Organic - Amino Acids, Proteins & DNA Flashcards
What are the roles of proteins in the body?
- Enzymes are proteins
- Muscle fibres are several fibres
- Antibodies are proteins
- Bone is a matrix of protein and calcium phosphate
What is the primary structure of a protein?
Concerned with the order in which the amino acids are joined together in the molecule.
What is the secondary structure of proteins?
Concerned with the folding, coiling and puckering of the chain of atoms of the protein molecule.
Beta pleated sheet
Alpha helix
What is the tertiary structure of a protein?
Concerned with the final folding of the protein molecule to form a globular protein as dictated by the interaction between groups attached to the main body of the chain.
What are the properties of amino acids?
- Melting points in excess of 200C
- Soluble in water and other polar solvents
- Insoluble in non-polar solvents such as ether or benzene
- Less acidic than most carboxylic acids and less basic than most amines.
- Contain ionic bonds
- Zwitterion structure - ion with two functional groups.
How is an alpha helix formed?
The shape is maintained by the hydrogen bonding between the polar C=O and N-H groups of different peptide bonds in the amino acid chain.
How is a beta pleated sheet formed?
The amino acid chain is lined up side by side with another section of the same chain and the hydrogen bonds occur between the C=O and N-H groups on peptide bonds which are facing eachother.
What interactions lead to the tertiary structure of an amino acid?
- Hydrogen bonding between polar side chain groups
- Disulfide bridges between cysteine amino acid residues in the protein chain.
- Hydrophilic and hydrophobic interactions
What are fibrous proteins?
Proteins which have a mainly secondary structure.
Form skin, muscle, artery walls and hair.
What are globular proteins?
- Small proteins
- Water soluble
How are proteins hydrolysed?
Proteins can be hydrolysed to the constituent amino acids by boiling with a dilute mineral acid such as HCl.
The amino acids can be analysed by TLC.
Amino acids are colourless and can be located on the chromatogram by staining with ninhydrin or using UV light.
What components make up DNA?
2-deoxyribose
Phosphate
Base (adenine, guanine, thymine or cytosine)
How are DNA molecules joined?
The nucleotides are joined in a condensation reaction between the OH of the carbon 3 and the OH of the phosphate ion group.
How does cisplatin prevent DNA replication?
Cisplatin acts by allowing a dative covalent bond to form between a nitrogen atom in guanine and the platinum in cisplatin.
Cisplatin can also bond to other guanine residues in the same strand or between strands. DNA cannot be replicated.
