Podcast
Questions and Answers
During the initiation of translation, what initially binds to the correct site on the mRNA?
During the initiation of translation, what initially binds to the correct site on the mRNA?
What is the role of the initiator tRNA during translation initiation?
What is the role of the initiator tRNA during translation initiation?
What is the specific function of release factor during translation termination?
What is the specific function of release factor during translation termination?
In which direction does the peptide chain grow during elongation?
In which direction does the peptide chain grow during elongation?
Signup and view all the answers
What directly catalyzes the formation of peptide bonds during elongation?
What directly catalyzes the formation of peptide bonds during elongation?
Signup and view all the answers
What is required for the translocation step in translation elongation?
What is required for the translocation step in translation elongation?
Signup and view all the answers
What happens to the discharged tRNA after translocation?
What happens to the discharged tRNA after translocation?
Signup and view all the answers
What recognizes the stop codons during translation termination?
What recognizes the stop codons during translation termination?
Signup and view all the answers
What role does tRNA play in protein synthesis?
What role does tRNA play in protein synthesis?
Signup and view all the answers
Which process during the elongation phase of transcription does not require energy from GTP hydrolysis?
Which process during the elongation phase of transcription does not require energy from GTP hydrolysis?
Signup and view all the answers
Which statement about the genetic code and codons is true?
Which statement about the genetic code and codons is true?
Signup and view all the answers
What are the three phases of translation?
What are the three phases of translation?
Signup and view all the answers
What consequence do rare errors in the genetic code lead to?
What consequence do rare errors in the genetic code lead to?
Signup and view all the answers
Which statement about the differences between DNA and RNA is false?
Which statement about the differences between DNA and RNA is false?
Signup and view all the answers
Which statement regarding mRNA processing is NOT true?
Which statement regarding mRNA processing is NOT true?
Signup and view all the answers
What process occurs at the ribosome?
What process occurs at the ribosome?
Signup and view all the answers
What is essential for ensuring the accuracy of protein synthesis?
What is essential for ensuring the accuracy of protein synthesis?
Signup and view all the answers
Which component serves as the interpreter of the genetic message in translation?
Which component serves as the interpreter of the genetic message in translation?
Signup and view all the answers
What role does the ribosomal RNA (rRNA) play in the ribosome?
What role does the ribosomal RNA (rRNA) play in the ribosome?
Signup and view all the answers
During translation, what is recognized by the anticodon on tRNA?
During translation, what is recognized by the anticodon on tRNA?
Signup and view all the answers
What is the function of aminoacyl-tRNA synthetase?
What is the function of aminoacyl-tRNA synthetase?
Signup and view all the answers
What is the role of the signal sequence in proteins destined for export from the cell?
What is the role of the signal sequence in proteins destined for export from the cell?
Signup and view all the answers
Which of the following statements about mutations is accurate?
Which of the following statements about mutations is accurate?
Signup and view all the answers
What is the nature of ribosomes in cellular biology?
What is the nature of ribosomes in cellular biology?
Signup and view all the answers
Which codon is recognized as the start codon in mRNA?
Which codon is recognized as the start codon in mRNA?
Signup and view all the answers
Which statement regarding tRNA is correct?
Which statement regarding tRNA is correct?
Signup and view all the answers
What typically initiates the synthesis of a polypeptide chain?
What typically initiates the synthesis of a polypeptide chain?
Signup and view all the answers
In the context of ribosomal function, what is a polyribosome?
In the context of ribosomal function, what is a polyribosome?
Signup and view all the answers
What occurs after the signal peptide is bound by SRP during protein synthesis?
What occurs after the signal peptide is bound by SRP during protein synthesis?
Signup and view all the answers
Flashcards
Differences between DNA and RNA
Differences between DNA and RNA
DNA has deoxyribose, uses thymine; RNA uses ribose and uracil.
mRNA Processing
mRNA Processing
mRNA undergoes modifications for protection, exiting nucleus, and splicing.
Ribosome Function
Ribosome Function
Ribosomes are the sites where translation occurs, converting mRNA into proteins.
Translation Process
Translation Process
Signup and view all the flashcards
Codons
Codons
Signup and view all the flashcards
tRNA Function
tRNA Function
Signup and view all the flashcards
Genetic Code
Genetic Code
Signup and view all the flashcards
Aminoacyl-tRNA Synthetase
Aminoacyl-tRNA Synthetase
Signup and view all the flashcards
Initiation of Translation
Initiation of Translation
Signup and view all the flashcards
Start Codon
Start Codon
Signup and view all the flashcards
Initiator tRNA
Initiator tRNA
Signup and view all the flashcards
Elongation Phase
Elongation Phase
Signup and view all the flashcards
Codon Recognition
Codon Recognition
Signup and view all the flashcards
Peptide Bond Formation
Peptide Bond Formation
Signup and view all the flashcards
Translocation
Translocation
Signup and view all the flashcards
Termination of Translation
Termination of Translation
Signup and view all the flashcards
tRNA
tRNA
Signup and view all the flashcards
Translation phases
Translation phases
Signup and view all the flashcards
Ribosome
Ribosome
Signup and view all the flashcards
Codon redundancy
Codon redundancy
Signup and view all the flashcards
GTP hydrolysis in transcription
GTP hydrolysis in transcription
Signup and view all the flashcards
Polyribosomes
Polyribosomes
Signup and view all the flashcards
Signal sequence
Signal sequence
Signup and view all the flashcards
Post-translational modification
Post-translational modification
Signup and view all the flashcards
Free ribosomes
Free ribosomes
Signup and view all the flashcards
Mutations
Mutations
Signup and view all the flashcards
Ribosome composition
Ribosome composition
Signup and view all the flashcards
Study Notes
Lecture 10: How Cells Make Proteins
- Lecture 8 covered DNA as a store of biological information
- Lecture 9 covered RNA and how genes are expressed
- Lecture 10 details how cells make proteins
False Statement about DNA and mRNA
- DNA contains deoxyribose sugars, mRNA contains ribose sugars
- DNA uses thymine, mRNA uses uracil
- DNA has a double helix, mRNA is single-stranded
- DNA and mRNA do not ALWAYS reside in the nucleus of cells (false statement)
mRNA Processing
- RNA is modified before leaving the nucleus
- mRNA processing protects mRNA from degradation
- mRNA processing helps mRNA exit the nucleus
- mRNA processing does NOT help anchor mRNA to ribosomes
- mRNA processing does help the splicing process by attracting snRNPs (small nuclear ribonucleoproteins)
Ribosomes
- Ribosomes are the site of translation
- Ribosomes are not involved in transcription, RNA processing, or splicing
Learning Objectives - Lecture 14 (Protein)
- Cells make polypeptides of specific lengths and sequences.
- Accurate protein synthesis requires base-pairing
- Protein synthesis (translation) utilizes ribosomes, aminoacyl-tRNAs, and mRNA (instruction tape)
- The genetic code defines how codons associate with anticodons
- Proteins are processed and targeted to specific cellular locations for proper function
From DNA to Protein
- Transcription occurs in the nucleus (eukaryotes) or cytoplasm (prokaryotes)
- DNA strand (template) is transcribed into mRNA
- mRNA carries the genetic code to the ribosome
- Translation occurs at the ribosome in the cytoplasm
- mRNA codons (triplet code) are translated into amino acids
- Translation uses tRNA anticodons for recognition and amino acid delivery
Translation: The Basic Concept
- The cell reads and interprets a genetic message, building a polypeptide
- Messenger RNA (mRNA) contains codons, decoded by tRNA
- mRNA moves through a ribosome, translating codons into amino acids, one by one
- Transfer RNA (tRNA) carries amino acids to the ribosome, matching anticodons with codons
- tRNA delivers amino acids to the growing polypeptide chain, when the anticodon recognizes the codon
tRNA Structure
- tRNA is a key part of accurate information transfer, through base pairing using hydrogen bonds
- tRNA transfers amino acids to the ribosome, the site of protein synthesis
- Several tRNA types exist for each amino acid type
- The tRNA anticodon interacts with the mRNA codon to ensure correct amino acid addition
Aminoacyl-tRNA Synthetase
- Aminoacyl-tRNA synthetase is an enzyme that attaches the correct amino acid to a tRNA molecule
- 20 different synthetases exist, one for each amino acid
- This process requires energy (ATP) to activate the amino acid
- Accurate loading of tRNA ensures precise protein synthesis
The Ribosome (Structure and Function)
- Ribosomes are large complex structures made of rRNA and protein
- Ribosomes have three binding sites (A, P, and E sites) for tRNA
- Ribosomes catalyze peptide bond formation between amino acids, acting as ribozymes and central to the process
- Ribosomes facilitate translation of mRNA to polypeptide chains, from amino to carboxyl end
Initiation of Translation
- Translation begins when the small ribosomal subunit binds to mRNA at the start codon (AUG)
- An initiator tRNA carrying methionine (Met) binds to the start codon
- The large ribosomal subunit joins to complete the initiation complex - which is required for protein synthesis to start
Elongation During Translation
- Amino acids are added to the growing polypeptide chain, one at a time
- Codon recognition brings the correct tRNA into the A site
- Peptide bond formation links the new amino acid to the growing polypeptide chain, by rRNA (large subunit)
- Translocation moves the tRNA in the A site to the P site, and discharged tRNA to the E site to leave the ribosome
Termination of Translation
- Elongation continues until a stop codon is reached (UAA, UAG, or UGA)
- A release factor binds to the stop codon, releasing the polypeptide chain
- The ribosome and other components are then released
Microscopic Analysis of Transcription
- Ribosomes can work in clusters on an mRNA, synthesizing multiple polypeptides simultaneously (polyribosomes)
- A single ribosome makes an average sized polypeptide in about a minute
The Genetic Code
- The genetic code translates the nucleotide sequence of mRNA into the amino acid sequence of a polypeptide
- A triplet codon of mRNA translates to a single amino acid
- The genetic code is degenerate (multiple codons can code for the same amino acid), and not ambiguous
- Genetic code is universal (works in all organisms)
The Genetic Code (Detail)
- The genetic code is a triplet code, non-overlapping
- The reading frame must be correct for accurate translation
- The code is degenerate (redundant), multiple codons can specify the same amino acid
- There are start and stop codons (AUG for methionine, UGA, UAA, UAG)
- The code is nearly universal (with some minor exceptions in certain organelles)
Protein Post-Translational Modification
- Polypeptide chains fold into their 3D structures
- Additional components (sugars, lipids) might be added or some amino acids removed
- Some proteins (e.g. membrane proteins) are moved to their required location
Mutations
- Mutations in DNA sequence can lead to changes or no changes in proteins
- Mutations can be base-pair substitutions (no shift, missense, or nonsense mutations) or frameshift mutations (causing extensive missense)
- Mutations can be insertions or deletions
Protein Structure
- Proteins have specific 3D structures, essential for function
- The three-dimensional shape is dictated by the amino acid sequence, interacting by multiple bonds and forces.
Ribosomes (Composition Question)
- Ribosomes are made of ribosomal RNA (rRNA) and protein
The Start Codon in mRNA
- The start codon in mRNA is AUG
Which statement is false for tRNA?
- tRNA molecules are NOT held together by disulfide bridges
Which process in the elongation phase of transcription does not require energy?
- Peptide bond formation; between adjacent amino acids
Triplet Code Details
- The number of possible codons is 64 and not 9
- There are 20 amino acids, but 64 codons
- Different codons code for the same amino acid
- Some codons are start and stop signals
Lecture 10 Translation Summary
- Translation involves initiation, elongation, and termination phases
- Ribosomes are essential for translation and protein synthesis
- The genetic code is involved in accurate protein sequence determination
- Mutations can cause protein synthesis errors
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your understanding of translation processes in biology. This quiz covers key concepts such as translation initiation, elongation, and termination, including the roles of tRNA and release factors. Perfect for students studying molecular biology and genetics.
