Metabolic Pathways Flashcards
Define “metabolic pathway”
Series of linked enzyme-controlled chemical reactions
What are the principles of a metabolic pathway? 2
- Each reaction is controlled and catalysed by a different specific intracellular enzyme
- The enzyme with the slowest activity is rate limiting: determines the overall rate of reaction
Why can metabolic pathways be branched?
So that it is possible to switch into another pathway should an accumulation of products occur at the end of one pathway
What do the end products of one reaction in a metabolic pathway often become?
The starting substrate for a second reaction or pathway
How are metabolic pathways continuously restimulated? 2
- The consumption of the end products may stimulate the first reaction
- In this way an equilibrium situation is
avoided and metabolic pathways are continuously restimulated.
How does the cell retain close control over the overall rate of reaction in metabolic pathways? 3
- Each step of a metabolic pathway is catalysed by a different enzyme
- Each enzyme effectively represents a control point
- The cell retains close control over the overall rate of reaction
How are the rates of reaction in a metabolic pathway maximised? 4
- The different enzymes may require different
biochemical conditions - So may occur in different parts of a cell.
- Allows optimum conditions to be maintained
- Maximises the rate of reactions
How do reactions occurring in cells respond to change? 3
- Varying the rates of reaction.
- By controlling the rate at which enzymes operate
- Enzymes can either be activated or inhibited
How can an overproduction of a substrate in a metabolic pathway lower rate of reaction? 4
- High concentration of the substrate;
- Inhibits enzyme
- By negative feedback
- Reduces rates of reaction
Give 2 advantages for metabolic pathways to have multiple steps rather than one
- Production of useful intermediate molecules
- Slow rather than rapid and potentially destructive release of energy
