Ch 4

Question 1

Hydrolysis

Answer 1

The breaking of bonds involving the addition of water

Question 2

Vmax

Answer 2

Reaction is at maximum rate, Enzyme activity is at maximum, all active sites are occupied

Question 3

Enzyme graph description

Answer 3

Rate of reaction increases as enzyme is made available
Increasing number of collisions between active site & substrate = More ESCs form = products form from substrate = less substrate
Platau in rate/reaction rate constant as all active sites are occupied by substrate - Vmax

Question 4

Benedict’s test

Answer 4

Add Benedict’s regent to sample
Heat in water bath
Colour change; 💚💛🧡🤎❤️
Use colorimeter to calculate absorbance
Calibrate colorimeter using water/blank
Use red filter
Measure and take reading of absorbance

Plot absorbance against concentration of reducing sugars
Use graph to read off concentration of reducing sugars

Question 5

End-product inhibition

Answer 5

= Product of reaction inhibits the enzyme that produces it.
Serves as negative feedback control mechanism
Prevents excess products made & waste of resources

Question 6

Describe the ‘Induced-Fit Hypothesis’

Enzyme action

Answer 6

Active site of enzyme Changes shape slightly as Substrate enters
Initial interaction between enzyme & substrate is weak, but these induce changes in the Enzyme’s Tertiary structure which Strengthen Binding = Strains molecule
This weakens bond/s in the substrate = Lowers Activation Energy

modified version of the Lock and Key hypothesis:

Question 7

Lock and Key Hypothesis

Answer 7

Active Site is complimentary to the subtrate, form = Enzyme-Substrate Complex
Substrate is held in such a way by the enzyme that the Atom-Groups are close enough to React.
The R-groups within the Active site of enzyme Interact with substrate, forming Temporary Bonds;
Temporary bonds Strain Bonds in Substrate = Lowering Activation Energy
Product/s are released
Enzyme left unchaged

Question 8

Mechanism of Enzyme Action

Answer 8

molecules in solution move & collide randomly
higher temperature or pressure speeds the molecules = more successful collisons = faster rate of reaction
Energy must be applied for reactions to start = Activation Energy (Reduced by Enzymes)

Question 9

Digestion of Starch
Steps?
Enzyme involved?
Product/s made?

Answer 9

1. Starch polymers broken down into MALTOSE (disaccharide) by Amylase - produced by Salivary glands & Pancreas - Saliva & Pancreatic Juice
2. MALTOSE broken down into GLUCOSE by Maltase - present in Small Intestine
3. Glucose small enough to be absorbed by cells lining digestive system & then into blood

2 steps: each involve different enzymes as they are specific to one reaction

Question 10

Digestion of Proteins

Answer 10

Proteases, e.g. TRYPSIN catalyse digestion of proteins into smaller PEPTIDES, which can be broken down into Amino Acids by other Proteases

1. TRYPSIN is produced by Pancrease, released in Pancreatic Juice into Small Intestine
2. Trypsin acts on proteins in Small Intestine = Peptides
3. Peptides acted on by other proteases = Amino Acids produced, then absorbed by cells lining digestive system then absorbed into Blood

Question 11

Describe action of Catalase?

Answer 11

Catalase = intracellular enzyme
Catalase ensures toxic Hydrogen Peroxide is Broken Down into Oxygen & Water
Fast action - prevents build up of toxic Hydrogen Peroxide