Protein Biosynthesis and Amino Acids
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Questions and Answers

What is the process called where ribosomes convert the genetic information carried by mRNA into a new protein?

Translation

Where does translation occur in a cell?

Cytosol on ribosomes

What is the name of the covalent bond formed between the carboxyl group of one amino acid and the amino group of the next amino acid?

Peptide bond

What are the basic requirements for translation?

<p>mRNA, tRNA, ribosomes, energy in the form of ATP and GTP, enzymes and specific protein factors</p> Signup and view all the answers

The process of translation in eukaryotes and prokaryotes is completely different.

<p>False</p> Signup and view all the answers

The tRNA has an attachment site for a specific amino acid at its 3'-end.

<p>True</p> Signup and view all the answers

What is the name of the enzyme that catalyzes the attachment of amino acids to their corresponding tRNA molecules?

<p>Aminoacyl-tRNA synthetase</p> Signup and view all the answers

The extreme specificity of the aminoacyl-tRNA synthetase in recognizing both the amino acid and its cognate tRNA contributes to the high fidelity of translation.

<p>True</p> Signup and view all the answers

What is the name of the sequence that is a purine-rich nucleotide base and is located six to ten bases upstream of the initiating AUG codon on the mRNA molecule?

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

Eukaryotic messages have a Shine-Dalgarno sequence.

<p>False</p> Signup and view all the answers

What are ribosomes made of?

<p>Protein and ribosomal RNA (rRNA)</p> Signup and view all the answers

What are the three main phases of protein synthesis?

<p>Initiation, elongation, termination.</p> Signup and view all the answers

What are the key components required for translation initiation?

<p>mRNA, ribosomal subunits, tRNA, GTP, initiation factors.</p> Signup and view all the answers

What is the name of the specific charged tRNA that is essential for translation initiation?

<p>Initiator tRNA</p> Signup and view all the answers

What is the function of guanosine triphosphate (GTP) in translation?

<p>Provides energy for the assembly of the initiation complex and other steps in translation.</p> Signup and view all the answers

What is the name of the set of soluble protein factors that are involved in translation initiation?

<p>Initiation factors (IFs)</p> Signup and view all the answers

What is the difference between the ribosomes found in eukaryotes and prokaryotes?

<p>Ribosomes in eukaryotes are larger and more complex than those in prokaryotes.</p> Signup and view all the answers

What are the key components required for peptide chain elongation?

<p>mRNA, ribosomes, tRNA, GTP, elongation factors.</p> Signup and view all the answers

What is the function of elongation factors in peptide chain elongation?

<p>They facilitate the binding of aminoacyl-tRNA to the A site, the formation of peptide bonds, and the translocation of the ribosome along the mRNA.</p> Signup and view all the answers

What is the function of release factors in translation?

<p>They recognize termination codons on mRNA and stop translation.</p> Signup and view all the answers

In eukaryotes, the translation termination factor is called eRF.

<p>True</p> Signup and view all the answers

What is the process of protein biosynthesis called?

<p>Translation</p> Signup and view all the answers

The pathway of protein biosynthesis is called [translation].

<p>True</p> Signup and view all the answers

Where does translation occur?

<p>cytosol, on ribosomes</p> Signup and view all the answers

The basic plan of protein synthesis in eukaryotes is similar to that in prokaryotes.

<p>True</p> Signup and view all the answers

What are some of the basic requirements for translation?

<p>Enzymes and protein factors</p> Signup and view all the answers

What does a tRNA molecule have an attachment site for?

<p>A specific amino acid</p> Signup and view all the answers

What is a tRNA molecule called when it has a covalently attached amino acid?

<p>charged</p> Signup and view all the answers

What is the name of the three-base nucleotide sequence that pairs with a specific codon on the mRNA?

<p>anticodon</p> Signup and view all the answers

What family of enzymes is required for attachment of amino acids to their corresponding tRNAs?

<p>Aminoacyl-tRNA synthetases</p> Signup and view all the answers

What kind of reaction do aminoacyl-tRNA synthetases catalyze?

<p>A two-step reaction</p> Signup and view all the answers

What is required for the overall reaction of aminoacyl-tRNA synthetases?

<p>Adenosine triphosphate (ATP)</p> Signup and view all the answers

What contributes to the high fidelity of translation of the genetic message?

<p>The extreme specificity of the synthetase in recognizing both the amino acid and its cognate tRNA.</p> Signup and view all the answers

Aminoacyl-tRNA synthetases are known to have only one function.

<p>False</p> Signup and view all the answers

What is required as a template for the synthesis of the desired polypeptide chain?

<p>mRNA</p> Signup and view all the answers

What is the name of the ribosomal binding proteins in prokaryotic cells?

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

What does the 16S rRNA component of the 30S ribosomal subunit have near its 3'-end?

<p>A nucleotide sequence complementary to the SD sequence</p> Signup and view all the answers

Eukaryotic messages have SD sequences.

<p>False</p> Signup and view all the answers

What are ribosomes?

<p>Large complexes of protein and ribosomal RNA (rRNA).</p> Signup and view all the answers

Ribosomes are composed of one large and one small subunit.

<p>True</p> Signup and view all the answers

The S (Svedberg) values are determined by shape, but not molecular mass.

<p>False</p> Signup and view all the answers

Prokaryotic 50S and 30S ribosomal subunits together form a 70S ribosome.

<p>True</p> Signup and view all the answers

What is the name of the site on a ribosome where the peptidyl-tRNA, carrying the growing polypeptide chain, is occupied?

<p>Peptidyl site</p> Signup and view all the answers

What is the name of the site on a ribosome where the empty tRNA occupies?

<p>Exit site</p> Signup and view all the answers

What is the name of the site on a ribosome that is the attachment site for an incoming aminoacyl-tRNAS?

<p>Acceptor site</p> Signup and view all the answers

The assembly of the rRNAs and ribosomal proteins to make the 40S and 60S subunits occurs within the nucleus.

<p>False</p> Signup and view all the answers

How is the protein synthesized during the elongation phase?

<p>Codons are read 5' to 3' from the amino end to the carboxyl end</p> Signup and view all the answers

How is the polypeptide chain released during the termination phase of protein synthesis?

<p>Special proteins hydrolyze the polypeptide from the last tRNA when a termination codon is reached</p> Signup and view all the answers

Which of the following are key components required for translation initiation?

<p>G-protein family members that use the energy released upon hydrolysis of bound GTP</p> Signup and view all the answers

Of what are the relative sizes of ribosomal subunits given in terms of?

<p>Their sedimentation coefficient (Svedberg values)</p> Signup and view all the answers

Prokaryotes have a larger ribosome than eukaryotes

<p>False</p> Signup and view all the answers

Eukaryotes use f-Met-tRNA, while prokaryotes use Met-tRNA to initiate translation.

<p>False</p> Signup and view all the answers

What are some of the key components required for peptide chain elongation?

<p>Aminoacyl-tRNAS</p> Signup and view all the answers

What does the amino acid activation by aminoacyl-tRNA synthetase require?

<p>ATP</p> Signup and view all the answers

What are the two main functions of aminoacyl-tRNA synthetase?

<p>Activates the amino acid and differentiates between amino acids and tRNA to synthesize aminoacyl-tRNA</p> Signup and view all the answers

Codon-anticodon pairing is parallel.

<p>False</p> Signup and view all the answers

TRNAs recognise more than one codon for a given amino acid.

<p>True</p> Signup and view all the answers

What is the name of the phenomenon in codon-anticodon pairing that allows for some flexibility in the pairing between the 3rd base of the codon and the 1st base of the anticodon?

<p>Wobble</p> Signup and view all the answers

What are the four main steps involved in the prokaryotic translation elongation and termination process?

<p>Loading of aminoacyl-tRNA on A site, peptide bond formation, translocation, termination</p> Signup and view all the answers

What are the major differences between eukaryotic and prokaryotic translation?

<p>Initiator tRNA</p> Signup and view all the answers

What are the names of the processes involved in post-translational modification of proteins?

<p>Protein folding, trimming by proteolytic degradation, intein splicing, and covalent changes</p> Signup and view all the answers

What is the process of removing portions of precursor molecules called?

<p>Trimming</p> Signup and view all the answers

The formation of insulin from preproinsulin is an example of trimming

<p>True</p> Signup and view all the answers

What are inteins?

<p>Intervening sequences in certain proteins.</p> Signup and view all the answers

Inteins must be removed and exteins ligated in the appropriate order for the protein to become active.

<p>True</p> Signup and view all the answers

Post-translational modifications can occur before the completion of protein synthesis.

<p>False</p> Signup and view all the answers

What are the four classes of glycans?

<p>N-linked glycans, O-linked glycans, Phospho glycans, C-linked glycans</p> Signup and view all the answers

Ubiquitination is the process by which a small protein called ubiquitin can be attached to proteins, leading to the destruction of the protein.

<p>True</p> Signup and view all the answers

Ubiquitination can only occur in cell cycle regulation.

<p>False</p> Signup and view all the answers

What is the name of the chemical messenger that reacts with free cysteine residues to form S-nitrothiols?

<p>Nitrosyl (NO)</p> Signup and view all the answers

What is the methyl donor in the process of methylation?

<p>S-adenosylmethionine (SAM)</p> Signup and view all the answers

What is the enzyme responsible for methylation?

<p>Methyltransferase</p> Signup and view all the answers

Methylation of lysine residues in histones in DNA is not an important regulator of chromatin structure.

<p>False</p> Signup and view all the answers

What is the name of the process involved in the addition of an acetyl group to the nitrogen of a protein?

<p>N-Acetylation</p> Signup and view all the answers

Histones are acetylated on lysine residues in the N-terminal tail as a part of gene regulation.

<p>True</p> Signup and view all the answers

N-Acetylation is not involved in the regulation of transcription factors, effector proteins, molecular chaperons and cytoskeletal proteins.

<p>False</p> Signup and view all the answers

What is the name of the enzyme responsible for N-terminal acetylation?

<p>Methionine aminopeptidase (MAP)</p> Signup and view all the answers

What is lipidation?

<p>The covalent attachment of a lipid group, such as a fatty acid, to a protein.</p> Signup and view all the answers

Disulfide bonds are ionic bonds.

<p>False</p> Signup and view all the answers

Disulfide bonds are involved in the correct folding of proteins.

<p>True</p> Signup and view all the answers

Study Notes

Protein Biosynthesis: Translation

  • Translation is the process where ribosomes use the genetic code from mRNA to synthesize proteins.
  • This process happens in the cytosol on ribosomes and is guided by mRNA.
  • Protein synthesis in eukaryotes is similar to the process in prokaryotes.
  • Proteins are high-molecular weight, nitrogen-containing organic compounds.
  • Polypeptides are made up of one or more amino acids.

Amino Acids

  • Amino acids are the building blocks for proteins.
  • Each amino acid has an amino group (NH2), a carboxyl group (COOH), a hydrogen atom, and a variable R group.
  • The R group is different for each amino acid.

Peptide Bonds

  • Polypeptides are linked together by peptide bonds.
  • A peptide bond is a covalent bond between the carboxyl group of one amino acid and the amino group of another amino acid.
  • This bond formation releases a water molecule.
  • Polypeptides have a N-terminus (amino) and a C-terminus (carboxyl) end.

Transfer RNA (tRNA)

  • tRNAs are crucial for translating the mRNA code into amino acids.
  • Each tRNA molecule has a specific anticodon that pairs with a codon on mRNA.
  • Each tRNA carries a specific amino acid.
  • There is at least one tRNA for each amino acid.
  • In humans, there are at least 50 types of tRNA, whereas bacteria have 30-40 types.
  • Amino acids are attached to the 3' end of the tRNA molecule. This attachment process is crucial in activating the amino acid for its role in protein synthesis.

Aminoacyl-tRNA Synthetases

  • Aminoacyl-tRNA synthetases are enzymes in charge of attaching specific amino acids to their corresponding tRNAs.
  • Each synthetase recognizes a particular amino acid and specific tRNAs for that amino acid.
  • These enzymes catalyze a two-step reaction with ATP where an amino acid is covalently attached to the tRNA.
  • The extreme specificity and proofreading activity of the enzymes ensure accuracy in protein synthesis.

Messenger RNA (mRNA)

  • mRNA carries the genetic code from DNA to the ribosomes.
  • The mRNA sequence is read in codons of three nucleotides.
  • The specific mRNA sequence determines which polypeptide chain is produced.
  • Prokaryotic mRNA has a Shine-Dalgarno (SD) sequence that aligns the ribosome with the start codon AUG. -Eukaryotic mRNA does not have a Shine-Dalgarno sequence, instead has a 5' cap followed by a start codon and protein coding sequence and eventually a stop codon and 3' polyA (adenine) tail.

Ribosomes

  • Ribosomes are large complexes of protein and ribosomal RNA (rRNA).
  • Ribosomes have two subunits (small and large).

Ribosome Binding Sites

  • Ribosomes have specific binding sites for mRNA and tRNAs.
  • A site: attachment site for tRNA carrying amino acids for assembly
  • P site: holds the growing polypeptide chain
  • E site: where the unloaded tRNA leaves

Protein Synthesis Phases

  • Initiation: the translation machinery locates the start codon AUG on mRNA.
  • Elongation: codons are read 5' → 3', and amino acids are added to the growing polypeptide chain.
  • Termination: a termination codon is reached, and the polypeptide is released.

Differences Between Prokaryotic and Eukaryotic Translation

  • Prokaryotic ribosomes are 70S while eukaryotes are 80S.
  • Prokaryotic initiator tRNA is formimethylmethionine (fMet-tRNAFmet) while eukaryotic initiator tRNA is methionine (Met-tRNAiMet).
  • Differences in initiation factors (IFs) and termination factors.
  • Eukaryotic mRNA has a Kozak sequence for initiation, in contrast to prokaryotic Shine-Dalgarno sequence.

Post-translational Modifications

  • Proteins aren't always functional immediately after translation.
  • Many changes take place after the initial synthesis of the protein through post-translational modifications.
  • Examples include protein folding, trimming by proteolytic degradation, intein splicing, and covalent changes.
  • Examples of specific modifications are: hydroxylation, glycosylation, phosphorylation, ubiquitination, S-nitrosylation, alkylation/methylation and N-acetylation, and lipidation, disulfide bonding.

Translation and Post-translational Modifications

  • Important processes that follow translation to achieve functional proteins.
  • Examples: proteolytic degradation (trimming of proteins via proteases), intein splicing (removal of intervening sequences from proteins), and various covalent modifications (hydroxylation, glycosylation, phosphorylation, ubiquitination).

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Translation and Protein Biosynthesis PDF

Description

This quiz explores the fascinating processes of protein biosynthesis, focusing on translation and the role of amino acids in forming proteins. You'll learn about peptide bonds, the structure of amino acids, and the function of transfer RNA (tRNA) in these biological processes.

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