cc5 Flashcards
what is the structure of a nucleotide?
phosphate group, a pentose sugar (ribose or deoxyribose), nitrogenous base
how are polynucleotides formed?
nucleotides join together by bond formation between sugar of one and the phosphate of the next. it is formed in a condensation reaction. bond name is called a sugar-phosphate bond (phosphodiester)
what are the two types of nitrogenous bases?
purine and pyramidine
what are the purine bases?
adenine and guanine
what are the pyramidine bases?
thymine, cytosine, uracil
what is the structure of DNA?
two polynucleotides wound around each other in a double helix, sugar-phosphate backbone faces out and organic bases in, nitrogenous bases in DNA are thymine, cytosine, adenine and guanine, cytosine always bonds to guanine by 3 hydrogen bonds, thymine always joins to adenine by 2 hydrogen bonds, C-G and T-A are complementary base pairs
what are the two ends of a sugar-phosphate backbone called?
5’ and 3’
what direction to the polynucleotides run in?
opposite directions. they are anti-parallel
how is DNA suited to its function?
very stable molecules and its information content passes unchanged from generation to generation, it is a very large molecule and carries a large amount of genetic information, the two strands are able to separate as they are held together by hydrogen bonds, as the bases are inside the helix the genetic information is protected
what’s different about RNA compared to DNA?
nucleotides contain the pentose sugar ribose, nitrogenous bases are guanine, cytosine, adenine and uracil not thymine, molecules are single not double stranded, shorter than DNA
what is mRNA?
long and single stranded, manufactured in the nucleus and carries the genetic code from DNA to the ribosomes in the cytoplasm, made by transcription
what is rRNA?
it is found in the cytoplasm and comprises large complex molecules
what are ribosomes?
ribosomes are made of ribosomal RNA and protein, it is the site of translation of the genetic code
what is translation?
the process where a polypeptide chain is made
what is tRNA?
transfer RNA is a short single-stranded molecule. forms a clover-leaf shape with one end of the chain ending in cytosine-cytosine-adenine sequence
