Transcript Chemical Reactions and Enzymes

Chemical Reactions and
Enzymes
Chemical Reactions
Chemical 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 Reactions
Reactants – 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  H2CO3
Reactants
Product
Energy in Chemical Reactions
Energy 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.
Enzymes

Enzymes 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:
1. Temperature
Each enzyme has an optimal temperature range.
At low temperatures the enzyme works slowly
At high temps they may denature (break down) and
not work correctly.
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
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
Substrate
Enzyme
Competitive inhibitor
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Type 2: Non Competitive Inhibitors
Substrate
Enzyme
Enzyme
Noncompetitive16
Inhibitor
active site
changed
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Quiz!!!
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There are 13 Questions!

It will count as a test grade
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You can only use YOUR notes.
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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 enzymesubstrate 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
The diagram below represents a process that occurs In organisms.
9. Which row in the chart indicates what 1 and 2 in the boxes
could represent?
A. A
B. B
C. C
D. D
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?