structures of ribonucleic acid Flashcards
what is the role of RNA?
important information-carrying molecule.
In all living cells, RNA transfers genetic information from DNA to the ribosomes
what is RNA a polymer of?
nucleotides. Each nucleotide is formed from a ribose, a nitrogen-containing organic base and a phosphate group
a condensation reaction between two nucleotides forms a phosphodiester bond
what are the components of an RNA nucleotide?
ribose, a phosphate group and one of the bases; adenine, cytosine, guanine or uracil
what are the two types of RNA that are important for protein synthesis?
messenger RNA (mRNA) and transfer RNA (tRNA)
what is the structure of mRNA?
long strand that is arranged in a single helix
what is the base sequence of mRNA determined by?
the sequence of bases on a length of DNA in a process called transcription
what happens once mRNA leaves the nucleus?
leaves via pores in the nuclear envelope and enters the cytoplasm, where it associates with the ribosomes.
there it acts as a template for protein synthesis
how does the structure of mRNA relate to its function?
it possesses information in the form of codons (three bases that are complementary to a triplet in DNA)
the sequence of codons determines the amino acid sequence and hence the specific polypeptide that will be made.
what is the structure of tRNA?
relatively small molecule that is a single stranded chain folded into a clover-leaf shape
what is the part of a tRNA molecule to which an amino acid can attach?
one end of the chain that extends beyond the other
what is at the opposite end of the tRNA molecule to the amino acid?
a sequence of three bases forming the anticodon
how does knowledge about the code being degenerate help us understand how many tRNA molecules there are?
there must be as many tRNA molecules as there are coding triplets.
However, each tRNA is specific to one amino acid and has an anticodon that is specific to that amino acid
what are ribosomes formed from?
RNA and proteins
