ADL Lecture 2: 9

Question 1

Translation

Answer 1

synthesis of protein by an mRNA originally copied from DNA

Question 2

What are the two processes of protein production?

Answer 2

1. information-transfer processes: RNA base sequence determines an amino acid sequence
2. chemical processes: amino acids are linked together

Question 3

Polypeptide chains

Answer 3

linear polymers of amino acids

Question 4

How many amino acids are there in the genetic code?

Answer 4

20

*Amino acids are the building blocks of proteins

Question 5

peptide bond

Answer 5

carboxyl group of one amino acid to amino group of next AA by hydrolysis

Question 6

Ribosomes

Answer 6

“machines” that contain multiple ribosomal RNAs (rRNAs) and proteins

Question 7

What are the three task ribosomes perform in bacteria/eukaryotes?

Answer 7

1. bind mRNA and identify start codon (where translation begins)
2. facilitate complementary base pairing of mRNA codons and the corresponding tRNA anticodons
3. catalyze formation of peptide bonds between amino acids on growing polypeptide chain

Question 8

What are the five major components of the translation system?

Answer 8

1. mRNA
2. Ribosome
3. tRNA
4. aminoacyl-tRNA synthetases
5. initiation, elongation and termination factors

Question 9

aminoacyl-tRNA snthetases

Answer 9

set of molecules catalyzes the attachment of particular amino acid to its corresponding tRNA molecule

Question 10

tRNA (main action)

Answer 10

small adaptor molecule that translates codons into amino acid

Question 11

Eukaryotic (E) translational initiation

Answer 11

• eukaryotic 40s ribosomal subunit complexes w/ eIF proteins
• eIFs & charged tRNA^met bind small subunit to form pre initiation complex
• complex recruited to 5’ region
• once complex is formed, it “scans” for start codon (AUG) Kozak sequence –> 60s subunit

Question 12

elongation factors (EF) use what type of energy? and what do EFs perform?

Answer 12

GTP hydrolysis;

1. recruit charged tRNAs to A-site
2. Form peptide bonds btw sequential AA
3. translocate ribosome in 3’ direction along mRNA

Question 13

peptidyl transferase

Answer 13

catalyzes couple reaction in which bond connecting methionine to tRNA^met is transferred to amino group of next AA (=peptide bond)

Question 14

what are the three stop codons?

Answer 14

UAA
UAG
UGA

Question 15

Bacteria and eukaryotes use ___ to bind a stop codon in the __ site.

Answer 15

release factors (RF)
A-site

Question 16

iso-accepting tRNAs

Answer 16

tRNA molecules with different anticodons for the same amino acids

Question 17

Post-translational polypeptide processing

Answer 17

modifies polypeptides into functional proteins by removal or chemical alteration of amino acids

Question 18

Protein sorting/ signal sequences (leader sequences)

Answer 18

direct proteins to their cellular destinations

Question 19

Chaperone Proteins

Answer 19

help proteins fold correctly and/or trigger destruction of incorrectly folded protein

Question 20

What is the most common AA modification?

Answer 20

phosphorylation carried out by kinases

Question 21

Incorrectly folded proteins cause mutations… what happens to these proteins?

Answer 21

Within the ER, proteins that are incorrectly folding are bound by molecules called chaperones that help proteins fold correctly (if folded correctly-released; in nor folded properly-destroyed)