Ch. 22b Post-Translational Processing & Genetic Code (Final Exam) Flashcards

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1
Q

Why does post-translational processing occur?

A

The polypeptide coming from the ribosome is inactive

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2
Q

What are the 4 structures of protein folding?

A

Primary, secondary, tertiary, and quarternary

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3
Q

Protein folding is aided by molecular chaperons. Where do they bind?

A

Hydrophobic regions of proteins

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4
Q

Why is chaperon binding important?

A

They keep protein in open conformation until it is ready to fold

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5
Q

What are the 2 functions of proteolytic cleavage?

A

1) Trimming to remove pieces of the N and/or C terminal to provide a shortened active protein
2) Cutting polypeptides into active protein segments

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6
Q

What drug is a common result of proteolytic cleavage?

A

Insulin

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7
Q

Post-translational chemical modification involves the…

A

Addition of small chemical functional groups to animo acids

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8
Q

What is the most common mode of chemical modification in animal cells?

A

Protein phosphorylation

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9
Q

Chemical modification promotes…

A

Protein diversity

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10
Q

What 3 amino acids are subjected to phosphorylation?

A

Serine, tyrosine, and theonine

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11
Q

What is the premise of protein degradation/ubiquitination?

A

Adding ubiquitin to misfolded proteins

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12
Q

What does the proteasome do once a protein is tagged with ubiquitin?

A

The proteasome recognizes the need for degradation into peptide subunits

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13
Q

In sum, how do post-translational mods affect proteins?

A

They change the structure, dynamics, behavior, and characteristics of proteins to allow for full activity

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14
Q

What do you call codons that code for the same amino acids?

A

Synonomous

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15
Q

Out of the 64 possible codons, how many represent amino acids, and how many are stop codons?

A

61 - represent
3 - stop codons

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16
Q

The tendency for identical or chemically similar amino acids to be represented by related codons minimizes…

A

The likelihood that a single base pair change will result in mutation

17
Q

Are codons with chemically similar amino acids similar or different in sequence?

A

Similar

18
Q

What is third-base degeneracy?

A

The insignificance of the base in a codon’s 3rd position (3’ end)

19
Q

Why is a codon’s 3rd base in a set of 4 codons insignificant?

A

Often, the 4 codons only differ in the 3rd base and represent the same amino acid

20
Q

What is the principle behind the wobbling hypothesis?

A

Multiple codons encoding the same amino acid most often differ at the 3rd base position

21
Q

Does each triplet codon require its own tRNA with a complementary anticodon, or can a single tRNA respond to related codons?

A

Often, 1 tRNA can recognize more than one codon

22
Q

An mRNA codon’s 3rd base position is a tRNA anticodon’s { } base position.

A

1st

23
Q

What explanation did Crick give for the wobble hypothesis?

A

The anticodon’s 5’ end doesn’t have strict base-pairing requirements, so it can form hydrogen bonds with several bases at the codon’s 3’ end

24
Q

Which ribosomal site permits the increased flexibility at the anticodon’s 1st base?

A

A

25
Q

What would happen if the genetic code was no degenerative (i.e. allow for wobbling)?

A

Only 20 codons would code amino acids, and 44 would be stop codons, resulting in mutation

26
Q

Anticodon 1st position base U corresponds to this codon 3rd position base(s).

A

A or G

27
Q

Anticodon 1st position base C corresponds to this codon 3rd position base.

A

G

28
Q

Anticodon 1st position base A corresponds to this codon 3rd position base.

A

U

29
Q

Anticodon 1st position base G corresponds to this codon 3rd position base(s).

A

C or U