protein synthesis 3.10 Flashcards
where is DNA contained within the cell
DNA is contained within a double membrane called the nuclear envelope that encloses the nucleus
where does protein synthesis occur
protein synthesis occurs in the cytoplasm at ribosomes
why Is transcription needed
because chromosomal DNA molecules are to large to leave the nucleus to supply the coding information needed to determine the proteins amino acid sequence
what is meant by transcription
base sequences of genes are copied and transported to ribosome
how is transcription similar to DNA replication
-although transcription results in a different polynucleotide
-A section of DNA that contains the gene unwinds and unzips under the control of DNA helicase, beginning at a start codon (this involves the breaking of hydrogen bonds between the bases)
what is the sense strand
- The DNA strand that shows the sequence that codes for proteins
^ runs from 5’ to 3’
- what is the antisense strand
- what is its function
- it is the complementary strand for the sense strand (strand that codes for proteins)
- it does not code for a protein
- acts as template strand during transcription
- ^complementary RNA strand formed carries same base sequence as sense strand
- complementary strand can leave nucleus and codes for proteins
which strand is used to actually produce the RNA strand
Free RNA nucleotides will base pair with complementary bases exposed on the antisense strand when the DNA unzips
what enzyme forms what bonds between RNA nucleotides
- RNA polymerase forms phosphodiester bonds between the RNA nucleotides
where does transcription stop
transcription stops at the end of the gene
what is produced from transcription of a single gene
a completed short strand of RNA called messenger (m)RNA
what happens to mRNA after transcription from a gene within DNA
- mRNA detaches from unzipped DNA strand and leaves nucleus via nuclear pore.
- DNA double helix reforms
- mRNA molecule then travels to ribosome for translation
what are ribosomes made up from in eukaryotic cells
formed from protein and ribosomal RNA
froms 2 sub units
1 large and 1 small
what is the function of rRNA
its important in maintaining the structural stability of the protein synthesis sequence and plays a biochemical role in catalysing the reaction
what does the mRNA do after it leave the nucleus
After leaving the nucleus, the mRNA binds to a specific site on the small subunit of a ribosome.
what is the structure of tRNA
it is composed of a strand of RNA folded in such a way that 3 bases, called anticodon, are at one end of the molecule
explain the steps of translation
mRNA binds to ribosome at start codon
tRNA with the complementary anticodons binds start codon
complementary tRNA carrying amino acid binds to adjacent codon, as tRNA binds, anticodon at previous codon is release
as more tRNA molecules bind bringing amino acids, the acids bind together via peptide bonds (catalysed by peptidyl transferase)
ribosome moves along mRNA until reachesn stop codon and then releases polypeptide
