1.4.2 Enzymes Flashcards
Enzymes are described as biological catalyst, what does this mean
Biological- means produced by living tissue
Catalyst- means speeds up the rate of reaction and they don’t get changed by the reaction
What is a catabolic enzyme
An enzyme that breaks down large molecules into smaller ones
What is an anabolic enzyme
An enzyme that builds up smaller molecules into larger molecules
What type of protein is an enzyme
Globular protein
Enzymes don’t cause reactions to happen, instead they do what to reaction
They speed up reactions that were already taking place
What is the name of the specific region of the enzymes
The active site
Is the enzymes’ active site made from many or few amino acids
Relatively few amino acids
What is the name given to the molecule that the active site acts upon
Substrate
What is formed when an enzyme and substrate fit neatly
An enzyme-substrate complex
The enzyme is ——- to the substrate (fill in blank)
Complementary
What are the 2 locations of enzyme action
- Intracellular
- Extracellular
In intracellular enzyme action, what are the 3 organelles in which enzymes are located
- Lysosomes
- Cytoplasm
- Mitochondrial membrane
In extracellular enzyme action, what is the main system in which enzymes action occurs
Digestive system, alimentary canal
What is an exergonic reaction
A reaction which releases energy
What is an endergonic reaction
A reaction which requires energy
How do enzymes catalyse a reaction
By lowering the activation energy
Name the 2 enzyme action theories
- Lock and key mechanism
- Induced fit
What forms when a substrate binds to an enzyme
Enzyme-substrate complex
A substrate bust be complementary in —— to the active site (fill in the blank)
In shape
How does the induced fit model describe the active site
That it’s not quite complementary in shape but then moulds to the shape of the substrate
In the induced fit model, what happens to the active site once the products are released
They go back to their original shape, so they’re unaltered by the reaction
True or false: enzymes are generally large complex fibrous proteins
False, they are globular
True or false: the active site forms only a small part of the whole enzyme and is highly specific for its substrate
True
True or false: Enzymes increase the rate of reaction by lowering the activation energy of the reaction
True
True or false: The formation of an enzyme-substrate complex makes the substrate more stable
True
True or false: In the induced fit model, the enzyme and its active site change shape when the substrate binds
True
True or false: Enzymes can catalyse reactions that would not otherwise occur
False
True or false: Anabolic reactions involve the break down of large substrates into smaller ones
False, catabolic reactions break down, anabolic build up
True of false: Endergonic reactions require an intake of energy
True
True or false: ATP hydrolysis is an endergonic reaction
False, its an exergonic reaction
True or false: Enzyme action in the alimentary canal is an example of intracellular digestion
False, its an example of extracellular
What is the equation to calculate rate when the dependent variable is time
1/ Time (in seconds)
What is the unit for rate of reaction when the dependent variable is time (2 answers)
s ^-1
s^-1 x 10^-3
What is the calculation for rate of reaction when the dependent variable is mass or volume
Volume/ time (in seconds)
Mass/ time (in seconds)
What are the 4 factors that affect enzyme action
- Temperature
- pH
- Substrate concentration
- Enzyme concentration
On a rate of reaction against temperature on an enzyme action graph, why does the graph initially increase
Because there is an increase in kinetic energy of both enzymes and substrates so there is an increase of successful collisions so there is an increase in enzyme-substrate complexes formed so there is more product formed in a certain period of time
On a rate of reaction against temperature on an enzyme action graph what does the peak of the graph mean
The optimum temperature
On a rate of reaction against temperature on an enzyme action graph why does the graph decrease after the peak
Because the amino acids which make up the protein begin to vibrate so the hydrogen bonds between the R groups begin to break so the tertiary structure of the enzyme changes shape which in turn alters the shape of the active site- denaturing the enzyme so the substrate is no longer complementary so fewer enzyme-substrate complexes form so fewer products are produced per period of time
In extreme pH what type of bonds in the enzyme are broken
Ionic bonds
What is an enzyme inhibitor
A molecule that interferes with/ slows down enzyme activity
What are the 2 types of enzyme inhibitors
- Competitive
- Non- competitive
Can maximum rate of reaction still be achieved when a competitive inhibitor is present
Yes, when you increase the substrate concentration
How does a competitive inhibitor work
By binding to the active site so fewer enzyme-substrate complexes form per unit of time
How does a non-competitive inhibitor work
It binds somewhere other than the active site, known as the allosteric site, which changes the tertiary structure, so changes the shape of the active site preventing substrate from binding, fewer enzyme-substrate complexes form
What is a metabolic pathway
A series of reactions in which each step is catalysed by an enzyme
Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst (3 marks)
- Substrate binds to the active site
- Active site changes shape slightly so it is complementary to substrate
- Reduces activation energy
A competitive inhibitor decrease the rate of an enzyme-controlled reaction. Explain how. (3 marks)
- Inhibitor similar shape to substrate / complementary to active site
- Binds to active site
- Reduces enzyme-substrate complex forming
Explain how the active site of an enzyme causes a high rate of reaction (3 marks)
- Lowers activation energy
- Induced fit causes the active site to change shape
- So enzyme-substrate complex causes bonds to form/break
Describe how a non-competitive inhibitor can reduce the rate of an enzyme-controlled reaction (3 marks)
- Attaches to the enzyme at a site other than the active site
- Changes shape of the active site
- So active site and substrate no longer complementary so less substrate can bind
Formation of an enzyme-substrate complex increases the rate of reaction. Explain how. (2 marks)
- Reduces activation energy
- Due to bending bonds / without enzyme, very few substrates have sufficient energy for reaction
Describe how an enzyme can be phosphorylated (2 marks)
- Attachment/association of (inorganic) phosphate
(to the enzyme); - (Released from) hydrolysis of ATP
OR
(Released from) ATP to ADP + Pi;
Suggest one advantage to a bacterium of secreting an extracellular protease in its natural environment. Explain your answer (2 marks)
- To digest protein;
- (So) they can absorb amino acids for
growth/reproduction/protein synthesis/synthesis
of named cell component;
OR
(So) they can destroy a toxic substance/protein;
Describe the action of membrane-bound dipeptidases and explain their importance (2 marks)
- Hydrolyse (peptide bonds) to release amino
acids; - Amino acids can cross (cell) membrane;
OR
Dipeptides cannot cross (cell) membrane;
OR
Maintain concentration gradient of amino acids
for absorption;
OR
Ensure (nearly) maximum yield from protein
breakdown;
