Enzymes

Give an example of extracellular enzymes

Digestive enzymes

What type of proteins are enzymes?

globular proteins

Describe the lock and key model

An enzyme has a specifically shaped active site. The shape of the active site is complementary to the shape of the substrate molecule(s) involved in the reaction. This means that the substrate molecule(s), which are usually much smaller than the enzyme molecule can fit into the active site. Because the substrate fits into the enzyme, the term lock-and-key is sometimes used to describe how enzymes work. In this model, the substrate 'key' fits into the active site 'lock'. The substrate is then held in one place so the reaction can go ahead.

What effect does enzymes have on activation energy?

Lowers it

How can you overcome activation energy without enzyme?

By heating

What happens to the rate of reaction in substrate- enzyme controlled reactions and why?

It slows down with passage of time; fewer substrate molecules as time proceeds

How does enzyme concentration affect enzyme activity?

The more enzyme molecules there are, the more likely there are to be collisions between enzyme and substrate molecules, forming more enzyme-substrate complexes. So initial curve will be steep, then it will plateau and rate becomes constants

For enzyme concentration what is the initial graph like and why?

Linear, high gradient because there are lots of free active sites, rate is substrate conc dependant

Why do enzymes denature?

Mainly breakage of hydrogen bonds, loses its shape

How does low pH slow reactions?

Excess H+ ions will interact with R groups of amino acids ionisation, which will effect ionic bond and disrupt 3D structure of enzymes.

What is enzyme inhibitors?

Slows or prevents reaction by fitting perfectly at active site

example of competitive inhibitor

In Ethylene glycol poisoning, ethanol acts a as a competitive inhibitor of an enzyme, which removes ethylene glycol substrate, which otherwise would form a toxic substrate for kidney.

How does body control metabolic reactions?

By using end-product as non-competitive reversible inhibitor (called end product inhibition)