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1. Molecular Biology > Translation - Ribosomes and overview of process > Flashcards

Translation - Ribosomes and overview of process Flashcards

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1
Q

What are the two steps of translation?

A

Capturing complementary tRNA molecules and holding them in position (to allow the tRNA anticodons to base-pair with mRNA codons)

Covalently linking the amino acids that tRNAs carry so as to form a protein chain

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2
Q

What is the protein manufacturing machine?

A

The ribosome

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3
Q

Where are ribosomal subunits made in eukaryotes?

A

Made in nucleus

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4
Q

What does the small ribosomal subunit do?

A

Matches tRNAs to codons of mRNA

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5
Q

What does the large ribosomal subunit do?

A

It catalyses formation of peptide bonds that link amino acids together into a polypeptide chain

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6
Q

Where and why do the 2 ribosomal subunits come together?

A

They come together on an mRNA molecule - near 5’ end

This allows them to begin synthesis of protein

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7
Q

How does the ribosome work?

2

A

It moves along mRNA

As it does so it translates the nucleotide sequence into an amino acid sequence, one codon at a time

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8
Q

How does the ribosome work with tRNA

A

The ribosome uses tRNAs as adaptors to add each amino acid in the correct sequence

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9
Q

What happens to the ribosome when protein synthesis is completed?

A

The 2 subunits of the ribosome separate

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10
Q

How many amino acids are added per second to a polypeptide chain by ribosomes in eukaryotic cells?

A

Ribosomes add 2 amino acids to a polypeptide chain per second in eukaryotes

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11
Q

How much faster are prokaryotic ribosomes than eukaryotic ribosomes?

A

Prokaryotic ribosomes are ten times faster than eukaryotic

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12
Q

What are the three binding sites for tRNA?

A

P site

A site

E site

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13
Q

What is the P site of a ribosome?

2

A

The peptidyl-tRNA site

It holds the tRNA that is carrying the growing polypeptide chain

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14
Q

What is the A site of a ribosome?

2

A

The aminoacyl-tRNA site

It holds the tRNA that is carrying the next amino acid to be added to the chain

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15
Q

What is the E site of a ribosome?

2

A

The exit site

This is where discharged tRNAs leave the ribosome

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16
Q

Why do the three ribosome binding sites need to be close together?

A

So that tRNA anticodons in the binding sites can form base-pairs with the adjacent codons on mRNA molecule

17
Q

How does mRNA bind to a ribosome?

A

mRNA has a single binding site in the small subunit

18
Q

In total how many binding sites do ribosomes have?

A

4

1 for mRNA and 3 for tRNA

19
Q

List the order of the tRNA binding sites on a ribosome

A

A site, P-site, E-site

20
Q

What are the three stages of translation?

A

Chain initiation

Chain elongation

Chain termination

21
Q

What do all three stages of translation need?

A

They all need protein factors

22
Q

What provides the energy needed for translation?

A

Energy is provided by the hydrolysis of GTP

23
Q

What is GTP?

A

Guanosine triphosphate

24
Q

How does translation begin?

A

Translation begins with start codon (AUG) and a special initiator tRNA

25
Q

What does initiator tRNA always carry?

A

The amino acid methionine

26
Q

What is always found at the N-terminal end of a protein?

A

A methionine

27
Q

How do the amino acids join together?

2

A

The carboxyl end of the polypeptide chain uncouples from tRNA at the P-site

It then joined by a peptide bond to the amino acid linked to tRNA in the A site

28
Q

What happens after a new amino acid has been added to the polypeptide chain?

A

Each tRNA moves along the mRNA a space until the A site is free again

29
Q

What are the three stop codons?

A

UAA

UAG

UGA

30
Q

What binds to the stop codon?

A

Release factors

31
Q

What happens when the release factors bind to a stop codon?

2

A

This frees the carboxyl end of the growing polypeptide chain from its attachment to tRNA

The completed polypeptide is then released into the cytoplasm

32
Q

What must proteins do before they can become a fully functioning protein?

A

They must undergo post translation modification

1. Molecular Biology (12 decks)

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