honors biology ch. 5 Notes Energy, atp, enzymes

honors biology
ch. 5 Notes
Energy, atp, enzymes
5.12 Define and compare endergonic and exergonic
reactions
ender- inward
exer- outward
gonic- energy
Exergonic:
Releases energy overall
-ΔH: “negative change in heat content”
Reactantsʼ bonds contain more energy than the productsʼ
bonds. “Downhill” energy reaction
These reactions feel hot.
Examples:

Wood burning

Sugar burning

Cellular respiration
Endergonic:
Requires energy overall
+ΔH: “positive change in heat content”
Reactantsʼ bonds contain less energy than the productsʼ
bonds. “Uphill” energy reaction
These reactions feel cold.
Examples:

First aid cold pack

Photosynthesis
Metabolism: The total of an organismʼs chemical reactions.
Which of the following is not a part of metabolism?
a. photosynthesis
b. hydrolysis of lipids
c. protein synthesis
d. blood typing
e. phagocytosis
f. dehydration synthesis
g. buffering of blood
5.12 Explain how cells use cellular respiration and energy
coupling to survive.
Energy coupling: the use of energy released from exergonic
reactions (“downhill”) to drive essential endergonic (“uphill”)
reactions. fig. 5.13c
Use a series of diagrams of energy couplings to show
photosynthesis, respiration, the ATP cycle, and energy to
do work.
5.13 Describe the three main types of work.
Chemical: synthesis of molecules
Mechanical: muscle contraction
Transport work: active transport by proteins.
5.13 Explain how ATP functions as an energy shuttle
Adenosine Triphosphate
ATP= the energy currency of the cell
Structure of ATP: 5.13a
• A-P∼ P∼ P
• Adenine + Ribose (adenosine) + PO4-3+ PO4-3 + PO4-3
Mrs. Loyd
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Energy Shuttle: fig. 5.13c
Phosphorylation:

High-energy bond + phosphate ( ∼ P ) transfer by
hydrolysis to molecule to do work.

Adenosine Diphosphate

Adenosine Monophosphate
Summary:

ATP → ADP + Pi + ∼

ADP → AMP + Pi + ∼
Questions for Review
1. How many high-energy phosphate bonds does ATP
contain?
2. What does it mean when a molecule becomes
phosphorylated?
3. Where does the energy to do cellular work come from?
The hydrolysis of…
4. Is this reaction endergonic or exergonic?
5. Is cellular work an endergonic or exergonic reaction?
6. Where does the energy to make ATP come from?
The hydrolysis of…
7. Is this reaction endergonic or exergonic?
8. Is the synthesis of ATP endergonic or exergonic?
HOW ENZYMES FUNCTION
5.14 Explain how enzymes speed up chemical reactions.
Enzymes are:
•
Biological catalysts
•
Proteins made by cells
•
Structure determines function
•
Denatured proteins (unraveled) donʼt work
•
Denaturation caused by:
o high temperatures shake apart tertiary structure
o extremes of pH
Enzymes:
•
lower the energy of activation (EA) to Cellular temperatures
•
have an active site that bonds their substrate
•
are SPECIFIC for their substrate
•
example: sucrase/sucrose fig. 5.15
•
are reused
5.15 Describe the structure of an enzyme-substrate interaction.
use induced fit to bond to substrate
(demo: meterstick-ase)
5.15 Explain how the cellular environment affects enzyme
activity.
Reaction Rates of Enzyme-Catalyzed reactions
determined by:

substrate concentration

enzyme concentration

temperature (optimum) body temp for humans

pH (optimum) pH = 6-8 for humans, buffers help

cofactors are required by many enzymes and may be:
o trace minerals (inorganic) or
o vitamin fragments (organic).

inhibitors (poisons are irreversible inhibitors)
Mrs. Loyd
[email protected]
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10/20/11
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