Nucleic Acids, ATP and water Flashcards
define genome
all the genetic material a cell contains
what is a nucleotide made of?
phosphate group, nitrogenous base and deoxy/ribose sugar
describe the structure of DNA
- sugar phosphate backbone so provides stability
- long molecule so can store lots of information
- helix so compact
- base sequence so allows information to be stored
- double stranded so semi conservative replication can occur/ each strand can act as a template
- complememntary base pairing so accurate replication
- weak hydrogen bonds for easy strand separatio
- many weak hydrogen bonds so stable molecule
describe semi-conservative replication
- DNA helicase breaks hydrogen bonds and strands separate as double helix unwinds
- both strands acts as a template
- free dna nucleotides are attracted to the complementary bases
- complementary base pairing (A-T, C-G)
- DNA polymerase joins adjacent nucleotides
- phosphodiester bonds, condensation reaction
- DNA molecules contain one old strand and one new strand
describe the role of DNA polymerase in the semiconservative replication of DNA
- Joins adjacent DNA nucleotides
- condensation reactions
- formation of phosphodiester bonds between adjacent nucleotides
name the two scientists who proposed models of the chemical structure of DNA and of DNA replication
Crick and Watson
give two features of DNA and explain how each one is important in semi conservative replication
- two strands so both can act as a template
- complementary base pairing allows accurate replication
- weak hydrogen bonds between bases allow two strands to separate
why are strands of dna called antiparallel
- run in opposite directions
- DNA polymerase only complementary active site to 5’ end of the molecule
- DNA pol synthesises DNA in a 5’ to 3’ direction only
hershey and chase’s experiment
proves that DNA is hereditary material passed between generartions NOT proteins
- protein coat of phages are radioactively labelled (35 S)
- phages inject bacteria with viral DNA to create a new generation of phages
- no radioactivity in the next generation, so NO proteins passed onto generation
vs
when DNA of phages is radioactively labelled
- phages’ DNA is radioactively labelled (32P)
- same experiment but 32P in next generation, showing DNA hereditary material
-
Griffith’s experiment
- first mouse injected with rough strain of virus (non virulant/infectious) ant it lived
- second injected withn smooth (virulent) and died
- third with smooth that had been heat killed (all proteins denatured) and lived
- fourth injected with heat killed smooth strain mixed with living rough stain and died
- ## information to be harmful passed from dead bacteria to living safe bacteria
meselston and stahl experiment
proved if dna was semi conservative or conservatively replicated
- grew bacteria in “heavy” 15N and light 14N
- dna in bacteria after many generations either heavy or light
- took samples of bacterial culture, processed it to get dna solution
- equal volumes if DNA solutions mixed together
- centrifuged, 15N migrates further down than 14N, more dense
GEN 1 = INTERMEDIATE
GEN 2 = 50% LIGHT, 50% INTERMEDIATE
GEN 3 = 75% LIGHT, 25% INTERMEDIATE
ATP is used as energy source in many cell processes. give 2 ways in which ATP is a suitable energy source for cells to use.
- releases small amounts of energy
- releases energy instantly
- phosphorylates other compounds, making them more reactive
- can be rapidly resynthesised
- does not leave cells
give 2 ways in which hydrolysis of ATP used in cells
- phosphorylates other compounds so makes them more reactive, lowers Ea
- provides energy for: muscle contraction, protein synthesis, active transport
ATP structure
Adenosine Triphosphate
3 phosphate groups
Adenine base
ribose sugar
describe how ATP is resynthesised in cells
ADP + Pi
by ATP synthase
in aerobic respiration (or PS)
