1. IB Biology HL 1 Mrs. Peters Fall 2014
2.5 & 8.1 Enzymes
IB Biology HL 1
Mrs. Peters
Fall 2014

2. 2.5 Enzymes
All enzymes are proteins with characteristic three dimensional shape
Found in all living cells
Thousands of enzymes are produced by cells

3. 2.5 Enzymes Shape determines the function of the enzyme
Enzymes will work until shape is changed and can’t function any longer

4. 2.5 U1. Enzymes The Parts of the Enzyme-Substrate Complex
Enzyme: globular protein that conducts specific reaction
Substrate: substances the enzyme converts into a product

5. 2.5 U1. Enzymes The Parts of the Enzyme-Substrate Complex
Active site: site on the enzyme where the substrate attaches
Shape and chemical properties of the active site and the substrate must match each other

6. 2.5 U1. Enzymes The active site fits a specific substrate.
Substrate bonds to the active site and are converted into a product, then product released

7. 2.5 U1. Enzymes
Draw the enzyme-substrate complex, yellow only!

8. 2.5 U1 Enzyme Specificity
Enzyme Specificity: each enzyme fits only 1 substrate.

9. 2.5 U1 Enzyme Specificity Lock and Key Model
Enzyme is like the lock, substrate is like the key…only one key fits the lock

10. 2.5 U1 Enzyme Specificity Induced Fit
A substrate enters the active site, inducing the enzyme to change its shape slightly, so the active site fits the substrate more snuggly
Ex: like a clasping handshake

11. 8.1 U2. Enzymes
Biological catalysts that lower the activation energy of a reaction which speeds up the rate of a reaction such as digestion or respiration.

12. 8.1 U2. Enzymes
Enzymes reduce the amount of energy required to make the reaction take place; lower the activation energy

13. 8.1 U2. Enzymes
DRAW THIS DIAGRAM!

14. 8.1 U2. Activation Energy
Activation Energy: the input of energy required for any reaction to start

15. 8.1 U2. Activation Energy
Enzymes function to lower the activation energy of a specific reaction
The amount of energy required to start the reaction is reduced because the enzyme is doing the reaction.

16. 2.5 U2. Enzyme Activity
Most reactions take place in solution, dissolved substances in water
Each particle moves separately
Direction of the movement is random and constantly changes

17. 2.5 U2. Enzyme Activity
Substrates are smaller and move faster than enzymes.
Substrates collide with enzymes
When the collision is correctly aligned, substrate will attach to the active site.

18. 2.5 U2. Enzyme Activity
Substrate attaches to enzyme active site by weak bonds (hydrogen and ionic)
Enzyme completes the reaction, converting substrate to product

19. 2.5 U2. Enzyme Activity 3. Product leaves the active site
4. Enzyme takes up the next substrate in the active site, repeating cycle.

20. 8.1 U1 Enzymes & Metabolic Pathways
Metabolism
Huge range of chemical reactions that take place in living cells
Most chemical changes happen in a sequence of small steps which form a metabolic pathway

21. 8.1 U1 Enzymes & Metabolic Pathways
A chain or cycle of reactions
Several enzymes are used to complete a pathway
The product of each enzyme is the substrate for the next enzyme until the final product is produced.

22. 8.1 U1 Enzymes & Metabolic Pathways
Draw this diagram

23. 2.5 U3. Enzyme Activity and Substrate Concentration
Enzyme activity is directly affected by substrate concentration
Amount of substrate present at the time of the reaction
Enzymes can only make as much product as there is substrate available

24. 2.5 U3. Enzyme Activity and Substrate Concentration
Enzymes will continue to work until all substrate is used up
Adding additional substrate will produce more product

25. 2.5 U3. Enzyme Activity and Substrate Concentration
Reaction Rate:
When substrate concentration is increased, more collisions are possible, reaction rate increases
DRAW THIS DIAGRAM!

26. 2.5 U3. Enzyme Activity and Substrate Concentration
Reaction Rate:
As active sites fill with substrate, the rate of reaction increases, increasing the amount of product produced
DRAW THIS DIAGRAM!

27. 2.5 U3. Enzyme Activity and Substrate Concentration
Reaction Rate:
When all active sites are full and there are no more available sites, the reaction will continue at a stable rate producing products
DRAW THIS DIAGRAM!

28. 2.5 U3. Enzyme Activity and pH
Enzyme activity affected by pH
All enzymes have an optimum pH at which most active (work the most efficiently)
Draw this diagram!

29. 2.5 U3. Enzyme Activity and pH
Enzyme activity affected by pH
pH range for enzyme activity is relatively small, won’t work outside that range
reaction will increase to a point before being disrupted
Draw this diagram!

30. 2.5 U3. Enzyme Activity and pH
Enzyme activity affected by pH
changes in environmental pH will cause denaturation
Draw this diagram!

31. 2.5 U3. Enzyme Activity and Temp.
Enzyme activity affected by temperature
All enzymes have an optimum temperature at which most active
If temperature increases, reaction will increase to a point before being disrupted
Draw this diagram!

32. 2.5 U3. Enzyme Activity and Temp.
Enzyme activity affected by temperature
Significant increased temperature causes denaturation
Enzyme won’t function after denaturation
Draw this diagram!

33. 2.5 U4 Denaturation
Denaturation is a structural change in a protein that results in the loss (usually permanently) of its biological properties.

34. 2.5 U4 Denaturation
Enzymes can be denatured by changes in temperature and pH.
Original environment is changed in some way
Placed in environments that are outside their optimum range
Temperature usually has to be hotter than it’s optimum range, if it is colder, the enzyme will work slowly or not at all, but won’t be effected permanently

35. 2.5 U4 Denaturation Denatured Enzymes:
The active site is altered in some way and the substrate can not bind
If substrate binds, the reaction does not occur
usually become insoluable

36. 8.1 U3 Enzyme Inhibitors
Inhibitors: molecules which selectively disrupt the action of enzymes
Two types: competitive and non-competitive

37. 8.1 U3 Enzyme Inhibitors Inhibitor Types
Competitive: a molecule similar in shape to the substrate that competes with substrate for active site, blocks substrate from attaching to the active site, temporarily shutting down the enzyme

38. 8.1 U3 Enzyme Inhibitors Inhibitor Types
Non-competitive: a molecule that binds to a location separate from active site (the allosteric site), changing shape of enzyme, blocking the substrate from attaching to the active site, temporarily shutting down the enzyme

39. 8.1 U3. Enzyme Inhibitors Comparison
Competitive
Structurally similar to the substrate molecule
Occupies and blocks the active site, lowering the rate of the reaction
If inhibitor concentration is low, increasing the substrate concentration will reduce the inhibition
Noncompetitive
Structurally unlike the substrate molecule
Binds to allosteric site away from the active site, changing the shape of the active site, lowering the rate of the reaction
If inhibitor concentration is low, increasing the amount of substrate has no effect, enzyme stays inhibited

40. 8.1 U4 Enzyme Inhibition
End-Product Inhibition: the end product of a metabolic pathway reaction acts as an inhibitor of an enzyme earlier in the pathway (usually the first enzyme) causing the pathway to stop producing product

41. 8.1 A1 End Product Inhibition Example
Pathway converting amino acid threonine to isoleucine
Start with threonine (substrate 1) and threonine deaminase (enzyme 1)
5 enzyme reactions later isoleucine is produced (end product)

42. 8.1 A1 End Product Inhibition Example
As Isoleucine concentration builds, it binds to the allosteric site of the first enzyme (threonine deaminase) in the pathway
Isoleucine acts as a non-competitive inhibitor

43. 8.1 S1. Inhibition Graphs
Must be able to identify different types of inhibition from graphs.
Rate of Reaction
Substrate concentration
Alevelnotes.com

44. 8.1 S1. Inhibition Graphs Competitive is slightly lower than normal
Non-competitive is significantly lower than normal
Rate of Reaction
Substrate concentration

45. 2.5 U5. Immobilized Enzymes - History
1897 Hans and Eduard Buchner used an extract of yeast, which contained no yeast cells, to convert sucrose to alcohol
This provided additional evidence against the theory of vitalism
Enzymes can be used outside the cell

46. 2.5 U5. Immobilized Enzymes
Over 500 enzymes are used for commercial uses

47. 2.5 U5. Immobilized Enzymes
Enzymes are usually immobilized, (attached to another material)
Attached to glass
Trapped in a gel
Bonded together to form aggregates

48. 2.5 U5. Immobilized Enzymes Advantages:
Enzyme is easily separated from product, stopping the reaction at the ideal time
Enzymes can be recycled, saving costs (enzyme use is expensive)

49. 2.5 U5. Immobilized Enzymes Advantages:
Increases stability of enzyme to changes in temp and pH
Substrate exposed to higher conc. of enzymes, speeding up reaction rate

50. 2.5 A1. Production of Lactose-free milk
Lactose is the sugar in milk
Can be converted into glucose and galactose by the lactase enzyme.
Lactase is extracted from Kluveromyces lactis, a yeast that grows naturally in milk.
Biotech companies culture the yeast, extract and purify the lactase for sale to food manufacturers.

51. 2.5 A1. Production of Lactose-free milk
Advantages of Lactose-free milk
Lactose intolerant people can drink milk to get its benefits without the trouble of digesting lactose
Galactose and glucose are sweeter than lactose, less sugar needs to be added to foods that contain milk

52. 2.5 A1. Production of Lactose-free milk
Advantages of Lactose-free milk
Lactose crystallizes during ice cream production creating a gritty texture, glucose and galactose are more soluble creating a smooth texture
Bacteria ferment glucose and galactose more quickly producing yogurt and cottage cheese more quickly

53. Enzyme Practice Questions
With a partner, write the answer first without notes!
Explain how competitive and non-competitive inhibition can include allostery.
Explain how the concentration of substrate and competitive inhibitors can effect enzyme reactions.
Describe how lock and key and induced fit explain enzyme specificity.
Now, go back and use your notes, a new color writing utensil, and Mrs. Peters to fill in more information for each answer.