AP Biology Questions: Ribosome Structure, tRNA, and Translation

📚 Quick Study Guide

• 🧬 Ribosome Structure: Ribosomes are made of two subunits: a large subunit and a small subunit. Each subunit is composed of ribosomal RNA (rRNA) and proteins.
• 🧪 tRNA's Role: Transfer RNA (tRNA) molecules bring amino acids to the ribosome. Each tRNA has an anticodon that is complementary to a specific mRNA codon.
• 📝 Translation Initiation: Translation begins when the small ribosomal subunit binds to mRNA. The initiator tRNA carrying methionine (Met) then binds to the start codon (AUG).
• 📈 Elongation Process: During elongation, amino acids are added one by one to the growing polypeptide chain. This involves codon recognition, peptide bond formation, and translocation.
• 🛑 Termination: Translation ends when a stop codon (UAA, UAG, or UGA) in the mRNA reaches the A site of the ribosome. Release factors bind to the stop codon, causing the release of the polypeptide chain.
• 💡 Codon-Anticodon Pairing: Remember that codons on mRNA pair with anticodons on tRNA according to base-pairing rules (A with U, and G with C).
• 🧮 Energy Requirements: Translation requires energy in the form of GTP (Guanosine triphosphate) for various steps including initiation, elongation and translocation.

Practice Quiz

1. Which of the following is NOT a component of a ribosome?
   1. mRNA
   2. rRNA
   3. Protein
   4. tRNA


2. What is the function of tRNA during translation?
   1. To carry genetic information from the nucleus to the ribosome.
   2. To bind to the mRNA and initiate translation.
   3. To transport amino acids to the ribosome.
   4. To catalyze the formation of peptide bonds.


3. The start codon AUG codes for which amino acid?
   1. Alanine
   2. Methionine
   3. Glycine
   4. Serine


4. Where does translation take place in eukaryotic cells?
   1. Nucleus
   2. Mitochondria
   3. Ribosome
   4. Golgi Apparatus


5. Which of the following is a stop codon?
   1. AUG
   2. GUA
   3. UAC
   4. UAA


6. What provides the energy for translation?
   1. ATP
   2. GTP
   3. cAMP
   4. NADPH


7. What happens when a stop codon enters the A site of the ribosome?
   1. tRNA binds to the stop codon.
   2. A release factor binds to the stop codon.
   3. The ribosome moves to the next codon.
   4. The mRNA is degraded.