Bio Unit 1.4 - Enzymes and Biological Reactions

Question 1

What are metabolic pathways controlled by?

Answer 1

Enzymes

Question 2

Anabolic Reaction

Answer 2

Building up of molecules (protein synthesis)

Question 3

Catabolic Reactions

Answer 3

Breaking molecules down (digestion)

Question 4

What are enzymes?

Answer 4

Globular proteins that acts as a biological catalyst - alters rate of chemical reactions without being used up by the reaction

Question 5

What is the structure of an enzyme?

Answer 5

Tertiary structure - folded into globular shape, hydrophilic R groups on outside making enzymes soluble

Question 6

What determines the bonds the amino acids make with each other in enzymes?

Answer 6

Elements in R groups

Question 7

What bonds can form between amino acids in enzymes?

Answer 7

Hydrogen bonds, disulphide bridges, ionic bonds

Question 8

Three sites where enzymes act

Answer 8

Extracellular, Intracellular in solution, Intracellular membrane bound

Question 9

How do enzymes act extracellularly?

Answer 9

Some enzymes are secreted from cells by exocytosis and catalyse extracellular reactions

Question 10

Examples of enzymes acting intracellular in solution?

Answer 10

Glucose breakdown in glycolisis

Question 11

Example of enzymes acting intracellular membrane bound

Answer 11

Cristae of mitochondria, grant of chloroplasts (transfer electrons and hydrogen ions in ATP formation)

Question 12

Induced Fit Model

Answer 12

Change in shape of the active site induced by the entry of the substrate so the enzyme and substrate can bond temporarily

Question 13

Activation Energy

Answer 13

Minimum energy required for molecules to react, breaking existing bonds in reactants and making new ones in the products

Question 14

How do you increase rate of reaction?

Answer 14

Increase kinetic energy to make successful collisions more likely

Question 15

How do enzymes make sure reaction requires lower activation energy?

Answer 15

Modifying substrate allowing reaction to occur at lower temperatures

Question 16

How do temperature and PH affect enzyme action?

Answer 16

Change three dimensional structure of enzymes, bonds are broken and configuration of active site altered

Question 17

How does concentration affect enzyme activity?

Answer 17

Changes number of enzyme-substrate complexes formed

Question 18

How does temperature above 40 degrees change enzyme activity?

Answer 18

Molecules have more kinetic energy but rate of reaction goes down, increasing vibration breaks hydrogen bonds changing tertiary structure, altering active site shape, enzyme denatured

Question 19

At low temperatures the enzyme is…

Answer 19

Inactivated

Question 20

How does PH affect enzyme activity?

Answer 20

Charges of amino acid side chains on active site affected by hydrogen ions/hydroxide ions

Question 21

What happens to enzymes at low PH?

Answer 21

Excess hydrogen ions are attracted to negative charges and neutralises them

Question 22

What happens to enzymes at high PH?

Answer 22

Excess hydroxide ions neutralise the positive charges

Question 23

How does excess H+/OH- ions change active site?

Answer 23

Disrupts ionic and hydrogen bonds maintaining active site shape and shape changes, denatured

Question 24

What happens at low substrate concentration?

Answer 24

Enzyme molecules only have a few substrate molecules to collide with, active sites not working to full capacity

Question 25

Concentration of substrate controls rate of reaction and is therefore…

Answer 25

Limiting factor

Question 26

As enzyme concentration increases…

Answer 26

more active sites available so rate of reaction increases

Question 27

Inhibitor

Answer 27

Molecule/ion that binds to an enzyme and reduces the rate of the reaction the enzyme catalyses

Question 28

What shape do competitive inhibitors have?

Answer 28

A shape complementary to the active site of the enzyme and similar shape to the substrate (competes for active site)

Question 29

Where do non competitive inhibitors bind and what do they do?

Answer 29

Allosteric Site, affects bond within enzyme molecule and its overall shape including active site

Question 30

If the concentration of substrate increases what happens to the affect of the competitive inhibitor?

Answer 30

Lesser effect, more substrate molecules, greater chance of binding to an active site leaving fewer available to inhibitor

Question 31

Examples of non competitive inhibitors?

Answer 31

Heavy metal ions like lead, As3+,Pb2+

Question 32

Immobilised Enzyme

Answer 32

Enzyme molecules bound to an inert material over which the substrate molecules move

Question 33

What do immobilising enzymes do?

Answer 33

Allows reactions to occur at higher temperatures/more extreme PHs than normal as trapping an enzyme prevents denaturing of active site

Question 34

Where are immobilised enzymes used?

Answer 34

Fermentation, column can be used repeatedly

Question 35

Advantages of immobilised enzymes

Answer 35

increased stability and function over a wider range of temperatures and PHs, enzymes are easily recovered, enzymes can be easily added/removed, greater control over reaction, products not contaminated with enzyme

Question 36

Examples of where Immobilised Enzymes are used?

Answer 36

Lactose free milk, Biosensors, HFCS