8.3 Structures of ribonucleic acid Flashcards
Where does the synthesis of proteins occur in eukaryotic cells
Why is this a problem for protein synthesis
In the cytoplasm, in ribosomes.
However, DNA is found in the nucleus.
So how is the coded information on the DNA transported to the cytoplasm to be translated into proteins
What happens to allow the coded information on DNA to be transferred from the nucleus to the cytoplasm
Sections of DNA code are transcribed onto a single stranded molecule called RNA
What is the role of messenger RNA (MRNA)
How does it leave the nucleus
It transfers the DNA code from nucleus to cytoplasm , acting as a messenger.
It is small enough to leave the nucleus through a nuclear pore to enter cytoplasm.
In the cytoplasm, it associates with ribosomes and acts as a template for protein synthesis.
Here, the coded info it contains can determine the sequence of amino acids in the proteins that are synthesised there
What is a codon
The sequence of 3 bases on mRNA that codes for a single amino acid.
These 3 bases are complimentary to a triplet on DNA
The sequence of codons determines amino acid sequence of a polypeptide that will be made
What is a genome
The complete set of genes in a cell, including those in chloroplasts or mitochondria
What is a proteome
The full range of proteins produced by the genome, in a cell.
May be called the complete proteome, where the term proteome refers to the proteins produced by a given type of cell under certain conditions
Describe the structure of ribonucleic acid
How many strands
what are the subunits that make it up
. It is a polymer made of repeating mononucleotide sub-units
. Forms a single strand in which each nucleotide is made up of:
- Pentose sugar ribose
- Bases A, U, C, G so thymine is swapped for uracil
- A phosphate group
What are the two types of RNA that are important in protein synthesis
. Messenger RNA (mRNA)
. Transfer RNA (tRNA)
Describe structure of mRNA
Consists of thousands of nucleotides
Single long strand arranged in a helix
The base sequence of mRNA depends on the base sequence of DNA in a process called transcription.
What is tRNA
What is the shape of it
What is each end of it called
It is much smaller than mRNA, and made of 80 nucleotides. But still consist of ribose sugar etc.
Single stranded chain folded into clover leaf shape, with one end of the chain extending beyond the other.
This longer end is where the amino acid can attach.
On the opposite end of the shape is a sequence of 3 other organic bases called the anticodon.
This anticodon is specific to one amino acid.
As the genetic code is degenerate, there are as many tRNA molecules as there are coding triplets.
Each tRNA molecule is specific to one amino acid
What are the complimentary base pairings in RNA
. Guanine and cytosine
. Adenine and Uracil
As thymine is swapped for uracil
What does tRNA do during protein synthesis
. The anticodon on it pairs with a codon (made of 3 organic bases) of mRNA
. The end chain attaches to an amino acid
So it lines up amino acids on the mRNA template during protein synthesis
Where are mRNA and tRNA made
which of the two is more stable
which of the two is smaller
manufactured in the nucleus but found throughout the cell
tRNA is more stable than mRNA
tRNA is smaller than mRNA
