Final Unit: Translation

Question 1

In translation, mRNA is converted to ___

Answer 1

Protein

Question 2

What are the monomers for proteins?

Answer 2

Amino acids

Question 3

BACTERIA: How long is the typical polypeptide?

Answer 3

A few hundred amino acids

Question 4

BACTERIA: Where do ribosomes attach?

Answer 4

At the 5’ ribosomal-binding site

Question 5

What is the start codon’s code and amino acid it codes for?

Answer 5

AUG, Methionine

Question 6

What are the stop codons?

Answer 6

UAA, UAG, UGA

Question 7

What are two other names for the stop codons?

Answer 7

Termination or nonsense codons

Question 8

What is the role of ribosomes?

Answer 8

Catalyze translation of mRNA into protein

Question 9

BACTERIA: When do ribosomes begin translating an mRNA?

Answer 9

Before RNA polymerase has finished transcribing it

Question 10

BACTERIA: When multiple ribosomes attach to an mRNA, what is formed?

Answer 10

Polyribosome

Question 11

Why is everything more complicated in eukaryotes?

Answer 11

mRNA has to be transported from the nucleus to the cytoplasm

Question 12

What is tRNA?

Answer 12

An adaptor molecule that delivers amino acids to ribosome

Question 13

What is the name used for the enzymes that attach tRNA to its correct amino acid?

Answer 13

Amino acyl-tRNA synthetases

Question 14

How many different Amino acyl-tRNA synthetases are there?

Answer 14

20

Question 15

What amino acid does tRNA(ser) carry?

Answer 15

Serine

Question 16

What are three common features of tRNA?

Answer 16

1. Cloverleaf structure
2. Anticodon
3. Acceptor stem for amino acid binding

Question 17

What is the tRNA anticodon?

Answer 17

It is the opposite of a codon on mRNA. For example, if mRNA has a codon of UCA, then the tRNA anticodon would be AGU.

Question 18

Although there are 61 different codons, how many tRNAs are there in most cells?

Answer 18

Only about 40

Question 19

To resolve the difference in codons and tRNAs, Francis Crick proposed the …

Answer 19

Wobble hypothesis

Question 20

What is the wobble hypothesis?

Answer 20

The third base in codons doesn’t need correct pairing. For example, the anticodon GAG could bind to the codon CUU even though for the third base, G isn’t the correct pairing for U.

Question 21

What is tRNA with an amino acid attached called?

Answer 21

Aminoacyl tRNA

Question 22

What is step 1 of how Aminoacyl-tRNA synthetase works?

Answer 22

A specific amino acid and ATP bind to the Aminoacyl-tRNA synthetase

Question 23

What is step 2 of how Aminoacyl-tRNA synthetase works? (2 parts)

Answer 23

The amino acid is activated by the covalent binding of AMP

Pyrophosphate is released

Question 24

What is step 3 of how Aminoacyl-tRNA synthetase works? (3 parts)

Answer 24

The correct tRNA binds to the synthetase.

The amino acid is covalently attached to the tRNA

AMP is released

Question 25

What is step 4 of how Aminoacyl-tRNA synthetase works?

Answer 25

The charged tRNA is released

Question 26

What do ribosomes contain (2 parts)?

Answer 26

Protein and rRNA

Question 27

What are the 2 subunits of ribosomes?

Answer 27

Large subunit and small subunit

Question 28

What is the role of the small subunit of ribosomes?

Answer 28

Holds the mRNA in place

Question 29

What happens at the large subunit of ribosomes?

Answer 29

The peptide bonds form

Question 30

During translation, how many distinct tRNAs line up within the ribosome?

Answer 30

3

Question 31

What is the difference between the structures of prokaryotic and eukaryotic ribosomes?

Answer 31

Prokaryotic: 50S and 30S subunits Eukaryotic: 60S and 40S subunits

Question 32

Are eukaryotic or prokaryotic ribosomes larger?

Answer 32

Eukaryotic

Question 33

The differences in the structures of prokaryotic and eukaryotic ribosomes led to what?

Answer 33

The design of numerous classes of antibiotics

Question 34

What are the three tRNA binding sites in ribosomes?

Answer 34

A (aminoacyl) P (peptidyl) E (exit)

Question 35

What happens at the A site?

Answer 35

The new incoming charged tRNA binds

Question 36

What happens at the P site?

Answer 36

The tRNA binds with the growing polypeptide chain

Question 37

What happens at the E site?

Answer 37

The empty tRNA binds, getting ready to leave

Question 38

What is the sequence of binding sites?

Answer 38

APE (A --> P --> E)

Question 39

What are the three steps of translation?

Answer 39

Initiation, Elongation, Termination

Question 40

BACTERIA: What are the three steps for translation initiation in bacteria?

Answer 40

1. mRNA binds to small subunit of ribosome 2. Initiator aminoacyl tRNA binds to start codon 3. Large subunit of ribosome binds, completing ribosome complex

Question 41

BACTERIA: What is the initiator tRNA?

Answer 41

tRNA (f-Met)

Question 42

BACTERIA: What is the ribosome binding site on mRNA called in bacteria?

Answer 42

Shine-Dalgarno sequence

Question 43

EUKARYOTES: What is the first difference in translation initiation of eukaryotes?

Answer 43

Instead of a ribosomal-binding sequence, mRNAs have a 5' guanosine cap

Question 44

EUKARYOTES: What recognizes the 5' cap during translation initiation?

Answer 44

Cap-binding proteins

Question 45

EUKARYOTES: What is the second difference in translation initiation of eukaryotes?

Answer 45

The position of the start codon is more variable, but in many cases the first AUG codon is used as the start codon

Question 46

During elongation, which site is the initiator tRNA bound to?

Answer 46

P

Question 47

What are the three steps of elongation?

Answer 47

1. Incoming aminoacyl tRNA 2. Peptide bond formation 3. Translocation of ribosome

Question 48

When does the termination start?

Answer 48

When the A site encounters a stop codon

Question 49

What is enters the A site when a stop codon is encountered?

Answer 49

Release factor

Question 50

What are the three steps for termination?

Answer 50

1. Release factor binds to stop codon 2. Polypeptide and uncharged tRNAs are released 3. Ribosome subunits separate

Question 51

Most proteins go through an extensive series of processing steps called ...

Answer 51

Post-translational modification

Question 52

Post-translational modification happens before...

Answer 52

Before proteins are ready to go work in a cell

Question 53

What speeds the folding of a protein?

Answer 53

Molecular chaperones

Question 54

What determines the protein's shape and therefore its function?

Answer 54

Folding