A QUICK INTRODUCTION

Protein Synthesis

Key Terms

GeneRNAmRNAtRNArRNATranscriptionTranslationCodon AnticodonRibosomeDenatureRNA Polymerase

Protein What?

Synthesis!! The combination of parts into a whole

Protein Synthesis The process our cells go through to make proteins

Protein Synthesis Video

We will watch this twiceWrite down things YOU think are important

from this video (write at least 5)http://www.youtube.com/watch?v=D3fOXt4M

rOM&feature=related

Protein Synthesis

There are 2 steps of protein synthesis Transcription Translation

The central dogma states that information flows in one direction from DNA to RNA to proteins. DNA RNA Protein

RNA connects the 2 steps mRNA carries DNA’s instructions

replication

transcription

translation

What is a protein?

A chain of molecules called amino acidsUsed in almost every process of our cells

(replication, respiration)Provides structure (used to create cell

walls, bone and muscle)Examples:

Hemoglobin Insulin DNA polymerase major component of cartilage and hair

DNA contains the information required to make proteins

DNA must be copied before proteins can be made

Why? DNA is master blueprint of the cell – needs to be kept

safe Cell needs to make a lot of proteins

Needs to make a lot of copies of DNA

mRNA is the copy of DNA used to make proteins

RNARNA (Ribonucleic Acid) is very similar to

DNA but there are a few differences Different sugar - ribose instead of

deoxyribose Single-stranded Uses uracil instead of thyamine

Types of RNA

There are 3 types of RNA mRNA - messenger RNA, carries the message or

instructions to make a particular protein rRNA - ribosomal RNA, makes up ribosomes tRNA - transfer RNA, transport amino acids (the

building blocks of protein) to the ribosome

Step 1: Transcription

Protein Synthesis starts in the nucleus with transcription.

Transcription is very similar to replication. Transcription and replication both involve complex enzymes and complimentary base pairing. The two processes have different end results.

Replication copies all the DNA; transcription copies a gene. RNA Polymerase complex binds to DNA at the

beginning of a specific gene unzips DNA Like DNA Polymerase, RNA Polymerase matches

base pairs Remember, instead of using thymine to pair with

adenine we use uracil to pair with adenine.

After Transcription

Once the gene is completely copied DNA is zipped back up mRNA leaves the nucleus DNA is left unchanged

As many copies of RNA can be made as needed

http://www.youtube.com/watch?v=vJSmZ3DsntU&feature=related

Step 2: Translation

During translation the mRNA is used to create a polypeptide, or protein.

After the DNA has been copied mRNA leaves the nucleus and enters the cytoplasm where it binds to a ribosome.

Translation

The ribosome “reads” the mRNA strand 3 bases at a time – called a codon

Each codon codes for a specific type of amino acid One start codon, AUG Three stop codons UAA, UAG, UGA

Regardless of the organism, codons code for the same amino acid.

As the ribosome reads the mRNA codons, tRNA brings(transfers) the correct amino acid to the ribosome

An anticodon is a set of three nucleotides that are complementary to an mRNA codon. An anticodon is located on the tRNA.

The amino acid is attached to the growing chain with peptide bonds by the ribosome

Translation: Detailed View

For translation to begin, tRNA binds to a start codon and signals the ribosome to assemble. a complementary tRNA molecule binds to the exposed

codon, bringing its amino acid close to the first amino acid

the ribosome helps form a peptide bond between the amino acids

the ribosome pulls the mRNA strand length of one codon the now empty tRNA molecule exits the ribosome a complementary tRNA molecule binds to the next

exposed codon. once the stop codon is reached, the ribosome detaches

the protein and disassembles

Once the amino acid is added to the protein chain the tRNA detaches and leaves the ribosome to get another amino acid.

http://www.youtube.com/watch?v=NJxobgkPEAo

Protein Structure

Proteins are more than long strings of amino acids.

They must be folded in order to function correctly

Proteins can be damaged or “denatured”Denature is a change in shape and function

of a protein caused by forces such as temperature or pH changes

Can Proteins be Damaged?

Important! Every somatic cell in your body has the exact same DNA!!

How come the cells in your body act different if they all contain the same DNA? Some cells make hair while some digest your lunch.

It is all in the genes and proteins they express!