ENZYMES http://www.kscience.co.uk/animations/model.swf http://www.kscience.co.uk/animations/ectopeptidase.swf http://www.kscience.co.uk/animations/enzyme.swf http://www.youtube.com/watch?v=XTUm-75-PL4

Figure 6.7 Enzymes Accelerate Chemical Reactions How is lactose split into glucose and galactose? Without an enzyme, the amount of energy necessary to activate this reaction is high. In the presence of the enzyme lactase, however, a low activation energy is sufficient to get the process started. The energy released from the splitting of lactose is the same in both cases.

Figure 6.7 Enzymes Accelerate Chemical Reactions How is lactose split into glucose and galactose? Without an enzyme, the amount of energy necessary to activate this reaction is high. In the presence of the enzyme lactase, however, a low activation energy is sufficient to get the process started. The energy released from the splitting of lactose is the same in both cases.

In all metabolic activities of our body and cells, lots of small molecules called ENZYMES work. If we destroy enzymes in the body, all reactions will slow down and stop. Because enzymes reduce activation energy of the reactions. The minimum amount of energy that is needed to start the reaction is called ‘ ACTIVATION ENERGY ’

Substance which is used to decrease the activation energy of a reaction is called ‘ CATALYSTS ’ . Enzyme is a catalyst which is found in living organisms ; It REDUCES the activation energy and makes reaction FAST and EASY

Usually they are named as: Heat can also decrease activation energy, but in cells heat can harm/denature molecules, so instead of heat enzymes speed up reactions. Usually they are named as: Enzyme that breaks down sucrose : SUCRASE Enzyme that breaks down lipid : LIPASE Sometimes they have special names . For example : The enzyme that breaks down starch is called amylase. -ase

STRUCTURE OF ENZYMES Enzymes are PROTEINS. Enzyme synthesis is controlled by DNA (genes) But in most enzymes protein part joins with other molecules. (SIMPLE AND COMPLEX ENZYMES)

COFACTOR( mineral ) Activated enzyme APOENZYME + or ( HOLOENZYME ) COENZYME( vitamin ) 1. Enzymes acts on their SUBSTRATES. A SUBSTRATE is the molecule that is affected by enzymes. Enzyme+Substrate→ Enzyme-Substrate Complex → Enzyme + Products

c. b. a. d. f. e. substrate Active site Apoenzyme Enzyme-subtrate complex d. Products f. Enzyme-subtrate complex e. 9

1. Each enzyme has a specific substrate . Properties of enzymes: 1. Each enzyme has a specific substrate . 2. The site that binds to substrate is called as ACTIVE SITE . The relation between an enzyme and its substrate is called LOCK AND KEY MODEL 3. The enzyme isn’t SPENT during reaction(only used), So it can be used MANY TIMES. (never changed)

4. Reactions of Enzymes are Reversible.(not digestive ones) Starch+ amylase enzyme glucose+ enzyme 5. Enzymes can’t work unless being water less than %15 6. Enzymes can work as a team. (ex.in digestion) 7. Enzymes are produced inside the cell but they can work inside OR outside of the cell. 8.Enzymes start their action from the outer surface of the substrate.

The factors that affect enzyme activity 1.TEMPERATURE : At lower temperature ;the reactions slows down or stops but as the temperature increases the rate of the reaction increases until optimum. But denatures after 60 C.

2.pH : Each enzyme works best at a certain pH ,that is called optimum pH. ( Ex: Optimum pH=2 in the stomach for digestion ) Enzymes are (denatured) broken down above or below the optimal pH. 1 2 3

3. WATER Enzymes can’t work unless being water less than %15. Ex : Dry plant seeds can’t germinate

4.CONCENTRATION OF ENZYME Increasing the enzyme concentration increases the rate of reaction. But after all substrate molecules are used and no change will be in the rate of reaction

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5.CONCENTRATION OF SUBSTRATE If we increase the concentration of substrate, the rate of the reaction increases. But after all enzyme molecules are full, they can not change the rate of reaction.

6. SURFACE AREA OF THE SUBSTRATE increasing the surface area of substrate,increases the activity of enzymes Substrate surface

For example ; if we cut meat into pieces to make the surface bigger For example ; if we cut meat into pieces to make the surface bigger. Minced meat is digested easier than a piece of meat. Enzyme activity

6.INHIBITORS Some chemicals like Mercury (Hg) slows or completely stops the activity of enzymes . These molecules are inhibitors . Reaction rate Enzyme Enzyme+ inhibitor

7.ACTIVATORS Some chemicals increase the activity of enzyme and they are called activators Rate of the reaction With Activator Without activator

  I K + M N + O + M II By looking at the reaction above, answer the questions. a. What kind of a reaction is I and II ? b. Which of them is the enzyme?WHY? c. Which of them is the product and substrate?

H202 H202 H202 Fresh liver Liver grounded Liver boiled pieces in mortar in water 2 ml of H202 solution is placed in each tube. Fresh , grounded and boiled liver are placed in the tubes as shown in the figure. a. Write the reaction of equation? b. Write the correct order of reaction rates from the fastest to the slowest ? Explain the reasons H202 H202 H202

Enzyme 1 Enzyme 2 Enzyme 3 X Y Z M As you see in the above reaction, some chemical reactions can ocur in chains. They follow each other. What is the advantage of this working together? Reactions can be reversible(occur in BOTH ways) Activation energy is lowered Reaction speeds up Types of products increases Amount of substrate used is reduced. (decreases)