Amino Acids, Proteins and DNA Flashcards
Do amino acids have acidic or basic properties?
Acidic and Basic properties
What happens to an amino acid in acidic solution?
The zwitterion’s NH2 group will be protonated to NH3+
What happens to an amino acid in basic solution?
The zwitterion’s COOH group will be deprotonated to COO-
What do amino acids exist as? What does this mean?
Zwitterions - They have a permanent positive and negative charge
What are proteins?
Sequences of amino acids joined by peptide bonds.
What types of bonding are important in a protein? Why?
Hydrogen bonding, Sulfur-Sulfur bonds
Disulphide bridges are stronger than Hydrogen bonds
Primary, Secondary, Tertiary structure of Proteins
Primary: The sequence of amino acids along the protein chain. Bonded by covalent bonds
Secondary: The shape of the protein chain - Alpha helix/ beta pleated sheets
Tertiary: Alpha-helix or beta-pleated sheet is folded into a complex 3D shape - Ionic, disulphide bridges, VDW’s
What does hydrolysis of a peptide link produce
Its constituent amino acids
How can amino acids be separated and identified
Thin layer chromatography
Located using developing agents like ninhydrin or UV light
Identified by RF value
What is a TLC plate made of
Plastic sheet coated with silica
How do you carry out Thin Layer Chromatography
Spot the samples onto a pencil line a few cm above the base of the TLC plate.
Place this in a beaker or tank, with solvent level below the pencil line. Ensure there is a lid on the beaker to keep the inside saturated with solvent vapour.
Wait until the solvent front is almost at the top of the TLC plate;
Then remove from the beaker and analyse.
Why does TLC separate amino acids
Solvent carries amino acids up the TLC plate. The rate of movement depends on the balance between that amino acid’s affinity for the solvent (solubility in it) and affinity for the stationary phase (attraction to the silicon with hydrogen bonding).
How do you find the primary structure of a protein.
Reflux with HCl for 24 hours.
Do TLC
What type of proteins are enzymes?
Globular
What are enzymes?
Biological catalysts
What does the stereospecificity of enzymes mean
Only 1 enantiomer is catalysed
How are enzymes inhibited?
A molecule with a very similar shape and structure to the substrate is devised. Binds to the enzyme’s active site. Blocks the active site (does not desorb easily). Substrate cannot adsorb to the active site, so reaction cannot be catalysed
How are molecules modelled on computed
Now we understand factors that affect the shapes of
extremely complex proteins, we can model drugs that haven’t even been synthesised, predict their properties and design drugs that will treat a range of medical conditions
What is a nucleotide made up of?
A phosphate ion, 2-deoxyribose, a nitrogenous base
Why is DNA a polymer
nucleotides are monomers linked by covalent bonds between the phosphate and sugar
In what form does DNA exist
As 2 complementary strands in a double helix
What is the main anti-cancer drug
Cisplatin
How does cisplatin work?
It prevents DNA replication by ligand replacement.
The cl –> H20 –> N on guanine
Why is N a better ligand than Cl-
N atoms have a lone pair that can datively bond to the Pt so are better ligand
Cons of Cisplatin
Affects healthy cells that replicate quickly e.g. hair
Damages kidneys
State the meaning of the term complementary when it is used to refer to DNA strands.
(Complementary means the two strands must have base sequences) that match (all) A to T and C to G
