PROTEIN SYNTHESIS

WHAT YOU NEED TO MAKE PROTEINS DNA = instructions to make the protein Amino acids = parts that make up proteins RNA = “workers” to help assemble the “parts”

Amino acids are the building blocks (monomers) of proteins PROTEIN SYNTHESIS Amino acids are the building blocks (monomers) of proteins The sequence of nucleotides in each gene contains information for how to assemble a chain of amino acids that make up a single protein ***(one gene, one protein)***

Nucleic Acids DNA RNA Double-stranded Sugar = deoxyribose Thymine = T Single-stranded Sugar = ribose Uracil = U

RNA Messenger RNA (mRNA) 2. Ribosomal RNA (rRNA) Take info from DNA in nucleus to cytoplasm (factory floor) 2. Ribosomal RNA (rRNA) Assemble amino acids in correct order 3. Transfer RNA (tRNA) Transports amino acids to the ribosome to be assembled into protein

1. TRANSCRIPTION: DNA  mRNA PROTEIN SYNTHESIS In the nucleus, enzymes make an RNA copy of part of a DNA strand (similar to DNA replication) DNA  mRNA

1. TRANSCRIPTION: FROM DNA to mRNA PROTEIN SYNTHESIS 1. TRANSCRIPTION: FROM DNA to mRNA RNA is like DNA except A pairs with U, not T THERE IS NO T IN RNA! For example: DNA: C T C A G G A T mRNA: G A G U C C U A Now do your example:

1.TRANSCRIPTION: DNA  mRNA PROTEIN SYNTHESIS DNA: ATC CGA ATG GTA mRNA: UAG GCU UAC CAU DNA  mRNA Once mRNA has copied a strand of DNA, it now LEAVES THE NUCLEUS and moves to the RIBOSOME where the protein will be made!

Quick Review Transcription What is happening? Where in the cell? Which types of nucleic acids are involved, DNA, RNA, or both? What is the purpose of producing an RNA copy of the code in DNA? What part of the cell produces proteins?

2. TRANSLATION: from mRNA to Protein PROTEIN SYNTHESIS 2. TRANSLATION: Takes place at ribosomes so proteins can be made from mRNA to Protein

PROTEIN SYNTHESIS 20 amino acids mRNA has only 4 bases (A, U, C, G) Message is read 3 nucleotides of mRNA at a time CODON = 3 mRNA nucleotides Examples: U-U-U A-G-C U-G-C

PROTEIN SYNTHESIS A gene codes for a A codon codes for an PROTEIN AMINO ACID

PROTEIN SYNTHESIS Not all codons code for amino acids Key Codons: AUG = start codon UAA = stop codon

2. TRANSLATION: from mRNA to Protein PROTEIN SYNTHESIS 2. TRANSLATION: from mRNA to Protein Takes place at ribosomes in cytoplasm tRNA brings amino acids through cytoplasm to ribosomes Each tRNA attaches to only one type of amino acid Anticodon (tRNA) pairs with codon (mRNA)

CODON tRNA

TRANSLATION: from mRNA to Protein PROTEIN SYNTHESIS TRANSLATION: from mRNA to Protein Amino acids are joined by peptide bonds Chain of amino acids is formed until ribosome reaches a stop codon on the mRNA strand When the amino acid chain is released from ribosome and assumes its 3-D shape, it becomes a protein!

Summary of Protein Synthesis DNA in nucleus has instructions Message from DNA goes to ribosome Proteins are assembled on the ribosome according to the directions from the DNA Transcription = taking message from nucleus to ribosome Translation = using message directions to assemble proteins

Now watch and think – don’t write

TRANSLATION: from mRNA to Protein PROTEIN SYNTHESIS TRANSLATION: from mRNA to Protein About those amino acids: Which amino acid goes with which mRNA codon? Example: U-G-U SEE CODON CHART Now you try it…

TRANSLATION: from mRNA to Protein PROTEIN SYNTHESIS TRANSLATION: from mRNA to Protein Now you try it CODONS (p. 292) mRNA amino acid UCC GCG GGA CUU serine alanine glycine leucine

Gene Regulation All cells of an organism have the same DNA. What type of cell develops depends on which genes get turned on or off. This is why a multicellular organism is able to differentiate into many types of cells. For example: skin cells, muscle cells, bone cells.

Gene Regulation Cells respond to their environment by producing different types and amounts of protein. Examples: 1. You get cut and your skin cells need to make proteins to repair your skin. 2. Cancer may result when your cells make too many cells (protein). 3. Diabetes may result if your pancreatic cells don’t make enough insulin (protein).