1 / 15

Protein Synthesis

Protein Synthesis. Introductory Remarks. Protein synthesis is a cellular process that requires energy, as do all cell functions. DNA in the nucleus codes for the sequence of amino acids in proteins. But proteins are synthesized (made) on the ribosomes outside the nucleus.

yama
Télécharger la présentation

Protein Synthesis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Protein Synthesis

  2. Introductory Remarks • Protein synthesis is a cellular process that requires energy, as do all cell functions. • DNA in the nucleus codes for the sequence of amino acids in proteins. • But proteins are synthesized (made) on the ribosomes outside the nucleus. • Therefore, Messenger RNA (ribonucleic acid) (mRNA) carries the information in DNA from the nucleus to the ribosomes. Mr. Peters (c) 1999 Revised (c) 2003

  3. RNA • There are a variety of RNA, but they all share three traits that make them distinctive from DNA: • RNA normally exists as a single-stranded molecule (as opposed to double). • The nucleotides in RNA contain the sugar ribose (as opposed to deoxyribose). • RNA contains adenine, guanine, and cytosine bases. But instead of thymine, RNA contains the base uracil. • Uracil matches up with adenine the same way that thymine does in DNA. Mr. Peters (c) 1999 Revised (c) 2003

  4. Messenger RNA (mRNA) • mRNA’s carry the information coded in DNA because they are synthesized from DNA molecules. Mr. Peters (c) 1999 Revised (c) 2003

  5. The Synthesizing (making) of mRNA. • mRNA synthesis begins when part of a DNA molecule unwinds, and the two DNA strands separate. • Free RNA nucleotides present in the nucleus of a cell match up and form bonds with the complementary bases along one of the DNA strands. Mr. Peters (c) 1999 Revised (c) 2003

  6. The Synthesizing (making) of mRNA. 3. The RNA nucleotides that line up along the DNA strand are bonded together covalently, forming a strand of mRNA. Mr. Peters (c) 1999 Revised (c) 2003

  7. The Synthesizing (making) of mRNA. • The hydrogen bonds between mRNA and the DNA strand break, and the mRNA molecules moves away from the DNA. • Then, the two strands of the DNA molecule rejoin. • The synthesis of mRNA is known as transcription. Mr. Peters (c) 1999 Revised (c) 2003

  8. The End Product of mRNA Transcription – the Codon • A strand of mRNA is the exact compliment of a strand of DNA. • For example, let us say mRNA was transcripted from the amino acid tyrosine. • The DNA code for Tyrosine is ATA (adenine-thymine-adenine). • The complimentary transcription of mRNA from Tyrosine would result in UAU (uracil-adenine-uracil). • Remember: Adenine’s complimentary base is thymine, but thymine actually becomes uracil in RNA. • Another example: Histidine (GTA) transcribes to CAU. (Guanine → Cytosine; Thymine → Adenine; Adenine → Uracil [in RNA]) • This mRNA code which is derived from the DNA is called a codon. Mr. Peters (c) 1999 Revised (c) 2003

  9. The Heart of the Matter – Protein Synthesis • An mRNA molecule leaves the nucleus and attaches itself to a ribosome. Mr. Peters (c) 1999 Revised (c) 2003

  10. The Heart of the Matter – Protein Synthesis • tRNA’s (tranfer RNA) carry amino acids to the ribosome. • On one end the tRNA attaches itself to an amino acid, and the other end has a triplet of exposed bases (anticodons). • Remember the mRNA triplet is called a codon, therefore, these anticodons are complimentary to the codons. Mr. Peters (c) 1999 Revised (c) 2003

  11. The Heart of the Matter – Protein Synthesis • Anticodons of tRNA’s match up with the complimentary codons of the mRNA. • So, the amino acids line up in a sequence directed by the codons in the mRNA. Mr. Peters (c) 1999 Revised (c) 2003

  12. Covalent bonds form between the amino acids, beginning the process of forming a protein. Mr. Peters (c) 1999 Revised (c) 2003

  13. The Heart of the Matter – Protein Synthesis • The tRNA’s detach from the bonded amino acids and the mRNA. • The mRNA moves down the ribosome to the next codon, and so on. • Other tRNA’s match up with those codons, and the amino acid chain continues to grow and a protein is eventually formed. • The process ends when a stop codon is reached. Mr. Peters (c) 1999 Revised (c) 2003

  14. Closing Remarks • The entire process by which a cell reads codons on mRNA molecules to synthesize protein is called translation. • Special proteins control each step of the translation process. • The ribosomes consist of proteins and a specific kind of RNA called ribosomal RNA (rRNA). • Scientists are not certain of the function of rRNA, but speculate that it helps position mRNA on the ribosome. Mr. Peters (c) 1999 Revised (c) 2003

  15. Assignment • Read pp. 634-639 • Sequence Chain for protein synthesis • Do #1-7 p. 639 Mr. Peters (c) 1999 Revised (c) 2003

More Related