The Saylor Foundation’s “Answer Key to Problem Set 3”
Putting on Winter Weight
1. What can you conclude about anything that has mass and its relationship to
matter?
Anything that has mass is composed of matter.
2. Where does the extra weight come from?
Animals preparing to hibernate or migrate spend time before winter eating extra
food and increasing their fat stores. In some migrating animals, they continue to
forage along the migration route. When organisms consume more calories than
they use in cellular processes, they convert the excess glucose into fat in the
process of fatty acid synthesis.
3. In what form is this extra weight in hibernating animals? In migratory animals?
The weight in hibernating animals and migratory animals is in the form of the
macromolecule: lipids (fats).
4. Why do hibernating animals need to put on extra weight?
When an animal goes into true hibernation (e.g. bats, chipmunks, etc.), its normal
bodily functions are greatly affected. The body temperature of a hibernating
animal drops and almost matches the external temperature. Additionally, the
animal’s heart rate, breathing rate, and metabolic rate decrease. This allows the
hibernating animal to slowly use the extra weight (fat) that it gained in the spring,
summer, and fall as an energy source. The animal uses less energy during
hibernation than it would if it stayed awake and tried foraging (which may be
unsuccessful).
5. Where does the energy necessary to migrate come from?
The stored fat that the migrating animal accumulated earlier in the year is used to
create the body’s energy source, ATP (Adenosine TriPhosphate), during the
migration.
There are three steps that occur in the process of breaking down fat to get the
components to create ATP for the body’s cells: lipolysis, the Krebs Cycle, and the
Electron transport chain.
The stored fat (triglycerides) is converted through a series of chemical reactions
into ATP. The triglicerides are broken into gylcerol and fatty acids through a
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process known as lipoysis. These components are converted to acetyl CoA,
which then enters a process known as the Krebs Cycle or Cytric acid cycle (TCA
cycle) within the mitochondria of the cell. The acetyl CoA is broken down and
carbon dioxide and hydrogen are removed (the carbon dioxide makes its way to
the lungs and is exhaled). The freed hydrogen protons move into a process
known as the electron transport chain. Ultimately, energy derived from the
movement of hydrogen protons through protein channels results in the
production of ATP.
When ATP is broken down into its components during cellular processes, energy
is released.
6. What is the relationship between matter and energy?
Matter (composed of atoms) is the physical substance within the universe.
Energy is the ability to cause change or do work. Energy is a PROPERTY of
matter.
Taking Off the Extra Pounds
1. How do matter and energy differ?
Energy cannot be created or destroyed. Energy can be transfer by different
mechanism (e.g. light energy transferred to chemical energy in photosynthesis or
chemical energy transferred to heat and light energy during combustion). In
biological systems, some energy may be lost to the system when conversion of
energy occurs (usually in the form of heat). Matter stays within the system (e.g.
the carbon cycle).
2. In what form is energy necessary to survive migration or hibernation stored?
The energy is in a stored form of the macromolecule fat.
3. Are these animals converting matter into energy?
No, the animals are not converting matter into energy. The cellular process of
respiration transform the matter from one molecule to another molecule or atom
(e.g. from lipids into water, hydrogen, etc.). The atomic energy within the
hydrogen protons is used to convert ADP (Adenosine DiPhosphate) and P
(phosphate) into ATP (Adenosine TriPhosphate). Later, the bonds within ATP
are broken, releasing energy for metabolic processes.
4. Where does the weight go during migration or hibernation?
During the process of cellular respiration, waste products such as water and
carbon dioxide are formed and then expelled, reducing the weight of the
organism. The water is expelled in waste excretion in migrating animals or as
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water vapor (during breathing) in hibernating animals. Carbon dioxide is expelled
during breathing.
5. How do the laws of conservation of matter and thermodynamics apply?
Law of Conservation of Matter: During an ordinary chemical change, there is no
detectable increase or decrease in the quantity of matter.
The first law of thermodynamics: Energy can neither be created nor destroyed
The second law of thermodynamics: The entropy of the universe increases
during any spontaneous process.
During the chemical reactions of cellular respiration, no matter is created or
destroyed (molecules of one type are converted into molecules of another).
Additionally, Energy is neither created nor destroyed but is converted into
different forms (e.g. heat).
6. What cellular metabolic processes are involved in the weight loss?
Lipolysis, the Krebs cycle, and the Electron transport chain
7. Where does this metabolism take place within cells?
Within the mitochondria
8. How are matter and energy related to these metabolic processes?
During the metabolic process, matter is converted from one atom or molecule to
others. This process helps to form ATP, the body’s energy source.
9. Are these metabolic processes unique to hibernating and migrating animals or
do they apply to other living organisms? How do humans lose weight, for
example?
No, these processes are not unique to hibernating and migrating animals.
Weight loss is related to the amount of energy you expend and the calories you
consume. If you consume fewer calories than you use in metabolic processes,
your body will begin to convert and use the stored fat, and you will lose weight.
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