Download From DNA to Protein (11.2)

From DNA to Protein (11.2)
What is a Protein?
• Complex, 3-dimensional structures made from chains of amino acids
• Regulate cell functions
• Produced at the ribosomes
• Ex: Blood contains red blood cells (RBC) that transport oxygen to
different parts of our bodies.
• RBC’s use a protein called “hemoglobin” to capture and carry the
oxygen.
• If the instructions (DNA) are changed or “mutated” changes in the
hemoglobin protein could result. The RBCwould no longer be able to
carry oxygen (Sickle Cell Anemia).
Sickle Cell Anemia
How are proteins made?
Protein Synthesis
• RNA (Ribose Nucleic Acid)
How does RNA differ from DNA?
▫ Single stranded (half-zipper)
▫ The sugar in RNA is ribose (DNA has deoxyribose)
▫ Instead of Thymine (T), RNA contains Uracil (U)
in RNA
 Adenine (A) pairs with Uracil (U)
3 types of RNA
•
Messenger RNA (mRNA)
-Brings instructions from DNA in the nucleus to the
cytoplasm
•
Ribosomal RNA (rRNA)
-binds to the mRNA and uses instructions to
assemble the amino acids in the correct order
•
Transfer RNA (tRNA)
-Supplier. Delivers amino acids to the ribosome to be
assembled into a protein. (amino acid delivery truck)
Transcription
(DNA mRNA)
• Enzyme unzips DNA molecule
• Free RNA nucleotides form with complementary
base pair (GC and AU)
• New mRNA strand leaves nucleus and enters
the cytoplasm (finds ribosome)
• http://www.stolaf.edu/people/giannini/flashani
mat/molgenetics/transcription.swf
DNA replication vs. Transcription
• Double stranded DNA
▫ Purpose?
• Single stranded RNA
▫ Purpose?
Genetic Code
• 3 nitrogenous bases of mRNA
code for one Amino Acid
• Each group is known as a
codon
• Ex: The codon GCU results in
the amino acid Alanine
• 64 combinations are possible
when using a sequence of 3
nitrogenous bases
• Universal Code for all
organisms
Genetic Code “Alphabet”
Proteins
Chains of amino acids
Amino Acids (Serine, Leucine, etc)
Codons (3 nucleotides -UCA,
CUA, etc)
Nucleotide
Nitrogenous
Base
Translation
(mRNA protein) p.294
• Occurs in the cytoplasm at the ribosomes
• mRNA attaches to ribosome. tRNA (carrying a
specific AA) approaches ribosome
• tRNA (anticodon) attaches with mRNA (codon)
• A new tRNA molecule attaches next to previous
tRNA molecule and AA from each tRNA bond
together (peptide bond)
• Ribosome slides down mRNA molecule to allow
a new tRNA to attach. Old tRNA molecules are
released.
• A long chain of AA is formedprotein!!
Protein Synthesis Animation
Do it yourself