Overview
This lecture explains protein synthesis, covering its definition, importance, where and how it occurs, the roles of DNA and three types of RNA, and the two main processes: transcription and translation.
Introduction to Protein Synthesis
- Protein synthesis is the process by which cells make proteins using DNA and RNA.
- Proteins are essential for enzymes, hormones, and structural components in cells.
- Protein synthesis occurs in all cells and uses processes called transcription and translation.
Importance and Examples of Proteins
- Proteins are built from amino acids, the building blocks.
- Examples include hemoglobin (carries oxygen), insulin (regulates blood sugar), and collagen (found in skin).
Types of RNA and Their Functions
- Messenger RNA (mRNA) carries genetic information from DNA in the nucleus to ribosomes in the cytoplasm.
- Ribosomal RNA (rRNA) forms the structural part of ribosomes.
- Transfer RNA (tRNA) brings amino acids to the ribosome during translation.
Transcription (First Step of Protein Synthesis)
- Transcription occurs in the nucleus, where the DNA double helix unwinds and separates.
- One DNA strand serves as a template for forming complementary mRNA.
- mRNA forms by matching RNA bases to the template DNA bases (using uracil instead of thymine).
- mRNA carries the coded genetic message out of the nucleus via nuclear pores to the ribosome.
Translation (Second Step of Protein Synthesis)
- Translation takes place at the ribosome in the cytoplasm.
- mRNA codons (three-base sequences) are read by the ribosome.
- tRNA molecules bring specific amino acids to the ribosome, each tRNA having an anticodon complementary to an mRNA codon.
- Amino acids are joined by peptide bonds, forming a polypeptide chain (protein).
Key Terms & Definitions
- Protein Synthesis — the process of creating proteins from DNA instructions.
- Transcription — forming mRNA from a DNA template in the nucleus.
- Translation — converting mRNA information into a protein at the ribosome.
- mRNA (Messenger RNA) — RNA that carries genetic code from DNA to ribosomes.
- rRNA (Ribosomal RNA) — RNA making up the structure of ribosomes.
- tRNA (Transfer RNA) — RNA that transfers amino acids to the ribosome during protein synthesis.
- Codon — a three-base sequence on mRNA coding for one amino acid.
- Anticodon — a three-base sequence on tRNA complementary to an mRNA codon.
- Peptide Bond — the bond that connects amino acids in a protein.
Action Items / Next Steps
- Review and memorize the steps of transcription and translation.
- Know the functions of mRNA, rRNA, and tRNA.
- Practice identifying and matching codons and anticodons.
- Prepare questions for clarification if any concepts are unclear.