2A - Flashcards
What is a metabolic pathway?
Metabolic pathways are integrated and controlled pathways of enzyme-catalysed reactions within a cell.
Metabolic pathways can have reversible and irreversible steps and alternative routes.
What are the functions of proteins in a membrane?
Proteins embedded in phospholipid membranes have roles as pores, pumps and enzymes.
What is the function of membranesaround organelles within a cell. Eg nuclear membrane, mitochondrial membrane, chloroplast membrane?
Membranes form compartments to localise metabolic pathways in the cell.
What is the purpose of localising metabolic pathways in the cell through membranes?
-makes the metabolic pathway easier to control
Functions of pores in a membrane?
Pores: allow materials to diffuse passively through the membrane
Functions of pumps in a membrane?
Pumps: use energy for active transport to move material against the concentration gradient
Functions of enzymes in a membrane?
Enzymes: carry out reactions and have active site exposed to one side of the membrane
How does the substrate concentration effect rate of an enzyme reaction?
Increasing the substrate concentrationmeans more enzyme-substrate complexes can form so speeds upthe rate of a reaction. Eventually the rate will level offwhen a maximum rate for the concentration of enzyme is reached.
How can some metabolic reactions be reversible?
Some metabolic reactions are reversible. The presence of a substrateor the removal of a productwill drive a sequence of reactions in a particular direction.
How do competitive inhibitorsaffect enzyme activity?
Competitive inhibitorsbind at the active site preventing the substrate from binding. Competitive inhibition can be reversed by increasing substrate concentration.
How do non-competitive inhibitorsaffect enzyme activity?
Non-competitive inhibitorsbind 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 increasing substrate concentration.
What is an anabolic reaction?
Reactions within pathways can be anabolic or catabolic.
Anabolic reactionsbuild up large molecules from small molecules(biosynthetic) and require energy.
What is a catabolic reaction?
Reactions within pathways can be anabolic or catabolic.
Catabolic reactions break down large molecules into smaller molecules(degradative) and release energy.
Explain the Induced Fit Hypothesis of enzyme action.
According to the Induced fit hypothesis the active site of an enzyme reduces (lowers) the activation energy and affects the affinity of the substrate and products for the active site.
· Induced fit occurs when theactive site changes shape to better fit the substrate after the substrate binds.
· The substrate molecule(s)have a high affinity for the active siteand the subsequentproducts have a low affinity allowing them to leave the active site.
What other ways can the rate of a pathway be controlled other than by substrate/product concentration?
Pathways can be regulated by the presence or absence of particular enzymesor by regulation of the rates of reaction of key enzymes.
Three ways to control metabolic pathways include: through competitive, non-competitive and feedback inhibition of enzymes.
How does Feedback Inhibition work?
Feedback inhibition occurs when the end-product in the metabolic pathway reaches a critical concentration.
The end-product then inhibits an earlier enzyme, blocking the pathway, and so prevents further synthesis of the end-product.
Define metabolism
- all the biochemical reactions in a cell
- enzymes catalyse these biochemical reactions
What is the purpose of controlling metabolic pathways?
-controlling the rate and direction of pathways ensures the cell makes the right amounts of what it needs to make
What is the purpose of integrating metabolic pathways?
integration allows the cell to divert resources to other pathways that need them eg. lipids join the energy pay-off phase of glycolysis
What is the purpose of alternative routes in metabolic pathways?
-materials can be diverted to alternative routes to allow control of what is produced or used by metabolism
Some enzymes are reversible - when does reversing happen?
-reversing happens when concentrations of substrate concentration is low and product concentration is high
What is the importance of reversible enzymes?
-allow metabolic pathways to be redirected so metabolism makes the products that the cell needs
What does the effect of increasing the substrate concentration have?
Increases the rate of reaction
What does the effect of decreasing the substrate concentration have?
Reduces the rate of reaction
