Amino Acids, Proteins And DNA Flashcards
What is the structure of an amino acid?
Contains both an amine and carboxyl group
NH2RCHCOOH
What are zwitter ions?
Amino acids exist as zwitter ions
Where the amine group has accepted an extra hydrogen to become positively charged and the carboxyl group has donate a hydrogen to become negatively charged
Gives amino acids it’s amphoteric properties
What are the amphoteric properties of amino acids?
The amine group is able to accept hydrogen atoms and therefore act as a base
The carboxyl group can donate hydrogen atoms and act as an acid
What reactions can take place with the acid end of an amino acid?
React with:
Metal oxides to form a salt and water
Alkalis to form a slay and water
Carbonates to form a salt CO2 and water
Alcohols to form an Ester and water
What reactions can take place with the amine end of an amino acid?
The lone pair of electrons in the nitrogen can accept a hydrogen atom and form an ammonium salt.
How are proteins formed?
Via a condensation reaction between the carboxyl is acid end of one amino acid and the amine group of another amino acid
Forms a peptide bond
Proteins are polypeptides (50+ amino acids)
How can proteins be hydrolysed?
By heating with conc HCL
How can individual amino acids be separated?
Using thin layer chromatography
Use ninhydrin to make them visible
What is the primary structure of a protein?
Sequence of amino acids in the polypeptide chain
What is the secondary structure of a protein?
How the amino acid forms an alpha helix or beta pleated sheet due to hydrogen bonding.
This can easily be disrupted by temperature or pH
What is the tertiary structure of a protein?
The 3D shape the alpha helix or beta pleated sheet is folded into.
This is held together by hydrogen bonds, ionic bonds or disulphide bridges between the R groups of the amino acids.
Are amino acids chiral molecules?
Yes all except from glycine which has the R group of H
What are enzymes?
Biological catalysts which increase the rate of metabolic reactions
What are the structures of enzymes?
Usually globular tertiary proteins
Catalytic activity at the active site
Substrates fit into the active site and bind temporarily via intermolecular forces
This bonding promotes the movement of electrons within the substrate lowering the activation energy for the reaction
Why are enzymes said to have stereospecificity?
Only the complementary shape substrate will fit into the active site as the bonds have to be in exactly the right place.
Even the wrong stereoisomers (enantiomer) will not be catalysed by the enzyme.
How can enzymes be inhibited?
Denaturing the enzyme via heating or pH changes will change the active site shape and therefore mean the enzyme will no longer function.
Inhibitors also bind to an enzyme preventing an enzyme from functioning.
Doctors can use inhibitors as drugs to prevent harmful reactions taking place (penicillin)
Why is computer modelling used in drug discovery
Chemists can use computer programs to model complex molecules before synthesis enabling hem to understand the properties of he molecule before they have made it.
What are the components of DNA?
A phosphate group
Pentose sugar (deoxyribose)
A nitrogenous base:
Adenine, thymine, cytosine, guanine
These parts create a nucleotide.
What is the structure of DNA?
A polynucleotide with strands formed via condensation reactions of phosphate groups and sugars.
This creates a sugar phosphate backbone.
DNA exists as a double helix
The two complementary strands of DNA are held together via hydrogen bonds between the bases. A=T C=G
How is DNA replicated?
The strands are separated by DNA helicase and then each strand acts as a template for a new complementary strand to be synthesised onto.
Free complementary nucleotides hydrogen bond to the template strands and form new daughter strands via the hell of DNA polymerase.
What is Cis-platin?
An anti cancer drug
Platinum is bonded to two chlorine and two Ammonia molecules via dative covalent bonds.
Has a square planar structure
How does Cis-platin prevent cancer?
- It binds to the nitrogen atoms on two adjacent guanine molecules via a ligand exchange reaction with the chlorine molecules.
- The nitrogen atoms are better Ligands and therefor displace he chloride ions.
- This causes a kink in the structure of DNA preventing the DNA from replicating
Why does Cis-platin cause side effects?
Cos-platin does not just attack cancer cells but all cells that divide quickly (such as hair follicles) and therefore prevents these cells dividing
Side effects include:
Hair loss
Sickness
Fatigue
Why is trans-platin not an effective cancer drug?
Only 1 guanine molecule can bind to the drug either side of the molecule (not adjacent) and therefore his can easily be corrected by the body and does not produce a kink in the DNA structure
