Final Unit: Translation Flashcards

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1
Q

In translation, mRNA is converted to ___

A

Protein

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2
Q

What are the monomers for proteins?

A

Amino acids

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3
Q

BACTERIA: How long is the typical polypeptide?

A

A few hundred amino acids

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4
Q

BACTERIA: Where do ribosomes attach?

A

At the 5’ ribosomal-binding site

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5
Q

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

A

AUG, Methionine

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6
Q

What are the stop codons?

A

UAA, UAG, UGA

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7
Q

What are two other names for the stop codons?

A

Termination or nonsense codons

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8
Q

What is the role of ribosomes?

A

Catalyze translation of mRNA into protein

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9
Q

BACTERIA: When do ribosomes begin translating an mRNA?

A

Before RNA polymerase has finished transcribing it

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10
Q

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

A

Polyribosome

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11
Q

Why is everything more complicated in eukaryotes?

A

mRNA has to be transported from the nucleus to the cytoplasm

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12
Q

What is tRNA?

A

An adaptor molecule that delivers amino acids to ribosome

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13
Q

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

A

Amino acyl-tRNA synthetases

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14
Q

How many different Amino acyl-tRNA synthetases are there?

A

20

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15
Q

What amino acid does tRNA(ser) carry?

A

Serine

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16
Q

What are three common features of tRNA?

A
  1. Cloverleaf structure
  2. Anticodon
  3. Acceptor stem for amino acid binding
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17
Q

What is the tRNA anticodon?

A

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.

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18
Q

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

A

Only about 40

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19
Q

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

A

Wobble hypothesis

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20
Q

What is the wobble hypothesis?

A

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.

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21
Q

What is tRNA with an amino acid attached called?

A

Aminoacyl tRNA

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22
Q

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

A

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

23
Q

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

A

The amino acid is activated by the covalent binding of AMP

Pyrophosphate is released

24
Q

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

A

The correct tRNA binds to the synthetase.

The amino acid is covalently attached to the tRNA

AMP is released

25
Q

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

A

The charged tRNA is released

26
Q

What do ribosomes contain (2 parts)?

A

Protein and rRNA

27
Q

What are the 2 subunits of ribosomes?

A

Large subunit and small subunit

28
Q

What is the role of the small subunit of ribosomes?

A

Holds the mRNA in place

29
Q

What happens at the large subunit of ribosomes?

A

The peptide bonds form

30
Q

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

A

3

31
Q

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

A

Prokaryotic: 50S and 30S subunits

Eukaryotic: 60S and 40S subunits

32
Q

Are eukaryotic or prokaryotic ribosomes larger?

A

Eukaryotic

33
Q

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

A

The design of numerous classes of antibiotics

34
Q

What are the three tRNA binding sites in ribosomes?

A

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

35
Q

What happens at the A site?

A

The new incoming charged tRNA binds

36
Q

What happens at the P site?

A

The tRNA binds with the growing polypeptide chain

37
Q

What happens at the E site?

A

The empty tRNA binds, getting ready to leave

38
Q

What is the sequence of binding sites?

A

APE (A –> P –> E)

39
Q

What are the three steps of translation?

A

Initiation, Elongation, Termination

40
Q

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

A
  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
41
Q

BACTERIA: What is the initiator tRNA?

A

tRNA (f-Met)

42
Q

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

A

Shine-Dalgarno sequence

43
Q

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

A

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

44
Q

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

A

Cap-binding proteins

45
Q

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

A

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

46
Q

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

A

P

47
Q

What are the three steps of elongation?

A
  1. Incoming aminoacyl tRNA
  2. Peptide bond formation
  3. Translocation of ribosome
48
Q

When does the termination start?

A

When the A site encounters a stop codon

49
Q

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

A

Release factor

50
Q

What are the three steps for termination?

A
  1. Release factor binds to stop codon
  2. Polypeptide and uncharged tRNAs are released
  3. Ribosome subunits separate
51
Q

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

A

Post-translational modification

52
Q

Post-translational modification happens before…

A

Before proteins are ready to go work in a cell

53
Q

What speeds the folding of a protein?

A

Molecular chaperones

54
Q

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

A

Folding