BIOL 1001 Chapter : Chapter 6
Chapter 6
Matter and Energy
Some basics you should know:
---matter is anything that takes up space and has mass
-the physical material of the universe
---Energy is the capacity to do work.
There are two major categories of energy
1) potential energy
2) kinetic energy
---Potential energy is energy stored in matter because of its position or
location.
---Kinetic energy is the energy of motion.
- Matter and energy cannot be created or destroyed
- Potential energy in biological systems can be stored in chemical bonds
The Laws of Thermodynamics Describe the Properties of Energy
Energy transfer by organisms is subject to two laws of thermodynamics
• First Law of Thermodynamics that states that energy can be transferred and
transformed, but it cannot be created or destroyed (i.e., the energy of the
universe
is constant).
• Second Law of Thermodynamics that states that every energy transfer or
transformation makes the universe more disordered (i.e., every process
increases entropy at the cost of useful energy)
• Entropy is the measure of disorder, randomness.
• Every chemical reaction either requires heat or gives off heat, so there
will never be a 100% efficient energy transfer
Why do you get hot when you work out?
• As the energy in food is converted to the energy of movement, some of the
original energy is converted to heat.
If every energy transfer loses usable energy, why doesn’t life on the planet
simply run out of energy?
- Ultimate source of energy: sun
- Sun allows plants to make their own food and start the food chain, the
“energy chain”
- Planet is not a closed system, energy is constantly flowing from the sun
ENERGY FLOW IN CHEMICAL REACTIONS
In all chemical reactions you begin with one set of substances, reactants, and
end with a different set of substances, products.
Thermodynamics determines whether or not a chemical reaction will occur in the
cell, and how much energy it will consume or release
- reactions will either require energy to occur or release energy
Chemical reactions are either exergonic or endergonic
Exergonic: release energy – spontaneous
o Reactants will have more energy than products (energetically
downhill)
o Usually something is broken down
▪ chemical bonds break
o Ex: glucose – combusts into carbon dioxide and water and releases
energy (see power point for picture)
Endergonic: require energy to happen – non-spontaneous
o Will produce products with more energy than its reactants
(energetically uphill)
o Something is being produced/ getting synthesized
▪ chemical bonds are formed
o Ex: photosynthesis: combine carbon dioxide and water to make
glucose and oxygen
▪ requires energy (SUN)
*See power point here for chart on exergonic or endergonic
If energy is given off in a reaction, you can assume that:
• It is an exergonic reaction.
Although exergonic reactions release energy overall, they require some
energy to get them started.
This “starter energy” is called activation energy.
All chemical reactions require activation energy
Coupled reactions
• Chemical reactions that release energy can be coupled to chemical reactions
that require energy.
*Remember energy can’t be created or destroyed – it is being exchanged
(think currency)
• The energy that exergonic reactions release cannot disappear, so it could be
used in another endergonic reaction
• An endergonic reaction cannot happen without an exergonic reaction nearby
to release the energy needed for the endergonic reaction