Topic 1 - Enzymes Flashcards
(30 cards)
What are enzymes?
Biological catalysts that increase the rate of a chemical reaction without being permanently altered themselves
What is an advantage of enzymes in the body?
They enable cellular reactions to take
place at lower temperatures
What is the active site of an enzyme?
The region of an enzyme to which a substrate molecule binds and the reaction takes place
Why are enzymes described as having a ‘high
specificity’ for their substrate?
Only substrates with a specific, complementary shape can fit into an enzyme’s active site.
Describe the ‘lock and key’ model
- Substrate collides with the active site of an enzyme
- Substrate binds, enzyme-substrate complex forms
- Substrate converted to products
- Products released from the active site which is now
free to bind to another substrate
What factors affect the rate of an enzyme-controlled reaction?
● Temperature
● pH
● Substrate concentration
Explain how increasing temperature initially affects the rate of an enzyme-controlled reaction
● As temperature increases molecules have more KE
● Movement of molecules increases
● Probability of a successful collision increases
● More enzyme-substrate complexes form
● Rate of reaction increases
Explain how increasing temperature above the optimum affects the rate of an enzyme-controlled reaction
● Temperature increases above the optimum
● Increased vibrations break bonds in enzyme’s structure
● Active site changes shape, enzyme is denatured
● No more enzyme-substrate complexes can form
● Rate of reaction decreases
Draw a graph to show the effect of increasing temperature on the rate of an enzyme-catalysed reaction.
upside down U
Explain how pH affects the rate of an enzyme-controlled reaction
● Enzymes have an optimum pH
● pH shifts from the optimum
● Bonds in the enzyme’s structure are altered
● Active site changes shape, enzyme is denatured
● Rate of reaction decreases
Draw a graph to show the effect of increasing pH on the rate of an enzyme-catalysed reaction
kinda like ^ but with lil flares
Explain how the substrate-concentration affects the
rate of an enzyme-controlled reaction
● Substrate concentration increases
● Number of substrate molecules in the same volume increases
● Probability of a successful collision increases
● More enzyme-substrate complexes form
● Rate of reaction increases
● Once all active sites become full, the rate of reaction plateaus
Draw a graph to show the effect of increasing
substrate concentration on the rate of an enzyme-catalysed reaction
little rise then flat
How can the rate of an
enzyme-controlled reaction be calculated when given a value for time?
rate = 1 / time
What are the units for rate?
s^-1
Why must large organic molecules be broken down into smaller, simpler molecules in the body?
● Large molecules are too big to be absorbed across
the surface of the gut wall
● ∴ large molecules are broken down into smaller
molecules for absorption into the bloodstream
Give an example of the breakdown of large molecules into smaller molecules in plants
Starch is broken down by enzymes into simpler sugars which are respired to release energy.
What type of molecules are proteins and carbohydrates?
Polymers
What are the monomers of
carbohydrates?
Simple sugars
Which group of enzymes catalyses the breakdown of carbohydrates?
Carbohydrases
Which type of carbohydrase catalyses the breakdown of starch?
amylase
What are the monomers of proteins?
Amino acids
Which type of enzyme catalyses the breakdown of proteins?
Proteases
What is the function of lipases?
Enzymes which catalyse the breakdown of lipids into fatty acids and glycerol
