1B (more bio mols) Flashcards
What are nucleotides made up of?
Pentose sugar
Nitrogen containing organic base
Phosphate group
DNA bases and sugar
what makes each nucleotide different?
Pentose sugar- deoxyribose
Bases- adenine, thymine, cytosine, guanine
Each DNA nucleotide has same sugar and phosphate but diff bases
Bases and sugar in rna
Penrose sugar- ribose
Bases- adenine, uracil, cytosine, guanine
Each nucleotide same apart from bases
What is a polynucleotide?
How does it form?
Polymer of nucleotides eg DNA
Join via condensation reaction between phosphate of one and sugar of another forming phosphodiester bond- sugar phosphate backbone
DNA structure
2 polynucleotide chains joined by H bonds between bases
Complimentary base pairing- A,T(2 H bonds) G,C(3 H bonds)
2 anti parallel stands form double helix
Pyramidines and purines
Pyramidines- T and C, single ringed
Purines- A and G, double ringed
Pyramidines join to purines
When was DNA discovered?
First in 1800s but doubted it carried whole genetic code
1953- proved it did
1953- Watson and Crick discovered double helix
RNA structure
Single polynucleotide chain
Shorter than DNA polynucleotide
Properties of DNA
Stable- backbone protects chemically reactive organic bases in double helix
3 H bonds c-g so more c-g means more stable
Diverse- infinite variety- 3.2 bill base pairings
DNA adapted to function
Stable- doesn’t mutate when passes to generations
Stands joined by H bond so can separate
Large- carries lots of info
Bases protected by backbone
Base pairing means it can replicate and transfer info as mRNA
Semi-conservative replication process
1) DNA helicase breaks H bonds between bases so unwinds forming 2 single strands
2) each og strand acts as template for new one. free floating nucleotides attach to complimentary exposed bases on template strands
3) condensation reaction joins nucleotides together catalysed by DNA polymerase. H bonds form between bases on new and old strands’
4) each new DNA molecule has 1 strand of og DNA molecule and one of new
4 requirements for semiconservative DNA replication
1) 4 types of nucleotide w bases present
2) both strands act as template for attachment of nucleotides
3) dna polymerase present
4) source of chem energy required
what does antiparallel mean?
dna strands run in opposite directions
which way does dna polymerase work?
3’-5’ of the template strand so nucleotides added from 3’ of the template strand as active site of polymerase compliments 3’
which direction is the new strand made in?
5’-3’
which carbon does phosphate attach to?
which carbon does hydroxyl attach to?
5’
3’
does dna polymerase run in the same direction or opposite on each strand?
opposite
meselson and stahl’s experiment
1) 2 bacteria samples grown. 1 in broth w 14N other w 15N. bacteria reproduce taking up N from broth to help make nucleotides so becomes part of DNA
2) sample of dna taken from each batch and centrifuged. dna from heavy N settled lower
3) bacteria in heavy n put in light broth. replicated once and centrifuged
4)if conservative, og heavy would settle at bottom and light at top
5) if semi, would contain 1 old and 1 new strand so would settle in middle
6) it did settle in middle showing it contained 14N and 15N
why is water vital to living organisms?
about 80% of cells contents
important metabolite in hydrolysis etc
solvent- most metabolic processes happen in solutions
very cohesive- helps water transport in plants etc
does water have a high or low latent heat of vaporisation and specific heat capacity? advantages of this?
high
helps control body temperature
is water polar or not? why?
polar
h positive as electrons pulled more to o
o negative as unshared electrons
allows hydrogen bonding
6 useful properties of water
- metabolite- many metabolic reactions involve condensation
- high latent heat of vaporisation- lots of energy to break h bonds so lots needed to vaporise so can use water loss through evaporation to cool down wo losing too much water
- can resist changes in temp- h bonds absorb lots energy so high spec heat cap so no rapid temp changes
- good solvent- water polar so can surround ionic structures and dissolve them
- not easily compressed- supportive eg hydro-elastic skeleton in worms and turgor in plants
- transparent- aquatic plants can photosynthesise, light can penetrate fluid in eyes to reach retina
what is cohesion?
why are water molecules so cohesive and benefits?
attraction between molecules of the same type/ tendency of molecules to stick together
because theyre polar
helps water flow- transporting substances up xylem
surface tension
water has high surface tension when in contact w air as it is cohesive- water molecules pulled back into body of water
