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 RNADeoxyribose sugar Ribose sugar

Double-sided Single-sided

Guanine, Cytosine, Adenine,

& Thymine

Guanine, Cytosine, Adenine,

& Uracil

Millions of base pairs long

100’s / 1000’s ofbases long

In nucleus 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 madeRNA Polymerase (an enzyme) opens DNA, assembles mRNA nucleotides floating around in nucleoplasm (5’ to 3’ direction)

How mRNA is madeAs mRNA strand is assembled, it lengthens until a stop signal cuts it off. RNA Polymerase then detaches, DNA closes.

How mRNA is madeThis process is Transcription (copying, rewriting) movie

RNA Polymerase

producing (transcribing) mRNA

TRANSLATION1. 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

mRNA

Ribosome

New polypeptide chain of a.a. : Protein

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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