WATER AND DNA Flashcards
Water properties related to function
Polar- oxygen is slightly negatively charged and hydrogen is slightly positively charged. Opposites attract so hydrogen attracted to other oxygen molecules attractive force between these= hydrogen bond.
Cohesive hydrogen bonds mean that water mo,cubes can stick to one another useful eg in xylem transportation tubes
High latent heat of vaporisation a lot of energy needed ti evaporate therefore evaporation as sweat is very useful in cooling mammals
High spec heat capacity- because water molecules are cohesive a lot of heat energy is needed to separate them. Water acts as a buffer against temp changes useful in organisms so don’t experience extreme changes in body temp.
Metabolite- water used in hydrolysis to break down many complex molecules. Produced in condensation reactions, chemical reactions take place in an aqueous solution and water needed for photosynthesis in plants.
Solvent- water dissolves substances, gases eg co2 and o2, wastes such as ammonia and urea, inorganic ions and small hydrophilic molecules eg ATP, enzymes that react in water.
Nucleic acids
Individual nucleotides made up of three components
- a pentose sugar
-a phosphate group
- a nitrogen containing organic base Adenine, Thymine, Guanine, Cytosine and U
These components are joined by condensation reactions to form a mononucleotide
Two mononucleotides can be joined to create a dinucleotide, by joining the deoxyribose of one and the phosphate group of another forming a phosphodiester bond
RNA structure
Ribonucleic acid is a polymer made up of nucleotides, relatively short polynucleotide chain in which the pentose sugar is always ribose and organic basses are A G C U
one type of RNA transfers info from DNA to ribosomes ribosomes made up of protein and another type of RNA . Third type used in protein synthesis
DNA structure
Watson and Crick worked out structure of DNA
The pentose sugar= deoxyribose
Bases are A T C G
Made up of two long strands of nucleotides joined by hydrogen bonds formed between certain bases .a ladder in which phosphate and deoxyribose molecules alternate to form the uprights and organic bases pair
BASE PAIRING: adenine always pairs with thymine
Guanine always pairs with cytosine complementary base pairings
Quantities of A and T the same as well as quantities of C ans G but ratios of AT and GC vary between species
DOUBLE HELIX:
Ladder like structure or two polynucleotide being twisted, uprights of deoxyribose and phosphate twist around each other causing structuralbackbone
Stability and function of DNA
The phosphodiester backbone protects mode chemically reactive organic bases inside helix
Hydrogen bonds link organic base pairs forming bridges between the phosphodiester uprights as there are three hydrogen bonds between cytoskeleton guanine the more CG parings the more stable the DNA molecule
Function: responsible to passing genetic info cell to cell generation to generation
Adaptations:
Stable structure so passes generation to gen without significant change most mutations
are repaired so persistent mutations are rare.
Two separate strands held together by H bonds so easily separated for protein synth and during DNA replication
Large molecule carries a large amount of genetic info
Base pairs protected In helical cylinder from external chemical and physical forces
Base pairing leads to DNA being able to replicate and transfer info as mRNA
DNA replication
DNA replicates before cell division so that each cell has a full amount of DNA.
The method is called semi conservative replication because half of the strands in each new dna molecule are from the original dna molecule.
1) the enzyme DNA heli case breaks the hydrogen bonds between bases on the two polynucleotide dna strands making the helix unwind to form two single strands
2) each original single strand acts as a template for a new strand
Complementary base pairing means that free floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand.
3) condensation reactions join the nucleotides of the new strand together-catalysed by the enzyme dna polymerase
Hydrogen bonds from between the bases on the original and new strands.
Each new dna molecule contains one strand from the original dna molecule and one new strand.
Nucleotides
Nucleotide structure= phosphate, pentose sugar and a base
Can join together in a condensation reaction forming a phosphodiester bond between the sugar and the phosphate of a another. If many bond together a polynucleotide is formed and a chain of these is a sugar phosphate backbone.
