1. CH 2.4
Chemical Reactions &
Enzymes

2. Everything that happens in an organism – growth…movement…reproduction…
is based on
chemical reactions.

3. Chemical reactions involve changes in the
chemical bonds that join atoms in compounds.

4. … pretty
important
thing.
Breathing, for example…

5. Your cells constantly produce carbon dioxide as a normal part of their activity.
CO2 + H2O H2CO3
H2CO3 CO2 + H2O

6. Your cells constantly produce carbon dioxide as a normal part of their activity.
As it enters the blood, CO2 reacts with water to form the highly soluble
compound – carbonic acid.
CO2 + H2O H2CO3
H2CO3 CO2 + H2O

7. Your cells constantly produce carbon dioxide as a normal part of their activity.
As it enters the blood, CO2 reacts with water to form the highly soluble
compound – carbonic acid.
CO2 + H2O H2CO3
In your lungs, this reverse reaction produces CO2 gas – released when you exhale.
H2CO3 CO2 + H2O

8. Energy is released or absorbed
whenever chemical bonds
form or are broken.

9. Because chemical reactions
involve breaking & forming
bonds, they involve
changes in energy.

10. Reactions that release
energy often occur
spontaneously.

11. Reactions that absorb
energy will not occur
without an energy
source.

12. 2H2 + O H2O

14. 2H2O 2H2 + O2

15. To stay alive,
organisms must
carry out
reactions that
require energy.
Every organism
must have
a source of
energy to
carry out
chemical reactions.

16. Plants get that energy
through photosynthesis.

17. Humans get that energy by eating plants and/or animals,
then metabolizing (breaking down) that food via
chemical reactions during digestion.

18. Activation Energy: the energy needed to start a chemical reaction.

19. Activation energy is a factor
in whether the reaction
releases or absorbs energy.

20. Energy absorbed
Which is which???
Energy released

21. Some chemical reactions necessary
for life are too slow, or have very
high activation energies that
make them impractical for
living tissue.
Catalysts speed up reactions
by lowering the activation energy.

22. Enzymes are proteins
that act as biological catalysts.
Enzymes speed up the reactions
that take place in cells.

23. CO2 + H2O H2CO3 …remember this reaction?
Without the enzyme carbonic anhydrase to speed it up, CO2 would build up in your bloodstream and cause severe health issues!

25. Enzymes are affected by:
• pH
• temperature (your enzymes
work best at 98.6⁰)
Enzymes play essential roles in:
• regulation of chemical pathways
• making material needed by cells
• releasing energy
• transferring information