Lecture 2 - Protein Flashcards
What is the basic structure of amino acid?
Amino group (NH2), carboxyl group (COOH), H and R side chain
3 main categories of amino acids
Non polar (hydrophobic), Polar (charged), Polar (uncharged)
2 example of hydrophobic non polar AA
Tryptophan and Glycine
2 examples of uncharged polar AA
Serine and Asparagine
2 examples of charged polar AA
Lysine and aspartic acid
What are ampholytes?
They can act as either base or acid
Define zwitterions
Molecules have both positive and negative charge
What are the characteristics of AA
AA are ampholytes, zwitterions and due to their ionic nature, they have extremely high melting temperatures
What is primary structure of AA
Linear sequence of AA joined together by peptide bond
What is secondary structure of AA
Local folding by hydrogen bonding of residues into regular patterns such as alpha helix and beta sheet structure
What is alpha helix structure
Helical arrangement of AA in the polypeptide chain maintained by hydrogen bonds parallel to the helix axis
What is beta sheet?
Hydrogen bonding formed between adjacent sections of polypeptides that are either running in the same direction (parallel) or opposite direction (anti-parallel)
What is beta turn reverse?
There is a reversal in the direction of the polypeptide chain and it is found in the connecting ends of anti-parallel beta pleated sheets
Definition of tertiary structure of protein
3D arrangement of the amino acids in the polypeptide chain. It is biologically active
Definition of quaternary structure of protein
Composed of more than one polypeptide chain in a spatial arrangement. It is fully developed and functional
What are the 3 main classes of protein?
1) Functional - enzymes, structural, transport and defence
2) Structural - globular and fibrous
3) Cellular localization -membrane, water soluble
Definition of enzyme
1) Biological catalysts that control a reaction without being changed itself
2) Convert substrates into product
3) lower the action energy to speed up the rate of reaction
Definition of activation energy
Energy required to initiate a chemical reaction
Define induced fit model
This model describes the formation of the enzyme-substrate complex as a result of the interaction between the substrate and a flexible active site. The substrate produces slight changes in the active site of the enzyme for better bonding of substrate and catalytic effects
Describe Lock and Key model
This model describes the formation of substrate and enzyme complex by substrate bonding onto the active site of the enzyme. There is no change to the active site as the product is being formed.
The active site is highly specific and substrate which has a complementary shape as active will be able to bind.
What are the factors affecting enzyme structure and activity?
1) Temperature - At high temperatures, hydrogen bonding and other forces that stabilise protein structure is disrupted causing the enzyme to change its shape and lose activity
2) pH - alters the charge of the amino acids of a protein, thus affecting the structure and the ability for substrate to bind
What are nucleotides composed of?
Sugar (pentose), phosphate group and base
What are the characteristics of DNA?
1) Genetic blueprint - carries all the instructions needed to build a new material, one gene codes for information to make one protein
2) Arranged into chromosomes and is located in the nucleus
3) Genes are located in the chromosome
What are the different types of RNA?
Messenger, transfer and ribosomal
