Protein Synthesis and Ribosome Function
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Questions and Answers

What is the primary function of ribosomes in cells?

  • To store genetic information
  • To synthesize lipids
  • To break down proteins
  • To create proteins from amino acids (correct)

    • What percentage of the ribosome's mass is composed of ribosomal RNA (rRNA)?

  • 60-70% (correct)
  • 70-80%
  • 50-60%
  • 40-50%

    • What is the primary function of the large subunit of ribosomes?

  • tRNA binding
  • amino acid activation
  • mRNA binding and decoding
  • peptide bond formation (correct)

    • What is the recognition site for ribosome binding in prokaryotes?

    <p>Shine-Dalgarno sequence</p> Signup and view all the answers

    What is the role of initiator tRNA (tRNAi) in translation initiation?

    <p>to bring the first amino acid to the ribosome</p> Signup and view all the answers

    What is the sequence of events in translation initiation?

    <p>recruitment of the small subunit to the mRNA, followed by the binding of the large subunit</p> Signup and view all the answers

    What is the coefficient of sedimentation of the eukaryotic ribosome?

    <p>80 S</p> Signup and view all the answers

    How many proteins make up the small subunit of the eukaryotic ribosome?

    <p>33 proteins</p> Signup and view all the answers

    What is the length of the 23 S rRNA in the large subunit of the prokaryotic ribosome?

    <p>3,200 nucleotides</p> Signup and view all the answers

    What is the molecular weight of the large subunit of the prokaryotic ribosome?

    <p>1.8 x 10^6</p> Signup and view all the answers

    How many proteins make up the large subunit of the eukaryotic ribosome?

    <p>47 proteins</p> Signup and view all the answers

    What is the length of the 16 S rRNA in the small subunit of the prokaryotic ribosome?

    <p>1,540 nucleotides</p> Signup and view all the answers

    What is the molecular weight of the small subunit of the eukaryotic ribosome?

    <p>1.4 x 10^6</p> Signup and view all the answers

    How many nucleotides are in the 18 S rRNA in the small subunit of the eukaryotic ribosome?

    <p>1,900 nucleotides</p> Signup and view all the answers

    What is the length of the 5 S rRNA in the large subunit of the prokaryotic ribosome?

    <p>120 nucleotides</p> Signup and view all the answers

    How many proteins make up the small subunit of the prokaryotic ribosome?

    <p>21 proteins</p> Signup and view all the answers

    What is the main difference between the core of eukaryotic ribosomal subunits and prokaryotic ribosomal subunits?

    <p>Eukaryotic ribosomal subunits have a highly conserved core, while prokaryotic ribosomal subunits do not</p> Signup and view all the answers

    What is the function of the E site in ribosomes?

    <p>It is the site where tRNAs exit the ribosome after completing their function</p> Signup and view all the answers

    What is the function of the 16S rRNA in bacterial and archaeal ribosomes?

    <p>It recognizes the Shine-Dalgarno sequence in mRNAs</p> Signup and view all the answers

    What is the function of the 23S rRNA in eukaryotic ribosomes?

    <p>It has peptidyl transferase activity</p> Signup and view all the answers

    What is the main difference between ribosomes in different cells?

    <p>The sequence of the rRNA</p> Signup and view all the answers

    What is the function of the P site in ribosomes?

    <p>It is the site of peptide bond formation</p> Signup and view all the answers

    What is the function of the A site in ribosomes?

    <p>It is the site of aminoacyl-tRNA binding</p> Signup and view all the answers

    What is the function of the polysome?

    <p>It is a complex of multiple ribosomes translating the same mRNA</p> Signup and view all the answers

    What is the function of the rRNA modifications?

    <p>They affect the specificity of translation</p> Signup and view all the answers

    What is the function of the ribosomal proteins?

    <p>They interact with the rRNA to form the ribosomal subunits</p> Signup and view all the answers

    Study Notes

    Protein Synthesis

    • Ribosomes are responsible for protein synthesis, which is the process of creating proteins from amino acids.
    • They read messenger RNA (mRNA) sequences and assemble amino acids into polypeptide chains.
    • The process occurs in three stages: initiation, elongation, and termination.
    • Ribosomes can produce proteins with varying lengths and sequences.

    Structure and Composition

    • Ribosomes are complex organelles composed of:
      • Ribosomal RNA (rRNA): 60-70% of the ribosome's mass
      • Ribosomal proteins: 30-40% of the ribosome's mass
    • Prokaryotic ribosomes (70S) are smaller than eukaryotic ribosomes (80S)
    • Ribosomes have two subunits:
      • Large subunit (50S in prokaryotes, 60S in eukaryotes): responsible for peptide bond formation
      • Small subunit (30S in prokaryotes, 40S in eukaryotes): responsible for mRNA binding and decoding

    Ribosome Binding

    • Ribosomes bind to mRNA through interactions between the small subunit and the mRNA sequence.
    • The Shine-Dalgarno sequence (in prokaryotes) or the Kozak sequence (in eukaryotes) serve as recognition sites for ribosome binding.
    • Ribosome binding is a crucial step in translation initiation.

    Translation Initiation

    • Translation initiation involves the recruitment of the small subunit to the mRNA, followed by the binding of the large subunit.
    • Initiator tRNA (tRNAi) brings the first amino acid to the ribosome.
    • The start codon (AUG) is recognized by the ribosome, and translation begins.

    Cellular Function

    • Ribosomes are found in the cytoplasm of cells, often attached to the endoplasmic reticulum (ER) in eukaryotes.
    • They are responsible for synthesizing proteins that are used for various cellular functions, such as:
      • Enzymes
      • Hormones
      • Structural proteins
      • Receptors
      • Transport proteins
    • Dysfunctional ribosomes can lead to various diseases, such as ribosomopathies.

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    Description

    Learn about the process of protein synthesis, the structure and composition of ribosomes, and their role in translation initiation. Understand how ribosomes bind to mRNA and synthesize proteins for various cellular functions.

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