Enzymes

Question 1

What are enzymes

Answer 1

biological catalysts and globular proteins

Question 2

What are the two forms of enzyme

Answer 2

Intracellular or Extracellular

Question 3

What is an extracellular enzyme

Answer 3

enzymes active outside of the cell

Question 4

What is an intracellular enzyme

Answer 4

enzymes active inside of the cell

Question 5

Give an example of an intracellular enzyme

Answer 5

Catalase

Question 6

Give an example of an extracellular enzyme

Answer 6

Amylase

Question 7

What does catalase do

Answer 7

Converts hydrogen peroxide, which is harmful to cells and a by product of many processes, into water and oxygen - preventing damage to cells and tissues.

Question 8

What does Amylase do

Answer 8

Hydrolyses starch into simple sugars. Digestion is usually carried out by extracellular enzymes, as macromolecules are too large to enter the cell.

Question 9

What forms when an enzyme and substrate combine

Answer 9

An enzyme-substrate complex

Question 10

What can denature enzymes

Answer 10

Heat and pH

Question 11

What is the shape of the active site determined by

Answer 11

The complex tertiary structure of the protein that makes up the enzyme.

Question 12

What determines the shape of an enzyme

Answer 12

the order of amino acids (if altered the 3D shape changes)

Question 13

Is enzyme substrate complex temporary or fixed

Answer 13

Temporary

Question 14

What two types of enzyme reactions are there

Answer 14

Catabolic or Anabolic

Question 15

What is a catabolic reaction

Answer 15

When a single substrate is drawn into the active site and broken apart into two or more distinct molecules. E.g. Cellular respiration and hydrolysis

Question 16

What is an anabolic reaction

Answer 16

When two or more substrates are drawn into the active site, forming bonds between them and releasing a single product. E.g. Protein synthesis and photosynthesis

Question 17

What do enzymes do to activation energy

Answer 17

Lower it

Question 18

What is activation energy

Answer 18

Amount of energy needed for a substrate to be unstable enough for a reaction to occur and products form

Question 19

How do enzymes speed up chemical reactions

Answer 19

They influence the stability of bonds in reactants.

Question 20

What does lock and key model suggest

Answer 20

Enzyme and substrates are a rigid shape that locked in together.

Question 21

What does induced fit model suggest

Answer 21

Prior to binding substrate and active site aren’t completely complementary in shape. When substrate binds the active site alters shape and moulds around substrate.

Question 22

What evidence is there to support induced fit model

Answer 22

X-ray diffraction techniques allow for 3D pictures of molecules to be formed. Can take pictures of enzyme before and after bond to see if it changes shape.

Question 23

What are changes in shape known as

Answer 23

Conformational changes

Question 24

How does a conformational change support the enzyme

Answer 24

It maximises the ability of the enzyme to catalyse the reaction

Question 25

What do lower temperatures do to reactions

Answer 25

Prevent or slow them down

Question 26

What do higher temperatures do to reactions

Answer 26

Speed them up

Question 27

What happens if temperature is too high

Answer 27

Rate at which enzyme catalyses a reaction drops sharply. Enzymes starts to denature

Question 28

How does pH affect enzymes

Answer 28

Below or Above optimum pH of enzyme, solutions with too much H+ ions (acidic) and OH- ions (alkaline) can cause bonds to break.

Question 29

How can you estimate an enzymes optimum pH

Answer 29

Where an enzyme functions can be an indicator of its optimal pH.

Question 30

How can you investigate the effect of pH on the rate of enzyme - catalysed reactions

Answer 30

Use buffer solutions of different pHs to measure the rate of reaction at different pH values. Buffer solutions will maintain their pH. Use same volume of each buffer solution when adding to reaction mixture.

Question 31

How can you work out the pH of a solution if the hydrogen ion (H+) concentration is known

Answer 31

Put in calculator: -log(H+)

Question 32

How does Enzyme concentration affect rate of reaction

Answer 32

If enzyme concentration is fixed but the concentration of substrate is increased past a certain point, all available active sites eventually become saturated and any further increase in substrates won’t increase rate of reaction. Substrates will begin to ‘queue up” for an active site instead.

Question 33

What is it known as when substrates must queue up for an active site

Answer 33

Vmax (velocity = V)

Question 34

What are the two types of reversible inhibitors

Answer 34

Competitive inhibitors and Non competitive inhibitors

Question 35

What do competitive inhibitors do

Answer 35

Have a similar shape to that of the substrate molecules and therefore compete with substrate for active site.

Question 36

What do non competitive inhibitors do

Answer 36

Bind to enzyme at an alternative site which alters the shape of the active site

Question 37

What else other than reducing or stopping enzyme activity can reversible inhibitors do

Answer 37

Act as regulators in metabolic pathways so that no single enzyme can ‘run wild’ and continuously and uncontrollably generate more and more of a particular product.

Question 38

How can metabolic reactions be controlled

Answer 38

Using the end - product of a particular sequence of metabolic reactions as a non - competitive, reversible inhibitor.

Question 39

How is the process of enzymes converting substrates to products slowed down by itself

Answer 39

The end - product of the reaction chain binds to alternative sites of the original enzyme, changing the shape of the active site ad preventing the formation of more enzyme substrate complexes.It can then detach and be used elsewhere. Allows active site to reform.

Question 40

What happens as you increase concentration of inhibitors

Answer 40

Rate of reaction decreases or can stop completely

Question 41

How can you counter competitive inhibitors

Answer 41

Increase substrate concentration

Question 42

Does increasing substrate concentration help counter non - competitive inhibitors

Answer 42

No