module 2 - 3.10 protein synthesis

Question 1

what is the central dogma of molecular biology?

Answer 1

DNA —transcription–> / <–reverse transcription– RNA –translation–> polypeptide

Question 2

what is transcription?

Answer 2

• the process of making a copy of something
• info held on DNA molecule is transcribed into info held on mRNA molecule

Question 3

how is a copy of the DNA base sequence made?

Answer 3

made as an mRNA molecule by RNA polymerase

Question 4

what does mRNA do?

Answer 4

moves genetic information and genes from nuclear pores to ribosomes

Question 5

what is translation?

Answer 5

the process of conversion of something from one form into another e.g. language

Question 6

what is the sequence of codons on the mRNA translated into?

Answer 6

a sequence of amino acids, making a polypeptide

Question 7

what does translation use to transfer tRNA molecules?

Answer 7

ribosomes

Question 8

what is 1 language?
what is 2 language?

Answer 8

1. codons
2. amino acids

Question 9

why is information in DNA transcribed into mRNA?

Answer 9

so it can be used multiple times

Question 10

what is the first stage of transcription?

Answer 10

initiation

Question 11

what is the promoter region?

Answer 11

RNA polymerase binding site for DNA

Question 12

what is the sense strand of DNA?

Answer 12

holds the triplet code for the sequence of amino acids

Question 13

what is the antisense strand of DNA?

Answer 13

does not code for the sequence of amino acids but is complementary in base sequence to the sense DNA strand

Question 14

what does the antisense strand act as?

Answer 14

acts as the template DNA strand for RNA polymerase so that the mRNA has the same base sequence as the sense DNA strand

Question 15

what is the second stage of transcription?

Answer 15

elongation

Question 16

what is RNA polymerase’s error rate from its proof reading ability?

Answer 16

1 in 10^4 to 10^6

Question 17

what is the fidelity of RNA polymerase making mRNA?

Answer 17

high fidelity

Question 18

how many nucleotides can RNA polymerase synthesize per second?

Answer 18

40-80 nucleotides per second

Question 19

what is the third stage of transcription?

Answer 19

termination

Question 20

what do all polypeptides have as their first amino acid?

Answer 20

methionine

Question 21

why don’t all proteins start with methionine?

Answer 21

because some polypeptides go through post translational modification from the golgi

Question 22

if methionine (ATG) is the start codon, what is the codon and anticodon for methionine?

Answer 22

codon - AUG
anticodon - UAC

Question 23

what does a tRNA molecule consist of?

Answer 23

a single RNA strand - 80 nucleotides long

Question 24

where is the anticodon on a tRNA molecule?

Answer 24

at the end (bottom) 3 single stranded bases that are complementary to a codon on mRNA

Question 25

what is the amino acid acceptor site?

Answer 25

a short sequence of bases that can bind to the only amino acid that the anticodon is complementary to on the mRNA

Question 26

what do tRNA molecules serve as?

Answer 26

the physical link between mRNA and amino acids used to make a polypeptide

Question 27

how many tRNA molecules are there compared to codons?

Answer 27

the same amount - there is a tRNA molecule for every codon

Question 28

where are tRNA molecules coded?

Answer 28

in the nucleolus

Question 29

what 2 components are ribosomes made from?

Answer 29

- ribosomal RNA (rRNA) - proteins

Question 30

what are ribosomes?

Answer 30

- complex macromolecular machines, found within all living cells - site of biological protein synthesis

Question 31

what are the 2 subunits of ribosomes?

Answer 31

- small ribosomal subunit that 'reads' the mRNA - the large ribosomal subunits that has 2 binding sites for tRNA molecules and catalytic site for joining amino acids together

Question 32

which bonds join amino acids?

Answer 32

peptide bonds

Question 33

what is the first stage of translation?

Answer 33

initiation by forming an initiation complex

Question 34

how does the tRNA anticodon UAC bind to the complementary codon AUG?

Answer 34

complimentary base pairing

Question 35

how many tRNA's are there with the anticodon UAG? and why is this?

Answer 35

- one - it can only bind to the amino acid methionine (at he amino acid acceptor site)

Question 36

what is formed when a large ribosome subunit is joined to the party?

Answer 36

a ribosome

Question 37

what is the second stage of translation?

Answer 37

elongation of the polypeptide

Question 38

what is the second amino acid that is brought into the second tRNA binding site on the ribosome during elongation of the polypeptide?

Answer 38

valine

Question 39

what is the catalytic site on the polypeptide called/

Answer 39

peptidyl transferase

Question 40

what is peptidyl transferase made of?

Answer 40

rRNA

Question 41

what does the catalytic site on the ribosome create?

Answer 41

a peptide bond between methionine and valine by a condensation reaction

Question 42

what happens to the first tRNA (UAC/ valine)?

Answer 42

it detaches to the ribosome and will be bound to the fresh amino acid of methionine

Question 43

how many does the ribosome move along the mRNA strand after the first tRNA molecule detaches?

Answer 43

moves along by one codon, the second tRNA bind site is now clear

Question 44

what type of bond is formed from the peptidyl transferase between valine and histidine?

Answer 44

peptide bond through a condensation reaction

Question 45

how many amino acids are joined by the ribosome per second?

Answer 45

60

Question 46

what is the third stage of translation?

Answer 46

termination of a polypeptide

Question 47

how long does the termination of a polypeptide continue for?

Answer 47

until ribosome encounters a stop codon on the mRNA

Question 48

what are the stop codons in RNA?

Answer 48

UAG UAA UGA

Question 49

what are the stop codons in DNA?

Answer 49

TAG TAA TGA

Question 50

what do stop codons do?

Answer 50

cause the ribosomal subunits to detach from each other and from the mRNA

Question 51

when the polypeptide folds up into its final shape, what may it undergo?

Answer 51

post translational modification to form a protein (from the golgi)