Nucleotides And Enzymes Flashcards
what is the genetic code
-DNA (doexyribonucleic acid)
-which codes for everything in an organism
-It is universal
-each code produces the same instructions in all living organisms and cells
-essential that cells contain a copy of this genetic code and that it can be passed to new cells without being damaged
chromosones
-23 pairs of chromosones in every body cell
-excluding gametes (23 individual)
-associated with proteins called histomes
-chromosones are made up of DNA
basics of what is DNA
- dna is a polymer
-of monomers called nucleotides
-in a double helix shape
structure of DNA
- a double helix
-two long polynucleotide chains wound around eachother
-each chain runs in opposite directions- antiparallel
-one chain runs 3’ to 5’ while the other runs 5’ to 3’
-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 protein
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DNA nucleotide
-monomer that makes up DNA is a nucleotide
-made up of deoxyribose (a pentose sugar)
-a nitrogenous base
-one phosphate group
what are the 4 nitrogenous bases
- guanine
- cytosine
- adenine
- thymine
polynucleotides
polymer of nucleotides is called a polynucleotide
created via a condensation reaction between deoxyribose sugar and the phosphate group, creating a phosphodiester bond.
what is a phosphodiester bind
strong covalent bonds
therefore help to ensure that the genetic code is not broken down
sugar phosphate backbone
part of the polynucleotide
describes the strong covalent bonds between the sugar and the phosphate groups that hold the polymer together
how is the double helix shape created
DNA polymer occurs in pairs
these pairs are joined together by hydrogen bonds between bases
creating the double helix structure as the two chains twist
hydrogen bonds can only form between complementary base pairs
the complementary base pairs
cytosine only form hydrogen bonds with guanine
adenine only bond with thymine
adenine and thymine form two hydrogen bonds, whereas cytosine and guanine can form 3 hydrogen bonds
why is the complementary base pairing important
help maintain the order of genetic code when DNA replicates, therefore reducing chance of mutations
How the DNA structure links to its function
- stable = due to sugar phosphate backbone and the double helix to prevent damage
-double stranded so replication can occur using one strand as a template
-weak hydrogen bonds for easy separation of the two strands in a double helix during replication
-large molecules to carry lots of genetic information
-complementary base pairing allows identical copies to be made
What is RNA
a polymer of a nucleotide formed of ribose, a nitrogenous base and a phosphate group
the nitrogenous bases in RNA are adenine, guanine, cytosine and uracil
has a uracil base instead of thymine- in comparison to the DNA polymer, the RNA polymer is a relatively short polynucleotide chain and it is single stranded.
what is the function of RNA
copy and transfer the genetic code from DNA in the nucleus to the ribosomes. Some Rna is also combined with proteins to make ribosomes
Three main types of RNA
-mRNA
-tRNA
-rRNA
Messenger RNA (mRNA)
-is a copy of a gene from DNA
-created in the nucleus
-it then leaves the nucleus to carry the copy of the genetic code of one gene to a ribosome in the cytoplasm
why cant DNA leave the nucleus ?
-too large
-be at risk of being damaged by enzymes - therefore destroying the genetic code permanently.
-mRNA is much shorter, because it is only the length of one gene and can therefore leave the nucleus as it is small enough ti fit through the nuclear pores
how long will mRNA live
- short lived
-as only needed to temporarily make a protein, therefore by the time the enzymes could break it down, it would have already carried out its function
structure of mRNA
-single stranded
-every 3 bases in the sequence code for a specific amino acid
these three bases are called codons
transfer RNA (tRNA )
-only found in the cytoplasm
-single stranded but folded to create a shape that looks like a cloverleaf
–this cloverleaf shape is held in place by hydrogen bonds
what is the function of tRNA
-attach to one of the 20 amino acids and transfer this amino acid to the ribosome to create a polypeptide chain
-specific amino acids attach to specific tRNA molecules and this is determined by 3 bases found on the tRNA which are complementary to the bases on mRNA
-these bases are called the anticondon because they are complementary to the condon on mRNA.
ribosomal RNA (rRNA)
-the type of RNA that makes up the bulk of ribosomes
-the rest of the ribosome is made of protein
e.g 80s ribosome = 30s small subunit and 50s large subunit.
DNA compared to RNA
differences between the DNA and RNA monomer
-DNA contains the base thymine, whereas RNA contains uracil instead
-DNA contains the pentose sugar deoxyribose, whereas RNA contains the pentose sugar ribose.
differences between the DNA and RNA polymer
- DNA is much larger because it contains approximately 23,000 genes (the entire genome) whereas RNA is much shorter because it is only the length of one gene
- DNA is double stranded, whereas RNA is single stranded.
DNA replication and semi conservative replication
-before cells divide all DNA need to replicate to provide a copy for the new cell.
-The process of DNA replication is semi-conservative replication(in the daughter DNA, one strand is from parental DNA and one strand is newly synthesised)
-This process relies on the complementary base pairs ( cytosine and guanine, thymine and adenine) and involves the enzymes DNA helicase and DNA polymerase
Four key stages to semi-conservative DNA replication
- DNA helicase breaks the hydrogen bonds between the complementary base pairs between the two strands within a double helix. This causes the DNA double helix to unwind.
- Each of the separated parental DNA strands acts as a template.
Free floating DNA nucleotides within the nucleus are attracted to their complementary base pairs on the template strands of the parental DNA. - -DNA polymerase-
The adjacent nucleotides are joined together (to form the phosphodiester bond ) by a condensation reaction
DNA polymerase catalyses’ the joining together of adjacent nucleotides - The two sets of daughter DNA (the name given to the new DNA molecules ) contain one strand of the parental (original) DNA and one strand of the newly synthesised DNA
What is conservative replication ?
-one DNA molecule contains both parental strands of DNA
-The other molecule contains only newly-synthesised DNA
What is dispersive DNA?
-parental DNA is interspersed between two molecules
-both new strands have some new and some original DNA
The structure of water
-water is an important biological molecule which is around 60-7- % of your body
- water is a polar molecule
-unevenly distributed charge due to the fact that the oxygen atom is slightly negative and the hydrogen atom slightly positive
-the delta symbol indicates a slightly positive/negative on the diagram of water.
-water is a compound
-known as a covalent compound
-as it has covalent bonds.
The five key properties of water
-hydrogen bonds form between different water molecules between the oxygen and hydrogen atom.
The formation of these hydrogen bonds and the fact that water is dipolar results in 5 key properties of water :
- metabolite
2.important solvent - has a high heat capacity and buffers temperature
- has a large latent heat of vaporisation
5.has strong cohesion
metabolite- water
water involved in many reactions such as photosynthesis, hydrolysis and condensation reactions.
-this is one of the reasons why its essential that approcimately 90% of the plasma in the blood and the cytoplasm in cells is largely composed of water.
solvent-water
-a good solvent- many substances dissolve in it polar molecules dissolve readily in water due to the fact that water is polar.
-The slight positive charge on the hydrogen atoms will attract any negative ions in solutes and the slight negative charge on the oxygen atoms of water will attract any positive ions in solutes.
-these polar molecules are often described as hydrophilic, attracted to water.
- non polar molecules, such as lipids cannot dissolve in water and are therefore described as hydrophobic, repelled by water
- the fact that so many essential polar substances dissolve in water enables them to be transported easily around animals and plants through blood or xylem
High specific heat capacity-water
-lot of energy is required to raise the temperature of the water - because some of the heat energy is used to break the hydrogen bonds between water molecules
useful to organisms - means that temperature of water remains relatively stable, even if the surrounding temperature fluctuates significantly. Therefore the internal temperature of plants and animals should remain relatively constant- despite outside temperature.
important so enzymes dont denature, reduce activity with temperature fluctuations
provides a stable environment in terms of temperature for aquatic organisms
Large latent heat of vaporisation
A lot of energy is required to convert water in its liquid state to a gaseous sate. This is due to the hydrogen bonds, as energy is needed to break the hydrogen bonds between water molecules to turn it into a gas.
Advantage to organisms as it means that water provides a significant cooling effect
e.g when humans sweat they release water onto their skin- providing a cooling effect.
Strong cohesion
Cohesion is the term used to describe water molecules ‘ sticking’ together by hydrogen bonds
due to water molecules sticking together, when water moves up the xylem in plants due to transpiration it is as a continuous column of water– advantage as it is easier to draw up a column rather than individual molecules.
cohesion also provides surface tension to water. This enables small invertebrates to move and live on the surface providing them with a habitat away from predators within the water.
What is ATP
Adenosine troposphere is an immediate energy source of energy for biological processes.
metabolic reactions in cells much have a constant steady supply of ATP
ATP contains three phosphate ions that play a significant role in energy transfer
this biology molecule is essential to metabolism which is all the chemical reactions that take place in the cells
ATP is compromised of :
Adenine is a nitrogenous base ( meaning a base that contains nitrogen )
ribose ( a pentose sugar )
Three inorganic phosphate groups
why is the phosphate group describe as being inorganic
because they do not contain any carbon atoms. For this reason in chemical reactions they symbol to represent this is a P for phosphate and i for inorganic -Pi
When is ATP made ?
during respiration from ADP, adenosine diphosphate, by the addition of an inorganic phosphate via a condensation reaction which uses the enzyme ATP synthase
ATP hydrolysed
into ADP + Pi using the enzyme ATP hydrolase
ATP + water —> ADP + Pi (energy)
How is ATP an immediate energy source
By breaking one of the bonds between the inorganic phosphate groups in a hydrolysis reaction, a small amount of energy is released to the surroundings, which can be used in chemical reactions
Therefore ATP is an immediate energy source as only one bond has to be hydrolysed to release every
what is Phosphorylation
ATP can also transfer energy to different compounds, the inorganic phosphate released during hydrolysis of ATP can be bonded onto different compounds to make them more reactive
this happens to glucose at the start of respiration to make it more reactive
five key properties of ATP that make it a suitable immediate source of energy
energy in small manageable amounts
small and soluble
one bond is hydrolysed
enable phosphorylation
can’t pass out the cell
ATP releasing energy in small, manageable amounts
so no energy is wasted, This means that calls do not overheat from wasted energy and cells are less likely to run out of recourses. IN COMPARISON TO GLUCOSE this would release large amounts of energy that could result in wasted energy
ATP small and soluble
easily transported around cell, ATP can move around the cytoplasm with ease to provides energy for chemical reactions within the cells. property ATP has in common with GLUCOSE
ATP one bond hydrolysed
to release energy which is why energy release is immediate GLUCOSE would need several bonds to be broken down to release all its energy
ATP enabling phosphorylation
transfer energy to another molecule by transferring one of its phosphate groups, enabling phosphorylation making the compound more reactive. GLUCOSE cannot do this as it does not contain phosphate groups
ATP can’t pass out of the cell
the cell always has an immediate supply of energy.
ATP cannot leave the cell whereas GLUCOSE can this means that all cells have a constant supply of ATP but a cell can run out of glucose
inorganic ions
dissolve to form solutions found within the cytoplasm of cells and and other body fluids
some inorganic ions are required in high concentrations, whereas others are required in very low concentrations. each inorganic ions performs a different function and this is due to their different properties
The inorganic ions
hydrogen bonds
iron irons
sodium ions
phosphate ions
what are ions
an atom or molecule that carries a charge
what are inorganic ions
ions that don’t contain carbon
necessary for vital cellular activity
what are inorganic ions
ions that don’t contain carbon
necessary for vital cellular activity
Evidence for DNA replication
Meselsohn and stahl experiment
Have dna would fall to the bottom of the tube
mixed with light nitrogen
if conservative- all heavy or all light
semi conservative- both had a middle band
not dispersive as some did light only not dispersive through ought the whole tube
hydrogen ion
buffers pH
enzymes don’t denature
iron ion
component of haemogloblin- quaternary non protein structure
transport oxygen for respiration
phosphate ion
nucleic acids, ATP, phospholipids
DNA replication and cell membrane
calcium ion
strong teeth and bones
structure and support
magnesium ion
produce cholophyll
photosynthesis
ADP
once ATP has released energy, it becomes ADP (adenosine diphosphate), which is a low energy molecule. ADP can be recharged back into ATP by adding a phosphate. This requires energy.
What happens when ATP becomes ADP
phosphate released and a small amount of energy.
why is the induced fit model of enzyme action better than the lock and key theory.
active site change to fit substrate 9flexible/ tertiary structure)
-lowers activation energy.
Competitive and non competitive description
competitive- binds to active site so that more substrate cannot bind
non-competitive- competitors binds to the allosteric site ( elsewhere)
Graphs for effect on enzyme rate of reaction
Enzyme activity increases as reactions occur between the active site and substrate. The graph then levels off when all the active sites have became saturated and the substrate cannot bind to anymore active sites
Enzyme that resynthesizes ATP
ATP synthase
When the breakdown of ATP to ADP is needed.
- phosphate phosphorylates- more reactive
-photosynthesis
-muscle contraction
-respiration
-active transport
