Lecture 14 - Translation Micrographs - LC2024WT1 POST

Lecture Overview

• Topic: Translation micrographs

• Date: October 18, 2024

• Focus: Protein synthesis in bacterial versus eukaryotic cells.

Micrograph Analysis

• Key Questions:

  • Which images depict bacterial cells?

  • Ability to interpret the images and understand the occurring processes.

Targeted Learning Goals

• Interpret electron micrographs of isolated DNA/RNA/ribosome complexes during transcription and translation phases.

  • Identify visible macromolecules in each image.

  • Label the polarity (directionality) of macromolecules.

  • Identify the transcription direction by RNA polymerase.

  • Distinguish between electron micrographs of transcription and translation within bacterial and eukaryotic cells.

• Note: This material will be covered in the final exam.

Differences in Translation: Prokaryotes vs. Eukaryotes

• Key Differences:

  • Location: Translation occurs in the cytoplasm for both, but eukaryotes have nuclei separating transcription from translation.

  • Process Overview:

    • Prokaryotes:

      • DNA → RNA process occurs concurrently.

    • Eukaryotes:

      • DNA is transcribed into pre-mRNA, which is then processed into mature mRNA before translation.

Electron Micrograph Details

• Electron Micrographs are images taken utilizing an electron microscope, capturing protein synthesis in cellular components like the cytoplasm.

Identifying Organisms in Images

• Comparison of bacterial and eukaryotic translation micrographs:

  • Micrographs A and B distinguish between bacterial and eukaryotic cells.

  • Transcription and translation happen simultaneously in bacteria, but they are separate processes in eukaryotes.

RNA Polymerase Movement

• In Bacterial Cells:

  • Determine RNA polymerase direction in given micrographs:

    • Options: A. Left to right; B. Right to left.

  • The direction indicates where RNA synthesis is occurring along the DNA strand.

Understanding mRNA Orientation

• Positions and ends of RNA:

  • mRNA is synthesized in the 5’ to 3’ direction.

  • Recall:

    • Addition of nucleotides occurs at the 3’ OH

    • The 5’ end of the mRNA is opposite to the 3’ end of the RNA polymerase.

Ribosome Binding During Translation

• Identifying the first ribosomes that bind to mRNA:

  • Ribosomes are involved in translating mRNA into polypeptides.

  • The first ones to bind indicate the start codon and initial translation events.

Movement of Ribosomes in Bacterial Translation

• Ribosomes translate mRNA, moving from:

  • 5’ end to 3’ end, with multiple ribosomes operational simultaneously on the mRNA.

• Multiple ribosomes can synthesize polypeptides, indicated in the electron micrograph sequence.

Key Directions in Translation

• Pointing out key features in the micrographs:

  • Identify the 3’ and 5’ ends of the mRNA.

  • Point out the N-terminus and C-terminus of the growing polypeptide chain.

In Conclusion: Bacterial Translation Context

• Highlights key aspects of bacterial cell translation:

  • Ribosome directionality and simultaneous transcription and translation.

Upcoming Topics and Assignments

• Next topics: DNA mutations.

• Upcoming tasks:

  • Complete readings/videos for tutorials.

  • Study for the October 22 midterm exam.

  • Practice problems.

  • Create a double-sided memory aid sheet (8.5" x 11") for exam preparation.