4.1 - Enzyme Action

Question 1

Why are enzymes important

Answer 1

Processes necessary to life require chemical reactions that need to happen quickly. Having high temperatures and pressures would not be possible in living cells. Enzymes catalyse the reactions

Question 2

What are enzymes

Answer 2

Biological catalysts. Globular proteins that interact with substrate molecules causing them to react at much faster rates without the need for harsh environmental conditions.

Question 3

Anabolic reactions

Answer 3

Synthesis of large polymer based components. Components are synthesised and assembled into cells, which then form tissues, organs and the whole organism. Chemical reactions required for growth that are all catalysed by enzymes

Question 4

Examples of large polymer based compounds

Answer 4

Cellulose forms the walls of plant cells

Long protein molecules form contractile filaments of muscles in animals

Question 5

Where are the large organic molecules obtained from?

Answer 5

Digestion of food. From even larger organic molecules e.g. starch. Digestion is also catalysed by enzymes

Question 6

Vmax

Answer 6

Maximum initial velocity / rate of the enzyme-catalysed reaction

Question 7

Definition of specificity of an enzyme

Answer 7

Each enzyme catalysed one biochemical reaction, of which here are thousands in any given cell.

Question 8

Role of enzymes in metabolism

Answer 8

Reactions rarely happen in isolation but as part of multi-step pathways. Metabolism is sum of all the different reactions and reaction pathways in a cell or organism, can only happen as result of control and order imposed by enzymes.

Question 9

What is needed for a reaction to happen

Answer 9

Molecules need to collide in right orientation.

Question 10

Factors affecting rate of temp (not enzymes)

Answer 10

Temperature and pressure. Speed of molecules will increase - number of successful collisions and overall rate of reaction

Question 11

Activation energy

Answer 11

Energy that needs to be supplied for most reactions to start

Question 12

How do enzymes affect activation energy

Answer 12

Help molecules collide successfully, reducing activation energy needed.

Question 13

Active site

Answer 13

Area within tertiary structure of enzyme that has a shape that is complementary to shape of a specific substrate molecule

Question 14

Why is it called lock and key hypothesis

Answer 14

Same way only the right key will fit into a lock, only a specific substrate will fit the active site of an enzyme

Question 15

Enzyme substrate complex

Answer 15

When substrate is bound to the active site

Question 16

Enzyme product complex

Answer 16

Products that are formed from substrates reacting in enzyme.

Question 17

Step after enzyme product complex

Answer 17

Product/s are released, enzyme left unchanged and able to take part in subsequent reactions

Question 18

How is substrate held in enzyme

Answer 18

Held to enzyme so atom groups can interact. R-groups within the active site of the enzyme will also interact with substrate forming temporary bonds. These put strain on bonds within the substrate which also helps reaction along.

Question 19

Induced-fit hypothesis

Answer 19

• Active site of enzyme changes shape slightly as substrate enters
• Initial interaction between enzyme and substrate is relatively weak but weak interactions rapidly induce changes in enzymes tertiary structure that strengthen binding, putting strain in substrate molecule - lowers activation energy

Question 20

Intracellular enzymes

Answer 20

Enzymes that act within cells

Question 21

Example of an intracellular enzyme

Answer 21

Enzyme catalase ensure hydrogen peroxide (toxic waste product of many metabolic pathways) is broken down to oxygen and water quickly, preventing accumulation. Found in both plant and animal tissues.

Question 22

Extracellular enzymes

Answer 22

Work outside the cell that made them.

Released from cells to break down large nutrient molecules into smaller molecules in the process of digestion.

Question 23

Function of extracellular enzymes in single called organisms

Answer 23

Bacteria & yeast release enzymes into their immediate environment. Enzymes break down larger molecules (eg proteins) and the smaller molecules produced (eg amino acids and glucose) are then absorbed by the cells.

Question 24

Example of extracellular enzymes involved in human digestion

Answer 24

Amylase and trypsin

Question 25

How do multicellular organisms gain nutrient

Answer 25

Eating food

Question 26

Why do large molecules of nutrients need to be broken down

Answer 26

So they can be absorbed into the bloodstream

Question 27

Why are smaller molecules absorbed into the bloodstream

Answer 27

So they can be transported around the body to be used as substrates in cellular reactions

Question 28

Where does digestion of starch occur

Answer 28

Mouth and small intestine

Question 29

Why are different enzymes needed in digestion of starch

Answer 29

Each enzyme only catalyses one specific enzyme

Question 30

Step 1 of starch digestion

Answer 30

Starch particles partially broken down into maltose (disaccharide)
Enzyme is amylase

Question 31

Where is amylase produced and released

Answer 31

Produced by salivary glands and pancreas

Released into saliva in mouth, and in pancreatic juice in small intestine

Question 32

2nd step of digestion of starch

Answer 32

Maltose broken down into glucose
(Monosaccharide)
Enzyme maltase

Question 33

Where is maltase

Answer 33

Small intestine

Question 34

Why is starch broken down to glucose

Answer 34

Glucose is small enough to be absorbed by cells lining digestive system and subsequently absorbed into bloodstream

Question 35

What type of enzyme digests proteins

Answer 35

Protease

Question 36

Type of protease

Answer 36

Trypsin

Question 37

Function of trypsin

Answer 37

Catalyses digestion of proteins into smaller peptides which can then be broken down into amino acids by other proteases

Question 38

Where is trypsin produced and released

Answer 38

Produced in pancreas and released into pancreatic juice in small intestine where it acts on proteins

Question 39

Why are peptides broken down into amino acids

Answer 39

Amino acids that are produced by proteases can be absorbed by the cells lining the digestive system and are absorbed by the bloodstream