2 - Nucleic Acids Flashcards
DNA stands for
deoxyribonucleic acid
RNA stands for
ribonucleic acid
components of a nucleotide
pentose sugar, phosphate group, nitrogen bases
DNA structure
deoxyribose sugar
nitrogen bases: adenine and thymine, guanine and cytosine
two polynucleotide strands bond with weak H bonds between the bases, the H bonds cause the double strand to coil up and form a double helix
RNA structure
ribose sugar
nitrogen bases: adenine and uracil, guanine and cytosine
single stranded, short polynucleotide chain
Stability of DNA
DNA is very stable because the phosphodiester backbone protects the more chemically reactive organic bases
adaptations of DNA for its function
very stable structure which passes from one generation to the next and rarely mutates
weak hydrogen bonds between the strands allow the strands to separate easily during DNA rteplication and protein synthesis
large molecule so carries huge amounts of genetic info
phsophate-sugar backbone protects reactive bases
base pairing allows DNA to replicate and transfer info as mRNA
semi-conservative DNA replication
DNA helicase breaks the H bonds between the two DNA polypeptide strands, causing them to separate
free nucleotides bind specifically to complementary bases on the separated DNA strands
DNA polymerase joins together the free nucleotides that are bound to their complementary base pairs
produces two identical copies of DNA, each copy retaining half of the original DNA material
ATP
adenosine triphosphate
a nucleotide consisting of adenine, ribose sugar, and three phosphate groups
bonds between the phosphate groups are unstable and so have a low activation energy, when broken they release a considerable amount of energy
hydrolysis of ATP
ATP + H2O»_space; ADP + Pi
releases large amounts of energy
catalysed by ATP hydrolase
synthesis of ATP
ADP + Pi»_space; H2O + ATP
requires energy catalysed by ATP synthase
occurs during photophosphorylation in photosynthesis, oxidative phosphorylation in respiration, substrate-level phosphorylation
ATP is a much better immediate energy source than glucose because:
each ATP molecule releases less energy than a glucose molecule so energy is released in smaller, more manageable quantities
the hydrolysis of ATP to ADP is a single reaction releasing immediate energy (glucose breakdown is a long series of reactions)
polar properties of water
hydrogens have a slight +ve charge and the oxygen has a slight -ve charge
causes opposite poles of different water molecules to attract and form hydrogen bonds
impact of hydrogen bonds on properties of water
gives water a high specific heat capacity - water acts as a buffer against temperature change
high latent heat of vaporisation - lots of energy required to evaporate water (makes sweat an effective means of cooling)
