protein synthesis

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where does protein synthesis take place?
ribosomes in cytoplasm
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where is the DNA that codes for proteins found?
inside the nucleus; DNA from nucleus never found in cytoplasm so message cannot be carried directly
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what carries the information from the nuclear DNA to the ribosomes?
RNAs (ribonucleic acids)
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what three main functions does RNA have in protein synthesis? (3)
1.carries instructions for polypeptide from nuclear DNA to ribosomes 2.picks up specific amino acid from protoplasm & carries them to surface of ribosomes 3.makes up bulk of the ribosomes
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what are the names of the three types of RNA? (3)
transfer RNA (tRNA), messenger RNA (mRNA), ribosomal RNA (rRNA)
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where is mRNA formed?
in the nucleus
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how many polypeptides does a strand of mRNA carry instructions for?
one polypeptide
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where does mRNA form?
on the antisense strand (template strand) of the DNA
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what is the coding strand of DNA known as?
sense strand (coding strand)
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what would happen in mRNA formed on the sense strand?
strand would be nonsense and would not code for a protein
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what are the two stages of protein synthesis called, in order?
transcription and translation
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what does DNA-directed RNA polymerase do?
unravels parts of the DNA molecule and transcribes onto strands of mRNA
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what is a common name for this enzyme?
RNA polymerase
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what happens in transcription? (3)
complementary bases in DNA & RNA line up alongside each other, RNA nucleotides from nucleoplasm line up along exposed DNA, h bonds hold complementary bases in place
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what happens in transcription? (5)
RNA polymerase catalyses formation of phosphodiester bonds between sugars and phosphate groups of bases, to form mRNA strand, bases of mRNA form triplet code, mRNA molecules pass through nuclear pores, carrying instructions to cytoplasm
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how does RNA maintain it's helical structure during this process?
h bonds maintain helical structure of RNA
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where is tRNA found?
in the cytoplasm
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what complex shape is it often described as?
clover leaf
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what is this shape the result of?
hydrogen bonding between different bases
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what special type of codon does tRNA have?
anticodon
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what is an anticodon?
sequence of three bases that are complementary to the bases in the mRNA codon
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what does the anticodon do?
the three bases determine precisely to which piece of mRNA on the ribosomal surface the tRNA will join; decides exact order of amino acids in resulting polypeptide chain
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what is the binding site on the tRNA molecule?
binding site is for picking up particular amino acid from vast numbers free in cytoplasm
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what happens in translation? (2)
tRNA molecules, each carrying specific amino acid, line up alongside mRNA on surface of ribosome, anticodons of tRNA line up with codons of mRNA (held in place by h bonds between corresponding bases)
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what happens in translation? (1)
once amino acids are lined up together, peptide bonds form between them, building up long chain of amino acids
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what happens to the tRNA after it contributes amino acid?
breaks away and returns to cytoplasm to pick up another amino acid
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what links the amino acids together?
enzymes
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what percentage of rRNA makes up the structure of a ribosome?
50%; most common form of RNA found in cells
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where is rRNA made?
in nucleus, under control of nucleoli
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what does it bind to when released into cytoplasm?
proteins; together they form ribosomes
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what do ribosomes consist of?
large subunit and small subunit
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what are their jobs?
to hold together the mRNA and tRNA and act as enzymes controlling process of protein synthesis
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what are polysomes?
groups of ribosomes joined by thread of mRNA
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what do they do and how do they do it?
form of mass production of particular proteins; ribosomes attach in steady stream to mRNA and move along one after the other producing lots of identical polypeptides
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Other cards in this set

Card 2

Front

where is the DNA that codes for proteins found?

Back

inside the nucleus; DNA from nucleus never found in cytoplasm so message cannot be carried directly

Card 3

Front

what carries the information from the nuclear DNA to the ribosomes?

Back

Preview of the front of card 3

Card 4

Front

what three main functions does RNA have in protein synthesis? (3)

Back

Preview of the front of card 4

Card 5

Front

what are the names of the three types of RNA? (3)

Back

Preview of the front of card 5
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