Chapter 3, Objective 5: Protein Creation

Overview

• DNA: Contains instructions to make proteins.
• mRNA (Messenger RNA): Carries the instructions from DNA to ribosomes.
• Ribosomes: Structures where proteins are synthesized by assembling amino acids in sequence.

Protein Synthesis Phases

1. Transcription
2. Translation

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Transcription

• Location: Nucleus
• Process:
  • DNA (double-stranded) remains in the nucleus.
  • A segment of DNA is transcribed into mRNA.
  • mRNA carries the code for a specific protein and leaves the nucleus.
• Key Points:
  • Transcription involves converting DNA nucleotides to RNA nucleotides (from thymine in DNA to uracil in RNA).
  • Only specific sections of DNA are transcribed depending on the protein needed.
• Visual Identification:
  • DNA: Contains thymine.
  • RNA: Contains uracil.

Translation

• Location: Cytoplasm, at a ribosome
• Ribosome Structure: Composed of a large and small subunit.
• Process:
  • mRNA strand is read by a ribosome.
  • Ribosome synthesizes the protein by ordering amino acids.
  • tRNA (Transfer RNA) brings amino acids to the ribosome.
• Outcome:
  • Amino acids are linked together by peptide bonds forming a polypeptide, which is the protein.

Additional Resources

• A video link is provided that offers a visual explanation of transcription and translation.

Summary

• Transcription in the nucleus results in the formation of mRNA from DNA.
• mRNA exits the nucleus and is translated into a protein at the ribosome in the cytoplasm.
• tRNA plays a crucial role in delivering amino acids to form proteins.