3.2.2 Protein Synthesis Flashcards
Like DNA, the nucleic acid RNA (ribonucleic acid) is a what?
Polynucleotide
What is nucleic acid RNA (ribonucleic acid) made up of?
Many nucleotides linked together in a long chain
Like DNA, RNA nucleotides contain what nitrogenous bases?
adenine (A)
guanine (G)
cytosine (C)
Unlike DNA, what do RNA nucleotides never contain ?
The nitrogenous base thymine (T)
What do RNA nucleotides contain instead?
The nitrogenous base uracil (U)
How many strands are RNA molecules made up of?
RNA molecules are only made up of one polynucleotide strand (they are single-stranded)
Each RNA polynucleotide strand is made up of what?
Alternating ribose sugars and phosphate groups linked together, with the nitrogenous bases of each nucleotide projecting out sideways from the single-stranded RNA molecule
What is an example of an RNA molecule?
Messenger RNA (mRNA)
Messenger RNA is the transcript copy of a gene that encodes what?
A specific polypeptide
What are 2 more examples of an RNA molecule?
Transfer RNA (tRNA) and ribosomal RNA (rRNA)
What makes RNA different to DNA?
RNA is single-stranded
RNA contains uracil instead of thymine
A gene is a sequence of nucleotide bases in a DNA molecule that does what?
It codes for the production of a specific sequence of amino acids, that in turn make up a specific polypeptide (protein)
There are 2 stages to protein synthesis. Name them both
Transcription – DNA
Translation – mRNA
Transcription – DNA is transcribed and what is produced?
An mRNA molecule is produced
Translation – mRNA (messenger RNA) is translated and produces what?
An amino acid sequence (protein)
Transcription - Where does this stage of protein synthesis occur?
In the nucleus of the cell
Part of a DNA molecule unwinds and exposes what?
The gene to be transcribed
A complimentary copy of the code from the gene is made by building what?
A single-stranded nucleic acid molecule known as mRNA (messenger RNA)
The mRNA molecule leaves the nucleus via what?
A pore in the nuclear envelope
The translation stage of protein synthesis occurs where?
In the cytoplasm of the cell
After leaving the nucleus, the mRNA molecule attaches to what?
A ribosome
In the cytoplasm, there are free molecules of what?
tRNA (transfer RNA)
These tRNA molecules have a triplet of unpaired bases at one end (known as the anticodon) , what can attach at the other?
A specific amino acid
How many different tRNA molecules are there?
At least 20
The tRNA molecules bind with their specific amino acids (also in the cytoplasm), and do what?
Bring them to the mRNA molecule on the ribosome
The triplet of bases (anticodon) on each tRNA molecule pairs with what?
A complementary triplet (codon) on the mRNA molecule
Two tRNA molecules fit onto the ribosome at any one time, what do theycarry side by side?
Amino acid
A peptide bond is then formed between what?
The two amino acids
This process continues until a ‘stop’ codon on what, is reached?
The mRNA molecule
This acts as a signal for translation to stopand the …………chain coded for by the mRNA molecule is complete
Amino acid
This amino acid chain then forms the what?
The final polypeptide (protein)
The triplet code of DNA (carried by mRNA) is read by the what?
Ribosome and amino acids are attached together in a specific sequence to form the protein
