Amino Acids, Proteins and DNA Flashcards
Amino acid’s have both a:
Amino group and a carboxyl group.
Amino acid‘s have both an amino group and a carboxyl group, this means they’ve got what basic properties?
The amino group makes the amino acid acts as a base.
The carboxyl group makes the amino acid act as an acid.
The amino acid is amphoteric.
They are chiral molecules because the carbon has four different groups attached. So a single amino acid rotate plain polarised light.
What is a zwitterion?
A zwitterion is a dipolar ion - it has both a positive and a negative charge in different parts of the molecule.
Describe chromatography:
1) Draw a pencil line near the bottom of a thin layer chromatography paper and put a concentrated spot of the mixture of amino acid’s on it.
2) Dip the bottom of the plate into a solvent.
3) When the solvents nearly reached the top, take the plate out and mark the solvent front with a pencil. Leave plate to dry.
4) Amino acids aren’t coloured you add:
• Ninhydrin solution, which will turn the spots is purple.
• Use a special plate that has a close fluorescent die added to it. It lights up when UV light is shone it, the amino acids cover the fluorescent dye so the spots appear dark. You then put the plate under UV lamp and draw around the dark patches to show the spots are.
4) You then work out the RF value of each amino acid by using this formula:
distance travelled by spot
—————————————
distance travelled by solvent
5) Then you can use table of known amino acid Rf values to identify the amino acids in the mixture.
Describe how proteins are formed by the condensation polymers of amino acids:
Two amino acid’s are joined together to make a dipeptide:
The dipeptide still has an NH to group at one end and a COOH group at the other. So if you add more amino acid to the chain you just keep repeating the condensation reaction.
A protein can be hydrolysed if you add hot aqueous 6M hydrochloric acid and heat the mixture under reflux for 24 hours.
Describe the primary structure of a protein:
The primary structure is the sequence of amino acid in the long chain that makes up the protein (the polypeptide chain).
Describe the secondary structure of a protein:
The peptide links can form hydrogen bonds with each other, meaning the chain isn’t a straight line.
The shape of the chain is called its second airy structure.
You get an alpha helix or a beta pleated sheet.
Describe the tertiary structure of a protein:
The chain of amino acid’s is it self often coiled and folded in a characteristic way that identifies the protein.
Extra bonds can form between different parts of the polypeptide chain, which gives the protein a kind of three-dimensional shape. This is it tertiary structure.
What type of bonds are present in proteins?
Hydrogen bonds
Disulphide bonds
Ionic bonds
What factors affect the shape of proteins?
pH
Temperature
How are proteins biological catalysts?
They catalyse every metabolic reaction in the bodies of living organisms.
Enzymes are proteins. Some also have non-protein components.
Every enzyme has an area called its active site. This is the part that the substrate fits into circuit interact with the enzyme.
Why do enzymes have high specificity?
In order for an enzyme to work, the substrate must fit into the active site. If the substrate shape doesn’t match the active site shape, the reaction won’t be catalysed. This is called the ‘lock and key’ model.
How do chiral centres affect and enzymes specificity?
Enzymes are made up of amino acid’s, so they contain chiral centres.
This makes the active site stereospecific - they’ll only work on one enantiomer of a substrate. The other enantiomer won’t fit properly in the active site, so the enzyme can’t work on it.
What does DNA stand for?
Deoxyribonucleic acid
What is DNA made up of?
A phosphate group
A pentose sugar
A base (adenine, cytosine, guanine and thymine)
