2.1 Flashcards
Metabolism
The chemical reactions that occur in a cell that are necessary for life
These chemical reactions are single steps in large closely integrated pathways that ate controlled by enzymes
Reversible steps
The pathway can go in both directions using the same enzyme
Irreversible steps
The pathway can only go in one direction using an enzyme
Alternative pathways
Metabolic pathways can have alternative routes.
This can speed up the metabolic pathway
Anabolic pathways
Anabolic reactions build up large molecules from smaller molecules.
This requires energy
Catabolic pathways
Catabolic pathways break down large molecules into smaller molecules.
This releases energy
Organelles that contain membranes
Chloroplasts
Mitochondria
Cell membrane
Structure of a membrane
Protein pump
Protein pore
Enzyme
Double layer of phospholipid molecules
Role of protein pores
Pores allow molecules and ions to pass across the membrane through passive transport (diffusion and osmosis)
Role of protein pumps
Pumps carry molecules and ions across the membrane through active transport
Role of enzymes
Metabolic reactions are controlled by the presence or absence of particular enzymes and the regulation of the rate of key enzymes
Active site
The active site on an enzyme has a specific shape that is determined by the bond between amino acids
Induced fit
The active site changes its shape to better fit the substrate after the substrate binds
Substrate molecules affinity
The substrate molecules have a high affinity for the active site.
This pulls the substrate close to the active site.
Product affinity
The products produced have a low affinity.
This allows them to leave the active site.
Activation energy (Ea)
The energy needed to break or form bonds
Activation energy
Induced fit lowers the activation energy required to start a metabolic reaction
Enzymes lower the activation energy by bringing substrates of a reaction closer together
Enzyme reactions
Some metabolic reactions are reversible
The presence of a substrate or the removal of a product will drive a sequence of reactions in a particular direction
Competitive inhibitors
Bind at the active site which prevents the substrate from binding
This can be reversed by increasing substrate concentration
Non competitive inhibitors
Bind away from the active site but change the shape of the active site which prevents the substrate from binding
This cannot be reversed by increasing substrate concentration
Feedback inhibition
Occurs when the end product in the metabolic pathway reaches a critical (very high) concentration
The end product then inhibits an earlier enzyme, blocking the pathway, and so prevents more end product being made
