• Which of these supplies our cells with energy for cell metabolism?
• caffeine
• sugar
• oxygen
• water
• carbon dioxide
• other (explain)
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• Which of these supplies plant cells with energy for cell metabolism?
• sugar
• sunlight
• water
• oxygen
• carbon dioxide
• other (explain)
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Our cells get energy from:
1 2 3 4 5
0%
80%
0%0%
20%
1. Caffeine
2. Sugar
3. Oxygen
4. Water
5. Carbon dioxide
Plant cells run their metabolism using which of
the following?
1 2 3 4 5
40%
60%
0%0%0%
1. Sunlight
2. Sugar
3. Water
4. Oxygen
5. Carbon dioxide
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.”
• “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)
Potential energy is stored energy.
Examples: coiled spring, energy in chemical
bonds.
Kinetic energy is energy released to do work.
Examples: car in motion, heat, light, electrical
current.
When we consume food as an energy source, the energy in the food is:
1 2
0%
100%1. Potential energy
2. Kinetic energy
Energy Conversions
gas
Combustionby engine.
100 unitschemical energy(concentrated)
75 unitsheat
energy
25 unitskinetic energy
(motion)
+
All energy conversions involve a loss of energy, often as heat energy.
In living systems, too, energy conversions involve a loss of energy, about 90% at each
level.
energystored inchemicalbonds
producer primary consumer secondary consumer
detritus feeders and decomposers
heatHEAT
tertiary consumer(1 calorie)
producer(1000 calories)
primary consumer(100 calories)
secondary consumer(10 calories)
Top-level predators need huge territories. Use what you have just learned about energy
conversion to explain this.
• Why is only about 10% of energy passed from one organism to another in the food chain?
• If it takes about 30 acres of land to raise enough cattle to feed a family of five for a year, how much land would the family need if they went vegetarian?
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Which of these is true about photosynthesis?
1 2
100%
0%
1. Photosynthesis makes energy.
2. Photosynthesis consumes energy.
Which of these is true about cellular respiration?
1 2 3
0%
20%
80%1. Cellular respiration
creates energy.
2. Cellular respiration releases energy.
3. Cellular respiration consumes energy.
Endergonic reactions
energyused
products
reactants
Endergonic reactions consume (and may store) energy.
Inorganic mineral nutrients(nitrate, phosphate) areabsorbed from soil andused in plant tissues.
Energy iscapturedfromsunlight.
Oxygen isreleased.
Sugar issynthesizedand used inplant tissues.
planttissues,growth
Carbon dioxideis absorbedfrom the air.
Water is absorbedfrom soil, used inphotosynthesis, andstored in cells.
photosynthesisphotosynthesis
Photosynthesis is an example of an
endergonic reaction. Explain why.
energyinput
C6H12O6
(glucose) O2
(oxygen)6 CO2
(carbondioxide)
6 H2O(water)
+
+
Producers (such as plants) take in light energy and use it to bind carbon, hydrogen, and
oxygen into carbon-based compounds such as sugar.
Sugar is stored (potential) energy used by Eukaryotes to make ATP for their cells.
TERTIARY CONSUMER(4th trophic level)
PRODUCER(1st trophic level)
PRIMARY CONSUMER(2nd trophic level)
SECONDARY CONSUMER(3rd trophic level)
Metabolizing food (cellular respiration) is an example of an exergonic reaction. Explain why.
energyreleased
C6H12O6
(glucose) O2
(oxygen)6 CO2
(carbondioxide)
6 H2O(water)
+
+
Both producers and consumers break down sugars and other carbon compounds to get
usable energy for their cells.
All Eukaryotes use the process of cellular respiration to break down sugar in order to make ATP.
progress of reaction
energy releasedby burning glucose
activation energy neededto ignite glucose
CO2 + H2O
Burning glucose (sugar) : an exergonic reaction
high
low
energycontent
ofmolecules
glucose + O2
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?
ATP(a) Adenosine diphosphate (ADP)
ribose
Energycontent
Shorthandrepresentations
or
"high-energy"bond
adenine
phosphate groups
low
"high-energy"bond
phosphate groups
or
high
(b) Adenosine triphosphate (ATP)
What class of molecule is ATP?
net exergonic“downhill” reaction
glucose
protein
aminoacids
CO2 + H2O + heat
ADP + heat
Coupled reaction: glucose breakdown and protein synthesis
endergonic(ATP synthesis)
exergonic(ATP breakdown)
exergonic(glucose breakdown)
endergonic(protein synthesis)
What does this mean? (Think back to the first slides.)
Which process makes ATP for a plant cell to use?
1 2 3 4
40%
0%0%
60%
1. Photosynthesis
2. Cellular respiration
3. Both
4. Neither
When do plants carry out photosynthesis?
1 2 3
80%
20%
0%
1. Day only
2. Night only
3. Both day and night
When do plants carry out cellular respiration?
1 2 3 4
0%
20%
80%
0%
1. Day only
2. Night only
3. Day and night
4. Never. Plants only carry out photosynthesis.
Day
Night
When does a plant do photosynthesis (synthesizing organic, energy-rich molecules)?
When does a plant do cellular respiration (breaking down organic molecules to release
energy)?
Photosynthesis
Cellular Respiration
Cellular Respiration
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.
“Energy drinks”
In a scientific sense, what is the source of real energy in these
drinks?
Why does a 0-calorie “energy” drink make no
sense in science?
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