​Metabolic Pathways

​Metabolic pathways are a series of chemical reactions that start with a substrate and finish with an end product.

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They are controlled by enzyme-catalysed reactions within cells.

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In plants they can produce​ glucose and cholorophyll, and in animals vitamins and haemoglobin

​The 2 types of metabolic pathways...

​Anabolic

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​Requires energy and is used to build up large molecules from smaller ones (biosynthesis)

​Catabolic

​Releases energy and is used to break down large molecules into smaller ones (degredation)

​Examples of A&C reactions

​Photosynthesis is an example of an Anabolic reaction. In this process plants make glucose molecules from different raw materials

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Food digestion is an example of a Catabolic reaction, as it involves enzymes breaking down food particles so they can be absorbed by the small intestine​

​Proteins and the Membrane

​Enzymes are vital in metabolic pathways, however, some can be found embedded in the cell membranes.

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Proteins found embedded within cell membranes can act as 2 different things...​

​Pumps - For example the sodium potassium cell that pumps sodium out of the cell and potassium into the cell

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Pores - Which allow ions of a particular size to pass through the membrane

​Controlling Metabolic Pathways

​The control of Metabolic pathways is important in order to stop the build up of end products which aren't needed

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This can be done in the presence of a particular enzyme​

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​Controlling Metabolic Pathways

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​If an enzyme is present, the amount of energy needed to make a product is lowered

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As products are made they are no longer in affinity to the enzyme's active site, and are released.

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​Substrate concentration

​The rate of reaction is affected by the concentration of the substrate

​As substrate concentration increases, the rate of reaction also increases...

​Inhibition

​An inhibiter can be used to stop an enzyme from binding to its substrate

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As a result they can directly control the progress of a metabolic pathway

​The three types

​-Competitive inhibition

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-Non-competitive inhibition

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​-Feedback Inhibition

​Competitive Inhibition

​Occurs when an inhibitor binds itself to the active site of the enzyme.

​As a result, this prevents the substrate from binding

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They can compete with the substrate due to their similar molecular shape.

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Increasing the substrate concentration will eventually reverse competitive inhibition, because the substrate will eventually dilute the inhibitor allowing it to bind to the active site, and win the competition.​

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​Non-competitive Inhibition

​Occurs when the inhibitor does not bind to the active site, instead it binds to a different part of the enzyme therefor causing the active site to change shape.

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The substrate is unable to bind to the active sight as a result

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​Feedback Inhibition

​Occurs when the end product attaches itself to the enzyme.

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​This will stop the metabolic pathway and it will not continue until the concentration of the end product decreases.

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This allows further synthesis of the end product to occur

​List of Terms

​Anabolic - Metabolic activity which requires energy and builds up large molecules from smaller ones

Catabolic - Metabolic activity that releases energy and breaks down large molecules from smaller ones

Metabolic Pathway - Enzyme controlled sequence of chemical reactions in cells

Pores - Small gaps in the membrane which allow ions of particular sizes to pass into the cell

​Pumps - Protein in a membrane which carries substances across it by active transport

Competitive Inhibition - The slowing of a reaction rate due to a substance which attaches itself to the enzymes active site instead of the substrate

Non-competitive Inhibition - The slowing of a reaction rate due to a substance which attaches itself to the enzyme, changing the shape of the active sight

Feedback Inhibition - The slowing of a reaction rate due to the end product binding itself to the enzyme​

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​END OF KEY AREA