1.6 metabolic pathways Flashcards
State the meaning of metabolic pathways
A metabolic pathway is a series of integrated (linked) and controlled enzyme-catalysed reactions within a cell.
Identify the three types of step that can be part of a metabolic pathway.
reversible steps
irreversible steps
alternitive route
Identify the two types of reactions that take place within metabolic pathways
Reactions within metabolic pathways can be anabolic or catabolic.
Describe the two types of reactions that take place within metabolic pathways
Anabolic reactions build up large molecules from small molecules and require energy. Catabolic reactions break down large molecules into smaller molecules and release energy.
Explain how metabolic pathways are controlled by genes.
Each step in a metabolic pathway is controlled by the presence or absence of a particular enzyme. Since enzymes are made of protein and protein production is controlled and regulated by the genes, the presence or absence of a particular enzyme in a metabolic pathway is determined by the gene code. Therefore, expression of the gene code regulates the reaction rate of key enzymes in the metabolism.
Describe the term induced fit
The induced fit model of enzyme action is called ‘induced fit’
Describe what induced fit means
The active site of an enzyme binds to its specific substrate it changes the shape of its active site slightly to ensure that the fit between the two is an exact match.
how does induced fit happen
due to chemical interactions between the enzyme and substrate
State the effect of an enzyme on the activation energy of a reaction.
The presence of an enzyme attached to its substrate via its active site will lower the activation energy needed for the reaction.
Why are enzymes described as catalysts in term of the enzyme effect of activation energy
if the enzyme is present and the activation energy is lowered, then less energy is needed to initiate the chemical reaction and so it is more likely to take place i.e. faster than it would without the enzyme.
Explain the meaning of the term ‘high affinity’
Substrate molecules have high affinity for the active site of their specific enzyme. This means that there is a strong chemical attraction between the substrate and its specific active site.
Explain the meaning of the term low affinity
The product of a chemical reaction has a low affinity for the active site of the specific enzyme that helped to produce it. This means that as soon as the product is made there is no longer a chemical attraction and so it exits the active site of the enzyme to make way for another substrate molecule with high affinity to bind.
State the effect of substrate and product concentration on the direction and rate of a reaction
Some steps in metabolic pathways are reversible. The relative concentrations of the substrate/product for these reaction steps will drive the reaction in a particular direction at a particular rate
Describe the effect of increasing the substrate concentration on the reaction rate of an enzyme-controlled reaction.
As the substrate concentration of an enzyme-controlled reaction is increased, the reaction rate will increase until the enzyme concentration becomes the limiting factor and then as the substrate concentration is increased beyond this point, the reaction rate will remain constant.
Identify the three types of enzyme inhibition.
Competitive
non competitive
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