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Biochem > 20.6 - protein synthesis > Flashcards

20.6 - protein synthesis Flashcards

1
Q

The process of protein synthesis is called

A

translation

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2
Q

what is translation

A

It involves translating the genetic information from the sequence of nucleotides into the sequence of amino acids in the primary structure of a protein.

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3
Q

Each mRNA has a _______ followed by the sequences that carry the information for the order of the_________ that will be produced in the process of _____.

A

short untranslated region
amino acids in the protein
translation

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4
Q

That genetic information is the

A

sequence of codons along the mRNA

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5
Q

The decoding process is carried out by

A

tRNA molecules

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6
Q

translation is carried out on

A

ribosomes

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7
Q

what are ribosomes

A

complexes of ribosomal RNA (rRNA) and proteins.

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8
Q

each ribosome is made up of two subunits:

A

a small and a large ribosomal subunit

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9
Q

In eukaryotic cells, the small ribosomal subunit contains

A

one rRNA molecule and thirty-three different ribosomal proteins

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10
Q

the large subunit contains

A

three rRNA molecules and about forty-nine different proteins.

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11
Q

Protein synthesis involves the simultaneous action of many ribosomes on a

A

single mRNA molecule

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12
Q

These complexes of many ribosomes along a single mRNA are known as

A

polyribosomes or polysomes

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13
Q

Each ribosome synthesizes what

A

one copy of the protein molecule encoded by the mRNA. Thus, many copies of a protein are simultaneously produced

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14
Q

The molecule that decodes the information in the mRNA molecule into the primary structure of a protein is

A

transfer RNA (tRNA).

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15
Q

the tRNA must ____ bind ____, and only ___, specific _____.

A

covalently
one one
amino acid

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16
Q

There is at least one transfer RNA for each

A

amino acid

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17
Q

All tRNA molecules have the sequence ____ at their 3’ ends

A

CCA

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18
Q

The CCA is the site where the amino acid will be __________

A

covalently attached to the tRNA molecule.

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19
Q

Each tRNA is specifically recognized by the active site of an enzyme called an

A

aminoacyl tRNA synthetase

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20
Q

aminoacyl tRNA synthetase also recognizes the correct amino acid and covalently links the amino acid to the

A

3′ end of the tRNA molecule

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21
Q

The resulting structure is called an

A

aminoacyl tRNA.

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22
Q

The covalently bound amino acid will be transferred from the tRNA to a

A

growing polypeptide chain during protein synthesis.

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23
Q

the tRNA must be able to recognize the

A

appropriate codon on the mRNA that calls for that amino acid.

24
Q

Second, the tRNA must be able to recognize the appropriate codon on the mRNA that calls for that amino acid. This is mediated through a sequence of three bases called the

A

anticodon

25
Q

where is the anticodon located

A

at the bottom of the tRNA cloverleaf

26
Q

The anticodon sequence for each tRNA is complementary to the

A

codon on the mRNA that specifies a particular amino acid.

27
Q

___________ will bring the correct amino acid to the site of protein synthesis.

A

the anticodon-codon complementary hydrogen bonding

28
Q

The first stage of protein synthesis is

A

initiation

29
Q

Proteins called ______ assist in the formation of a translation complex composed of an______________________________________-

A

initiation factors

mRNA molecule, the small and large ribosomal subunits, and the initiator tRNA.

30
Q

This initiator tRNA recognizes the codon ____ and carries the amino acid _____.

A

AUG

methionine

31
Q

The ribosome has two sites for binding

A

tRNA molecules

32
Q

The first site, called the

A

peptidyl tRNA binding site (P-site)

33
Q

what does the peptidyl tRNA binding site (P-site) hold

A

holds the peptidyl tRNA, the growing peptide bound to a tRNA molecule

34
Q

The second site, called the

A

aminoacyl tRNA binding site (A-site)

35
Q

what does the aminoacyl tRNA binding site (A-site) hold

A

holds the aminoacyl tRNA carrying the next amino acid to be added to the peptide chain.

36
Q

Each of the tRNA molecules is hydrogen bonded to the

A

mRNA molecule by codon-anticodon complementarity.

37
Q

The entire complex is further stabilized by the fact that the mRNA is also bound to the

A

ribosome

38
Q

The second stage of translation is

A

chain elongation

39
Q

chain elongation occurs in

A

three steps that are repeated until protein synthesis is complete.

40
Q

We enter the action after a ______ has already been assembled, and a _______ occupies the P-site

A

tetrapeptide

peptidyl tRNA

41
Q

The first event in elongation is the

A

binding of an aminoacyl-tRNA molecule to the empty A-site.

42
Q

Next in elongation, ___ bond formation is catalyzed by a catalytic region of the ______.

A

Peptide

28S rRNA

43
Q

next, peptide bond formation is catalyzed by a catalytic region of the 28S rRNA. This is another example of a ribozyme, which is called

A

peptidyl transferase

44
Q

Now the peptide chain is shifted to the ____ that occupies the __-site

A

tRNA

A

45
Q

Finally, the ______ falls away, and the ribosome changes positions so that the next codon on the ______ occupies the _____

A

tRNA in the P-site
mRNA
A-site

46
Q

his movement of the ribosome is called

A

translocation

47
Q

The process shifts the new peptidyl tRNA from the

A

A-site to P-site

48
Q

The chain elongation stage of translation requires the hydrolysis of ____________
Several ________ factors are also involved in this process.

A

GTP to GDP and Pi

elongation

49
Q

The last stage of translation is

A

termination

50
Q

There are three termination codons

A

UAA, UAG, and UGA

51
Q

UAA, UAG, and UGA have no

A

no corresponding tRNA molecules

52
Q

When one of these “stop” codons is encountered, translation is

A

terminated

53
Q

A_____- factor binds the empty A-site

A

release

54
Q

The peptidyl transferase that had previously catalyzed peptide bond formation hydrolyzes the

A

ester bond between the peptidyl tRNA and the last amino acid of the newly synthesized protein

55
Q

At this point, the tRNA, the newly synthesized peptide, and the two ribosomal subunits are

A

released

56
Q

The peptide that is released following translation is not necessarily in its

A

final functional form

57
Q

In some cases, the peptide is _______ cleaved before it becomes functional.

A

proteolytically

Biochem (20 decks)

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