Nucleic acids and their functions (Meselson-Stahl ( They cultured the DNA…
Nucleic acids and their functions
pyrimidine base thymine, cytosine, uracil
purine bases adenine, guanine
polymers made up of monomers called nucleotides
phosphate- pentose sugar - nitrogenous base
energy in organisms is stored In lipids and carbohydrates, energy comes from adenosine triphosphate, the body only contains 5g at one time.
ATP is made from adenine, ribose and three phosphates. When energy is needed, the enzyme ATPase hydrolyses the bond between the second and third phosphate groups leaving ADP and an inorganic phosphate ion. A reaction that releases energy is exergonic. ATP+water = ADP + P change in energy =-30.6kJmol-1. The addition of phosphate to ADP is phosphorylation.
Energy is released immediately, only one enzyme is needed, small amounts of energy are released, increased efficiency
ATP needed for metabolic processes, active transport, movement, nerve transmission, secretion.
Adenine is complementary to thymine and cytosine and complementary to guanine.
The molecule is long and thin, with two strands held together with weak hydrogen bonds,
Function - replication and protein synthesis
Messanger RNA is a long single stranded molecule synthesised in the nucleus and carries the genetic code from DNA to the ribosomes
Ribosomal RNA is found in the cytoplasm, it makes up ribosomes, they are the site of translation
Transfer RNA is a small single stranded molecule, which folds, it has an anticodon, they transport specific amino acids to the ribosomes in protein synthesis
Single stranded polynucleotides, contains the pentose sugar ribose, doesn't contain thymine, uracil replaces it
They cultured the DNA with the N15 isotope and the bacteria incorporated it into it's amino acids when the cells replicated.
They were then transferred to a medium containing 14N and allowed to divide once more.
DNA was centrifuged and one band in the middle was shown.
After the second generation, one band settled at the top and one settled in the middle.
They ruled out conservative replication which is when the whole double helix remains intact and a new one is made.
Introns are non coding DNA, exons are coding DNA which are left and spliced together
Elongation-The first tRNA leaves the ribosome leaving it's attachment site vacant. It returns to the cytoplasm to bind to another copy of it's specific amino acid
Termination- the ribosome-mRNA-polypeptide complex seperates
Initiation- a ribosome attaches to a start codon, the first tRNA, with an anticodon complementary to first codon attaches to a ribosome, and they bond with hydrogen bonds.
The enzyme DNA HELICASE breaks the hydrogen bonds and unwinds the DNA. The enzyme DNA polymerase binds to the template strand of DNA at the beginning of the sequence to be copied. Free RNA nucleotides align opposite the DNA, complementary to the bases. RNA polymerase moves along the DNA forming bonds that add RNA to the strand, this creates an mRNA molecule. RNA polymerase separates from the template strand when it reaches a stop signal.