNA has 4 types of nucleotide bases: A, RNA has 4 types of nucleotide bases: A, C, G, U (U replaces T) C, G, U (U replaces T)

RNA is usually a single strand, not a RNA is usually a single strand, not a helix helix

Types of RNATypes of RNA

  Messenger RNA (Messenger RNA (m-RNAm-RNA) = An RNA copy ) = An RNA copy of a gene of a gene 

Transfer RNA (Transfer RNA (t-RNAt-RNA) Transfer amino acids ) Transfer amino acids to ribosome; have anticodons which match to ribosome; have anticodons which match the m-RNA codons. the m-RNA codons.

Ribosomal RNA (Ribosomal RNA (r-RNAr-RNA) Ribosomal ) Ribosomal structure; also includes the enzyme structure; also includes the enzyme peptidyl transferase (makes peptide peptidyl transferase (makes peptide bonds)bonds)

The transcribed code is carried from the The transcribed code is carried from the nucleus to the ribosomes by messenger nucleus to the ribosomes by messenger RNA (m-RNA) RNA (m-RNA)

The ribosomes contain ribosomal RNA (r-The ribosomes contain ribosomal RNA (r-RNA). This type is structural and also RNA). This type is structural and also acts as an enzyme when the protein is acts as an enzyme when the protein is lengthened lengthened

Transfer RNA (t-RNA) carries amino Transfer RNA (t-RNA) carries amino acids to the ribosomes: there must be at acids to the ribosomes: there must be at least 20 types of t-RNA least 20 types of t-RNA

Types and Fx of RNA

mRNA mRNA Formed in the nucleus.Formed in the nucleus. Made from DNA Made from DNA

template. template. Fx: Carries gen code Fx: Carries gen code

from DNA -cytoplasm from DNA -cytoplasm – ribosomes on the – ribosomes on the ER.ER.

Structure of mRNAStructure of mRNA the longest of the RNA moleculesthe longest of the RNA molecules Before entering the cytoplasm on its way Before entering the cytoplasm on its way

to the ribosomes, an mRNA molecule is to the ribosomes, an mRNA molecule is modified.modified.

A 7-methylguanosine "head" is added A 7-methylguanosine "head" is added which serves to help attach the mRNA to a which serves to help attach the mRNA to a ribosome during protein synthesis. ribosome during protein synthesis.

A poly-A "tail" ( 200 adenosine residues) is A poly-A "tail" ( 200 adenosine residues) is attached to the end of the mRNA molecule attached to the end of the mRNA molecule to prevent it getting destroyed by to prevent it getting destroyed by enzymes in the cytoplasm. enzymes in the cytoplasm.

tRNAtRNA

molecule which transfers the amino molecule which transfers the amino acid to the ribosome.acid to the ribosome.

There are at least 20 kinds of t-RNA There are at least 20 kinds of t-RNA because there are 20 different amino because there are 20 different amino acidsacids

Fx: Bonds to a2, transports them to Fx: Bonds to a2, transports them to ribosomes for assembly into ribosomes for assembly into polypeptides. Ipolypeptides. It is used in the t is used in the synthesis of proteinssynthesis of proteins

Structure of tRNAStructure of tRNA

On one end of the tRNA molecule is an area On one end of the tRNA molecule is an area to which a specific amino acid attachesto which a specific amino acid attaches

On the other end is a sequence of three base On the other end is a sequence of three base pairs called the anticodon, the complement pairs called the anticodon, the complement of the codon on the mRNA which codes for a of the codon on the mRNA which codes for a certain protein.certain protein.

mRNA binds to a ribosome where the codons mRNA binds to a ribosome where the codons are left exposed.are left exposed.

These codons needs to be recognised by These codons needs to be recognised by anticodons on anticodons on tRNAtRNA..

Amino acids attach to the new Amino acids attach to the new protein only if the t-RNA protein only if the t-RNA anticodon matches (is anticodon matches (is complementary to) the m-RNA complementary to) the m-RNA codoncodon

tRNAtRNA

rRNArRNA

Component of ribosomesComponent of ribosomes Place where polypeptide chains are built Place where polypeptide chains are built

up.up. Enzyme peptidyl transferase makes Enzyme peptidyl transferase makes

peptide bonds.peptide bonds.

Ribosome finds start codon (AUG), Ribosome finds start codon (AUG), then decodes the message, 3 bases then decodes the message, 3 bases at a time at a time

When the ribosome reaches the stop When the ribosome reaches the stop codon the protein is released and the codon the protein is released and the decoding can start over to make decoding can start over to make another proteinanother protein

SummarySummary

 Messenger RNA  m-RNA  An RNA copy of a gene

 Ribosomal RNA  r-RNA Ribosomal structure; enzyme peptidyl transferase (makes peptide bonds)

 Transfer RNA  t-RNATransfer amino acids to ribosomehave anticodons which match the m-RNA codons. At least 20 types required- one for each amino acid.