Topic 8: Metabolism, Cell Respiration and Photosynthesis

8.1 Metabolism

Methabolic Pathways

Definition: a chain or cycle of reactions that are catalysed by enzymes

  • Definition: a chain or cycle of reactions that are catalysed by enzymes

  • reactions happen mostly at small steps

  • Cycle pathways - the end product is used to start the pathway, such as in Krebs Cycle

add krebs cycle and glycolysis 


Enzymes and activation energy

  • Activation Energy: min. of energy required for a reaction to take place

    • is used to break or weaken the bonds in the substrates

  • binding of enzymes ⇾ lower the the activation energy 

  • Activation Energy ⇾  + rate of reaction 


Types of enzyme inhibitors

  • Definition: enzyme inhibitors bind to enzymes and reduce their activity 

  • Competitive:

    • competes for the same site - is similar to the substrate

    • interferes with the active site ⇾ enzyme can not bind

    • does not modify the active site 

    • + substrate = - effect of the inhibitor

  • Non-Competitive:

    • binds to a different location than the active site

    • changes the shape of the enzyme ⇾ enzyme can't bind

    • + substrate ⇾ does not change the impact of the inhibitor 


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End-product inhibition 

  • form of non-competitive inhibition: the end product binds to the allosteric site - inhibits products to be produced

  • allosteric interactions ⇾ happens away from the active site ⇾ on the allosteric site

  • excess of end product = stops the pathway 

  • Example: amino acid threonine is transformed in isoleucine














  • high concentration of isoleucine ⇾ makes isoleucine bind to the allosteric site of the first enzyme, threonine deaminase 


Bioinformatics and new antimalarial drugs

  • research of metabolic pathways is facilitated through chemogenomics

  • chemogenomics: a range of target sites and chemicals that work on those target sites are identified for each organism

  • those informations create a database used to help find cure for diseases

  • Example: new anti-malarial drugs

    • increasing drug resistance of the pathogen 

    • need to develop new drugs ⇾ identification of those


Calculating rate of reactions

  • measure rate of disappearance of substrate

  • measure rate of appearance of product


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