Protein Synthesis Flashcards
What are the two steps of protein synthesis and where do they occur in the cell?
transcription occurs in the nucleus (or cytoplasm of prokaryotes) and involves the synthesis of RNA from a DNA template, while translation occurs in the cytoplasm and involves the assembly of amino acids into a protein using the RNA sequence as a template.
What is the role of mRNA?
Messenger RNA (mRNA) is a type of RNA molecule that carries genetic information from DNA to the ribosomes, where it serves as a template for protein synthesis. The role of mRNA is to transcribe or copy the genetic information from the DNA into a complementary RNA sequence that can be read by the ribosomes during translation.
What is the difference between mRNA and DNA?
Structure: DNA is a double-stranded molecule, while mRNA is a single-stranded molecule. DNA has a deoxyribose sugar, while RNA has a ribose sugar. DNA contains four nitrogenous bases: adenine, thymine, guanine, and cytosine, while RNA contains adenine, uracil, guanine, and cytosine.
Function: DNA stores and transmits genetic information from one generation to the next, while mRNA carries genetic information from DNA to the ribosomes for protein synthesis.
Location: DNA is primarily located in the nucleus of eukaryotic cells, while mRNA is synthesized in the nucleus and then transported to the cytoplasm for protein synthesis.
Stability: DNA is more stable than mRNA and can remain intact for long periods of time, while mRNA is relatively unstable and is rapidly degraded in the cell.
When is mRNA made in the protein synthesis process?
mRNA is synthesized during the first step of protein synthesis, which is transcription.
Describe the role of each of the following in the process of protein synthesis?
a. mRNA
b. Ribosome
c. tRNA
d. amino acid
e. codon
f. anti-codon
g. peptidyl transferase enzyme
a. mRNA: mRNA stands for messenger RNA, and it carries the genetic information from the DNA to the ribosome, where it serves as a blueprint for protein synthesis.
b. Ribosome: Ribosomes are cellular structures that facilitate protein synthesis. They read the mRNA molecule and use the genetic information to synthesize a protein.
c. tRNA: tRNA stands for transfer RNA, and it is responsible for bringing the correct amino acid to the ribosome during protein synthesis. Each tRNA molecule carries a specific amino acid, and it has an anticodon sequence that binds to the complementary codon on the mRNA.
d. Amino acid: Amino acids are the building blocks of proteins. During protein synthesis, they are brought to the ribosome by tRNA molecules, where they are linked together in a specific sequence to form a protein.
e. Codon: A codon is a sequence of three nucleotides on the mRNA molecule that codes for a specific amino acid.
f. Anti-codon: An anticodon is a sequence of three nucleotides on the tRNA molecule that is complementary to the codon on the mRNA. The anticodon ensures that the correct amino acid is added to the growing protein chain.
g. Peptidyl transferase enzyme: Peptidyl transferase is an enzyme that is present in the ribosome. It catalyzes the formation of peptide bonds between adjacent amino acids during protein synthesis, allowing the protein chain to grow.
Name and describe the three steps of translation
Translation is the process of protein synthesis, which occurs in ribosomes. There are three main steps in translation:
Initiation: The first step of translation is initiation, which begins with the binding of the small ribosomal subunit to the mRNA. This occurs with the help of the initiator tRNA, which carries the amino acid methionine. The ribosome then moves along the mRNA until it reaches the start codon, which is AUG.
Elongation: During the elongation step, amino acids are added to the growing polypeptide chain. This is achieved through the formation of peptide bonds between adjacent amino acids. The ribosome moves along the mRNA, reading the codons and matching them to the appropriate tRNA. The tRNA then adds its amino acid to the growing chain.
Termination: The final step of translation is termination, which occurs when the ribosome reaches one of the three stop codons (UAA, UAG, or UGA) on the mRNA. At this point, the ribosome releases the newly synthesized polypeptide chain, and the components of the translation machinery dissociate from each other.
What are the functions of the start and stop codons?
The start codon (AUG) signals the beginning of protein synthesis and indicates where the ribosome should start translating the mRNA sequence into a protein. The stop codon (UAA, UAG, or UGA) signals the end of the protein-coding sequence and tells the ribosome to release the completed protein.
Are there stop amino acids?
No, there are no stop amino acids. Amino acids are the building blocks of proteins and are linked together during protein synthesis. Stop codons, not stop amino acids, are the signals that indicate the end of the protein-coding sequence and cause the ribosome to release the completed protein.
What is meant by the genetic code is redundant and universal?
The genetic code is redundant because multiple codons can code for the same amino acid, so a change in one nucleotide may not change the resulting protein. It is universal because the same genetic code is used by all living organisms on Earth, from bacteria to humans.
What are the functions of the three different types of RNA?
Messenger RNA (mRNA): It carries genetic information from DNA in the nucleus to the ribosomes in the cytoplasm, which is then used to synthesize proteins.
Transfer RNA (tRNA): It carries specific amino acids to the ribosome during protein synthesis and matches them to the corresponding codon on the mRNA.
Ribosomal RNA (rRNA): It forms the structural and catalytic components of ribosomes, which are responsible for the synthesis of proteins.
