3.13 Amino acids, proteins and DNA Flashcards
What are the 2 functional groups of amino acids
NH2 and COOH (amine and carboxylic acid)
Draw a general formula for alpha amino acids
Are alpha amino acids chiral, why
Yes one carbon has 4 different substituents
Except glycine where R=H
In what form do amino acids exist as solids
What consequence does this have
Zwitterions (ionic lattice) - high mtp and bpt
What colour solids are most zwitterions at room temp
White solids
Do zwitterions dissolve in water? Non polar solvents? Why?
Yes, but only in non polar solvents. Due to ionic nature/polar bonds
Define a zwitterion
Ions which have both a permanent positive and negative charge, but are neutral overall
How do zwitterions occur in amino acids? Draw a general structure of one
COOH is deprotonated –> COO-
NH2 is protonated –> NH3+
What happens to amino acids in acidic conditions
Gains a proton on NH2 group
What happens to amino acids in alkaline conditions
Loses a proton from COOH group
What is the peptide linkage
-CONH-
The peptide linkage
What is a dipeptide
2 amino acids bonded together
What is a TLC plate made of
Plastic sheet coated with silica, SiO2
This is the stationary phase (the solvent is the mobile phase)
Describe how you would carry out TLC
Spot the samples onto a pencil line a few cm above base of TLC plate
Place this in a beaker or tank, with solvent level below the pencil line. Ensure there is a lid of 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 (or other molecules)
Solvent carries amino acids up the TLC plate. The rate of movement depends on the balance between that amino acids solubility in the solvent and the affinity for the stationary phase
What do you often have to do to enable the amino acids to be seen on the chromatogram
Spray with ninhydrin (aa are colourless, turns their spots purple)
Shine UV light
How do you find the primary structure of a protein
Reflux with 6M HCl and reflux for 24 hours
Carry out TLC to find the number and type of amino acids present
How do enzymes increase the rate of reaction
Reacting molecules form temporary bonds (via imf) to the enzyme. This weakens the bonds in the molecules, promotes electron movement and lowers EA
What does the stereospecificity of enzymes mean
Active sites are so selective of the shape of substrates that only reactions involving one enantiomer are catalysed
What does DNA stand form=
Deoxyribonucleic acid
Draw a nucleotide
What forms between adjacent nucleotides
Hydrogen bonding
What kind of polymer does the polymerisation of DNA lead to
Condensation polymer chain - backbone of phosphate and sugar molecules, with bases attached
Draw the structure of cisplatin
