2.1 Metabolic Pathways and their control Flashcards
Define ‘metabolism of a cell’
Sum total of all biochemical reactions that occur within a cell
Define a metabolic pathway?
metabolic pathways are integrated and controlled pathways of enzyme-catalysed reactions within a cell.
What are the three types of steps in a metabolic pathway?
Reversible
Irreversible
Alternative
What is an advantage of having reversible steps in a metabolic pathway?
Allows processes to be kept under precise control
What is an advantage to having alternative steps in a metabolic pathway?
Allows an end product still to be reached if a specific enzyme / substrate is unavailable
Describe an ‘Anabolic’ pathway
Anabolic
- Synthesis/Build up of a larger molecule from smaller molecules
- Requires Energy
Give an example of an anabolic process
Photosynthesis
Describe a ‘Catabolic’ pathway
- Break down of larger molecules into smaller molecules
- Releases Energy
Give an example of a catabolic process
Aerobic Respiration
Describe the function of a cell membrane?
Controls the entry and exit of materials in a cell
What are the inner folds of a membrane called?
Cristae
What are the types of proteins found in a cell membrane?
- Protein Pump
- Channel forming protein
- Enzyme
Metabolic pathways are controlled by the … and the regulation of …
Metabolic pathways are controlled by the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes.
What is the ‘activation energy’
The minimum energy required to initiate a chemical reaction
How do enzymes speed up the rate of a chemical reaction?
Speed up the reaction but are not used up because they lower the activation energy
State the key characteristics of enzymes?
- Protein
- catalyses chemical reactions
- reduced activation energy of reaction
- converts substrate(s) to product(s)
- shape of substrate is complementary to shape of enzymes active site
- effected by temperature and/or pH
Do substrates have high or low affinity for the active site of an enzyme?
High
Do products have high or low affinity for the active site of an enzyme?
Low
How does substrate concentration effect reversible reactions?
Reversible reactions can go either way depending on the relative concentrations of substrate/products
Explain the process of ‘Induced Fit’
Induced fit is the process by which an enzyme molds its active site to fit more tightly around a substrate. It ensures the substrate is pulled in close and increases the chance of a reaction occurring.
Name the three methods of enzyme inhibition of metabolic pathways?
- Competitive inhibition
- Non-competitive inhibition
- Feedback inhibition
How does a competitive inhibitor work?
It has a similar shape to the substrate and so
competes with an enzyme’s substrate for binding to the active site.
Competitive inhibition can be decreased by …
Competitive inhibition can be decreased by increasing substrate concentration, as more substrates mean there is more chance the substrate will bind instead of the inhibitor.
A non-competitive inhibitor binds to an … on the enzyme and …
Non-competitive inhibitor binds to an allosteric site on the enzyme and changing the shape of the active site causing the enzyme to become denatured.
Explain how non-competitive inhibition can be overcome?
Non-competitive inhibition cannot be reversed and increasing substrate concentration has no impact as the enzyme is denatured.
Describe feedback inhibition
Feedback inhibition is when a build-up of a metabolic product inhibits the action of an enzyme earlier in the pathway, and this is an example of a self-regulating metabolic pathway.
Explain the advantage of feedback inhibition?
Feedback inhibition prevents further synthesis of the metabolic product until the concentration of the metabolic has decreased. Saving energy.
