C4: Enzymes

Question 1

what are cofactors

Answer 1

• an additional non protein molecule is an enzyme that doesn’t take part in the reaction
• so it isn’t used up
• allows for EZ-SS reaction to occur by keeping the EZ and SS bonded together

Question 2

one group of cofactors are called PROSTHETICS. explain what they are.

Answer 2

_ tightly bound together and a permanent part of the enzyme

• contributes to the 3D structure of the enzyme = it’s a vital property
• can be organic (eg. vitamins) or inorganic (eg. metal ions)

Question 3

one group of cofactors are called COENZYMES

Answer 3

• theyre cofactors with organic molecules (eg. vitamins) only in their structure
• they only bond for a short period of time = loosely bound and easily released
• they’re changed in some way after the reaction but can be reused again

Question 4

what are inactive precursor enzymes

Answer 4

enzymes that are made in an inactive form and can either cause damage within the cells, or can only be activated under certain conditions and needs to be controlled.

Question 5

to activate a precursor enzyme ….. by …

Answer 5

.. they need to undergo a change in their shape (tertiary) by adding a cofactor

Question 6

define enzymes

Answer 6

biological catalysts that speed up chemical/metabolic reactions by lowering the Ea

Question 7

levels of temperature on enzyme activity (on a graph)

Answer 7

(A/N: should memorise/do the graph)

• peak of graph = optimum temperature, the maximum rate of reaction
• low temp, aka inactive = EZ don’t have much KE so they move very slowly.
• too high temp = EZ are denatured, so the active site is destroyed and SS no longer fits.

Question 8

how temperature rise affects enzyme activity

Answer 8

• temperature rise = rise in KE, so particles collide more frequently = more successful collisions between SS and EZ = higher reaction rate
• but TOO HIGH temperature = molecules vibrate more = H bonds and ionic bonds break down = changes the active site of the EZ and less EZ SS complexes form = rate lowers and EZ completely denatures

Question 9

on an enzyme graph Q10 = how rate increases with a 10ºc increase. what is the formula for this

Answer 9

Q10 = rate of reaction @ (x+10)º/ rate of reaction @ (x)º

Q10 is usually 2-3

Question 10

how pH affects enzyme activity

Answer 10

• all enzymes have different optimum pH
• TOO MANY H+ ions (protons) interact with the polar groups in the amino acids and the H bonds + ionic bonds holding the tertiary structure = active site of EZ changes = SS can’t fit anymore
• NOT ENOUGH H+ ions means there aren’t enough interactions = loses the shape of active site

Question 11

how enzymes catalyse intracellular and extracellular reactions

Answer 11

intracellular: occurs inside the cell that produces the enzyme, eg.
extracellular: nutrients in the form of proteins and polysaccharides need to be broken down to enter the cells

Question 12

describe the lock & key theory

Answer 12

• only a specific substrate will fit into the active site of an EZ b/c they’re exactly complementary
• when the SS binds to the EZ it forms a EZ-SS complex, the SS reacts and products are formed in a product-SS complex, lowering the activation energy
• the products are released, leaving the EZ unchanged so it can react again

Question 13

describe induced fit theory

Answer 13

• SS collides with complementary active site. EZ is flexible and conforms to the shape of SS so the active site fits closer

Question 14

what part of the enzyme mechanism lowers the activation energy

Answer 14

the formation of an enzyme substrate complex

Question 15

what 5 factors affect the rate of enzyme reactions

Answer 15

1. pH
2. substrate concentration
3. enzyme concentration
4. temperature
5. inhibitors concentration