Biology - Unit 2 - Key area 1

Biology - Unit 2 - Key area 1

1. Part a

   • Metabolic pathways
     • Reversible and irreversible
     • Steps can be skipped
       • Only if there is an alternative route
   • Membrane compartments
     • Embedded in the phospholipid bilayer membrane
     • Can be pumps, pores or enzymes
   • Membrane compartments
     • Increases surface area
       • Increases the reaction rate
   • Key terms
     • Metabolism
       • Build up/breakdown of reactions in cells
       • controlled by enzymes
     • Anabolic pathways
       • Build up/synthesis reactions
       • Use up energy
       • glucose-1-phosphate ------> starch (GPS)
         • Amino acids ------> Proteins
     • Catabolic pathways
       • Breakdown/degradation reaction
       • Starch ---amylase---> Maltose (SAM)

2. Part B (Control of metabolic pathways)

   • Enzyme activity
     • Products
       • Low affinity with the active site
     • Substrate
       • Affinity for the active site
       • Induced fit (like a surgical glove)
         • Active site changes shape to perfect fit the molecule
     • Activation energy
       • Energy needed to start a chemical reaction
         • Enzymes lower the activation energy
   • Each step in a metabolic pathway is controlled by a specific enzyme
     • If an enzyme is missing (caused by a mutation) it will disrupt the pathway causing the reaction to stop
   • Inhibited
     • Slowed down/held back
     • Competitive inhibition
       • Inhibiter molecule has a similar shape to the substrate molecule
         • Inhibitor attaches to the substrate molecule to block it
     • Non competitive inhibition
       • The inhibitor attaches somewhere on the enzyme (not on the active site)
         • This changes the shape
           • Substrate no longer fits the active site
     • End product inhibition/feedback inhibition
       • End product of a reaction binds to the enzyme and inhibits its reaction
         • Substrate
           • Intermediate 1
             • Intermediate 2
               • Intermediate 3
                 • Product
                   • Enzyme 4
                 • Enzyme 3
               • Enzyme 2
             • Enzyme 1
         • If the environment has enough of the product then the organism conserves energy
           • So the inhibitor attaches to an enzyme in the pathway to stop the product being produced
             • If the product isn't in the environment anymore the inhibitor will detach to let the process start again

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