1. Energy Flow
in the Life of a Cell

2. Energy
“Energy” is the ability to do work, such as causing motion, or interaction between molecules. This is the idea of “energy” used in your textbook.
“Energy” is used in an everyday sense to mean “alertness,” “strength,” or “vitality.”

3. “Energy” is a not a material. It is best described as a phenomenon.
Energy can be measured a number of ways including:
calories (food energy)
degrees (heat energy)
voltage (electrical potential)

4. Potential vs. Kinetic Energy
________
________

5. Potential energy is ______ energy.
Kinetic energy is energy _____________________.
Examples: coiled spring, energy in chemical bonds.
Examples: car in motion, heat, light, electrical current.

6. All energy conversions involve a loss of energy, often as heat energy.
Combustion
by engine.
gas
100 units
chemical energy
(concentrated)
75 units
heat
energy +
25 units
kinetic energy
(motion)
All energy conversions involve a loss of energy, often as heat energy.

7. heat
HEAT
energy
stored in
chemical
bonds
producer
primary consumer
secondary consumer
detritus feeders and decomposers
In living systems, too, energy conversions involve a loss of energy, about _____ at each level.

8. tertiary consumer
(1 calorie)
secondary consumer
(10 calories)
primary consumer
(100 calories)
producer
(1000 calories)
Top-level predators need huge territories. Use what you have just learned about energy conversion to explain this.

9. Endergonic reactions _________ (and may _____) energy.
used
products
reactants
Endergonic reactions _________ (and may _____) energy.

10. Ammonium thiocyanate + Barium hydroxide
Endergonic Reaction
Ammonium thiocyanate + Barium hydroxide

11. Photosynthesis is an example of an endergonic reaction. Explain why.
Energy is
captured
from
sunlight.
Oxygen is
released.
Sugar is
synthesized
and used in
plant tissues.
Carbon dioxide
is absorbed
from the air.
plant
tissues,
growth
photosynthesis
Water is absorbed
from soil, used in
photosynthesis, and
stored in cells.
Inorganic mineral nutrients
(nitrate, phosphate) are
absorbed from soil and
used in plant tissues.

12. energy
input
C6H12O6
(glucose) + O2
(oxygen)
6 CO2
(carbon
dioxide) +
6 H2O
(water)
_________ (such as plants) take in light energy and use it to bind _____, _______, and ______ into carbon-based compounds such as ______.
Sugar is stored (potential) energy used by __________ to make ____ for their cells.

13. Exergonic reactions _______ energy.
released
reactants
products
Exergonic reactions _______ energy.

14. Exergonic Reaction

15. TERTIARY CONSUMER
(4th trophic level)
PRIMARY CONSUMER
(2nd trophic level)
SECONDARY CONSUMER
(3rd trophic level)
PRODUCER
(1st trophic level)
Metabolizing food (cellular respiration) is an example of an exergonic reaction. Explain why.

16. energy
released
C6H12O6
(glucose) + O2
(oxygen)
6 CO2
(carbon
dioxide) +
6 H2O
(water)
Both ________ and __________ break down sugars and other carbon compounds to get usable _______ for their cells.
All Eukaryotes use the process of cellular respiration to break down sugar in order to make _____.

17. activation energy needed
Burning glucose (sugar) : an exergonic reaction
high
activation energy needed
to ignite glucose
glucose + O2
energy
content of
molecules
energy released
by burning glucose
CO2 + H2O
low
progress of reaction
Getting energy out of sugar by burning requires a high input of energy. What kind of molecule do cells use to lower the activation energy in order to use sugar?

18. What class of molecule is ATP?
(a) Adenosine diphosphate (ADP)
(b) Adenosine triphosphate (ATP)
adenine
"high-energy"
bond
"high-energy"
bond
ribose
phosphate groups
phosphate groups
Shorthand
representations or or
Energy
content
low
high
What class of molecule is ATP?

19. Which is exergonic and which is endergonic?
energy
ADP
phosphate
ATP
Which is exergonic and which is endergonic?
energy
ATP
ADP
phosphate

20. What does this mean? (Think back to the first slides.)
Coupled reaction: glucose breakdown and protein synthesis
glucose
exergonic
(glucose breakdown)
endergonic
(ATP synthesis)
protein
exergonic
(ATP breakdown)
endergonic
(protein synthesis)
CO2 + H2O + heat
ADP + heat
amino
acids
net exergonic
“downhill” reaction
What does this mean? (Think back to the first slides.)

21. When does a plant do photosynthesis (synthesizing organic, energy-rich molecules)?
Day
Night
When does a plant do cellular respiration (breaking down organic molecules to release energy)?

22. Remember...
Photosynthesis does not “give a plant energy” or “make energy.”
Photosynthesis uses energy to make organic molecules.
Cellular respiration releases energy to the cells by breaking down organic molecules.

23. Recap Photosynthesis is an endergonic (energy-consuming) process.
Cellular respiration is an exergonic (energy-releasing) process.
Which process must ALL Eukaryotic organisms (including plants) do to make ATP?