B2 Nucleic Acids Flashcards
What is DNA
codes for the sequence of amino acids in the primary structure of a protein, which in turn determines the final 3D structure and function of a protein.
It’s essential therefore that cells contain a copy of this genetic code & that it can be passes onto new cells without being damaged.
DNA polymer = double helix
What is a dna nucleotide monomer made up of
DNA monomer = nucleotide
made up of deoxyribose (a pentose sugar), nitrogenous base and 1 phosphate group.
What’s a polymer of nucleotides called
Polynucleotide
How is a polynucleotide made
via condensation reaction
between the deoxyribose sugar and the phosphate group, creating a phosphodiester bond.
Phosphodiester bonds (strong covalent bonds) - help ensure that genetic code isn’t broken down
What is the name of the structure that holds a polynucleotide (polymer) together
a sugar-phosphate ‘backbone’
This’s describing the strong CBs between sugar and phosphate groups that hold polymer together.
How is the double helix structure of dna created
DNA polymer occurs in pairs that’re joined together by HBs between bases.
This’s how double helix structure’s created, as 2 chains twist.
HB in dna
HBs can only form between complementary base pairs.
This’s the term given to the fact that the base cytosine can only form HBs with guanine and adenine can only bond with thymine.
The number of HB between bases in DNA
Adenine and thymine form 2 HBs
cytosine and guanine can form 3 HBs
This complementary base pairing is important to help maintain order of genetic code when DNA replicates.
How the structure relates to the function in DNA
Stable structure due to sugar-phosphate backbone (CBs) and double helix.
Double stranded so replication can occur using 1 strand as a template.
Weak HBs for easy unzipping of 2 strands in double helix during replication.
Large molecule to carry lots of info
Complementary base pairing allows identical copies to be made.
What’s RNA made of
polymer of nucleotide formed of ribose, nitrogenous base and phosphate group.
bases are adenine, guanine, cytosine and uracil.
How is rna different to dna (talk about rna only)
RNA has base uracil instead of thymine
In comparison to DNA, RNA is relatively short polynucleotide chain & it’s single stranded.
What’s the function of RNA
function of RNA is to copy & transfer genetic code from DNA in nucleus to ribosomes.
Some RNA is also combined with proteins to create ribosomes.
What are the 3 types of RNA
(Messenger) mRNA
(Transfer) tRNA
(Ribosomal) rRNA
What is mRNA
A copy of a gene from DNA
Where is mRNA created
in nucleus and it then leaves nucleus to carry copy of genetic code of 1 gene to a ribosome in cytoplasm.
Why is mRNA able to leave the nucleus but DNA can’t
DNA too large to leave nucleus and would be at risk of being damaged by enzymes, therefore destroying the genetic code permanently.
mRNA much shorter (its only length of1 gene, and can therefore leave nucleus)
Why is mRNA short lived
mRNA is short lived as only needed temporarily to help create protein, therefore by time any enzymes could break it down it would’ve already carried out its function.
mRNA is single stranded and every 3 bases in sequence code for specific amino acid, these 3 bases are called codons.
Where is tRNA found
Only in cytoplasm
What’s rRNA
The type of RNA that makes up bulk of ribosomes.
Describe the shape of tRNA
single stranded, but folded to create shape that looks like cloverleaf.
This cloverleaf shape is held in place by HBs
What’s the function of tRNA
function = to attach to 1 of 20 amino acids & transfer this AA to ribosome to create polypeptide chain.
Specific AAs attach to specific tRNA & this’s determined by 3 bases found on tRNA which’re complementary to 3 bases on mRNA.
These are called anticodon, because they’re complementary to codon on mRNA.
Differences between DNA and RNA monomers:
DNA contains base thymine, RNA contains uracil
DNA contains pentose sugar deoxyribose, RNA contains pentose sugar ribose.
Differences between polymers DNA & RNA
DNA is much larger because it contains approx 23,000 genes (entire genome), RNA is much shorter because it’s only length of 1 gene
DNA is double stranded, RNA is single stranded
What does ATP stand for
Adenosine tri phosphate
What is ATP
An immediate source of energy for biological processes
What must metabolic reactions in cells have a constant steady, supply of
ATP
What does ATP contain
3 inorganic phosphate groups
Ribose sugar
Adenine
Why are the phosphate groups in ATP described as being inorganic
They don’t contain any C atoms
What does ADP contain
Adenine
Ribose
2 inorganic phosphate groups
What does AMP contain
Adenine
Ribosome
1 inorganic phosphate group
What does adenosine contain
Adenine
Ribose
In what process is ATP made
Respiration
What is ATP made from
ADP and an inorganic phosphate via condenstaion reaction and using enzyme ATP synthase
What can ATP be hydrolysed into
ADP and Pi using enzyme ATP hydrolase
Equation for hydrolysis of ATP
ATP + water —> ADP + Pi + Energy
What type of molecule is ATP
A phosphorylated macromolecule
How is energy released in the hydrolysis of ATP
By breaking 1 of bonds between Pi’s
Small amount of energy is released to surroundings
Why is ATP an immediate energy source
Only 1 bond has to be hydrolysed to release energy
Can ATP transfer energy to different compounds
Yes
Pi released during ATP hydrolysis can be bonded onto different compounds to make them more reactive
(Known as phosphorylation)
What is the 1st ATP property in comparison to glucose
ATP release energy in small, manageable amount so no energy wasted
(Means that cells don’t overheat from wasted heat energy + cells less likely to run out of resources)
Comparison to glucose = glucose would release large amounts of energy that could result in wasted energy
What is the 2nd ATP property in comparison to glucose
It’s small and soluble to easily transport around cell
ATP can move around cytoplasm with ease to provide energy for chem reactions in cells.
This is a property that ATP has in common with glucose
What is the 3rd ATP property in comparison to glucose
Only 1 bond’s hydrolysed to release energy -> which’s why energy release is immediate
Glucose needs several bonds to break to release all its energy
What is the 4th ATP property in comparison to glucose
It can transfer energy to another molecule by transferring 1 of its Pi
ATP can enable phosphorylation, making other compounds more reactive
Glucose can’t do this as it doesn’t contain Pi
What is the 5th ATP property in comparison to glucose
ATP can’t pass out of cell so cell always has an immediate supply of energy
Glucose can leave cell, means that all cells have constant supply of ATP or ADP + Pi, but a cell can run out of glucose
What bonds hold different H2O molecules together
HBs between O and H
Is water polar
Yes its dipolar
What are the 5 key properties of H2O
Metabolite
Solvent
High heat capacity - it buffers temp
Large latent heat of vaporisation - provides cooling effect with loss of H2O through evaporation
Strong cohesion between H2O molecules - supports H2O columns + provides surface tension
Structure of water
Is dipolar
Has unevenly distributed charge due to O being slightly Neg and H slightly pos.
Water is a metabolite
Involved in many reactions e.g. hydrolysis, photosynthesis and condensation reaction
Because of this 90% of blood plasma is water and cytoplasm is largely composed of H2O
Strong cohesion of water
H2O stick together by HBs
When H2O move up xylem in plants due to transpiration its a continuous column of water - easier draw up a column rather than individual molecules
Cohesion also provides surface tension to water.
This enables small invertebrates to move and live on surface, providing them habitat away from predators in water.
Large latent heat of vaporisation of water
a lot of energy’s required to convert water in (l) to (g)
due to HBs, as energy’s needed to break the HBs between water molecules to turn it into a gas.
advantage = water provides significant cooling effect. For example, humans sweat release water onto skin. Large amounts of heat energy from skin is transferred to water to evaporate it, and therefore removing a lot of heat and cooling organism.
High specific heat capacity of water
a lot of energy is required to raise temp of water because some of heat energy is used to break HBs between water molecules.
This useful to organisms as it means temp of water remains relatively stable, even if surrounding temp fluctuates significantly. Therefore, internal temp of plants and animals should remain relatively constant despite outside temp, as large proportion of organism is water.
This important so that enzyme don’t denature or reduce in activity with temp fluctuations. Finally, this provides a stable enviro, in terms of temperature, for aquatic organisms.
Water is a good solvent
many substances dissolve in it.
Polar molecules dissolve readily in water due to water being dipolar.
slight pos charge on H atoms will attract any neg ions solutes and the slight neg charge on the O atoms of water will attract any pos ions in solutes. These polar molecules are often described as hydrophilic, meaning they are attracted to water.
Non-polar molecules, such as lipids, cannot dissolve in water and are therefore described as hydrophobic- they are repelled by water.
The fact that so many essential polar substances dissolve in water enables them to be transported easily around animals and plants, either in the blood or xylem, to cells they are needed in inside of the organism.
Name of process of DNA replication
Semi-conservative replication
What must happen before cells divide by mitosis or meiosis
All DNA must replicate to provide a copy for new cell
What is the daughter DNA made of in semi-conservative replication
1 stand from parental DNA and 1 is newly synthesised
What are the enzymes used in semi-conservative replication
DNA helicase
DNA polymerase
What happens in semi-conservative replication
1) DNA helicase breaks HBs between complementary base pairs between strands in double helix - double helix unwinds
2) each of separated parental DNA strands act as template , free floating DNA nucleotides in nucleus are attracted to their complementary base pairs on template strands of parental DNA
3) DNA polymerase catalyses joining together of adjacent nucleotides by condensation reaction to form phosphodiester bond
4) 2 sets of daughter DNA contain 1 strand of parental DNA and 1 of newly synthesised strand.
What did Watson and crick hypothesise about dna replication
Conservative
Or
Semi-conservative
Hypothesis of semi-conservative replication
Each replicated dna contains 1 of original DNA strands and 1 newly synthesised dna strand
Hypothesis about conservative replication
Original dna remains intact following dna replication adn 2 newly synthesised strands of dna join toghter
Define isotope
different forms of an element in which proton and electron number is same, but diff number of neutrons
Experiment background info for meselson and stahl
DNA bases are nitrogenous (they contain nitrogen)
Nitrogen has two isotypes: 14N and I5N.
I4N is lighter and I5N is heavier
Bacteria take in the nitrogen isotopes to make new DNA nucleotides.
Meselson and stahl
Bacteria take in the nitrogen isotopes to make new DNA nucleotides.
Therefore:
Bacteria grown in a medium containing 14N will have DNA which only contains this isotope and be lighter.
Bacteria grown in a medium containing I5N will have DNA which only contains this isotope and be heavier.
DNA samples can be spun in a centrifuge to confirm density. Here were the results
