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Pennsylvania State University *

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230W

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Biology

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Apr 3, 2024

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BIOL230W Week 4 – Making Protein (Translation) 1 We are continuing our journey following the flow of information in a cell. Last week we focused on transcription. We discussed how the information is transferred from the genome (DNA) to a mRNA molecule and how this expression can be regulated resulting in differential gene expression. This week we will be discussing transferring the information in the mRNA into a functional protein. This process is known as translation. Day 1 Learning Objectives 1. Explain how mRNA is translated into different locations (cytoplasm vs. ER) and how this impacts final protein localization (cytoplasm vs. export vs. membrane). 2. Describe the structure and the role of the translocon, Sec 61, in the localization of proteins. 3. Describe the role of the amino acid side chain in the function of a proteins. 4. Describe the role of a peptide bond. 5. Explain the importance of R-groups or side chains in protein function. 6. Compare and contrast a DNA polymer and a polypeptide. 7. Describe the structure of tRNA and how its structure contributes to function. Central Dogma Recap Last week we determined that there is a deletion in the DNA of a patient (Maggie) with cystic fibrosis. This week we want to continue our exploration of how this different genotype results in a different phenotype. Use the image on the screen to answer the following questions. 1. Where, in relation to the cell, do proteins function (Hint - think of three general areas)? 2.Which organelle will “read” the information in the mRNA and convert it to a protein sequence? 3. Where in the cell is the ribosome located at the start of translation? What two locations can translation be terminated? Mini-Lecture: Co-translation Translocation Look out for the answers to these questions during the mini-lecture! 4. The translocon allows passage between which two areas of the cell? 5. If the signal peptide of a new protein directs the ribosome to the translocon, would it need to be translated first or last? 6. If translated through the translocon, where would be the protein’s ultimate destination? cytoplasm , plasma membrane , lysosome , or outside the cell ribosomes In the cytoplasm ; rough ER the cytoplasms the ER Lumen last : finishes translation into the ER endosome

BIOL230W Week 4 – Making Protein (Translation) 2 7. What characteristic do amino acids that span the hydrophobic core of a membrane share? Small Group Discussion: What is a protein? 8. What monomers make up a protein polymer? 9. What makes one amino acid different from another? 10. What is the name of the bond that connects monomers into the polymer (polypeptide)? Small Group Discussion: Compare and contrast polypeptide and DNA polymer. 11. How is a polypeptide analogous to a molecule of DNA or mRNA? 12. How are they different? Mini-Lecture: (Ready!) Player 1 - tRNA Now that we have all that information from the DNA transcribed to RNA, how is the information in a mRNA translated to the language of protein? We will be focusing on three main “players” or molecules that complete this process: tRNA, G-proteins, and the ribosome. The first player is another non-coding RNA molecule, tRNA, that acts as an adapter between the two languages! 13. Using the image on the screen, describe in your own words how the tRNA molecule facilitates the transfer of information from the mRNA into a polypeptide.

BIOL230W Week 4 – Making Protein (Translation) 3 Day 2 Learning Objectives 1. Identify the states where G-proteins are activated and inactivated. 2. Explain the role of G-proteins in the elongation process of translation. 3. Describe the structure of a ribosome and how its structure contributes to its function (eg. ribozyme function, A-site, P-site, E site). 4. Compare and contrast the function of different non-coding RNAs we have discussed in class. 5. Outline the factors (proteins) and the sequence of events involved in initiation of translation. 6. Analyze the interaction of codons and anticodons and match them to the appropriate amino acid using the provided genetic code. 7. Describe how the genetic code is redundant and how it affects codon:anticodon pairing (wobble). 8. Outline the major steps of translation (initiation, elongation, termination) using appropriate key words. Small Group Discussion: Player 2 - G-proteins Using the image on the screen answer the following questions: 1. G-proteins bind to a variety of target proteins in addition to one common molecule. What molecule do all G-proteins bind to and eventually hydrolyze? 2. G-proteins are active when bound to what molecule? 3. G-proteins are inactive when bound to what molecule? Mini-Lecture: Player 3 – Ribosome (rRNA, proteins and ribozyme) 4. RNA molecules that catalyze reactions are called ______________. 5. Why are ribosomes classified as ribozymes?

BIOL230W Week 4 – Making Protein (Translation) 4 Small Group Activity: Elongation of Translation Using Figure 1 answer the following questions concerning the three main events required for elongation, the process of building a polypeptide from the information in an mRNA molecule. Figure 1 . Steps of elongation. Step 1: Binding of aminoacyl tRNA. 6. What is the name and function of the G-protein in this step of elongation? 7. If the mRNA codon 5’ ACU 3’ is in the A-site of the ribosome, what is the sequence of the complementary tRNA anticodon 5’_______ 3’ and which amino acid would be added? 8. If the anticodon 5’ ACU 3’ is found on the incoming aminoacyl tRNA, which amino acid would it be carrying?

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