Nucleic acids, water and ATP Flashcards
What does the conservative model of DNA suggest?
DNA replication results in one molecule that consists of both original DNA strand and another molecule that consists of 2 new strands
What does the semi-conservative model of DNA suggest?
2 DNA molecules with with one original strand and one new strand
What does the dispersive model of DNA suggest?
2 DNA molecules that are a mixture or ‘hybrid’ of parental and daughter DNA
Watson and Crick’s role in DNA replication
Found that specific base pairing was involved in a way of copying sequences of genetic information
Each strand acts as a template from which the new complementary strand is copied
Didn’t know exactly how replication would take place
What did Meselson-Stahl experiment find in generation 0?
Single band produced after centrifugation
DNA only contained heavy 15N at that time
What did Meselson-Stahl experiment find in generation 1?
Single band higher and intermediate in density between the 15N DNA and 14N DNA
Mixture of light and heavy DNA
Not conservative - predicted 2 distinct bands
What did Meselson-Stahl experiment find in generation 2?
2 bands - one in same position as intermediate band from 1st generation and second was higher
not dispersive - impossible to get purely light molecule
ATP is an energy source in many cell processes
Give two ways in which ATP is a suitable energy source for cells to use
Releases relatively small amount of energy
Releases energy instantaneously
Phosphorylates other compounds making them more reactive
Can be rapidly re-synthesised
Does not leave the cell
Give 2 ways in which the hydrolysis of ATP is used in cells
Phosphorylated compounds to make them more reactive
Provides energy for processes
Describe how ATP is resynthesized in cells
ADP and Pi
By ATP synthase
In respiration
ATP is a nucleotide derivative
Contrast the structure of ATP and a nucleotide found in DNA to give two differences
ATP has ribose and DNA nucleotide has deoxyribose
ATP has 3 phosphate and DNA nucleotide has 1 phosphate
ATP base is always adenine and DNA nucleotide bases can be different
Give two properties of water that are important in biology
Explain the importance of each property
Polar - universal solvent
Metabolite - metabolic reactions
Cohesion - provides surface tension supporting small organisms
High specific heat capacity - reduces fluctuations in temperature
High latent heat of vaporisation - provides a cooling effect
Suggest why water becomes lighter as it expands
Density = mass/volume
Ice has the same mass of water but greater volume
Suggest why water becomes lighter as it expands
Density = mass/volume
Ice has the same mass of water but greater volume
Suggest one biological advantage of why water becomes lighter as it expands
Ice is colder than water
Ice floats on water as it is lighter
Reduces freezing of water below ice
