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Differentiate between a chiral molecule and an achiral molecule
- Chiral: a molecule whose mirror images are not superimposable.
- Happens with molecules with one stereogenic centre (4 different substituents around a single carbon atom)
- Achiral: mirror images are superimposable. Occurs when there is a plane of symmetry in the molecule
What are enantiomers and diastereomers?
- Enantiomer: stereoisomers that are mirror images of each other
- Diastereomer: stereoisomers that are not mirror images of each other
What is an optically active substance?
A chiral substance that is able to rotate plane polarised light through a characteristic angle
Define the following terms:
∂-amino acid, dipeptide, isoelectric point
- ∂-amino acid: a carboxylic acid with an amino group on the ∂ carbon
- Dipeptide: two amino acids which have reacted to create one molecule (condensation)
- Isoelectric point: the pH value where almost all molecules are in the zwitterion form (net charge=0)
Describe 4 levels of proteins
- Primary: the sequence of amino acids
- secondary: ordered structures via a network of H bonds
- Tertiary: the 3D structure of a complete protein, made via intermolecular forces and disulfide bridges
- Quaternary: How multiple proteins fit together in larger multiunit proteins
If the two pKa values for threonine are 2,63 and 10.43, determine the pI value at the isoelectric point.
- pI= pKa1 + pKa2 2
- =(2.63+10.43)/2= 6.53
How can you tell if a carbohydrate has a D or L configuration?
If in the fischer projection, the centre has the hydroxyle group on the right it is D- sugar
Describe a chemical test that will help distinguish sucrose and maltose.
Benedict's reagent: a copper containing reagent which can distinguish between reducing sugars such as maltose, (colour change observed) and non reducing sugars (no colour change)
What is a heterocyclic compound?
A heterocyclic compound is a cyclic compound that has atoms of at least two different elements as members of its ring(s).
1. Name 3 components of a nucleotide
2. What type of bond links nucleotide together?
3. What type of bond links adjacent nucleic strands
- 1. Nitrogenous base, Phosphate group, Ribose sugar
- 2. Phosphoester bond
- 3. Hydrogen bond
Define the terms 'monomer' and 'polymer'
- Monomer: A repeating unit, which may react with itself or other potential repeating units
- Polymer: A long chain consisting of one or more monomers
Define step growth and chain growth
- Chain growth: monomers become part of the polymer one at a time
- Step growth: growing chains may react with each other to form even longer chains
for the transition metals, how does atomic size change from the 3d series to the 5d series?
- Very little difference between 3d and 5d electron atomic size
- 4f electrons shield 5d electrons
Give a systematic name for:
tetraammine aqua bromido cobalt(III) bromide
Define ligand, bridging ligand, bidentate ligand
- Ligand: ions or neutral molecules that bond to a central metal atom or ion
- Bridging ligand: a ligand that connects two or more atoms, usually metal ions
- Bidentate ligand: Lewis bases that donate two pairs ("bi") of electrons to a metal atom