Organisation - enzymes

Question 1

what are enzymes

Answer 1

a protein that increases the rate of reaction / biological catalyst

Question 2

what is a catalyst

Answer 2

substances that speed up reactions without being changed or used up

Question 3

what is an active site

Answer 3

The active site of an enzyme binds a specific substrate and breaks it down into its products

Question 4

for the enzyme to work, what needs to happen

Answer 4

• the substrate needs to fit in the active site, if it doesn’t match the active site, the reaction won’t be catalysed

Question 5

Describe the lock and key mechanism of enzyme action.

Answer 5

-enzymes have a complementary shape, meaning their active site will only bind to a substrate of a specific shape. Once they have joined together, the chemical reaction will be catalysed

Question 6

what does denatured mean

Answer 6

stops working and is unable to catalyse a reaction

Question 7

what factors affect the rate of an enzyme- catalysed reaction

Answer 7

pH, temperature

Question 8

how does temperature affect the rate of an enzyme catalysed reaction

Answer 8

• increasing temperature increases rate of reaction
• this is because as temperature increases, the active site and substrate move faster, so there are more collisions per second between the substrate and active site
• too hot, bonds holding enzyme will break and this will change the shape of the active site so the substrate won’t fit anymore and be broken down into its products, the enzyme will become denatured

Question 9

what is an optimum pH or temperature

Answer 9

a pH or temperature that enzymes works best at

Question 10

how does pH affect the rate of enzyme - catalysed reactions

Answer 10

• enzymes have optimum pH
• too high or too low, changes shape of active site and enzyme becomes denatured
• optimum pH usually pH7

Question 11

how to calculate rate of reaction

Answer 11

calculated by picking two points on the graph, then dividing the change in the value on the y axis (mass) by the change in the x axis value (time), between those two points.

reaction rate=
change in time
change in mass
​

Question 12

what do digestive enzymes do

Answer 12

break down big molecules like starch, proteins and fats into smaller ones like sugars, amino acids, glycerol

Question 13

what are the main enzymes in digestion

Answer 13

amylase
protease
lipase

Question 14

what is amylase and what does it do

Answer 14

• amylase is an enzyme and a type of carbohydrase
• it breaks down starch into maltose and other sugars

Question 15

what does a carbohydrase do

Answer 15

converts carbohydrates into simple sugars

Question 16

what is protease and what does it do

Answer 16

• protease is an enzyme which converts proteins into amino acids

Question 17

what is lipase and what does it do

Answer 17

• lipids are enzymes that convert lipids into glycerol and fatty acids

Question 18

what does bile do

Answer 18

it neutralises the HCl in the stomach and turns it alkaline so that enzymes work, the enzymes in the small intestine work best at alkaline pH

• also emulsifies fats - breaks fat down into tiny droplets, giving fat a much bigger surface area for the lipase to work on, making digestion faster

Question 19

Why is it necessary to break down large, insoluble food molecules into smaller, soluble molecules

Answer 19

Large, insoluble food molecules can’t be absorbed into the bloodstream, small , soluble molecules can and are used to construct new carbohydrates, proteins and lipids in the body.
Some glucose produced by digestion is used for respiration.

Question 20

sites of action of amylase

Answer 20

mouth
small intestine
pancreas

Question 21

Action sites for proteases

Answer 21

small intestine
stomach

Question 22

where is lipase produced

Answer 22

small intestine
pancreas

Question 23

When investigating the rate of enzyme activity, what factors need to be kept constant?

Answer 23

pH
temperature
substrate concentration

Question 24

where is protease made

Answer 24

• stomach ( pepsin)
• pancreas
• small intestine

Question 25

where is lipase made

Answer 25

• small intestine
  -pancreas

Question 26

where is amylase made

Answer 26

• salivary glands
• pancreas
• small intestine

Question 27

what do digestive enzymes do

Answer 27

convert food into small soluble molecules that can be
absorbed into the bloodstream - e.g- starch to small sugars

Question 28

what is the role of bile

Answer 28

• helps speed up the digestion of lipids but is not an enzyme
• converts larger lipid droplets into smaller ones (emulsifies)
• this massively increases the surface area of the lipid droplets
• this increases the rate of lipids broken down by lipase
• also neutralises stomach acid, creating alkaline conditions, in the small intesting, and this also increases rate of lipid breakdown

Question 29

what is a substrate

Answer 29

the part of the enzyme that attaches to the active site and is broken down and released

Question 30

whats an example of an enzyme which would probably work best in acidic conditions

Answer 30

a protease enzyme in the stomach

Question 31

whats an example of an enzyme which would probably work best in alkaline conditions

Answer 31

lipase, released from the pancreas into the small intestine