Amino acids, proteins and DNA Flashcards
what is an amino acid
compound with amine groups and COOH groups. The amine group is always on the second carbon
The second carbon on an amino aicd
is often chiral as it has four different groups bonded to it - amino acids exist as optical isomers. however, nearly all amino acids exist a single negative enantiomer
what is a zwitterions
two functional groups within a single molecule means that amino acids can react as both acids and bases depending on the conditions
zwitterions features
- strong electrostatic forces of attraction
- high melting points
- dissolves in water
- most exist as white solid at room temp
The zwitterions in acidic conditions - low pH
The lone electron pair is more likely to accept a H+, producing a +ve (acidic) end to the molecule
The zwitterions in basic conditions - high pH
the hydrogen atom on the OH group is more likely to be lost, producing a negative (basic) end to the molecule
How can a zwitterion be formed
when the overall pH of the molecule is zero, known as the isoelectric point
how can you identify unknown amino acids
thin-layer chromatogrpaohy using UV light to view the traces on the silica plate
what are proteins
Sequences of amino acids joined together by peptide/amide links
How can the formation of a protein be reversed
boiling the prtoien is 6.0moldm-3 HCL for 24 hours - hydrolysis. This process is carried out by enzymes so harsh conditions are not required
what bonds hold together proteins
- hydrogen bonds
- van der waals
- sulfur-sulfur bonds
What is the primary structure of protiens
the covalently bound sequence of amino acids
what is the secondary structure of protiens
formed by hydrogen bonds between amide linkages
- alpha helix
- beta pelated sheet
what is the tertairy structure of proteins
chains foldeed inot a 3D coil with hydrogen and disulfide bonding
what is disulfide bonding
sulfur-sulfur bonds that hold together teratiry structures aka disulfide bridges. they keep the protein structure stable by losing two hydrogen atoms
thin layer chormoagroaphy of amino acids
Proteins need to be hydrolysed into amino acids
1. Wear gloves, draw pencil line 1cm away form the bottom of TLC plate
2. use the capillary tube to place a drop of sample on the TLC plate
3. Add solvent to a beaker with lid
4. place TLC on beaker with lid
5. when sovlent reached 1cm from top of plate. remove
6. allow plate to dry in fume cupboard
7. Spray paper with ninhydrin. Put in oven
8. calcautle rf value
what are enzymes
Proteins with a tertiary structure that acts as biological catalysts. they contain active sites that are specific to a molecule that they break down aka substrate
stereospecific active site
- active site will only bind to one enantiomer and not the other
- lock and key theory
example of a competitive inhibitor for an enzyme
drug molecules as they bind to the active site and prevent substrate binding
what is DNA
a condensation polymer formed from a sugar (2-deoxyribose), phosphate and a base
base pairs of guanine and cytosine
3 hydrogen bonds
base pairs of thymine and adenine
2 hydrogen bonds
cisplatins uses
anticancer drugs. It is the cis isomer of a square planar complex of platinum
how does cisplatin work
Cl- are displaced and a dative covalent bond is formed between a nitrogen atom on guanine and platinum. This stops replication of cancer cells
Negatives of cisplatin
- prevents replication of healthy cells, by binding to them
- unwanted side effects are reduced through small doses
- hair loss
