Lecture 20 - Highlights Translation 2

Front 1

Protein synthesis uses ____ as an energy source (not _____).

Back 1

Protein synthesis uses GTP as an energy source (not ATP).

Front 2

Translation initiation requires 6 things. What are they?

Back 2

Translation initiation requires 1) an mRNA; 2) a start codon in the mRNA - AUG; 3) the 30S ribosomal subunit; 4) the 50S ribosomal subunit; 5) proteins called initiation factors; and 6) GTP.

Front 3

During initiation of translation, the first tRNA (linked to fmet) forms base pairing between

Back 3

During initiation of translation, the first tRNA (linked to fmet) forms base pairing between its anti-codon and the codon of the mRNA.

Front 4

A sequence known as the Shine-Dalgarno sequence in the mRNA (in prokaryotes only) helps

Back 4

A sequence known as the Shine-Dalgarno sequence in the mRNA (in prokaryotes only) helps the ribosome to properly align the mRNA in the ribosome.

Front 5

The Shine-Dalgarno sequence forms

Back 5

The Shine-Dalgarno sequence forms a base paired region with the 16S rRNA of the 30S subunit of the ribosome.

Front 6

Elongation of translation occurs by

Back 6

Elongation of translation occurs by binding of an incoming tRNA (which will base pair with the next codon)

Front 7

Elongation of translation occurs by binding of an incoming tRNA (which will base pair with the next codon) in a region of the ribosome known as

Back 7

Elongation of translation occurs by binding of an incoming tRNA (which will base pair with the next codon) in a region of the ribosome known as the 'A' site.

Front 8

The previous tRNA is found on the

Back 8

The previous tRNA is found on the adjacent 'P site' of the ribosome.

Front 9

A third site of the ribosome where tRNAs are found is the

Back 9

A third site of the ribosome where tRNAs are found is the 'E site'

Front 10

the 'E site' is where

Back 10

the 'E site', which is where tRNAs exit the ribosome after they have been used.

Front 11

Translation involves linking amino acids properly together via

Back 11

Translation involves linking amino acids properly together via peptide bonds.

Front 12

the growing polypeptide chain is held on a

Back 12

the growing polypeptide chain is held on a tRNA.

Front 13

After the peptide bond forms, the tRNA with the polypeptide chain moves to the _____ site nd a new tRNA with an amino acid comes into the _____ site.

Back 13

After the peptide bond forms, the tRNA with the polypeptide chain moves to the P site and a new tRNA with an amino acid comes into the A site.

Front 14

After the peptide bond forms, the tRNA with the polypeptide chain moves to the P site and a new tRNA with an amino acid comes into the A site. This process also involves the mRNA

Back 14

After the peptide bond forms, the tRNA with the polypeptide chain moves to the P site and a new tRNA with an amino acid comes into the A site. This process also involves the mRNA sliding one codon down the chain to put a new codon in the A site.

Front 15

After the tRNA properly binds in the A site, a peptide bond is formed between the peptide on the tRNA in the P site and the amino acid on the tRNA in the A site. The catalyst for the peptide bond is the ______________.

Back 15

After the tRNA properly binds in the A site, a peptide bond is formed between the peptide on the tRNA in the P site and the amino acid on the tRNA in the A site. The catalyst for the peptide bond is the 23S rRNAs in the ribosome.

Front 16

peptide bonds are formed by

Back 16

peptide bonds are formed by ribozymes (catalytic RNAs).

Front 17

peptide bonds are formed by ribozymes (catalytic RNAs). The result is a

Back 17

peptide bonds are formed by ribozymes (catalytic RNAs). The result is a peptide linked to the tRNA in the A site.

Front 18

The next step in elongation occurs when the tRNA with the polypeptide in the A site moves over to the ____ site (displacing the tRNA previously there to the ____site, from which it exits the ribosome).

Back 18

The next step in elongation occurs when the tRNA with the polypeptide in the A site moves over to the P site (displacing the tRNA previously there to the E site, from which it exits the ribosome).

Front 19

The next step in elongation occurs when the tRNA with the polypeptide in the A site moves over to the P site (displacing the tRNA previously there to the E site, from which it exits the ribosome). then what?

Back 19

The next step in elongation occurs when the tRNA with the polypeptide in the A site moves over to the P site (displacing the tRNA previously there to the E site, from which it exits the ribosome). The A site is thus left open. The ribosome slides three nucleotides along the mRNA, bringing a new complementary sequence into the A site.

Front 20

Movement of the ribosome along the mRNA is facilitated by

Back 20

Movement of the ribosome along the mRNA is facilitated by EF-G and requires GTP.

Front 21

EF-Tu is ________

it functions to _______________.

EF-Tu makes sure _______.

EF-Tu protects _______________.

Back 21

EF-Tu is the most abundant E. coli protein and it functions to carry the tRNA to the A site of the ribosome. EF-Tu makes sure that the properly base-paired tRNA is in the A site. EF-Tu also protects the bond between the amino acid and the tRNA from water.

Front 22

What is the last step of the process of making a protein?

Back 22

Proper termination of translation is the last step of the process of making a protein.

Front 23

When does Proper termination of translation occur?

Back 23

Proper termination of translation occurs when a stop codon appears in the 'A' site of the ribosome.

Front 24

Since there are no tRNAs with a complementary anti-codon to the stop codons what happens?

Back 24

Since there are no tRNAs with a complementary anti-codon to the stop codons, release factors bind to the stop codon.

Front 25

Release factors bind to the stop codon and cause

Back 25

Release factors bind to the stop codon and cause the bond between the polypeptide and the tRNA in the P site to be broken because they carry water to it and this breaks the bond. Thus, the final polypeptide is released from the ribosome and the entire complex then comes apart.

Front 26

Translation is a target for action of

Back 26

Translation is a target for action of antibiotics.

Front 27

Translation is a target for action of antibiotics. This works because the phenomenon of translation in prokaryotes is

Back 27

Translation is a target for action of antibiotics. This works because the phenomenon of translation in prokaryotes is different enough from that of eukaryotes that specific inhibitors of prokaryotic translation can be found that have no effect on eukaryotic translation.

Front 28

As a result of antibiotics

Back 28

As a result of antibiotics prokaryotes can be killed without any effect on eukaryotes taking said antibiotics.

Front 29

One translational inhibitor of prokaryotic translation is

Back 29

One translational inhibitor of prokaryotic translation is the antibiotic puromycin

Front 30

What does the antibiotic puromycin do?

Back 30

puromycin, acts to prematurely terminate prokaryotic translation at the elongation phase. This happens because puromycin looks like a tRNA and fits into the A (or P) site of the ribosome. In the A site, it can be attached to the growing polypeptid chain, but it is soon released, causing premature termination. In addition, puromycin can bind to the P site of ribosomes and prevents anything from binding there.

Front 31

Eukaryotic mRNAs have a 5' ____ and a 3' _______

Back 31

Eukaryotic mRNAs have a 5' cap and a 3' polyA tail

Front 32

One important difference of eukaryotic translation is that the initiation complex in eukaryotes involves

Back 32

One important difference of eukaryotic translation is that the initiation complex in eukaryotes involves both the 5' cap and the 3' polyA sequence in a looped structure.

Front 33

The 5' cap and 3' poly-A sequence both play roles in

Back 33

The 5' cap and 3' poly-A sequence both play roles in helping to increase the stability of eukaryotic mRNAs.

Front 34

Post-translational (= after translation has occurred) processing of proteins gives them

Back 34

Post-translational (= after translation has occurred) processing of proteins gives them their final structure and properties.

Front 35

Post-translational (= after translation has occurred) processing of proteins gives them their final structure and properties. One such modification was discussed for

Back 35

Post-translational (= after translation has occurred) processing of proteins gives them their final structure and properties. One such modification was discussed for insulin.

Front 36

The Post-translational modification for insulin involves

Back 36

proteolytic cleavage at two places in the insulin precursor, giving rise to a final structure that has two chains held together by disulfide bonds.

Front 37

How long do proteins live and how do they get broken down?

Back 37

Proteins do not have long lifetimes in the cell. They are broken down in cells in cellular structures called proteasomes.

Front 38

Proteins targeted for degradation are tagged with the peptide known as

Back 38

Proteins targeted for degradation are tagged with the peptide known as ubiquitin.

Front 39

Selenocysteine is

Back 39

Selenocysteine is a rare amino acid occasionally incorporated into proteins.

Front 40

Selenocysteine is sometimes called the

Back 40

Selenocysteine is sometimes called the 21st amino acid

Front 41

Selenocysteine is the only _________

Back 41

Selenocysteine is the only modified amino acid in proteins that gets there by direct incorporation rather than post-translational modification.

Front 42

Why are trace amounts of selenium are needed in the diet?

Back 42

Selenocysteine is a rare amino acid occasionally incorporated into proteins. It is sometimes called the 21st amino acid. It is the only modified amino acid in proteins that gets there by direct incorporation rather than post-translational modification. It is because of this that trace amounts of selenium are needed in the diet.