DNA, ATP & Water Flashcards
What are the monomers for DNA?
DNA nucleotides
Deoxyribonucleic Acid is the polymer
What are the monomers for RNA
RNA nucleotides
Ribonucleic Acid is the polymer
What is DNA
Deoxyribonucleic Acid
A biological molecule that’s a polymer of DNA nucleotides
A unit of hereditary present in all living organisms
Holds genetic information that codes for a specific sequence of amino acids to produce proteins
Structure of DNA nucleotides
Pentose sugar: Deoxyribose
Attached to a phosphate group
Attached to a nitrogenous, organic base (A, T, C, G)
Structure of RNA nucleotides
Pentose sugar: Ribose
Attached to a phosphate group
Attached to a nitrogenous, organic base (A, T, C, G)
Which bases are found in DNA
Adenine + Thymine
Cytosine + Guanine
Which bases are found in RNA
Adenine + Uracil
Cytosine + Guanine
Why is DNA ‘deoxy-‘
Missing an oxygen atom on the carbon 2 of the pentonse sugar so its just H not OH
Which bases are purine?
Adenine
Guanine
2 ringed bases
What bases are pyrimidine
Thymine
Cytosine
Uracil
1 ringed base
What bonds are present in DNA
Weak hydrogen bonds between complementary base pairs
2 between Adenine and Thymine
3 between Cytosine and Guanine
Phosphodiester bonds between the phosphate group of one nucleotide and the 3rd carbon on the pentose sugars adjacent nucleotide
What is DNAs structure
Double helix
Consisting of 2 polynucleotide chains of DNA nucleotides
Wound together and held in place by weak hydrogen bonds between complementary base pairs
Antiparallel strands
What is a sugar-phosphate backbone
Structural component of DNA consisting of phosphodiester bonds
Between the phosphate group of one nucleotide and the 3rd Carbon on the adjacent one
Makes nucleic acid very strong and stable
What is mRNA
A relatively short polynucleotide chain
A single stranded molecule
Used to transfer genetic information from DNA to ribosomes
Explain antiparallel
2 strands of DNA running in opposite directions
Both have a 5’ and 3’ end but in opposite directions
Explain the ends of DNA
5’ (5 prime end): end that has a phosphate group attached to the Carbon 5 on the deoxyribose sugar
3’ (3 prime end): end that has a hydroxyl group attached to the Carbon 3 on the deoxyribose sugar
Why are the ends of DNA important
Important when making proteins because it ensures only one strand is read to make it
Important in DNA replication because DNA polymerase is only complementary by its active site to the 5’ end (phosphate group)
How does DNA structure allow it to function
7
Sugar phosphate backbone and double helix structure
- provides strength and stability
- protects bases in the code
- protects hydrogen bonding between bases
Long/large molecule
-stores lots of information
Helical/coiled structure
-compact
Base sequence
-codes for amino acids for protein
Double stranded
-semi conservative replication, both templates
Complementary base pairing
-allows for accurate replication
Hydrogen bonding
- collectively strong makes it a stable molecule
- weak so easily separated for semi conservative replication
What are the 3 types of replication
Semi conservative
Conservative
Dispersive
Outline semi conservative replication
Each new DNA molecule contains one original template strand and one new synthesised strand, making it identical to the original
Each strand acts as a template
What is dispersive replication
Original strands break and recombine
New strand is synthesised in between the fragments
Leaving a hybrid of new and old strands
Parents DNA dispersed throughout both strands
What is conservative replication
Parent strands separate to act as templates and when two new strands are synthesised the new ones join up and the parents join back up
1 molecule 100% original
1 molecule 100% new
Explain semi conservative replication
DNA helicase unwinds the double helix, separating the strands
By breaking the weak hydrogen bonds between complementary base pairs
Both strands act as templates
Free DNA nucleotides are attracted to their complementary base pairs
(A to T and C to G)
DNA polymerase binds to 3’ of template strand and had an active sight complementary to the 5’ of free nucleotides
Joins adjacent nucleotides together by phosphodiester bonds
Synthesising DNA in a 5’ to 3’ direction
Leaving 2 DNA molecules, both identical and with one original and one new strand
How does DNA polymerase work
A complementary binding site to the 3’ end of template strand
A complementary active site to the 5’ end of free nucleotides
Synthesises in a 5’ to 3’ direction only
Strands are antiparallel
Explain Messelson and Stahls experiment
Grew ecoli DNA in N15 because nitrogenous bases used nitrogen
Isolated a DNA molecule
Spun it in a centrifuge
Removed DNA and grew it in N14 for one replication round
Spun again
Repeated 4 times
Explain Messelson and Stahls results
Generation 0: N15N15=1 molecule 100% N15
Generation 1: N14N15=2 molecules 50% N15
Generation 2: N14N14/N14N15=2 molecules 50% N15, 2 molecules 100% N14
Generation 3: N14N14/N14N15=2 molecules 50% N15, 6 molecules 100% N14
How did the results prove semiconservative replication
After 1 generation semi conservative would give a band in the middle because half is N14 half is N14
SEE NOTES?????
DNA polymerase function in DNA replication
Synthesises phosphpdiester bonds
Between adjacent nucleotides
Via condensation reaction
What is ATP
Adenosine Triphosphate
Nucleotide derivative
Consisting of a ribose sugar, 3 phosphate groups and a nitrogenous base adenine
Produced in the mitochondria in respiration or photosynthesis
Explain the hydrolysis of ATP
ATP is hydrolysed into Pi and ADP
Via ATP hydrolase
Releasing small manageable packets of energy
It is the terminal high energy bond between the 2nd and 3rd phosphate group that’s broken
Via a hydrolysis reaction
Releasing small manageable packets of energy
Pi can phosphorylate other compounds to make them more reactive
Explain the resynthesis of ATP
ADP and Pi (phosphorylation)
Catalysed by ATP synthase in a condensation reaction
Requires energy to add the phosphate group to ADP to form ATP, creating a high energy bond
Occurs in photosynthesis and respiration
Why is ATP useful/how is ATP a sustainable energy source
Releases small manageable packets of energy: little lost as heat energy
Releases energy instantaneously: efficient
Pi can be used to phosphorylate other compounds: more reactive
Can be rapidly resynthesised: continous energy source
Does not leave the cell
Soluble: most active processes occur in aqueous solutions
Where does ATP synthesis occur
Photosynthesis
Respiration
ATP vs DNA nucleotide
ATP has 3 phosphate groups/DNA nucleotide only one
ATP has a ribose sugar/DNA nucleotide have deoxyribose sugar
ATP base is always adenine/DNA nucleotide can be 4 different ones (including adenine) (ATCG)
How is the hydrolysis of ATP used in cells
Phosphorylate other compounds and make them more reactive
Releases energy for other processes such as protein synthesis, active transport, muscle contraction, semi-conservative replication
What is water
A dipole molecule consisting of 1 oxygen and 2 hydrogen
Major component of the cytoplasm
Slightly negative on oxygen because more protons so pulls electrons closer to its nucleus and since electrons are negative it makes it more negative
Slightly positive on both hydrogens because electrons pulled away from it and closer to oxygen
Unequal sharing of electrons
Why is oxygen a polar molecule
Charged
Unequal sharing of electrons
How does water act as a solvent
Dipole molecule
So polar molecules can dissolve in it
Universal solvent because can dissolved more molecules than any other liquid
Major component of the cytoplasm because allows chemicals and enzymes to dissolve
So essential for chemical reactions to occur
Why is water considered a universal solvent
Can dissolve more molecules than any other liquid
Explain waters cohesion
Dipole molecule
Slightly negative oxygen of one water molecule attracted to the slightly positive hydrogen of another
Forming a hydrogen bond
Individually weak (compared to covalent bonds)
But in large numbers very strong
When hydrogen bonds form between two water molecules
Explain waters adhesion
When hydrogen bonds form between water and another type of molecule
Dipole molecule
Slightly negative oxygen of one water molecule attracted to the slightly positive hydrogen of another molecule or vice versa
Forming a hydrogen bond
Individually weak (compared to covalent bonds)
But in large numbers very strong
Why can some insects walk on water
Surface tension created due to waters cohesion
Insects are light enough jot to break the hydrogen bonds between water molecules
Ways that water acts as a metabolite
Hydrolysis and photosynthesis use water
Condensation and respiration produce water
Chemical reactions taking place in aqueous mediums
Enzymes and substrates can diasolve in water and react
Explain waters specific heat capacity
Large/high
Requires a lot of heat energy to heat it up
Because it has lots of hydrogen bonds
Provides a habitat in water because can resist temperature fluctuations
Organisms have optimum temperature to function
Organisms mostly water (70%) so protects them against sudden temperature changes
Explain waters latent heat of vaporisation
Large/high
Takes a lot of heat energy to break hydrogen bonds in water
Hydrogen bonds increase the energy required to evapourate water
Lots of body heat is required to evaporate water in small volumes (sweat)
So lowers internal body temperature of organism
Explain waters cohesion in plants
Surface tension allows water to be pulled up xylem vessels in continuous columns
Water also pulled back into a body rather than escaping it
What can water dissolve
Gases: O2 can be transported from the lungs to respiring tissue, CO2 can be transported from respiring tissue to lungs
Waste: Ammonia and urea made in cells to be transported to kidneys and excreted
Inorganic ions, amino acids, ATP, monosaccharided
Enzymes and globular proteins
Benefits of water being transparent
Plants under water can photosynthesise
Light can pass through the eyeball
Benefits of water being hard to compress
Turgor (support) in plants
Hydroskeleton in worms
Benefits of ice being less dense than water
Habitats for animals
Insulates the water below and stops it all freezing
Allows nutrients to be cycled
Why is water denser than ice
Ice has the same mass as water
But takes up a bigger volume
Because molecules for crystalline structures
Density = mass/volume
So same mass but greater volume means ice has a lower density
List 8 inorganic ions
Hydrogen (H+) Hydroxide (OH-) Iron (Fe²+ / Fe³+) Sodium (Na+) Phosphate (PO4³-) Nitrites (NO2-) Nitrates (NO3-) Chloride (Cl-)
Use of hydrogen ions
Affects acidity of solutions (pH)
Used in respiration and photosynthesis to provide energy to make ATP
Uses of hydroxide ions
Affects acidity of solutions (pH)
Uses of Iron ions
Structural component of haemoglobin
Binds to oxygen to allow transport of it to respiring cells
Uses of sodium ions
Used in contransport of glucose and amino acids from lumen of small intestines into intestinal epithelial cells
Changes water potential of immediate area
Used in nervous conduction
Uses of phosphate ions
Components of phospholipids (cells and organelles membranes)
DNA
RNA
ATP
Uses of nitrate ions and nitrate ions
Taken up from soil by plant roots then used to make amino acids
Uses of chloride ions
Uses in regulating the water potential or the small intestine
