2.1 Metabolic Pathways Flashcards
What is Metabolism?
Metabolism is the biochemical process that life depends on
Metabolic pathways are controlled by enzymes
Identify 3 features of metabolic pathways
Reversible steps
Irreversible steps
Alternative routes
In what 2 ways can metabolic reactions be classified as?
Catabolic and Anabolic
What is a catabolic reaction?
The breakdown of large molecules into smaller ones releasing energy
What is an anabolic reaction?
The build up of large molecules from smaller ones requiring energy
What 2 compounds make up a membrane?
Proteins and Phospholipids
How do molecules travel through protein pores in the membrane?
Via diffusion
How do molecules travel though protein pumps in the membrane?
Via active transport
What is activation energy (Ea)?
An initial input of energy that all reactions need
What 2 ways can enzymes help to lower activation energy (Ea)?
Affinity for substrate
Substrate orientation
Describe ‘Induced Fit’
There is a high affinity between substrate and enzyme
The active site is flexible and slightly alters its shape when the substrate binds
The close fit ensures the active site is in close contact with the substrate
What does the word affinity mean?
The chemical draw between enzyme and substrate/end product
Can be high (s) or low (ep)
What has a high affinity for the enzymes active site?
Substrate
What has a low affinity for the enzymes active site?
The end products in a reaction
What limits the rate of a reaction at low substrate concentrations?
Substrate availability
What limits the rate of a reaction at high substrate concentrations?
Enzyme availability
How does a competitive inhibitor inhibit the rate of an enzyme controlled reaction?
It is also complementary to the enzymes active site and competes with the substrate. If it binds it prevents the reaction from taking place
What effect will a competitive inhibitor have in a reaction with a low concentration of substrate?
The rate of reaction is lowered.
The number of successful collisions that the enzyme has with the substrate is less frequent since the enzymes active site may be occupied by a competitive inhibitor.
What effect will a competitive inhibitor have in a reaction with a high concentration of substrate?
At high substrate concentrations the substrate molecules are abundant enough to out compete the competitive inhibitors. More successful collisions occur.
What effect does a non-competitive inhibitor have on an enzyme?
When a non-competitive inhibitor binds the enzymes allosteric site, the active site changes shape and is no longer complementary to the substrate and so it wont fit.
Where does a non-competitive inhibitor bind to on an enzyme?
The allosteric site
What effect does a non competitive inhibitor have on the rate of a reaction?
The maximum reaction rate is lowered, regardless of how much substrate is added. The active site has changed and enzyme concentration is reduced.
What inhibits enzyme action in feedback inhibition?
The end product of an enzyme catalysed reaction binding to an enzyme in the pathway.
Give two advantages of feedback inhibition in a metabolic pathway.
- Regulates the whole pathway.
- Prevents wasteful conversion and accumulation.
