Enzymes A-level Biology

How does the substrate stay attached to the active site?

How does the substrate stay attached to the active site?

Temporary bonds between certain amino acids in active site and groups on the substrate.

What type of bonds maintain the shape of enzymes?

Hydrogen bonds

How many amino acids bind to the substrate in the active site?

6

What is the induced fit model of the enzyme?

Active site changes shape as enzymes and substrate interact, enzyme moulds around the substrate, putting a strain on the substrate to distort it's bonds and lower it's activation energy.

How was the lock and key model of the enzyme disproven?

Found that other molecules bind to enzyme in other places than the active site which altered the activity and shape of the enzyme. Shows enzyme has a flexible structure, not rigid.

How do you measure the progress of an enzyme-catalysed reaction?

-formation of products of the reaction -disappearance of the substrate

Why does high temperature cause enzyme denaturation?

Begins to break hydrogen and other bonds in the enzyme making the active site change shape and so not fit to the substrates as well.

How does a change in pH effect enzymes?

-alters charges of amino acids in active site so substrate no longer attached -may cause bonds in enzyme's tertiary structure (between polypeptides) to break, changing the shape of the active site if significant change in pH.

What is the arrangement of the active site determined by?

hydrogen and ionic bonds between -NH2 and -COOH groups of polypeptides that make up the enzyme

excess substrate + increase in amount of enzymes leads to...?

proportionate increase in rate of reaction

Why will a graph of rate of reaction against enzyme concentration initially show a proportionate increase?

because there's more substrate than the enzymes can deal with.

If enzyme concentration is fixed and substrate concentration slowly increases, the rate of reaction...?

increases in proportion to substrate concentration

What is an enzyme inhibitor?

Substances that directly or indirectly interfere with the function of the active site to reduce its activity

What determines the effectiveness of competitive inhibitors?

difference in concentration of inhibitor and concentration of substrate.

What is key about competitive inhibitors?

aren't permanently attached to active site so sooner or later all active sites will be attached to normal substrate but the more competitive inhibitors there are, the longer it takes.