Transcript RNA - Mr. Blankenship's pages

RNA
And PROTEIN SYNTHESIS
What DNA is for……
• Making Proteins
• Why is this important?
Proteins Serve as…
• Enzymes that catalyze biochemical
reactions (catalyst  speeds up chem. Rx)
Proteins Serve as…
• Enzymes that catalyze biochemical
reactions
• Structural or mechanical factors
– actin and myosin in muscle
Proteins Serve as…
• Enzymes that catalyze biochemical
reactions
• Structural or mechanical factors
– actin and myosin in muscle
– Makes up cytoskeleton
Proteins Serve as…
• Enzymes that catalyze biochemical
reactions
• Structural or mechanical factors
– actin and myosin in muscle
– Makes up cytoskeleton
– Cell signaling, immune responses, cell
adhesion, cell cycle
Proteins Serve as…
• Enzymes that catalyze biochemical
reactions
• Structural or mechanical factors
– actin and myosin in muscle
– Makes up cytoskeleton
– Cell signaling, immune responses, cell
adhesion, cell cycle
– Necessity in animals' diets,
• Can’t synthesize (make) some amino acids, must eat
So How are Proteins Made?
• Remember, proteins are a chain of
amino acids that are folded up into a
particular shape.
So How are Proteins Made?
• DNA has all codes (GENES) for any
protein that’s needed
• Humans: Abt. 25,000 genes in 23 pairs of
chromosomes.
Ribonucleic Acid (RNA)
• Compared to DNA:
– Similar, built as a chain of nucleotides
– Unlike DNA:
•
•
•
•
Has Uracil (U), not Thymine (T) (so it has A, U, G, C)
5 Carbon Sugar is Ribose, not Deoxyribose
Is single stranded
Is shorter
Comparing the nucleic acids…
DNA
RNA
Deoxyribose sugar
Ribose sugar
Double-sided
Single-sided
Guanine, Cytosine,
Adenine, & Thymine
Guanine, Cytosine,
Adenine, & Uracil
Millions of
base pairs long
In nucleus
100’s / 1000’s of
bases long
In nuc. and cyt.
Ribonucleic Acid (RNA)
• 3 types of RNA:
– Messenger RNA (mRNA)
• It’s the message carrier
– Transfer RNA (tRNA)
• It transfers amino acids to the ribosomes
– Ribosomal RNA (rRNA)
• It makes up actual ribosomes
TRANSCRIPTION
• DNA never leaves nucleus:
1. DNA is opened / read by RNA Polymerase
2. Template side is copied (transcription)
into mRNA
3. DNA closes back
4. mRNA leaves nucleus through pore
Animation
How mRNA is made
RNA Polymerase (an enzyme) opens DNA, assembles mRNA
nucleotides floating around in nucleoplasm (5’ to 3’ direction)
How mRNA is made
As mRNA strand is assembled, it lengthens until a stop signal
cuts it off. RNA Polymerase then detaches, DNA closes.
How mRNA is made
This process is Transcription (copying, rewriting) movie
RNA Polymerase
producing
(transcribing)
mRNA
TRANSLATION
1. The mRNA moves to a ribosome;
bases read in 3’s (triplets,or codons)
2. tRNA floating in cytoplasm match up
their anticodons to mRNA codons,
delivering one amino acid at a time…
3. Amino acids link together (chain) then
fold to make protein.
Animation
mRNA connects to Ribosome
• Ribosome: assembly site for a.a. chains
• mRNA moves thru ribosome;
bases read in triplets (codons)
• tRNA floating in cytoplasm match up their
anticodons to mRNA codons, delivering
one amino acid at a time…
movie1 movie2 movie3 movie4
Codons and their Amino
Acids
A Codon
Chart is very
simple to use.
For this circle
type chart, go
from the
largest to
smallest
letters when
reading your
codon.
For example,
A-G-C codes
for Serine
Transfer
RNA
(model)
Transfer
RNA
(mapped)
Transfer
RNA
(mapped
&
modeled)
A Protein Forms
• tRNAs deliver the proper a.a’s., forming
chain.
• Each a.a. bonded together by
peptide bond
• a.a. chains always
– Begin with the A-U-G codon (methionine)
– End with one of three STOP codons
New polypeptide chain of a.a. : Protein
mRNA
Ribosome
A New Protein is
Born
The Protein is Completed
• The a.a. chain folds into its proper shape,
then sent to where it’s needed…
movie
• How proteins may be used in different
cells…
x
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