What is metabolism?

Most reactions are steps in a complex network of Cell metabolism is the collective term for thousands of biochemical reactions that occur in a living cell. Most reactions are steps in a complex network of connected and integrated pathways that are controlled by/ catalysed reactions by enzyme . Like respiration which will be looked at later Metabolism is the term used to describe all the chemical reactions that occur within an organism. A metabolic pathway is a sequence of reactions that is controlled by enzymes that change one metabolite to another. The metabolite produced at each stage is used as the substrate for the next stage of the pathway. Respiration and photosynthesis are two examples of metabolic pathways.

Learning Outcomes Explain the two type of metabolic reactions Examine how they are controlled. Explain what a pathway is and explain the different pathways available Regulation can be controlled by intra- or extracellular signal molecules.

Previously called synthetic 2 TYPES OF PATHWAYS ; CATABOLIC ; ANABOLIC; Breakdown of molecules Usually the release of energy Previously called synthetic Metabolic Pathways Biosynthetic processes Making complex molecules from simpler ones Usually needs energy

Synthetic reactions Example: glucose-1-phosphate phosphorylase starch This reaction requires the input of energy to proceed (anabolic reaction).

Breakdown reactions Example: starch amylase maltose Hydrogen Peroxide This reaction releases energy (catabolic reaction). Catalase Oxygen + Water Hint – to help remember, just know one, other opposite eg. “you breakup (complex to simple) and the cat(abolic) lady is released (energy created/released)!”

water + oxygen 2H2O2 2H2O + O2 hydrogen peroxide Hydrogen peroxide breaks down (catabolism) to water and oxygen hydrogen peroxide manganese oxide water + oxygen 2H2O2 2H2O + O2 See mgO and then let pupils do liver and potato. The escaping oxygen causes the foaming

HPCOW Do a quick experiment! Think about what you observed in the two test-tubes. How did the rate of reaction differ? Explain why this difference in rate of reaction occurred. Now PREDICT what has happen here; Use the S3 cards!

Respiration – Glycolysis stage! Glucose (C6H12O6) Intermediate 1 (C6H11O6P1) Intermediate 2 (C6H11O6P1) Intermediate 3 (C6H10O6P2) Pyruvate (C3H3O3P1) Glycogen (in mammals) Starch (in plants) Alternative route Enzyme B Sorbitol While leaving this on board – show blue bottle experiment. Several enzyme- controlled steps Respiration – Glycolysis stage!

Reversible/irreversible reactions and alternative routes As shown by the first stage in respiration you can have both; Reversible/irreversible reactions (intermediate 1 to 2, if more intermediate 2 is made then, it reverts into 1 where it can be stored) Alternative route (when excess sugar in cell, sorbitol as alternative pathway made) Metabolic pathways can have reversible and irreversible steps and alternative routes may exist that can bypass steps in a pathway.

Control steps ...... So how are the all the steps and rate controlled? Metabolic pathways are controlled by the presence or absence of particular enzymes The regulation of the rate of reaction controlled by key enzymes within the pathway. Regulation can be controlled by intra- and extracellular signal molecules – in this case the sugar concentration (sorbitol) or intermediate 1 concentration (stored as glycagon or starch)

Demonstrate your knowledge Use the cards and place them into true or false or don’t know categories. Metabolic pathways are controlled by the presence or absence of particular enzymes. Enzymes always act individually. Competitive inhibition can be reversed by increasing the substrate concentration.

Review - Concept Map Write all the key words from today’s lesson – leave some space so you can add more in coming lessons (2 word trigger meaning with it) Join different word – write how they are joint on the line .... Synthetic Pathway Enzyme Reversible Respiration Metabolism – chemical reactions 2 types Catabolism –breakdown , energy made