Proteins and Enzymes Flashcards
What is the the monomer of a protein and what does it consist of?
Amino Acids-
-Amine Group
-R-Group
-Carboxylic Group
Describe how a dipeptide is formed
two amino acids join together in a condensation reaction to form a dipeptide. When the amino acids join they form a peptide bond and water is released. The peptide bond forms from the carboxylic group of one amino acid and the amine group of another.
Describe the primary structure of a protein
the sequence of amino acids in a polypeptide chain, the amino acids are joined by peptide bonds.
describe the secondary structure of a protein
the polypeptide chain folds into an alpha helix or a beta pleated sheet. this is due to hydrogen bonding.
describe the tertiary structure of a protein
3D structure of a polypeptide. involes the addition of further bonds being formed; ionic (between carboxylic and amino), disulfide bridges (between two amino acids with sulfur in their R group), hydrogen bonds.
describe the Quaternary structure of a protein.
the combination of a number of different polypeptide chains to form a complex protein.
types of proteins and examples
globular proteins - antibodies, haemoglobin, hormones.
fibrous proteins - collagen. keratin.
describe the biuret test
add sodium hydroxide, few drops of copper (ll) sulfate. positive test indicated by a colour change from blue to purple.
what are enzymes
are globular proteins and are biological catalysts that alter the rate of a chemical reaction without being used up.
what is the active site
an area of the enzyme that is made up only a few amino acids and forms a small depression on the overall enzyme. It is where the substrate binds to.
describe the induced fit model
the active site of an enzyme and the substrate have similar shapes and interact. The enzyme is flexible and its active site can mould itself around the substrate to fit perfectly. once the substrate binds to the active site, the active site changes shape and moulds around the substrate to fit perfectly and becomes complementary.
what are the factors affecting enzyme action
temperature, pH, concentration of substrate and enzyme.
how does temp affect enzyme action
an increase in temp increases the kinetic energy in particles thus increasing the frequency of collisions between the enzyme and the substrate. more E-S complexes can form.
a decrease in temp means that the rate of reaction will become slower and less E-S complexes can form.
how does pH affect enzyme activity
a change in the pH changes the shape of the active site, the enzyme denatures and breaks the hydrogen bonds in the tertiary structure. enzyme is no longer complementary to substrate and no E-S complexes will form.
how does concentration of either enzymes or substrate affect enzyme activity.
as enzyme conc increases, more active sites become available and more substrates can bind to from more E-S Complexes. After a while there are no more substrates available, substrate conc becomes limiting factor and no more E-S complexes will form.
