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)
ATP is a nucleotide derivative.
contrast the structures of ATP and a nucleotide found in DNA
- ATP has ribose and DNA has deoxyribose
- ATP has 3 phosphate groups, DNA only has one
- ATP base is always adenine and DNA can vary
describe how an organism can be phosphorylated
attachment of phosphate group (to enzyme)
- hydrolysis of ATP TO ADP + Pi
explain 5 properties of water that make waTER IMPORTANT FOR LIVING ORGANISMS
- metabolite in condensation/PS/RP reactions
- solvent so metabolic reactions can occur
- high specific heat capacity so buffers changes in temperature
- large latent heat of vaporisation so provides cooling effect throuh evaporation
- cohesion so supports columns of water in plants
- cohesion of water molecules so produces surface tension supporting small organisms
what can dissolve in water?
gases (eg: O2 and CO2)
waste products like urea and ammonia
inorganic ions
amino acids
enzymes dissolve in water
give 2 properties of water thar are important in biology. explain the importance of each property you identify
polar so acts as a solvent
- metabolite so involved in condensation reactions
- cohesion provides surface tesnion
- high specific heat capacity so buffers changes in temperature
suggest why water becomes lighter as it expands
density = mass / volume
- ice has same mass of water but greater volume
suggest one biological advantage of this property of water
ice is colder than water
- ice floats on water
- reduces freezing of water belwo ice
scientists looking for extra-terrestrial life are looking for planets with evidence of free warer. explain why water is considered so important for life to occur.
- life thought to evolve in water
- water provides support for organisms
- water major component of cytoplasm
- universal solvent
- metabolite
- stagbilises temperature
describe the role of iron ions, sodium ions and phopsphate ions in cels
iron ions:
- haemoglobin associates with oxygen
sodium ions:
- cotransport of amino acids
- sodium moved out via atcive transport
- affects osmosis
- creates a cg
phosphate ions:
- affects osmosis
- joins nucleotides
- produces ATP
-phosphorylates other compounds
