pH_ edited

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Reminders
• Biospheres! Week 5
Question of the Day
Question: How are acids and bases different?
Take your best guess!
Answer: … … …
pH
#10.
• pH scalemeasure of H+
ions (acidity);
“power of
hydrogen”
H + = hydronium ion
OH- = hydroxide ion
pH
#11.
• acid- lots of H+
ions
– taste sour
– feel watery
pH
#12.
• base- lots of
OH- ions
– taste bitter
– feel slippery
pH
• neutral- equal
amounts of H+
and OH- ions
– Ex: water
#13.
• neutralizecombining an
acid and a base
to form water
pH
#14.
• buffer- any substance that resists a change in
pH
– Many life biological reactions have a small pH
range
– Example: blood (pH 7.35 – 7.45)
#15.
• buffering capacity- the ability to resist a
change in pH
p. 53 A.Q. 1ab, 3abc
1a. What happens to chemical bonds during chemical reactions?
1a. During chemical reactions, the bonds change—they are formed or
broken.
1b. Why is the melting of ice not a chemical reaction?
1b. The melting of ice is not a chemical reaction because new chemicals are
not formed.
3a. What are enzymes?
3a. Enzymes are proteins that act as biological catalysts.
p. 53 A.Q. 1ab, 3abc
3b. Explain how enzymes work, including the role of the enzyme-substrate
complex.
3b. Enzymes provide a site where reactants, called substrates, can be brought
together to react. The substrates bind to a site on the enzyme called the
active site, forming an enzyme-substrate complex. This reduces the
activation energy needed for the reaction.
3c. A change in pH can change the shape of a protein. How might a change
in pH affect the function of an enzyme such as carbonic anhydrase?
3c. A change in pH might affect the function of an enzyme such as carbonic
anhydrase because the change in pH could change the shape of the enzyme.
If the enzyme and substrates no longer fit properly, the enzyme would no
longer be able to speed up the chemical reaction.
Inv. 4.3: Catalase & H2O2
• Concentration: more enzymes = faster
Inv. 4.3: Catalase & H2O2
• Concentration: more enzymes = faster
• Temperature: catalase functions at a wide range
of temperatures; too hot would denature
Enzymes Have a Range:
Inv. 4.3: Catalase & H2O2
• Concentration: more enzymes = faster
• Temperature: catalase functions at a wide range
of temperatures; too hot will denature
Enzymes Have a Range:
• pH: catalase functions
at a wide range of pH
values; too extreme
will denature
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