Nucleic Acids and ATP

• The structure of a nucleotide consists of a nitrogen-containing base, a pentose sugar, and a phosphate group.
• The pentose sugars in DNA & RNA are deoxyribose and ribose respectively.
• The role of DNA in living cells is to store genetic information, which determines inherited characteristics and influences the structure & function of organisms.
• Genetic information determines inherited characteristics and influences the structure & function of organisms.
• The role of RNA in living cells is to serve as a template for protein synthesis and to regulate gene expression.
• mRNA is a complementary sequence to 1 gene from DNA with introns (non-coding regions) spliced out.
• Codons can be translated into a polypeptide by ribosomes.
• rRNA is a component of ribosomes (along with proteins).
• tRNA supplies complementary amino acid to mRNA codons during translation.
• ATP is suitable as the 'energy currency' of cells because it has high energy bonds between phosphate groups.
• DNA replication is described as 'semiconservative' because the strands from the original DNA molecule act as a template and the new DNA molecule contains one old strand and one new strand.
• ATP is resynthesised in cells by ATP synthase, which catalyses a condensation reaction between ADP and Pi during photosynthesis and respiration.
• The role of ATP in cells is to provide energy for metabolic reactions and to phosphorylate compounds to make them more reactive.
• The process of semiconservative DNA replication involves DNA helicase breaking H-bonds between base pairs, each strand acting as a template, free nucleotides from nuclear sap attaching to exposed bases by complementary base pairing, DNA polymerase catalysing condensation reactions that join adjacent nucleotides on new strand, H-bonds reforming, and Meselson-Stahl experiment validating semiconservative replication.
• Polynucleotides form through condensation reactions between nucleotides, forming strong phosphodiester bonds (sugar-phosphate backbone).
• The complementary base pairs in RNA are 2 H-bonds between adenine ( A ) + uracil ( U ) 3 H-bonds between guanine ( G ) + cytosine ( C ).
• Scientists initially doubted that DNA carried the genetic code because it is a chemically simple molecule with few components.
• The structure of DNA relates to its functions such as stability, long molecule storage of information, compact helix for storage in nucleus, base sequence of triplets codes for amino acids, double-stranded for semi-conservative replication, and complementary base pairing for accurate replication.
• The structure of transfer RNA (tRNA) is a single strand of about 80 nucleotides, folded into a clover shape with some paired bases, and has an anticodon on one end and an amino acid binding site on the other.
• DNA, mRNA and tRNA can be ordered according to increasing length.
• The structure of messenger RNA (mRNA) is a long ribose polynucleotide (but shorter than DNA), contains uracil instead of thymine, is single-stranded and linear (no complementary base pairing), and its codon sequence is complementary to exons of 1 gene from 1 DNA strand.
• The structure of DNA consists of a double helix of 2 polynucleotide strands (deoxyribose), with H-bonds between complementary purine & pyrimidine base pairs on opposite strands: adenine ( A ) + thymine ( T ) guanine ( G ) + cytosine ( C ).
• A & G are 2-ring purine bases, T & C & U are 1-ring pyrimidine bases.
• The complementary base pairs in DNA are adenine ( A ) + thymine ( T ), guanine ( G ) + cytosine ( C ).
• The complementary base pairs in RNA are adenine ( A ) + uracil ( U ), guanine ( G ) + cytosine ( C ).