ribosomes

Question 1

what is the role of ribosomes?

Answer 1

it is the site of protein synthesis

Question 2

what are the 4 specific sites in the ribosome that is significant to its role?

Answer 2

1. mRNA binding site
2. peptidyl-tRNA site (P site)
3. aminoacyl-tRNA site (A site)
4. exit site (E site)

Question 3

where is the mRNA binding site located in?

Answer 3

the small ribosomal subunit

Question 4

what is the role of the mRNA binding site?

Answer 4

it binds to the single-stranded mRNA

Question 5

where is the peptidyl-tRNA site located in?

Answer 5

the large ribosomal subunit

Question 6

what is the role of the peptidyl-tRNA site?

Answer 6

it binds to the aminoacyl-tRNA complexes

Question 7

where is the aminoacyl-tRNA site located in?

Answer 7

the large ribosomal subunit

Question 8

what is the role of the aminoacyl-tRNA site?

Answer 8

it binds to the aminoacyl-tRNA complex

Question 9

where is the exit site located in?

Answer 9

the large ribosomal subunit

Question 10

what is the role of the exit site?

Answer 10

to release the tRNA

Question 11

how does having an mRNA binding site enable ribosomes to carry out its role?

Answer 11

• in eukaryotes, the mRNA binding site (structural feature)
• recognizes & binds to the 5’ cap of the mRNA (1st point about significance to its role)
• upon binding, the small ribosomal subunit moves along the mRNA strand to identify the start codon (2nd point about significance to its role)
• so that the binding of the large subunit can take place to form the translation initiation complex (3rd point about significance to its role)

Question 12

how does having a peptidyl-tRNA site enable ribosomes to carry out its role?

Answer 12

• the peptidyl-tRNA site (structural feature) is where the initiator tRNA binds to the start codon
• which results in binding of the large ribosomal subunit (1st point about significance to its role)
• the peptidyl-tRNA site (structural feature)
• is also the site of peptide bond formation, catalyzed by peptidyl transferase on the large ribosomal subunit, which links the amino acids together to form a polypeptide chain (2nd point about significance to its role)

Question 13

how does having an aminoacyl-tRNA site enables ribosomes to carry out its role?

Answer 13

• the aminoacyl-tRNA (structural feature) is the site of binding of the next aminoacyl-tRNA complex
• to allow the next amino acid to be joined to the existing polypeptide chain (significance to its role)

Question 14

how does having an exit site enable ribosomes to carry out its role?

Answer 14

• the exit site (structural feature) is the site for the release of tRNA
• to be recycled in the cytoplasm (significance to its role)

Question 15

what do both ribosomal subunits help with?

Answer 15

both ribosomal subunits, which consists of rRNA & proteins, help to hold tRNA & mRNA in close proximity to form a polypeptide chain

Question 16

what does the large ribosomal subunit ensure?

Answer 16

it ensure that the codon of mRNA & the anti-codon of tRNA are properly positioned for accurate protein synthesis during translation

Question 17

what is a polyribosome?

Answer 17

a polyribosome is formed when an mRNA molecule is translated simultaneously by several ribosomes in a cluster

Question 18

what does the formation of a polyribosome do to the rate of protein synthesis?

Answer 18

the formation of a polyribosome increases the rate of translation, & hence the rate of polypeptide synthesis

Question 19

how are polyribosomes formed?