Energy and Cellular Metabolism: Protein Synthesis

Lecture Objectives

• Identify
  • Importance of a gene
  • Starting point of a gene
  • Process involved in protein synthesis
• Understand and Explain
  • Transcription and translation in depth
  • Importance of the genetic code
• Identify
  • Start and stop codons
  • Various types of RNA utilized in protein synthesis

Protein Synthesis Overview

• Way the body makes a protein
• Involves two main processes:
  1. Transcription
  2. Translation

Transcription

• Definition: Process of creating mRNA from DNA
• Location: Occurs in the nucleus
• Process:
  • DNA is transcribed to mRNA (messenger RNA)
  • Involves a promoter, which signals start of a gene
  • Terminator signals the end
  • RNA polymerase reads DNA and creates mRNA by matching nucleotides

Translation

• Definition: Decoding mRNA to form proteins
• Location: Occurs in the cytoplasm
• Process:
  • mRNA is read and translated into a polypeptide chain
  • Involves ribosomes and tRNA
  • Codons in mRNA are read, each coding for an amino acid

Gene and Protein Synthesis

• Gene: Segment of DNA coding for a protein
• Promoter: Identifies start of a gene
• Terminator: Identifies end of a gene
• Transcriptional factors: Activate promoters, often hormones

Steps of Transcription

1. Promoter activation
2. Enzyme entry and binding (RNA polymerase)
3. Production of immature mRNA
4. Editing of mRNA (removal of introns)
5. Addition of cap and tail
6. Release of mature mRNA

mRNA Editing

• Spliceosomes: Enzymes removing introns
• Mature mRNA: Only contains exons
• Post Transcriptional Modification: Adding a methyl cap and a poly-A tail

Genetic Code

• Codon: Set of three nucleotides coding for an amino acid
• 64 Codons: Represent 20 amino acids, with some redundancy
• Essential Codons to Know:
  • AUG: Start codon, codes for Methionine
  • UAA, UAG, UGA: Stop codons, do not code for any amino acid

Translation Steps

1. Initiation: Assembly of ribosome, mRNA, and initial tRNA
2. Elongation: tRNAs add amino acids to the growing chain
3. Termination: Ribosome reaches stop codon and disassembles

Types of RNA in Translation

• mRNA (Messenger RNA): Carries the genetic code
• tRNA (Transfer RNA): Brings amino acids to ribosome, contains anticodon
• rRNA (Ribosomal RNA): Structural component of ribosome

Translation Details

• Ribosomes: Composed of large (60S) and small (40S) subunits
• tRNA Function: Delivers amino acids to ribosome
• Peptide Bond Formation: Between amino acids, forming a polypeptide chain
• Ribosome Movement: Advances along mRNA, facilitating elongation

Conclusion

• Transcription and translation are critical for protein synthesis
• Mature mRNA and ribosomes play key roles
• Understanding genetic code is essential for decoding protein synthesis

Questions: Feel free to ask any questions if you need further clarification on protein synthesis or any related topics.