Cell metabolism 1

Contents Metabolism Enzymes Role of enzymes in plants and animals metabolism Enzymes involved in chemical breakdown Experiments Immobilised enzymes What are they? Methods of immobilisation Methods of immobilisation Advantages Uses Active Site Specificity Effect of pH on enzyme action Effect of temperature on enzyme action 2

Metabolism is the totality of chemical reactions that take place in an organism Anabolism = Reactions which join smaller molecules to make larger ones e.g. Catabolism = Reactions which break down big molecules e.g. 3

Sources of Energy Solar energy – sunlight is a source of energy capable of being absorbed by cellular pigments e.g. chlorophyll. Cellular energy – cell sources of energy capable of release by metabolic processes in cells e.g. heat given off from germinating peas. 4

Enzymes Highly specific, organic, protein catalysts that work very rapidly in both directions and are affected by heat, pH, radiation, substrate and product concentration and the presence or absence of co-factors and/or inhibitors. 5

Enzyme - definition Highly specific, organic, protein, catalysts that work very rapidly in both directions and are affected by heat, pH, radiation, substrate and product concentration and the presence or absence of co-factors and/or inhibitors. 6

Enzyme - definition Highly specific, organic, protein, catalysts that work very rapidly in both directions and are affected by heat, pH, radiation, substrate and product concentration and the presence or absence of co-factors and/or inhibitors. 7

Enzyme - definition Highly specific, organic, protein, catalysts that work very rapidly in both directions and are affected by heat, pH, radiation, substrate and product concentration and the presence or absence of co-factors and/or inhibitors. 8

Enzyme - definition Highly specific, organic, protein, catalysts that work very rapidly in both directions and are affected by heat, pH, radiation, substrate and product concentration and the presence or absence of co-factors and/or inhibitors. 9

Enzyme - definition Highly specific, organic, protein, catalysts that work very rapidly in both directions and are affected by heat, pH, radiation, substrate and product concentration and the presence or absence of co-factors and/or inhibitors. 10

Enzyme - definition Highly specific, organic, protein, catalysts that work very rapidly in both directions and are affected by heat, pH, radiation, substrate and product concentration and the presence or absence of co-factors and/or inhibitors. 11

Enzyme - definition Highly specific, organic, protein, catalysts that work very rapidly in both directions and are affected by heat, pH, radiation, substrate and product concentration and the presence or absence of co-factors and/or inhibitors. 12

Enzyme - definition Highly specific, organic, protein, catalysts that work very rapidly in both directions and are affected by heat, pH, radiation, substrate and product concentration and the presence or absence of co-factors and/or inhibitors. 13

Enzyme - definition YOU’RE BRILLIANT 14

Role of enzymes in plants & animals Control the rate of metabolic reactions e.g. Amylase – converts starch to maltose e.g. DNA polymerase – forms and repairs DNA 15

Role of enzymes in metabolism All metabolic activities are enzyme controlled reactions i.e. enzymes control the rate of respiration, photosynthesis, etc. 16

Enzymes involved in chemical breakdown Amylase Pepsin Catalase 17

Experiments 1.Investigate the effect of temperature on the rate of one of the following: amylase, pepsin or catalase activity. 2.Investigate the effect of pH on the rate of one of the following: amylase, pepsin or catalase activity. 18

Immobilised enzymes (1/5) NB: Enzymes are catalysts and are reusable. Amylase soln.+ Strarch soln.  Maltose soln. + Amylase soln. mixed together. Very difficult to separate the sugar soln. without destroying the amylase.  Amylase enzyme cannot be reused  This is very wasteful 19

Immobilised enzymes (2/5) If the enzyme is placed in beads of gel from which it cannot diffuse, then it can be retrieved and reused easily. This is enzyme immobilisation. Tanks can be filled with the beads (bioreactors) for large scale industrial processes. This is bioprocessing Slower but more cost effective 20

Immobilised enzymes (3/5) Methods of immobilisation: 1.physically attaching enzymes to insoluble surfaces e.g. glass beads, charcoal, clay 2.entrap them in gels – which must be permeable to the substrate and product – but must prevent the enzyme leaving the gel 3.enclosed by a membrane 4.bonded to a support e.g. collagen 5.bonded to each other 21

Immobilised enzymes (4/5) Advantages: 1.Easy recovery of enzymes for reuse 2.Easy harvesting of products (no enzyme contamination) 3.Greater enzyme stability 4.Extends the life of proteolytic enzymes (digest proteins) by preventing them digesting each other 5.Efficiency of the enzyme not affected 22

Immobilised enzymes (5/5) Uses: 1.Use in bioreactors e.g. corn starch to corn syrup. 2.Fructose production 3.Clarification of fruit juices 4.Meat tenderisation 5.Vinegar production 6.Diagnostic reagents See handout 23

Active Site The position on the enzyme where the substrate is attached. In an enzyme controlled reaction, the enzyme and substrate combine to form the enzyme-substrate complex. The substrate molecules react, the products are released and the unchanged enzyme is available to catalyse another reaction. 24

Specificity An enzyme is like a mould that fits the substrate exactly - only those substrates that will ‘fit’ the enzyme will react with the enzyme. 25

Effect of pH on Enzyme Action The shape of an enzyme relates to its function. If the shape is altered it makes the enzyme less effective. Hydrogen bonding in the enzyme helps maintain the shape. If the pH surrounding the enzymes changes it affects the hydrogen bonds, changes the shape and makes them less effective. 26

Optimum pH Each enzyme has a specific pH at which it has the shape that lets it work best. This is its optimum pH. 27

pH and rate of reaction graph 28

Effect of Temp on Enzyme Action In all chemical reactions an increase of 10°C will generally double the rate of a reaction. Temp will affect the rate of enzyme controlled reactions also – up to a point. If temp becomes too high – enzyme shape changes. If change is permanent – enzyme is denatured 29

Temp and rate of reaction graph 30

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