Metabolic Pathways Flashcards
What do we call integrated and controlled pathways of enzyme-catalysed reactions in a cell?
Metabolic pathways
What is metabolism?
All the chemical reactions that take place within an organism
Tell me 2 things about anabolic reactions.
- build up larger molecules from smaller molecules
2. Require energy
If a step within a metabolic pathway is one-way is is described as…
irreversible
If a product can be converted back into a substrate within a pathway, it is described as…?
reversible
With the induced fit model, what is it that changes shape?
The active site of the enzyme
There isn’t always one way to get to the same end product. If there is a different pathway, what do we call it?
An alternative route
Tell me 2 things about a catabolic reaction.
- Breaks down larger molecules into smaller molecules
2. Releases energy
‘Lock and Key’ in Nat 5 was a lie!!! What is a better model for how an enzyme works?
induced fit model
State 3 functions of proteins embedded within the cell membrane.
- Protein pores (diffusion)
- Protein pumps (active transport)
- Enzymes
If there is a mutation to a gene that controls the production of an enzyme, how would that affect the concentration of substrate and product?
Substrate would probably increase
Product would probably decrease (enzyme not present to carry out the reaction)
What does the term affinity mean?
an attraction
What is the affinity between an enzyme and its substrate.
High
What is the affinity between an enzyme and its product.
Low
What do we call the energy required to initiate a reaction?
Activation energy
How does an enzyme affect the activation energy for a reaction?
It lowers the activation energy
State the 3 roles of the active site.
- It orientates reactants and is a binding site for reactants (high affinity for substrates)
- It decreases the activation energy
- It releases products with low affinity
State 5 factors that can affect enzyme activity.
- temperature
- pH
- Enzyme concentration
- substrate concentration
- end product inhibition
Describe how increasing substrate concentration affects the rate of a reaction (2)
As the substrate concentration increases initially the rate of reaction increases and then rate of reaction levels out and remains the same.
Explain why continually increasing the substrate concentration does not continually increase the rate of reaction.
The enzymes reach saturation point - all the enzyme active sites are occupied.
In end product inhibition, what does the end product inhibit?
An enzyme at the start of the metabolic pathway
What is end product inhibition also known as?
Feedback inhibition
When does feedback inhibition take place?
When the end product reaches a critical concentration.
It the concentration of the end product decreases to below the critical concentration, what happens?
The enzyme at the start of the metabolic pathway is no longer inhibited.
What do we call substances that prevent enzyme activity?
inhibitors
Where does a competitive inhibitor join onto an enzyme?
active site
Why is a competitive inhibitor able to join to the active site of an enzyme?
It has a similar shape to the substrate
What is the result of the competitive inhibitor attaching to the active site?
It blocks the active site so no enzyme-substrate complex can be produced so the reaction rate is reduced
Why is a competitive inhibitor described an a reversible reaction?
When the inhibitor is released from the active site, the substrate can once again interact with the enzyme
How can you reduce the effect of a competitive inhibitor?
Increase the concentration of substrate, there is more chance of the substrate winning the competition and combining with the active site
Where does a non-competitive inhibitor join to an enzyme?
The allosteric site, somewhere else on the enzyme
NOT the active site
Why does a non-competitive inhibitor joining to the allosteric site affect the rate of a reaction?
It causes the active site of the enzyme to alter its shape, no longer complementary to the substrate
How does increasing the concentration of substrate affect a non-competitive inhibitor?
It doesn’t
Why is a non-competitive inhibitor described as reversible?
Once the inhibitor is released, the active site is restored to its original shape
