biological molecules (proteins) Flashcards
what is the primary structure of a protein?
the sequence of amino acids
what is the secondary structure of a protein?
hydrogen bonds
coils to form an alpha helix
or folds to form a beta pleated sheet
what is the tertiary structure of a protein?
hydrogen and ionic bonds, disulphide bridges, 3D structure
what is the quarternary structure of a protein?
when several polypeptides join together
what are amino acids composed of?
carboxyl group (COOH), amine group (NH2), R group
how many amino acids are there?
20
what causes the differences between amino acids?
their R group
what bonds are present in proteins?
peptide bonds
what are examples of protein functions?
enzymes, antibodies, transport proteins, structural proteins
how do you carry out the Biuret test for proteins?
add a few drops of sodium hydroxide solution
add some copper II sulfate solution
if protein present the solution turns purple
if no protein present stays blue
what is the job of an enzyme?
speeds up the rate of reaction by acting as a biological catalyst
what type of molecule is an enzyme?
protein
why is the shape of an enzyme specific?
due to its tertiary structure
how does an enzyme speed up the rate of reaction?
lowers the activation energy needed to start a reaction
eg) by reducing repulsion between substrates so they can bond more easily, when an enzyme enters the active site, puts a strain on bonds in substrate so it can be broken up more easily
what is the lock and key model?
suggests that the substrate fits into the enzyme in the same way that a key fits into a lock
what model was the lock and key replaced with?
induced fit
what happens in the induced fit model?
as the substrate binds, the active site slightly changes shape
how does temperature influence enzyme activity?
an increase in temperature means that the enzyme’s molecules have more kinetic energy (move faster, more collisions) which increases the rate of reaction
if the temperature goes above a certain level, the vibration breaks bond that hold together the active site, active site changes shape so substrate no longer fits= denatured
how does pH affect enzyme activity?
enzymes have an optimum pH value
significantly above or below this the enzyme is denatured
H+ and OH- ions found in acids and alkalis can disrupt the ionic/hydrogen bonds that hold the enzyme’s tertiary structure in place
=change in active site= denatured
how does enzyme concentration affect the rate of reaction?
more enzyme molecules available= more likely a substrate is to collide and form an enzyme-substrate complex
increasing enzyme concentration increases rate of reaction
if amount of substrate is limited- adding more enzyme molecules will have no further effect
how does substrate concentration affect the rate of reaction?
higher the substrate concentration, the faster the reaction
more substrate molecules means a collision is more likely so more active sites are used
only up to saturation point
substrate concentration will decrease with time so rate highest at the start of the reaction
what is a competitive inhibitor?
molecule that has a similar shape to a substrate molecule
how do competitive inhibitors work?
compete with the substrate molecules to bind to the active site, blocking the active site so that a substrate molecule cannot fit in
how is rate of reaction affected by competitive inhibition?
inhibitor takes up active sites, so hardly any substrate gets to the enzyme, decreases the rate of reaction
increasing the substrate concentration will help to increase the rate of reaction
what is a non competitive inhibitor?
molecule that binds to the enzyme away from its active site
how does a non competitive inhibitor work?
causes the active site to change shape, so the substrate molecules can no longer bind to it
how does a non competitive inhibitor affect rate of reaction?
increasing substrate concentration doesn’t make a difference, non competitive inhibitor will always decrease the rate of reaction