Human Cells: Metabolic Pathways
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What is metabolism?
All the chemical reactions that take place in cells
What is a metabolic pathway?
A series of stepwise chemical reactions that are controlled by enzymes
Metabolic pathways are integrated and controlled pathways of what?
Enzyme-catalysed reactions within a cell
Metabolic pathways can have what?
Reversible steps, irreversible steps and alternative routes
Reactions within metabolic pathways can be what?
Anabolic or catabolic
What do anabolic reactions do?
They build up large molecules from small molecules and require energy
What do catabolic reactions do?
Break down large molecules into smaller molecules and release energy
Metabolic pathways are controlled by what?
The presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes
The substrate molecule(s) have a what and the subsequent products have what?
They have a high affinity for the active site. They have a low affinity, allowing them to leave the active site.
When does induced fit occur?
When the active site changes shape to better fit the substrate after the substrate binds
What is the activation energy?
The energy required to initiate a chemical reaction
What do enzymes do to the activation energy?
Lower it
The concentration of substrate and end product affect what?
The direction and rate of an enzyme reaction
What happens as the substrate concentration increases?
The rate of the enzyme reaction increases until all of the active sites are occupied by the substrate
What are some metabolic reactions?
Reversible and the presence of a substrate or the removal of a product will drive a sequence of reactions in a particular direction
What can the concentration of substrate relative to the concentration of product(s) do to the direction of an enzyme-catalysed reaction?
It can change the direction of an enzyme-catalysed reaction
What does competitive inhibition involve?
It involves competition for the active site of the enzyme by molecules that resemble the substrate
Where do competitive inhibitors bind?
At the active site preventing the substrate from binding
Competitive inhibition can be reversed by doing what?
Increasing the substrate concentration
Where do non-competitive inhibitors bind?
Away from the active site but change the shape of the active site, preventing the substrate from binding
Non-competitive inhibition cannot be reversed by doing what?
Increasing substrate concentration
When does feedback inhibition occur?
When the end product in the metabolic pathway reaches a critical concentration
The end product inhibits what?
An earlier enzyme, blocking the pathway, and so prevents further synthesis of the end product