Ch 9 Metabolism 1

Syllabus – What do you need to know….. 1.Define the term: metabolism. 2.State that solar energy is source of energy on Earth. 3.State that cellular energy sourced from chemical energy in ATP 2

4. Define the term: enzymes 5. State the nature, folded shape & functions of enzymes. 6. Explain the role of enzymes in plants and animals including role in metabolism 7. Explain the effects of pH & temperature on enzyme activity. 8. State the procedure and advantages of Bio- processing. 9. State the use of Bio-processing. 3

10. Explain the active site theory to examine enzyme function & specificity. 11. Explain the term optimum activity with reference to temperature. 12. Explain the nature of heat denaturation 13. Explain the active site theory to examine enzyme function & specificity. 14. Explain the term optimum activity with reference to temperature. 15. Explain the nature of heat denaturation 4

Metabolism Question: When we speak about metabolism what do we mean? Answer: Metabolism describes all the chemical reactions in our bodies 5

Question: What kind of chemical reactions do you think take place in our bodies? Answer: 1.Growth (making proteins) 2.Response (nerve reactions) 3.Movement (energy needed from respiration) 6

Homeostasis The way our metabolism functions is extremely important as our bodies need to have constant and stable conditions The maintenance of stable conditions in our bodies is called homeostasis. 7

Learning check 1.What is meant by metabolism? 2.Can you name some example of metabolism in the human body 3.What word describes the maintenance of reactions in our body? 8

Cellular Energy is contained in bonds found in molecules such as carbohydrates When the bonds are broken down, energy is released during respiration in the mitochondria 9

Catabolic Reactions break down complex substances into simpler ones and release energy. E.g. respiration and digestion 10

Anabolic Reactions consume energy as they build larger, more complex, molecules from smaller ones e.g. Photosynthesis and muscle growth from amino acids are examples of anabolic reactions. 11

Enzymes can be either anabolic or catabolic. An example of a catabolic enzyme is amylase. Amylase converts starch into maltose. An example of an anabolic enzyme is DNA polymerase. This enzyme repairs (rebuilds) DNA. 12

In Summary Catabolic: Respiration breaks down glucose and releases this energy from the bonds Anabolic: Photosynthesis in plants builds up molecules with energy rich bonds (glucose) This is how plants provide energy from the sun for everything else on earth! Remember C.R.A.P. ! 13

Learning check 1.Where does cellular energy refer to? 2.In which organelle does it occur in? 3.What does the term catabolic reaction mean? 4.What does the term Anabolic reaction mean? 5.Can you give an example of each type? 14

Enzymes 15

Enzymes Question: What are enzymes? Answer: Proteins that function as biological catalysts are called enzymes. Enzymes control cellular reactions. A catalyst speeds up a reaction without being used up in the reaction. 16

are named by adding ‘-ase’ to the name of their substrate Examples: The enzyme that acts on Amylose (starch) is called amylase The enzymes that act on proteins are called proteases Naming Enzymes 17

Examples are: Lactase – breaks down lactose (milk sugars) diastase – digests vegetable starch sucrase – digests complex sugars and starches maltase – digests disaccharides to monosaccharides (malt sugars) glucoamylase – breaks down starch to glucose protease – breaks down proteins found in meats, nuts, eggs, and cheese lipase – breaks down fats found in most dairy products, nuts, oils, and meat cellulase – breaks down cellulose, plant fibre; not found in humans 18

EFFECTS OF ENZYMES 1.Enzymes lower the activation energy. This is the energy input needed to bring about the reaction. Enzymes enable the reaction to occur with less energy than would be needed if the enzyme were not present. 19

Enzymes Free Energy Progress of the reaction Reactants Products Free energy of activation Without Enzyme With Enzyme 20

2.Regulate the thousands of different metabolic reactions in a cell and in the organism. 3.The cell activity is determined by which enzymes are active in the cell at that time. 21

Learning Check 1.What is an Enzyme? 2.What are catalysts? 3.To what group of bio-molecules do enzymes belong? 4.Name 3 enzymes. 5.What are 3 effects of enzymes? 22

How do Enzymes work Enzymes are folded in GLOBULAR SHAPES. The enzyme’s shape enables it to receive only one type of molecule; that molecule that will fit into it’s shape. The place where the substance fits into the enzyme is called the active site and the substance that fits into the active site is called the substrate. Enzyme action occurs when the enzyme and substrate collide forming a product. 23

What Affects Enzyme Activity? Factors that affect enzymes include: 1.pH 2.Temperature 3.Substrate concentration 4.Enzyme concentration 24

pH pH scale goes from is acidic 7-14 is basic (or alkaline) 25 acidneutralbase 0714

Most enzymes work best at a pH of 6-8. A change in pH disrupts an enzyme's shape and structure, causing it to become less effective. The ideal (optimum) pH for most enzymes is 7. Stomach enzymes e.g. Pepsin work in an acidic environment of pH 2 26

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At 0°C enzyme action is low because the movement of molecules is low. Increasing the temperature, speeds up the movement of molecules and increases enzyme activity. Human enzymes work best at 37°C. Plant Enzymes work best at 20-30°C. 28 Temperature

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TEMPERATURE AND RATE OF ENZYME ACTION 30

Industrial use of Enzymes Bio-processing is the use of enzyme controlled reactions to produce a product Bio-processing can be used to produce a vast range of products such as cheeses, beer, antibiotics, vaccines, methane gas, food flavours, vitamins and perfumes Traditionally micro-organisms such as bacteria and yeast were used, but since the 1900’s and especially since the 1950’s enzymes are being used. 31

Some products of Bioprocessing 32

Immobilised enzymes If enzymes are used freely dissolved in a vessel it can be very wasteful as they are lost at the end of the process To prevent this problem enzymes are often immobilised or fixed. This means they are: 1.attached to each other or 2.an insoluble substance or 3.enclosed in a membrane or gel. 33

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The benefits of immobilised enzymes are: 1.they may be reused 2.they are easy to separate from the product (therefore it is easy to purify the product) 3.they are often more stable than the natural enzyme 4.the process is cheaper 5.their efficiency is not reduced 6.can provide increased resistance to changes in conditions such as pH or temperature.pH temperature 36

How to immobilise enzymes The enzyme is held in place / trapped in a gel e.g. Sodium alginate. This allows substrates in and products out. Immobilised enzymes are then used in bioreactors. 37

USES OF IMMOBILISED ENZYMES Products derived from immobilised enzyme action: 1.Fructose produced from glucose: Fructose is sweeter than glucose and is used in soft drinks and other sweet products. 2.Antibiotics: Enzymes are used to change penicillin into new, wider used, antibiotics. 3.Sewage Treatment: Instead of bacteria enzymes can be immobilised and used. 38

Learning Check 1.What is bio-processing? 2.What type of organisms are usually used in bio-processing? 3.Why is bio-processing advantageous? 4.What are the advantages of immobilising enzymes? 5.Can you name 3 things immobilised enzymes are used for? 39

Enzymes – Advanced Study 40

The place where the substance fits into the enzyme is called the active site and the substance that fits into the active site is called the substrate. Enzyme Substrate 41 Active Site

Enzyme action occurs when the enzyme and substrate collide. The substrate slots into the active site of the enzyme. When the substrate joins with the enzyme the entire structure is called the enzyme- substrate complex. The substrate becomes changed by the enzyme’s action and is then releases as the product. The enzyme is then free to join another substrate. 42

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Induced Fit Model. Sometimes the shape of the active site must be slightly changed. This situation is called the Induced Fit Model. The enzyme’s active site has a shape closely complementary to the substrate. The substrate locks into the active site of the enzyme. The active site alters its shape holding the substrate more tightly and straining it. 44

An enzyme-substrate complex is formed. The substrate undergoes a chemical change and a new substance, product, is formed. The product is released from the active site. The free unaltered active site is ready to receive a fresh substrate. 45

The Bean Bag Theory! The induced fit model can be compared to the way a bean bag will adapt to fit snugly around our body shape when we sit in it 46

Mechanism of Enzyme action (Induced fit model) 1.The substrate combines with the active site of the enzyme Active Site Substrate Enzyme 47

2. The active site is induced or caused to change shape slightly Active Site Substrate Enzyme 48

3. The substrate and enzyme form an enzyme substrate complex The bonds in the substrate are altered so that the substrate changes into the products Enzyme Substrate complex Substrate changed to products which are released 49

4.The products leave the active site. The active site returns to its original shape and is ready for a new substrate molecule Active Site New Substrate Enzyme Products 50

Enzyme Reaction substrate (sucrose) + enzyme (sucrase)  enzyme-substrate complex  and+ sucrase glucose fructose products +enzyme 51

Consider This Amylase is an enzyme found in saliva. It breaks starch molecules into smaller maltose molecules What is the substrate? What is the product? Will amylase break fats into fatty acids + glycerol? Why? Is this an example of a catabolic or an anabolic reaction? Why? 52

Learning Check 1.What is meant by saying that “enzymes are specific”? 2.What is meant by a substrate? 3.What is the area of the enzyme that the substrate combines with called? 4.What is meant by the Induced Fit model? 53

Learning Check 1.Can you describe how enzymes and their substrates fit together? 2.What is this model of enzyme action called? 3.Can the enzyme work on more substrate once the products have been formed? 54

The effect of pH on Enzyme action When the pH changes an enzyme's structure, the enzyme can't do its job. Changes in pH break the Hydrogen bonds that maintain an enzyme's shape. An enzyme will unravel, or denature, and become useless in a different pH. Each enzyme has an optimum pH. 55

Increasing the temperature will increase the rate of reaction of the enzyme and substrate. But too much heat can damage the bonds that hold the shape of the proteins This could lead to denaturation of the protein and thus inactivate the protein Causing a decrease in the rate of the enzyme catalysed reaction. Each enzyme has an optimum temperature. 56 The effect of Temperature on Enzyme action

Denaturation Proteins lose their 3 dimensional shape when they are 1.heated above 50 ⁰ C or 2.treated with certain chemicals or 3.radiation This means they will not be able to form the enzyme substrate complex 57

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Learning Check 1.What factors affect enzyme action? 2.What is the best temperature for (a) human enzymes and (b) plant enzymes to work at? 3.What is meant by pH? 4.What is meant by Optimum? 5.What is meant by denaturation? 59

Yeast contains the enzyme sucrase. This enzyme is immobilised by: 1.mixing yeast with sodium alginate 2.adding beads of the mixture to calcium chloride 3.filtering and rinsing the hardened beads 60

The application of an immobilised enzyme is shown by: adding sucrose solution to immobilised yeast (containing sucrase) in a separating funnel testing for the production of glucose 61

A movie on the action of Enzymes! ience/arthur/?sortby=3http:// ience/arthur/?sortby=3 emistry/ emistry/ 62

To investigate the effect of pH on catalase activity mix blended or chopped celery (catalase), hydrogen peroxide, pH buffer 4 and washing- up liquid note the volume of froth formed after 2 minutes at different pH values. 63

To investigate the effect of temperature on the rate of catalase activity: mix blended or chopped celery (catalase), hydrogen peroxide, pH buffer 9 and washing- up liquid note the volume of froth formed after 2 minutes at different temperatures 64

The effect of heat denaturation on catalase can be investigated by: boiling catalase testing if it will then form froth when it reacts with hydrogen peroxide 65

ADP (adenosine diphosphate) is a low-energy molecule; ATP (adenosine triphosphate) is an energy-rich molecule. 66

ATP is the source of energy used for most cell reactions. ADP and ATP are interconvertible, i.e. ADP + energy + P → ATP + water ATP + water→ ADP+ energy + P Phosphorylation is the addition of phosphate to a molecule. 67

NADP+ is a low-energy molecule; NADPH is a high-energy molecule. Both molecules are involved in photosynthesis. NADP+ and NADPH are interconvertible i.e. NADP+ + energy (high-energy electrons) + H+→ NADPH NADPH → NADP+ + energy (high-energy electrons) + H+ Respiration uses NAD+ (instead of NADP+) and NADH (instead of NADPH). 68

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