Protein synthesis

Question 1

What is the name of the structure that brings in a.a. from mRNA ?

Answer 1

Adapter (tRNA )
At one end, has specific triplet codon that complements the codon of mRNA
At the other end, charged with a.a.

Question 2

What is a codon, what are characteristics

Answer 2

3 nucletotides that codes for an a.a.
In cells, no overlapping code!
64 combinations: 61 for a.a. , 3 are termination codons

Question 3

What is the initaion codon, what does it code for?

Answer 3

AUG–> methionine

Also called met codon

Question 4

What are the overall steps of prot synthesis?

Answer 4

Intiation
Activation of a.a –> tRNA is aminoacylated
Elongation
Termination

Question 5

What are the arms of tRNA ?

Answer 5

D arm
Amino acid arm: most important
TorC arm: extra arm, not always there, variable in size
Anticodon arm

Question 6

True or false: a codon can code for more than one a.a.?

Answer 6

False!

a.a can be coded by more than one codon, but a codon code for only one a.a.

Question 7

What are some of the of the post-ytsndlsyionsl modifications ?

Answer 7

• Enzymatic removal of formyl group from first residue, or removal of Met and sometimes additional residues
• Acetylation of N-terminal residue
• REmoval of signal sequences or other regions
• Forming disulfide bonds
• Attaching carbohydrates : occurs on most prots (especially the ones excreated oustide)

Question 8

How are prots degraded?

Answer 8

Ubiquination

- attachment of ubiquitin on target prots

Question 9

Where does ubiquitin attaches?

Answer 9

always on lysine residue

Question 10

How many steps in ubiquination? describe

Answer 10

3 steps:

1. E1 (with ATP ) attaches to ubiquitin
2. E2 attaches to ubiquitin, removal of E1
3. E2 attaches ubiquitin on lysine resudue, by the help of E3