Kaplan Biochem Ch 4 Flashcards Preview

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Flashcards in Kaplan Biochem Ch 4 Deck (100)
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31

translation occurs in the ____ of ____

translation occurs in the cytoplasm of both prokaryotic and eukaryotic cells

32

in ______, ribosomes can begin translation the mRNA even before RNA polymerase completes its transcripton

- in Prokaryotes, ribosomes can begin translation the mRNA even before RNA polymerase completes its transcripton
- in eukaryotes, translation and transcription are completely separated in time and space with transcription in the nucleus and translation in the cytoplasm

33

streptomycin inhibits

initiation of protein synthesis (TRANSLATION)

34

Steps involved in elongation of protein synthesis

1. aminoacyl-tRNA binds to A site of the ribosome
- this is inhibited by shiga toxin (cuts 28S rRNA)
- tetracycline also inhibits step 1
2. peptide bond forms. this requires 2 high energy bonds per activation
- Peptidyl transferase is an enzyme that is part of the large subunit
- chloramphenicol inhibits peptidyl transferase
3. translation of ribosome 3 nucleotides along the mRNA
- requires GTP
- pseudomonas and diphtheria toxin inhibit ADP-ribosylation

35

In initiation of protein synthesis the ____ ribosomal subunit binds to the mRNA

In initiation of protein synthesis the small ribosomal subunit binds to the mRNA

36

in Prokaryotes, the ___ rRNA of the _____ subunit binds to the _______ in the 5' untranslated region of the mRNA

in Prokaryotes, the 16S rRNA of the small subunit binds to the Shine-Dalgarno in the 5' untranslated region of the mRNA

37

in ____, translation and transcription are completely separated in time and space with transcription in the _____ and translation in the _____

in eukaryotes, translation and transcription are completely separated in time and space with transcription in the nucleus and translation in the cytoplasm

38

Shiga toxin inhibits

step 1 of elongation of protein synthesis (TRANSLATION): aminoacyl-tRNA binding to A site of the ribosome
- cuts an adenine residue from 28S rRNA in the 60S subunit

39

chloramphenicol inhibits

chloramphenicol inhibits peptidyl transferase: step 2 of elongation of protein synthesis (TRANSLATION)

40

The initiator tRNA in eukaryotes carries ___

- Elongation is a 3-step cycle that is repeated for each AA added to the protein after the initiator methionine
- The initiator tRNA in eukaryotes carries met

41

Translation of protein synthesis ends when the stop codon reaches the ___
- what enzyme is involved?

- Translation of protein synthesis ends when the stop codon reaches the A site of the ribosome
- peptidyl transferase (with the help of release factor) hydrolyzes the completed protein from the final tRNA in the P site.
- the mRNA, ribosome, tRNA and factors can all be reused for additional protein synthesis

42

in Eukaryotes, the ____ subunit, binds to the ____ and slides down the message to the first AUG

in Eukaryotes, the small subunit, binds to the 5' cap structure and slides down the message to the first AUG

43

tetracycline inhibits

tetracycline inhibits step 1 of elongation of protein synthesis: aminoacyl-tRNA binding to A site of the ribosome

44

The charged initiation tRNA becomes bound to the AUG start codon on the message through _____
- the initiatior tRNA in prokaryotes carries ___
- the initiator tRNA in eukaryotes carries ___

The charged initiation tRNA becomes bound to the AUG start codon on the message through base pairing with its anticodon.

45

the initiatior tRNA in prokaryotes carries ___

- Elongation is a 3-step cycle that is repeated for each AA added to the protein after the initiator methionine
- The initiatior tRNA in prokaryotes carries fmet

46

pseudomonas and diphtheria toxin inhibit

in Eukaryotic cells, elongation factor 2 (eEF-2) used in translocation is inactivated through ADP-ribosylation by Pseudomonas and Diphtheria toxins

47

the P site is the site on the ribosome where ____ initially binds

- the P site is the site on the ribosome where (f) met initially binds.
- After formation of the first peptide bond, the P site is a binding site for the growing peptide chain

48

the aminoacyl site (A site) binds ??

the aminoacyl site (A site) binds each new incoming tRNA molecule carrying an activated AA

49

Elongation is a 3-step cycle that is repeated for each AA added to the protein after the initiator methionine
- Each cycle uses ?? high-energy bonds

Elongation is a 3-step cycle that is repeated for each AA added to the protein after the initiator methionine
- Each cycle uses 4 high-energy bonds:
- 2 from the ATP used in AA activation to charge the tRNA, and 2 from GTP

50

During elongation, the ribosome moves in the _____ direction along the mRNA, synthesizing the protein from ___ to _____ terminus.

During elongation, the ribosome moves in the 5' to 3' direction along the mRNA, synthesizing the protein from amino to carboxy terminus.

51

Peptidyl Transferase
- what is it and action

- an enzyme that is part of the large subunit, forms the peptide bond between the new AA and the carboxy end of the growing peptide chain
- The bond linking the growing peptide to the tRNA in the P site is broken, and the growing peptide attaches to the tRNA located in the A site.

This is step 2 of protein elongation

52

What occurs in the translocation step of protein synthesis
(aka the 3rd step in the elongation step of translocation)

- the ribosome moves exactly 3 nucleotides (one codon) along the message.
- This moves the growing peptidyl-tRNA into the P site and aligns the next codon to be translated with the empty A site.

53

in Eukaryotic cells, ____ used in translocation is inactivated through _____ by Pseudomonas and Diphtheria toxins

in Eukaryotic cells, elongation factor 2 (eEF-2) used in translocation is inactivated through ADP-ribosylation by Pseudomonas and Diphtheria toxins

54

Shiga and Shiga-like toxins clip an ____ residue from the ___ in the ___ subunit stopping protein synthesis in Eukaryotic cells

Shiga and Shiga-like toxins clip an adenine residue from the 28S rRNA in the 60S subunit stopping protein synthesis in Eukaryotic cells

55

Some well-known inhibitors of prokaryotic translocation include:

Some well-known inhibitors of prokaryotic translocation include:
- streptomycin
- erythromycin
- tetracycline
- chloramphenicol

56

Some well-known inhibitors of eukaryotic translocation include:

Some well-known inhibitors of eukaryotic translocation include:
- cycloheximide
- diptheria toxin
- pseudomonas toxin

57

Chloramphenicol inhibits ______ but not ______

Chloramphenicol inhibits mitochondrial protein synthesis but not cytoplasmic protein synthesis, because mitochondrial ribosomes are similar to prokaryotic ribosomes

58

Examples of eukaryotic proteins that are translated on ribosomes associated with the RER

- secreted proteins
- proteins inserted into the cell membrane
- lysosomal enzymes

Proteins translated on free cytoplasmic ribosomes include:
- cytoplasmic proteins
- mitochondrial proteins (encoded by nuclear genes)

59

the N-terminal hydrophobic signal sequence is used to ensure ____

the N-terminal hydrophobic signal sequence is used to ensure translation on the RER
- involves the signal recognition particle (SRP)
- crosses ER membrane (that's why it's hydrophobic, aka lipid soluble)
- translation begins in cytoplasm. Signal sequence causes ribosomes to attach to ER.
- a signal peptidase remove the signal sequence because its only function is entrance to the ER lumen.
- translation continues on RER.

* this only happens to proteins that leave the cytoplasm. i.e., go to lysosome, go to cell membrane, or are secreted

60

Phosphorylation of mannose residues is important for ___

Phosphorylation of mannose residues is important for directing an enzyme to a lysosome.