How Would You Make A Cake?

Objectives

• Identify where living things get energy.

• Understand how chemical reactions occur.

• Identify why enzymes are important to living things.

Vocabulary

• Energy• Reactant• Product• Activation Energy• Enzyme• Active State• Substrate

• Living things are made of matter, which consists of a substance with a form.

• In the case of the living, this form is always changing.

• A constant in the natural world is that changes constantly occur.– Development

– Seasons

– Metabolism

– Etc.

Changing Matter

Changes

• Change usually comes in two forms:

• Physical: change occurs when only the form or shape of the matter changes (it looks different).

• Chemical: change occurs when a substance changes into a different substance (the molecules & atoms change).

What types of change happened here?

A

B

Energy

• The necessary ingredient of change is energy.

• Energy is the ability to move or change matter.

• Energy exists in many forms and can be converted from one form to another.

• Every change in matter requires a change in energy.

Forms of Energy

• Kinetic (Thermal Heat): • Energy of motion

• Potential: • Energy that can be used at a

later time.• Mechanical:

• Energy transferred in machines• Electro-magnetic:

• Electrons transferring energy• Nuclear:

• Energy stored in the nucleus of atoms

• Sound: • Energy in waves

• Chemical: • Energy stored in bonds

Changing Matter– Where does this energy come from?...– From heat…from the sun, the Earth’s core, or some

other produced source (fires, etc.)– Or from bonds being broken…such as when food is

broken down.

Chemical Reactions

• Changing a substance requires a chemical reaction. During this process, bonds between atoms are broken, and new ones are formed.– The bonds are usually through C to C bonds or P to P

• There are two parts of a reaction• A reactant (aka substrate) is a substance that is changed

in a chemical reaction– It’s all the stuff that you start with that mixes and mingles together.

• A product is a new substance that is formed.– This is the stuff that you end up with after the mingling.

Reactants to Products

Reactants

Products

Reaction

Reactants to Products

• You will see several reactions in this course.• They are written in the same form:• Reactants Products• The arrow means “changes to” or “forms”• Sometimes the arrow only goes one way (like from

ingredients to cake) and sometimes the arrow goes both ways.

• When the arrow goes both directions it shows you that the reactants and products can switch positions… that the reaction can go both ways.

Building & Breaking

• The often see cycle of energy being stored and released.

• We need to eat because we lose a little with every reaction to entropy, heat lost to the universe that can’t be recovered.

Concept Check

• What are the two parts of a reaction and what are they called?

• Reactants & Products• How do you show a reaction on paper?• Reactants Products

Activation Energy

Activation Energy• Going through a reaction, or going from reactants to

products, can only occur under the right conditions.

• The right conditions to start a reaction involve overcoming the natural repulsion between their negatively charged electron clouds.

• Remember, like charges repel.• The activation energy of a reaction is the minimum

kinetic energy required to start a chemical reaction.

Reaction with the correct activation

energy

Activation Energy: Energy of Matter

• One of the universal laws, stated by Sir Isaac Newton thousands of years ago, was that objects in motion stay in motion…

• Think of activation energy like motivation.• When you are motivated to get off the couch and start

chores or work out it’s like molecules getting the energy to react with each other…

• The energy for reactions comes from temperature or how much movement the molecules have…its kinetics.– Sometimes this happens with stirring… = physical– Sometimes this happens with heating… = thermal

Activation Energy: Alignment

Alignment• Sometimes, even if enough energy is available,

the product still may not form.

• When the reactant particles collide, the correct atoms must be brought close together in the proper orientation.– Orientation means the correct parts of the molecules

must meet up.

Activation Energy: Summation

The point is…Chemical reactions can only occur when the activation energy is available and the correct atoms are aligned.

Activation Energy

Biological Reactions… Enzymes

Enzymes• An enzyme is a protein that increases the speed of

biochemical reactions.– Enzymes hold molecules close together and in the correct

orientation. – As such, an enzyme lowers the activation energy of a reaction.– By assisting in necessary biochemical reactions, enzymes help

organisms maintain homeostasis.

• In Essence: Enzymes help reactions happen that may not normally happen or may take too long to happen unaided.

Effect of Enzyme on Activation Energy

Chemistry of Life Section 4

Endergonic = “energy in”

Exergonic = “energy out”

Enzymes

Enzymes• Each enzyme has an active site, the region where the

reaction takes place.

• The shape of the active site determines which reactants, or substrates, will bind to it. Each different enzyme acts only on specific substrates.

• Binding of the substrates causes the enzyme’s shape to change. This change causes some bonds in the substrates to break and new bonds to form.

Enzyme Action

Click to animate the image.

Enzyme Action

Reactant A Reactant B

Enzyme

Right OrientationProduct AB

Wrong Orientation =

NO REACTION

EnzymesEnzymes

• Many enzymes are proteins.

• One problem with proteins is that they change with temperature.

• Changes in temperature and pH can change a protein’s shape.

• Ever cook an egg?

• If an enzyme changes shape, it won’t work well.

• Most enzymes need a certain range of temperatures and pH.

– What important property of life ensures this?

– Homeostasis

– What molecule help us maintain this in our bodies?

Enzymes & MetabolismMetabolism• Cells get most of the energy needed for metabolism by

breaking down food molecules.– What is metabolism again?

– Sum of all chemical reactions in an organism.• The release of energy from food molecules occurs in a

series of reactions using many enzymes to capture energy in the form of ATP molecules. – ATP is what?– The energy transporter in the body.

• The enzymes reduce the activation energy so much that only a little energy is needed to start the reactions. In this process, very little energy is lost as heat.

Concept Check

• What is Activation Energy?• The energy necessary to

start a reaction.

• How are enzymes useful?• They lower activation

energy to allow chemical reactions to occur.

• Where is the active site?• Where are the reactants?

A

B

C

Case Study• Some people cannot digest certain foods. For example, diabetics cannot

digest sugars properly and those that are lactose-intolerant cannot digest milk. Science has been working tirelessly to help solve these problems but one can’t be too sure if the drug companies are honest.

• A certain company claims that their drug will help you digest carbohydrates better (like those to combat lactose-intolerance).

• You suspect the active ingredient in the product is an enzyme…lactase.• In an attempt to prove the product’s claim you perform an experiment.

Digestive Enzyme

Your experiment involves 3 individuals; 1 individual with lactose intolerance and consuming milk, 1 person with normal lactose tolerance consuming milk, and 1 lactose intolerant individual consuming milk & the enzyme. You need to analyze the results.

Chemical ReactionsAnalyze the illustration of experimental data that tests whether a digestive enzyme supplement works.In-class: Answer these questions.

1. What do the curved arrows represent?2. What does the dotted line represent?3. What part of a reaction is A?4. What are B & C?5. Describe which reaction is which?6. How do the 2nd and 3rd reactions differ?7. Which reaction (2 or 3) would you think uses an enzyme?8. What does the enzyme do?9. Which reaction gives off heat to the environment? (remember conservation

of energy)

Sick/Intolerant

Healthy/Tolerant

1. The curved lines represent reactions over time. 2. The difference between taking or giving heat in the reaction, but the line represents time.

3. A: Reactant 4. B & C: Products

5. AC in lactose intolerant, AB is digesting lactose, 3 is with the enzyme

6. 3 has less activation energy.

7. Reaction 3 uses the enzyme because of the lowered activation energy.

8. Lowers the activation energy and can speed up reactions.

9. Reactions AB (2 & 3). 10. This reaction shows how lactose can be digested in those lactose intolerant. C is the control.

1.What do the curved arrows represent? 2. What does the dotted line represent?

3. What part of a reaction is A? 4. What are B & C?

7. Which reaction (2 or 3) would you think uses an enzyme?

9. Which reaction gives off heat to the environment?

10. Explain what this experiment did. What is ‘C’?

5. Describe which reaction is which.

8. What does the enzyme do?

6. How do the 2nd and 3rd reactions differ?

Chapter 3 Review: Answers3. (Reactant = substrate) product 4. Cohesion = attraction between like particles.

Adhesion = attraction between different particles

5. Nucleic acids are made of nucleotides 6. D

7. D 8. B 9. C 10. A

11. B 12. C 13. D 14. B

15. Forming compounds can make atoms more stable b/c an atom is more stable when the valence shell is filled.

16. Adhesion and cohesion are responsible for water being able to climb up a plant stem.

17. Simple carbs have 1-2 sugar, complex have more than 2

18. Waxes are waterproof and can form protective coatings

19. Physical changes the way something looks, chemical changes the substance

20.In order for a reaction to occur, molecules must both be in the correct orientation and overcome the repulsion of like particles.

21. pH 3 22. The stomach is more acidic then the intestines.

23. There are only one type of atom in any single element.

24. They are more stable when they are covalently bonded together. They are molecules but not compounds b/c there is only one element

25. Ionic bonds are between ions that swap electrons where covalent is between atoms that share them.

26. The freezing point is dependent upon the H-bonds in water. Ions of salt disrupt them and the freezing point of water.

27. Balanced diets give you enough of the essential materials for life.

Identifying an Enzyme, Word Usage

• Breaking a word down• In science, one can easily be confused in trying

to find out what a molecule is or what it does• Luckily scientists are smart people and

developed patterns to be able to identify the type of word you are reading and what it may do.

• Remember:– -ose = sugar (Lactose, glucose), – -ol, -oid = lipid (cholesterol, glycerol)

Biological Reactions, continued

• Enzymes:• An easy way to tell if a molecule is an enzyme is

by the suffix.– Suffix is the word ending

• Enzymes start with what they do and usually end in –ase– Protease: Breaks down proteins– Lactase: Breaks down lactose to glucose & galactose– Lipase: Breaks down _____?

Summary

• Living things use different chemical reactions to get the energy needed for life processes.

• An activation energy is needed to start a chemical reaction. The reactants must also be aligned to form the product.

• By assisting in necessary biochemical reactions, enzymes help organisms maintain homeostasis.