module 7 lec 6

Question 1

What is the function of the ribosome?

Answer 1

The ribosome is the site of polypeptide synthesis.

Question 2

What are ribosomes made of

Answer 2

Ribosomes are made of rRNA and proteins.

Question 3

How do ribosomes contribute to translation?

Answer 3

Ribosomes read mRNA codons and facilitate the pairing of tRNA to add amino acids to the growing polypeptide chain.

Question 4

What are the two main components of a ribosome?

Answer 4

Ribosomes have two main components: a large subunit and a small subunit.

Question 5

Are ribosomes found in all cells?

Answer 5

Yes, ribosomes are found in both prokaryotic and eukaryotic cells, where they carry out translation.

Question 6

What is translation initiation?

Answer 6

Translation initiation is the process where the ribosome assembles on the mRNA and starts protein synthesis.

Question 7

What are the key steps in translation initiation?

Answer 7

Small ribosomal subunit binds to mRNA.
Initiator tRNA binds to the start codon (usually AUG).
The large ribosomal subunit binds, forming the complete ribosome.

Question 8

What role does the start codon play in translation initiation?

Answer 8

The start codon (AUG) signals the beginning of translation and recruits the initiator tRNA carrying methionine.

Question 9

What is the role of the initiator tRNA in translation initiation?

Answer 9

The initiator tRNA carries the first amino acid (usually methionine) and pairs with the start codon on mRNA.

Question 10

What happens after translation initiation

Answer 10

After initiation, the ribosome moves along the mRNA, and translation elongation begins, adding amino acids to the growing polypeptide chain.

Question 11

What happens during translation elongation?

Answer 11

During translation elongation, amino acids are added to the C-terminus of the growing polypeptide chain.

Question 12

How are amino acids added during elongation?

Answer 12

tRNA molecules with the corresponding amino acids bind to mRNA codons in the ribosome, and the amino acids are added to the polypeptide.

Question 13

What is the direction of polypeptide growth during translation elongation?

Answer 13

The polypeptide grows in the C-terminus direction as amino acids are added one by one.

Question 14

What are the key steps in translation elongation?

Answer 14

Key steps include:

Codon recognition: tRNA with the matching anticodon binds to the mRNA codon.
Peptide bond formation: The ribosome catalyzes the formation of a peptide bond between amino acids.
Translocation: The ribosome moves along the mRNA to the next codon.

Question 15

What happens after translation elongation?

Answer 15

After elongation, the process continues until a stop codon is reached, triggering translation termination.

Question 16

What signals the end of translation?

Answer 16

Stop codons (UAA, UAG, UGA) signal the end of translation and trigger translation termination.

Question 17

What happens during translation termination?

Answer 17

During translation termination, the ribosome reaches a stop codon, and a release factor binds, causing the release of the newly synthesized polypeptide.

Question 18

What role do release factors play in translation termination?

Answer 18

Release factors recognize the stop codon and catalyze the release of the polypeptide from the ribosome.

Question 19

What happens to the ribosome after translation termination?

Answer 19

After translation termination, the ribosome dissociates from the mRNA, and the polypeptide is released to fold into its functional form.

Question 20

What is a polyribosome?

Answer 20

A polyribosome is a complex of multiple ribosomes translating the same mRNA simultaneously.

Question 21

What is the advantage of polyribosomes in translation?

Answer 21

Polyribosomes increase the efficiency of protein synthesis by allowing multiple copies of a protein to be made at once from a single mRNA.

Question 22

Where are polyribosomes typically found?

Answer 22

Polyribosomes are commonly found in the cytoplasm of both prokaryotes and eukaryotes, where they speed up protein production.

Question 23

What is posttranslational processing?

Answer 23

Posttranslational processing involves modifications to a protein after it has been synthesized, affecting its structure, activity, and function.

Question 24

How does enzymatic cleavage affect proteins?

Answer 24

Enzymatic cleavage may remove an amino acid, split a polyprotein, or activate a zymogen (inactive enzyme form)

Question 25

What is the role of chemical modifications in posttranslational processing?

Answer 25

Chemical modifications like phosphorylation, acetylation, or glycosylation can alter protein structure, activity, or its cellular location.

Question 26

What is a zymogen?

Answer 26

A zymogen is an inactive enzyme precursor that is activated by posttranslational cleavage.

Question 27

How do chemical modifications affect protein function?

Answer 27

Chemical modifications can enhance or inhibit a protein’s function, affect its stability, or influence its interaction with other molecules

Question 28

What is polyprotein cleavage?

Answer 28

Polyprotein cleavage involves splitting a large protein into smaller functional proteins after translation, often seen in viral proteins.

Question 29

Where does gene expression occur in prokaryotes?

Answer 29

In prokaryotes, gene expression occurs in the cytoplasm since they lack a nucleus.

Question 30

How is transcription and translation related in prokaryotes?

Answer 30

In prokaryotes, transcription and translation can occur simultaneously in the cytoplasm

Question 31

What is the key regulatory element for gene expression in prokaryotes?

Answer 31

Prokaryotes regulate gene expression using operons, which group related genes together under the control of a single promoter.

Question 32

Do prokaryotes have introns in their genes?

Answer 32

No, prokaryotes typically do not have introns in their genes, so mRNA is usually ready for translation right after transcription.

Question 33

Where does transcription and translation occur in eukaryotes?

Answer 33

In eukaryotes, transcription occurs in the nucleus, and translation happens in the cytoplasm.

Question 34

What is the key regulatory element for gene expression in eukaryotes?

Answer 34

: In eukaryotes, gene expression is regulated by promoters, enhancers, silencers, and other regulatory sequences that interact with transcription factors.

Question 35

How is RNA processed in eukaryotes?

Answer 35

n eukaryotes, RNA undergoes several post-transcriptional modifications like capping, splicing, and the addition of a poly-A tail before leaving the nucleus.

Question 36

How is gene expression in eukaryotes more complex than in prokaryotes

Answer 36

Eukaryotic gene expression is more complex due to chromatin remodeling, RNA processing, and regulation by multiple factors, including enhancers and repressors.

Question 37

Do eukaryotes have introns?

Answer 37

Yes, eukaryotic genes often contain introns that are removed during RNA splicing, leaving only the exons in the mature mRNA.