1. Chemical Reactions and Enzymes
Enzymes - Introduction

2. Why do we study chemical reactions in biology?
Chemistry isn’t just what life is made of, chemistry is also what life does
Everything that happens in an organism is based on chemical reactions (growth, response to environment, etc.)

3. What Are Chemical Reactions?
A process that changes reactants into products (the end substance in a the reaction).
Slow Reactions vs. Fast Reactions

4. What can chemical reactions do?
Chemical reactions  breaking bonds in reactants and forming bonds in products

5. What are the chemical pathways?
CATABOLIC PATHWAY (CATABOLISM) Release of energy by the breakdown of complex molecules to simpler compounds EX: digestive enzymes break down food
ANABOLIC PATHWAY (ANABOLISM) Consumes energy to build complicated molecules from simpler ones EX: linking amino acids to form proteins

6. What is THERMODYNAMICS? = the study of energy transformations
CLOSED system (EX: liquid in a thermos) = isolated from its surroundings
OPEN system energy + matter can be transferred between the system and its surroundings
Organisms are open systems

7. How does energy change?
Some reactions release energy and some absorb energy
Activation Energy: the energy required to start a reaction

8. What is the difference between endergonic & exergonic reactions?
- energy released
- digestion
energy absorbed
synthesis
+G
-G
G = change in free energy = ability to do work

9. What happens to the food we eat?
This is going to be our driving question for the explain lesson. Since we explored lactase, the students already have an example of a digestive enzyme. Once they understand enzymes in terms of digestion, they can apply what they know to other enzymes.
We think that students will probably answer these questions by saying things like it is digested or broken down. Hopefully this question will get the students to start thinking about what actually happens after they consume food.
Picture:

10. It breaks down into…. Carbohydrates Lipids Proteins Nucleic acids!
The purpose of this slide is to get students to think about the fact that foods are made up of macromolecules and that these things react.
Students should have already encountered macromolecules.
In this slide you should discuss proteins, carbohydrates, and fats. Also it would be helpful if you revisited how they are made up of smaller things and those smaller things have to react with each other.
This is a good chance for students to actively participate by raising their hands and recalling information about previous lessons.
Picture:
Carbohydrates
Proteins
Fats
Nucleic acids!

11. Let’s look at… Lactose What is lactose?
Lactose is a sugar found in dairy products
Disaccharide made up of
Galactose and glucose.
C6H12O6 + =
LACTOSE
GLUCOSE
GALACTOSE

12. What do people who are lactose-intolerant lack?
They lack an enzyme:
LACTASE
Vocabulary you should know:
Sugars end in “-ose”
Enzymes end in “-ase”
Get students to answer this question by drawing back on their common experience in the explore lesson.
“Lactase is an enzyme that breaks lactose down into galactose and glucose. Lactase can be purchased in pill form by people who are lactose intolerant.”
The explore lesson mentions that lactase is an enzyme, so they should kind of understand that.
Picture:

13. What happens if we don’t have Enzymes?
Example: Lactose – Lactase
We can’t convert it fast enough
into glucose
So it builds up..
Since our body can’t get rid of it..
We feel sick.
(nauseous, throwing up)
But…what is an enzyme?

14. What is an enzyme?
A protein that helps molecules react with one another.
It is a CATALYST!
Helps to speed up reaction
(it participates in the reaction but doesn’t change itself)
This is just an informational slide. It starts out by simply defining what an enzyme does… it helps reactions occur. The question at the end of this slide is an introduction to the concept of a catalyst, which an enzyme is. This question leads the student into the next slide. The next slide will reveal that the enzyme does not change in the reaction and go on to define enzymes as catalysts.
Picture:
A picture we took of the box of lactaid pills when we were doing the explore lesson.

15. How can we speed up reactions?
Slow reactions or reactions with high activation energies need a catalyst
Catalyst = any substance that lowers
the activation energy of a reaction
to “speed it up”
Enzymes are proteins which act like
a catalyst to speed up
reactions. (found in the
body, plants, animals,
food, etc.

16. How do catalysts work?
Catalysts lower the amount of energy that it takes to get a reaction started.
The energy it takes to get a reaction started is called activation energy.
In this slide, we explain in more detail what a catalyst actually does. The students know from the previous slide that an enzyme is a catalyst and that catalysts help reactions occur more efficiently. This slide just tells them more specifically how the catalysts and enzymes do achieve this. The term activation energy is introduced and an energy diagram is shown so that hopefully more visual students can see a representation of activation energy.
Picture:
The picture is of an energy diagram. The top (blue) line is a reaction that is not assisted by a catalyst. The bottom (red) line is a reaction that is assisted by a catalyst. The one that is assisted by a catalyst requires less energy for the reaction to occur.
YouTube

18. Reactions can occur without the help of catalysts, but not at the speed our body requires.
Mention that enzymes bring the molecules together so they are more likely to react and that without enzymes they are just bouncing around and don’t have a good chance of reacting.
DEMONSTRATION!!!! Without enzyme 
Have 2 students come up front and blindfold them.
Have the 2 students go to either side of the room.
The students have to find one another without making noise or gestures. (No help from audience!!!)
See how long it takes for them to “react”.
With enzyme 
Do this again, but then have one student un-blindfolded be in the middle of the room.
This student has to connect the other 2 students by leading them together
These students should “react” more quickly.
Observe and discuss.

19. What is so special about Enzymes?
Enzymes provide a site where reactants can be brought together to react.
In an enzyme-catalyzed reaction, the reactants are called substrates (the starting substance – found in the same place you would find the enzymes – binds to the enzyme and is than made into a product).

20. What are the parts of an Enzyme
What are the parts of an Enzyme? Each enzyme has a special place where the reaction occurs called the active site.
YouTube:
Enzyme
Emphasize that a reaction can only take place in the active site. The molecules have to go there for the reaction to take place.
Students should be getting the idea that enzymes and substrates have specific shapes. Try to get students to start thinking that way.
This is a picture that we want to burn into their heads. The idea that the enzyme has an active site and the active site is where the substrate binds and when the substrate(s) bind, the reaction can take place.
Use chair analogy…
Picture:
When a molecule needs the help of an enzyme, it goes to the active site and then the reaction takes place.

21. What is so special about the enzymes
What is so special about the enzymes? Lock and Key Hypothesis Each enzyme has a specific shape and structure that matches certain molecules That is why we say enzymes are “specific”.
Bring up “lock and key” example.
Ask the students if they have a key to their house or their car. Then ask them if they can get into their neighbor’s house with their key. They will of course say no and then you can relate that to enzymes and substrates.
Picture:

22. Where are enzymes found?
Enzymes are found in all cells
Mostly in the stomach and intestines
Enzymes - Introduction

23. Vocabulary you need to know…..
The substrates must fit exactly into the active site. This is called the lock and key model.
The active site changes shape slightly to hold the substrate – induced fit
Once the reaction is complete, the enzyme releases the products of the reaction.
Enzymes can join or break substrates into products.

24. Example: Breaking 1 Substrate into 2 Products
Enzymes can break or join substrates into products.

25. Example:Joining 2 Substrates into 1 Product
Roles of Enzymes:
1) regulating chemical pathways
2) making materials
3) releasing energy
4) transferring info

26. Digestive enzymes names match the foods they help react
Lactase helps break down lactose.
Each enzyme is specially designed to react a certain molecule
Can give other examples such as maltase breaks down maltose and sucrase breaks down sucrose.
Picture:

27. Lactase is just one enzyme that breaks down lactose but there are many different enzymes at work in your body.
This is the point where we can begin to use the example of lactase and their new knowledge about enzymes to make them understand that enzymes are used for many things in our bodies.
Picture:

28. More enzymes that break things down in your body…
Sucrose is table sugar!
Sucrase breaks down sucrose
Sucrase breaks down the sugar sucrose into glucose and fructose.
This picture compares sucrase to a “sugar-clipper”. Good example.
Picture of Sucrase:

29. AMYLASE: breaks down starch in your mouth and stomach
LIPASE: breaks down fats
Other digestive enzymes that should be discussed:
Maltase breaks down maltose
Amylase  breaks down starches into maltose and glucose
Lipase  breaks down fats into fatty acids and monoglycerides
Pepsin  MAIN GASTRIC ENZYME breaks down proteins
Picture of starch
Picture of fat
Picture of protein
PEPSIN: breaks down proteins

30. Each enzyme works best at a certain temperature and pH.
The students may have not been exposed to pH yet.
Should explain that pH is just a measure of how acidic or basic a substance is. Draw attention to the pH scale.
Explain that water’s pH is neutral at about 7.0.
Picture:

31. What keeps enzymes from doing their jobs?
Temperature can affect an enzyme by changing its shape
Talk about heat and what it can do to thing, example some things melt when they are heated. This changes the shape.
Examples can be candles, plastic next to the stove, candy bar out in the sun, and ice. (Things that change shape when they are heated up.)
Picture:

32. What can pH levels do to an Enzyme
What can pH levels do to an Enzyme? Changes in pH can also change an enzyme’s shape
Picture:
In this slide, we introduce the idea that temperature is not the only thing that can change the shape of enzymes. In the next slide we elaborate on pH and the fact that enzymes work best at certain pH and temperature.

33. What is DENATURED? When an enzyme changes its shape it can’t do its job. We say it is denatured!
May be helpful to break down the work “denatured”.
NATURE = natural
DE = not
No longer has its natural shape so it can’t do what it’s supposed to do.
Picture: Drawn in paint
ACTIVITY:
Modeling clay to show extreme environments (use modeling clay to show that extreme environments denature enzymes by moving the clay around)
Have a certain shape be the enzyme and a sphere be the substrate. Then make the active site be shaped like an oval. The sphere won’t fit.

34. What helps Enzymes work more efficiently?
What helps Enzymes work more efficiently?
COFACTORS = non-protein enzyme helpers
EX: Zinc, iron, copper
COENZYMES = organic enzyme helpers
Ex: vitamins

35. What are Enzyme Inhibitors?
COMPETITIVE inhibitor REVERSIBLE; Mimics substrate and competes with substrate for active site on enzyme

36. Competitive Inhibitor
Inhibitor & substrate “compete” for active site
penicillin blocks enzyme bacteria use to build cell walls
Overcome by increasing substrate concentration
saturate solution with substrate so it out-competes inhibitor for active site on enzyme
Ethanol is metabolized in the body by oxidation to acetaldehyde, which is in turn further oxidized to acetic acid by aldehyde oxidase enzymes. Normally, the second reaction is rapid so that acetaldehyde does not accumulate in the body.
A drug, disulfiram (Antabuse) inhibits the aldehyde oxidase which causes the accumulation of acetaldehyde with subsequent unpleasant side-effects of nausea and vomiting. This drug is sometimes used to help people overcome the drinking habit.
Methanol (wood alcohol) poisoning occurs because methanol is oxidized to formaldehyde and formic acid which attack the optic nerve causing blindness. Ethanol is given as an antidote for methanol poisoning because ethanol competitively inhibits the oxidation of methanol. Ethanol is oxidized in preference to methanol and consequently, the oxidation of methanol is slowed down so that the toxic by-products do not have a chance to accumulate.

37. What Are Enzyme Inhibitors?
NONCOMPETITIVE inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective
ENZYME ANIMATION

38. Non-Competitive Inhibitor
Inhibitor binds to site other than active site
allosteric inhibitor binds to allosteric site
causes enzyme to change shape
conformational change
active site is no longer functional binding site
keeps enzyme inactive
some anti-cancer drugs inhibit enzymes involved in DNA synthesis
stop DNA production
stop division of more cancer cells
cyanide poisoning irreversible inhibitor of Cytochrome C, an enzyme in cellular respiration
stops production of ATP
Basis of most chemotherapytreatments is enzyme inhibition. Many health disorders can be controlled, in principle, by inhibiting selected enzymes. Two examples include methotrexate and FdUMP, common anticancer drugs which inhibit enzymes involved in the synthesis of thymidine and hence DNA.
Since many enzymes contain sulfhydral (-SH), alcohol, or acid groups as part of their active sites, any chemical which can react with them acts as a noncompetitive inhibitor. Heavy metals such as silver (Ag+), mercury (Hg2+), lead ( Pb2+) have strong affinities for -SH groups.
Cyanide combines with the copper prosthetic groups of the enzyme cytochrome C oxidase, thus inhibiting respiration which causes an organism to run out of ATP (energy)
Oxalic and citric acid inhibit blood clotting by forming complexes with calcium ions necessary for the enzyme metal ion activator.

39. Every reaction in your body is helped by an enzyme
Every reaction in your body is helped by an enzyme Enzymes are the “workers” of your body.
Picture:
Lewport Enzyme Animation
Enzymes

40. Enzymes
Video

41. Factors affecting enzyme function
Substrate concentration
as  substrate =  reaction rate
more substrate = more frequently collide with enzyme
reaction rate levels off
all enzymes have active site engaged
enzyme is saturated
maximum rate of reaction
Why is it a good adaptation to organize the cell in organelles?
Sequester enzymes with their substrates!
substrate concentration
reaction rate

42. Factors affecting enzyme function
Enzyme concentration
as  enzyme =  reaction rate
more enzymes = more frequently collide with substrate
reaction rate levels off
substrate becomes limiting factor
not all enzyme molecules can find substrate
Why is it a good adaptation to organize the cell in organelles?
Sequester enzymes with their substrates!
enzyme concentration
reaction rate

43. pH pepsin trypsin reaction rate pH 1 2 3 4 5 6 7 8 9 10 11 12 13 14
What’s happening here?!
pepsin
trypsin
pepsin
reaction rate
trypsin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH

44. TEMPERATURE & ENZYME ACTIVITY
Each enzyme has an optimal temperature at which it can function (Usually near body temp)
Optimum T°
greatest number of molecular collisions
human enzymes = 35°- 40°C
body temp = 37°C
Heat: increase beyond optimum T°
denaturation = lose 3D shape (3° structure)
Cold: decrease T°
molecules move slower

45. Pennyase Activity Pennyase Activity Introduction:
Enzymes are proteins made by living cells. They act as catalysts and affect the rate of a chemical reaction. For example, the enzyme amylase in your saliva speeds up the breakdown down of starch (the substrate) into simple sugars. The enzyme itself does not get used up during the chemical reaction.
Objective:
In this activity you will become the enzyme called "pennyase", that picks up and turns pennies over (the substrate) in timed intervals. Calculations will be completed to determine how many pennies are turned over per second to determine the rate of reaction of the enzyme pennyase. Consider that your hands are like an enzyme called pennyase. Your hands (the enzyme) can turn over the pennies (your substrate).

46. ChainObead Polymerase Lab
Get into groups of two (person sitting next to you)
Assign who will be the timer/recorder and who will be the enzyme
You will be given a timer, beads, and possibly an inhibitor
When Timer says go, the enzyme will have 15 seconds to connect as many beads into a single chain as possible
record the time and amount of beads connected on a half sheet of paper.
Dissemble the chain
Repeat steps 4 and 6 but use 30 seconds and then 45 seconds
NOW…tape your finger and thumb together (this represents an increase/decrease in temperature or pH levels) and repeat steps 4-7