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An Introduction to Metabolism and Enzymes

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1 An Introduction to Metabolism and Enzymes
Substate Active site Enzyme

2 Metabolism Is the totality of an organism’s chemical reactions

3 Catalase

4 Activation energy-barrier to reaction

5 Activation energy

6 Mechanism of enzyme reaction
The substrate is the reactant an enzyme acts on The enzyme binds to its substrate, forming an enzyme-substrate complex

7 The catalytic cycle of an enzyme
Substrates Products Enzyme Enzyme-substrate complex 1 Substrates enter active site; enzyme changes shape so its active site embraces the substrates (induced fit). 2 Substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds. 3 Active site (and R groups of its amino acids) can lower EA and speed up a reaction by • acting as a template for substrate orientation, • stressing the substrates and stabilizing the transition state, • providing a favorable microenvironment, • participating directly in the catalytic reaction. 4 Substrates are Converted into Products. 5 Products are Released. 6 Active site Is available for two new substrate Mole.

8 The active site can lower an EA
The active site can lower an EA barrier by Orienting substrates correctly Straining substrate bonds Providing a favorable microenvironment Covalently bonding to the substrate

9 Reaction pathway

10 3D / tertiary structure of an enzyme

11 Binding sites of an enzyme

12 Specificity-lock and key hypothesis

13 Induced Fit model of enzyme action

14 Induced fit hypothesis
Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction

15 Effect of Enzyme concentration

16 Effect of Substrate concentration

17 Effect of temperature

18 Effects of Temperature
Each enzyme Has an optimal temperature in which it can function Optimal temperature for enzyme of thermophilic Rate of reaction 20 40 80 100 Temperature (Cº) (a) Optimal temperature for two enzymes typical human enzyme (heat-tolerant) bacteria

19 Optimal pH for different enzymes
Rate of reaction (b) Optimal pH for two enzymes Optimal pH for pepsin (stomach enzyme) Optimal pH for trypsin (intestinal enzyme) 1 2 3 4 5 6 7 8 9

20 Effect of pH on enzyme

21 Cofactors -- enzyme helpers
Are nonprotein enzyme helpers—can be either inorganic or organic Coenzymes Are organic cofactors

22 Co-enzyme e.g. NAD+ NAD+ helps by accepting H removed from substrates by the enzyme dehydrogenase

23 Denaturation and renaturation of enzyme

24 Denaturation and renaturation of enzyme

25 Enzyme Inhibitor_types

26 Competitive inhibition

27 Competitive inhibition

28 Competitive inhibition–e.g. sulphonamide

29 Non competitive inhibition

30 Com vs non comp inhibition

31 End product inhibition –helps regulate enzyme activities

32 End product inhibition

33 End product_cellular respiration

34 Allosteric activator

35 Allosteric inhibitor

36 Allosteric regulation
Is the term used to describe any case in which a protein’s function at one site is affected by binding of a regulatory molecule at another site

37 Specific Localization of Enzymes
Within the cell, enzymes may be Grouped into complexes Incorporated into membranes Contained inside organelles 1 µm Mitochondria, sites of cellular respiraion Figure 8.22

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40 Bacteria in Hot springs

41 Enzyme application_thermophilic


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