Chemical Reactions and Enzymes

Chemical ReactionsChemical Reaction – the process that changes one set of chemicals into another.

Chemical reactions involve the breaking of bonds in the reactants and the formation of new bonds in the products

CO2 + H2O → H2CO3

Carbon dioxide and water form carbonic acid

Chemical ReactionsReactants – elements or

compounds that you start with, found on the left hand side of the reaction arrow.

Products – elements or compounds produced from the reactants, found on the right hand side of the reaction arrow.

CO2 + H2O H2CO3Reactants Product

Energy in Chemical ReactionsEnergy can be released or absorbed in

chemical reactions.Most chemical reactions require some

initial input of energy in order to start the reaction; this is called the activation energy.

Catalysts

A catalyst speeds up the rate of a reaction by lowering the amount of activation energy needed to start the reaction.

EnzymesEnzymes are PROTEINS that act as

biological catalysts. They speed up reactions in cells.

Enzyme-Substrate Complex

Enzymes provide a site for the reactants (substrates) to react. This site is called the activation site.

The activation site and the substrate have complementary shapes, similar to a lock & key.

Enzyme-Substrate Complex

A lock will only accept one key just as an enzyme will only accept a specific substrate.

After the substrates have bound to the activation site the substrates will react with one another.

Once the reaction is complete then the products are released and the enzyme is free to bind additional reactants (substrates).

Enzyme-Substrate Complex

If the substrates do not fit in the activation site then the reaction will not take place.

Each enzyme is very specific. There are usually only 1 or two molecules that will the active sites exactly.

Rate of Enzyme Activity

There are factors that can affect an enzyme:

At low temperatures the enzyme works slowly

At high temps they may denature (break down) and not work correctly.

1. TemperatureEach enzyme has an optimal temperature range.

Rate of Enzyme Activity

2. pH There is an optimal pH for every enzyme

to function at. (usually at 7, neutral pH)

Many enzymes become denatured at low pH levels (when acid is present).

However some enzymes, like those that work in the stomach, function very well in acidic environments

Rate of Enzyme Activity

3. Concentration of Substrate or Enzyme

• The more substrate available, the faster the reaction tends to go

• The more enzyme that is available, the faster the reaction tends to go

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4.Cofactors and Coenzymes

Help Enzymes work faster (like some minerals and

vitamins)

Example:Iron must be present in blood in order for it to pick up oxygen.

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5. Inhibitors

Stop enzymes from doing their jobs

Two types

1. Competitive inhibitors: look like the substrate and block the active site

2. Noncompetitive inhibitors: bind to the enzyme causing its shape to change, changing the active site.

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Type 1: Competitive Inhibitors

Stop enzymes from doing their jobs.

Two types◦ Competitive inhibitors:

look like the substrate and block the active site Enzyme

Competitive inhibitor

Substrate

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16

Enzyme

active site changed

NoncompetitiveInhibitorSubstrate

Enzyme

Type 2: Non Competitive Inhibitors

Quiz!!!There are 13 Questions!

It will count as a test grade

You can only use YOUR notes.

Name_______________________________________ pd.________

1.___2.___3.___4.___

5.___6.___7.___8.___

9. ___10.___11.___

12. ________________________________________________

13. ________________________________________________

1.In 1953 Stanley Miller and Harold Urey designed

and experiment to test the Primordial Soup Theory.

What were Miller and Urey able to produce in their

experiment.

A. Oxygen for heterotrophic organisms to

survive

B. Single celled organisms

C. Photosynthetic bacteria

D. Organic molecules out of inorganic material

2. What is a cell membrane mainly composed of?

 

A. Lipids

B. Nucleic acids

C. Carbohydrates

D. Proteins

3. The graph above shows the reaction rates of two different

reactions. Which of the following statements could explain

the difference in the two reactions?

A. Reaction A is catalyzed by an enzyme

B. Reaction B is catalyzed by an enzyme

C. Reaction A occurs at a faster rate than Reaction B

D. Reaction A and reaction B have the same reaction

rate

4. Enzymes catalyze chemical reactions that keep cells

alive. Imagine that a cell had no enzymes. How would

having no enzymes affect the chemical reactions in the

cell?

A.They would happen too slowly to support cellular

processes

B.They would happen too rapidly to support cellular

processes

C.They would happen at the same rate as they do with

enzymes

D.They would happen normally, only they use different

reactants

5. Which statement best describes the specificity

of the enzyme for the substrate in a chemical

reaction?

A.The suffix –ase is used to identify the specific enzyme- substrate pairing.

B.The bonding sites of enzymes to substrates fit like pieces in a jigsaw puzzle.

C.Cells use enzymes to manage cell metabolism.

D.Enzymes created during protein synthesis.

6. What are the monomers that make up complex

carbohydrates?

 

A. Amino acids

B. Fatty acids

C. Monosaccharides

D. Nucleotides

7. Diagram above shows how living organisms use enzymes in

chemical reactions to release energy. How do enzymes affect the

reactions in which they take part?

A. Most enzymes slow down chemical reactions

B. Enzymes are converted into products in the reaction

C. Enzymes increase the activation energy of reaction

D. Enzymes decrease the activation energy of the reaction

8. The diagram above is a model of a cellular process called

transcription. What class of biological molecules is represented

in the diagram?

A. Carbohydrates

B. Nucleic acids

C. Lipids

D. Proteins

9. Which row in the chart indicates what 1 and 2 in the boxes could represent?

A. AB. BC. CD. D

The diagram below represents a process that occurs In organisms.

10. Many of the proteins in the human body are enzymes that catalyze

chemical reactions. What is the relationship between enzymes and

activation energy?

A. When an enzyme catalyzes a reaction, it increases the activation energy of the reaction.

B. When an enzyme catalyzes a reaction, it increases the activation energy of the product.

C. When an enzyme catalyzes a reaction, it decreases the activation energy of the reaction.

D. When an enzyme catalyzes a reaction, it does not affect the activation energy of the reaction

The sweet taste of freshly picked corn is due to the high sugar content in the kernels. Enzyme action converts about 50% of the sugar to starch within one day after picking. To preserve its sweetness, the freshly picked corn is immersed in boiling water for a few minutes, and then cooled.

11. Which statement most likely explains why the boiled corn kernels remain sweet?

A. Boiling destroys sugar molecules so they cannot be converted to starch.

B. Boiling kills a fungus on the corn that is needed to convert sugar to starch.

C. Boiling activates the enzyme that converts amino acids to sugar.

D. Boiling deactivates the enzyme responsible for converting sugar to starch.

12. How does the presence of an enzyme affect the rate of a chemical reaction?

13. What 3 things can affect the rate at which an enzyme works?