Nucleic Acids Flashcards
What are the nitrogenous based in DNA called?
Adenine ——— Thymine
Cytosine ——— Guanine
How are the components of a nucleotide joined?
Via condensation reactions
What are the nitrogenous based in RNA called?
Adenine —— Uracil
Cytosine —— Guanine
Name the roles of different types of RNA
Transferring genetics from DNA to ribosomes
Making up ribosome
Protein synthesis
What sugar makes up
DNA
RNA
DNA = deoxyribose
RNA =ribose
what do DNA + RNA stand for?
Deoxyribonucleic acid
Ribonucleic acid
What are the purine bases called?
Adenine
Guanine
What are the pyrimidine bases called?
Thymine
Cytosine
What does anti-parallel mean?
They are parallel but run in opposite directions
Why are the polynucleotides in DNA anti-parallel?
DNA polymerase is only complementary to 3 prime end so can only bond nucleotides in one directions
What are chromatins?
DNA +Histone
What makes two DNA molecules different?
Proportions and sequence of bases
Why is DNA charged?
Phosphate group are negative
Why must DNA be stable?
To ensure genetics are passed in unchanged
How is DNA a stable molecule?
Phosphodiester bonds= strong covalent bond
Sugar phosphate Backbone and double helix = protect more chemically reactive bases
Hydrogen bonds= collectively strong
What is base stacking ?
Forces of attraction between adjacent bases on one polynucleotide
Why is it useful for hydrogen bonds to be present between bases?
To easily separate polynucleotides for DNA replication
What allows DNA to carry so much genetic info?
Very large molecule
What do the backbone and helical structure ensure?
Protection of genetic info from chemical and physical forces
Why is base pairing used?
For easy transfer of information (as RNA) and replication of DNA
What biological molecule was thought to carry genetic info? +why
Proteins
DNA was though to have to few components
Briefly describe the puemonia experiment
Nice injected with:
Dead harmful strain= alive
Live safe strain= alive
Both= dead
Safe strain developed ability to produce toxins using DNA from dead strain.
What were the possible explanations for the puemonia experiment?
1) not all harmful strain was killed
2) Safe strain mutated (unlikely as repeats were taken)
3) safe strain used DNA as instructions to produce toxins
How were viruses used to prove DNA is hereditary material ?
One viruse has radioactive DNA
other virus had radioactive Protein
Only bacteria infected with first virus showed signs of radioactivity
What’s a bacteriophage?
A virus that infects and kills bacteria
How are viruses made to have radioactive protein and DNA
DNA= Radioactive phosphorus
Protein= radioactive sulfur (r groups)
What are the two main stages of DNA replication?
Nuclear division-
Nucleus divides by mitosis or meiosis
Cytokinesis-
Whole cell divides
What conditions are necessary for DNA replication to occur and why
DNA polymerase must be present- to catalyse formation of phosphodiester bonds
Free nucleotides- to form new polypeptide
Energy- in form of ATP
Two DNA strands- act as template
What is the first stage of DNA replication?
Breaking hydrogen bonds between base pairs
Replication form forms
ATP activates free nucleotides
What is stage two of DNA replication?
Polynucleotide strands act as templates
Hydrogen bonds form between complementary base pairs between free and original bases
What is stage three of DNA replication?
DNA polymerase catalyses the condensation reaction to form phosphodiester bonds between nucleotides on new polynucleotide.
Why is DNA replication called semi-conservative?
Half of the original DNA is preserved
What occurs to speed up DNA replication?
Two replication forks form
What is conservative DNA replication?
Where the original DNA is unchanged and acts like a template for the new strand
What is dispersive DNA replication?
When the original DNA is dispersed and combines with free nucleotides randomly
Who conducted an experiment to prove semi-conservative DNA replication?
Meselson and Stahl
What were the conditions for Meselsons and Stahls experiment?
Bacteria grown in light (14) nitrogen
Bacteria grown in heavy (15) nitrogen
For many generations
Briefly describe Meselsons and Stahls experiment?
1) grow bacteria in 15N for many generations
2) transfer to 14N for one generation
3) Centrifuge
4) repeat for 2nd and 3rd generation
Describe the distribution of 15N and 14N in the first and second and third generation
15N. 14N
0) 100. 0
1) . 50. 50
2) . 25. 75
3) . 12.5. 87.5
How was nitrogen supplied in Meselson and Stahls experiment?
By ammonium ions
NH4+
What were the expected results for Meselson and Stahls experiment for the conservative model of DNA replication?
Never hybrid DNA
(No medium density)
Only ever heavy and light DNA
After generations more light DNA forms
What were the expected results for Meselson and Stahls experiment for the dispersive model of DNA replication?
Only ever hybrid DNA
What does ATP stand for?
Adenosine triphosphate
When is ATP produced?
During oxidation of organic molecules
Aerobic and anaerobic respiration
And photosynthesis
Is ATP soluble or insoluble?
Soluble
What does ATP comprise of?
Adenine
Ribose sugar
Three phosphate groups
What is ATP also know as ?
A phosphorylated RNA nucleotide
Or
Nucleotide derivative
Name the enzyme involved in the hydrolysis of ATP
ATP hydrolase
What is the removed phosphate group uses for after ATP hydrolysis?
To phosphorylate other molecules
Why does ATP hydrolysis have a low activation energy?
Due to unstable bonds
What is required for ATP hydrolysis?
Water
What enzyme is involved in the formation of ATP?
ATP synthase
What symbol represents a phosphate group?
Pi
Is the synthesis of ATP exothermic or endothermic?
Endothermic Because: Reversible reaction ATP hydrolysis releases energy so must be exothermic Other direction= endothermic
Where does the energy stores in ATP come from?
The hydrolysis of carbohydrates or lipids
What type of reaction is the synthesis of ATP?
Condensation reaction
Where does ATP synthesis occur?
In chloroplasts + mitochondria
What are the different ways ATP can be made?
1) photophosphorylation
During photosynthesis in chlorophyll
2) oxidative phosphorylation
Animal and plant cells during respiration
3) substrate-level phosphorylation
In animal and plant cells when donor molecular provide phosphate
Why is ATP used as an immediate energy source not glucose?
The hydrolysis of ATP occurs in one quick reaction whereas the hydrolysis of glucose is slower. ATP provides immediate energy
ATP stores less energy than glucose so energy released is more manageable. No waste (thermal) energy.
Why is ATP an immediate energy source?
Because of its unstable bonds
How many ATP molecules are made from one glucose molecule?
38
What are the main uses or ATP?
1) movement
2) metabolic processes
3) activating molecules
4) active transport
5) secretion
How is energy used for movement?
Allows muscle filaments to slide past each other so whole muscle shortens
How is energy used in metabolic processes?
In the condensation reactions needed to form larger molecules
How is energy used in secretion?
For the formation of lysosomes
How is energy used in active transport?
To alter the shape of carrier proteins in the plasma membranes allowing molecules to move against the concentration gradient
How is ATP used in the activation of molecules ?
The phosphate groups removed via condensation reactions attach to other molecules which lowers their AE
How can you tell that lots of movement, active transport, secretion, metabolic processes or activation of molecules occurs within a cell/ tissue ?
Large and/or many mitochondria for ATP synthase
What is a dipolar molecule?
A molecule with two poles
What bonds cause cohesion ?
Hydrogen: between oxygen and hydrogen
What is specific heat capacity?
The energy needed to raise 1KG of a substance by 1 degree
Does water have a high or low specific heat capacity?
+ why
High:
Due to hydrogen bonds which are collectively strong
Why is waters specific heat capacity important to organisms?
1) allows an optimum temperature for proteins so they don’t denature
2) provides a thermo stable environment for organisms to live in.
(Aquatic)
3) provides thermo stable environment within organisms (blood)
How does waters high specific heat capacity link to its function?
Allows water to act as a buffer against sudden temperature changes
What is latent heat of vaporisation?
The energy needed to change state of 1KG of a substance from liquid to gas without a temp change
Does water have a high or low latent heat of vaporisation ?
+why
High:
Due to the high amounts of energy required to break hydrogen bonds
How many calories are needed to evaporate 1g of water?
577
How does waters latent heat of vaporisation link to its function?
Allows lots of energy to be removed from body.
Thermal energy (placed into breaking hydrogen bonds) converted to kinetic energy in water molecules
What is surface tension?
A measure of the force needed to stretch/ break the surface of a liquid
Why is waters surface tension so high?
Due to cohesion and adhesion
Why is waters high surface tension useful for organisms ?
Allows animals to live on water
Allows water to travel up xylem
How does water latent heat of vaporisation and surface tension link?
High surface tension means water is pulled into body of water instead or evaporating
How much of a mammals body is water?
65%
How much of a jellyfishes body is water?
98%
What are the main functions of water?
1) a metabolite
2) a solvent
3) cooling
4) allowing light through
5) structure
What is a metabolite?
A substance used up in a metabolic reaction
How is water used in reactions?
In hydrolysis
In photosynthesis (as raw material)
Reactions occur whilst aqueous
Why is water a good solvent ?
Is dipolar -
has ability to attract charges particles to opposite ends of particle -
can separate molecules
What can water dissolve?
Urea Oxygen Polysaccharides Amino acids Enzymes Ammonia
Why is it important for water to be a good solvent?
To allow the transportation of substances
Why does water offer support?
Not easily compressed
Responsible for the turgid pressure of plants and hydrostatic skeleton of earthworms
Why is it useful for water to be transparent?
Allow light through jelly-like substance in eye to retina
To allow light through palisade layer for photosynthesis
What is an inorganic ion?
An atom or compound that has lost or gained electrons
Where can inorganic ions be found?
Cytoplasm
Body fluids
Give examples of inorganic ions and their functions
Iron:
Transport oxygen
Phosphate:
ATP and DNA formation
Hydrogen:
Regulate PH to allow optimum conditions for proteins
Sodium:
Transport glucose and amino acids across plasma membranes
Who proposed the theory of semi-conservative DNA replication?
Watson and crick
Why is waters high latent heat of vaporisation an efficient tool?
Allows lots of energy to be transferred to the environment without losing lots of energy
What is the role of single stranded DNA in DNA replication?
Act as a template
Determines order of bases
What is a nucleotide made of?
Pentose sugar
Nitrogenous base
Inorganic phosphate ion
Why is there variability in the stability in the stability of DNA?
3 H bonds between C+G
Only 2 between A+T
