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Flashcards in 4 - ENZYMES Deck (19)
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1
Q

What are enzymes?

A

They are globular proteins which act as biological catalysts becauses they speed up metabollic reactions in living organisms without running out by lowering the activation energy

2
Q

What are catabolic enzymes?

A

Enzymes which break down substances

3
Q

What are anabolic enzymes?

A

Enzymes which synthesise large molecules

4
Q

What are intracellular enzymes?

A

Enzymes which act within the cells which they are made in

5
Q

What are extracellular enzymes?

A

Enzymes which leave the cells they are made in by exocytosis and act outside on other target cells

6
Q

Describe the lock and key model.

A

The active site of an enzyme is specific to substrates with a complementary shapes and when they collide they form temporary bonds in an enzyme-substrate complex (ESC)

7
Q

Describe the induced fit theory.

A

Although the shape of the active site is complementary to that of a substrate, subtle changes occur in the shape of the side chains or R groups of amino acids which give them a more precise conformation in the active site

8
Q

What is a co-factor?

A

A substance that aids the function of an enzyme, either in the form of a co-enzyme (temporarily bonded) or a prosthetic group (permanently, covalently bonded)

9
Q

What is the role of a co-factor?

A
  • eases the formation of ESCs
  • acts as co-substrate by combining with the substrate to make it fit perfectly in the enzyme’s active site
  • changes the charge distribution on the surface of the enzyme or the substrate to make the temporary bonds between them easier to form
10
Q

What happens once an ESC forms?

A

The enzyme acts anabollically or catabollically, forming an enzyme-product complex (EPC) before release the products

11
Q

What factors affect the rate of enzyme-controlled reactions?

A

Temperature, pH, enzyme concentration, substrate concentration, cofactors and inhibitors

12
Q

What is Vmax?

A

The maximum rate of reaction/activity of an enzyme

13
Q

What is the effect of temperauture on enzyme activity?

A
  • increases kinetic energy of the enzyme and the substrate so they collide together more, forming more ESCs
  • at the enzyme’s optimal temp, Vmax is achieved
  • further increases to the temp cause H bonds to breqk but there is chance of their reformation
  • once temp is increased even further, the enzyme denatures
14
Q

What is the affect of pH on enzyme activity?

A
  • different enzymes have different optimum pH levels at which they work most efficiently and achieve Vmax
  • further changes to pH cause H bonds to break but there is chance of their reformation
  • once pH changes even further, the enzyme denatures
15
Q

How does an enzyme become denatured?

A
  • hydrogen bonds and ionic bonds in its tertiary structure break
  • the shape of the active site changes permanently
  • the enzyme can no longer carry out its function
16
Q

What is the effect of enzyme/ substrate concentration on enzyme activity?

A
  • as concentration (of one) increases, rate of reaction increases
  • concentration becomes limiting factor of the reaction, since the rate begins to slow
  • once the concentration increases further, Vmax is achieved
  • further increases in concentration have no effect on the rate
  • the concentration of the other now becomes the limiting factor
17
Q

What are competitive inhibtors?

A

Inhibitors which:

  • can fit into active site of an enzyme without reacting
  • compete with subtrate molecules for access to the active site
  • affects activity depending on concetration
  • can be minimised by raising the concentration of substrate
  • have reversible effects on the enzyme as they detach themselves after a while
18
Q

What are non-competitive inhibitors?

A

Inhibitors which:

  • binds to allosteric site (the place on an enzyme where a molecule that is not a substrate may bind)
  • change the shape of the molecule, preventing it from working
  • effect is independent of substrate concentration and irreversible
18
Q

What are metabollic inhibitors?

A

Poisons and medicines which inhibit the metabollic reactions of cells for an adverse or beneficial effect