energy

Chapter 8 Notes

Chemical Reactions
• CHEMICAL REACTION
is the process that
changes one set of
chemicals into another
set of chemicals
– REACTANTS are
compounds that enter the
chemical reaction (what
you start with)
– PRODUCTS are compounds
produced by a chemical
reaction (what you end up
with)

Energy
• ENERGY is the capacity
for doing work or
causing a change in
matter.
– Two forms of energy:
• KINETIC energy – energy
that is actively expressed
• POTENTIAL energy –
energy that represents
the capacity for doing
work or causing change
(stored energy)

Laws of Thermodynamics
• FIRST Law of Thermodynamics
– Energy cannot be CREATED nor
DESTROYED
– It can be CHANGED from one form to
another
– Also known as CONSERVATION OF
ENERGY

Laws of Thermodynamics
• SECOND Law of Thermodynamics
– Energy cannot be changed from one form to
another without a LOSS of USEABLE
energy
– Much of the energy is lost in the form of
HEAT
– Heat CANNOT be converted to one of the
other forms of energy.

Cells and Entropy
• The second law of thermodynamics can also
be stated as: Every energy transformation
makes the universe LESS organized and more
disordered
• ENTROPY is the tendency of the universe to
become disordered
• Living things use energy to MAINTAIN their
own organization.
– Without energy they would die and decompose
(entropy)
– All living organisms require energy for survival
– For this reason, living things are dependent on an
outside source of energy that ultimately comes
from the SUN

Cells and Entropy
• All living things need some type of
ENERGY to survive.
• In addition, cells use ENERGY for
everything they do.
• METABOLISM is all of the chemical
changes that occur within an organism
• Where do the cells get this energy
from?

ATP
• ADENOSINE
TRIPHOSPHATE or
ATP.
– This is a phosphorus
compound that
STORES energy
(works just like a
battery!! ATP =
energy currency of
the cell)

ATP
• Structure:
• ADENINE
• RIBOSE
• 3 PHOSPHATE groups
• ADENOSINE
TRIPHOSPHATE

ADP AND AMP
• ADP – adenosine
DIPHOSPHATE
– Has 2 phosphate
groups
• AMP – adenosine
MONOPHOSPHATE
– Has 1 phosphate
group
– Like an uncharged
battery

ATP and Energy
• It takes ENERGY to attach a phosphate to
AMP or ADP
– (Just like it takes energy to push to opposing
magnets together)
• This energy is stored in the phosphate
BONDS
• Energy is stored when a phosphate group is
ADDED and a bond is FORMED
• Energy is released when a phosphate group
is RELEASED and a bond is BROKEN

ATP and Energy
• ADP + energy + P
ATP
• ATP ADP + P + ENERGY
• ADP forms when ATP releases energy
• The energy released by converting ATP
to ADP provides energy for the
MECHANICAL FUNCTIONS of cells

ATP and Energy
• Used ATP is then RECYCLED ADP and P
are used to make more ATP.
• The formation/breakdown recycling
activity is very important because then
cells do not have to STORE all the
ENERGY it needs.
– (Trying to pay for pop with $1 bill vs. $50 bill)
• PHOSPHORALATION is the addition of a
phosphate group to a molecule (involves
the transfer of energy)

Where does the energy stored in
ATP come from?
1. PHOTOSYNTHESIS is the process by which
green plants use the energy of sunlight to
produces high energy SUGARS and
STARCHES
1. Occurs in the CHLOROPLAST of a cell
2. CELLULAR RESPIRATION is the breakdown
of food molecules and release of chemical
energy within the cell
1. Occurs in the MITOCHONDRIA of a cell.
3. Each step in photosynthesis and respiration
is activated by ATP

Organisms are classified
according to the origin of their
food energy.
1. AUTOTROPHS are
organisms, such as
plants, that make their
own food (also called
PRODUCERS).
2. HETEROTROPHS are
organisms that cannot
make their own food
and must obtain energy
from the food they eat
(also called
CONSUMERS).

Photosynthesis
• Chemical Reaction
• 6CO2 + 6H2O C6H12O6 + 6O2
– Reactants: 6CO2 + 6H2O
– Also needed: ENERGY FROM SUN
– Products: C6H12O6 + 6O2

Summary of Photosynthesis
• Needed by plants for photosynthesis:
SUNLIGHT, CARBON DIOXIDE and
WATER
• Produced by plants during
photosynthesis: high energy SUGARS
and STARCHES
• The gas GIVEN OFF by plants during
photosynthesis: OXYGEN
• Place in the eukaryotic cell where
photosynthesis takes place:
CHLOROPLASTS

CHLOROPLAST
STEM
BLADE

Structure of the Chloroplast
• THYLAKOIDS: membranes are
flattened disk shapes membranes that
contain PHOTOSYSTEMS
• STROMA is the region outside of the
thylakoids
• GRANA: is a stack of thylakoids
• PHOTOSYSTEM: is the place in the
chloroplast where chlorophyll is found

Chloroplast
STROMA
THYLAKOID
PHOTOSYSTEMS -
CHLOROPHYLL (INSIDE)
GRANA
DOUBLE MEMBRANE

Light Absorption
• Plants take in the sun’s energy by
absorbing SUNLIGHT
• PHOTOSYSTEMS are clusters of pigments
used as light-collecting units
– PIGMENTS are substances that absorb visible
light
– Found in the
THYLAKOID
MEMBRANE
– This is where
CHLOROPHYLL
pigment can be
found

Chlorophyll
• Absorb red, orange, yellow, blue, and
violet light
• Reflect GREEN light; This makes plants
look GREEN
• Most important function is that they
ABSORB light energy
• Two types: chlorophyll A and chlorophyll
B
• When chlorophyll absorbs light, much of
the energy from that light is used to
make PHOTOSYNTHESIS work

Accessory Pigments
• Plants also contain ACESSORY pigments
such as carotene that absorb light in
other regions of the spectrum.
• Most of the time, the GREEN COLOR of
the chlorophyll OVERWHELMS OR
HIDES the other pigments, but as THE
TEMPERATURE DROPS THE
CHLOROPHYLL MOLECULES BREAK
DOWN FIRST, LEAVING THE
REDS/ORANGES OF THE ACCESSORY
PIGMENTS TO SEE

Summary of Photosynthesis

LIGHT DEPENDENT
REACTIONS (REQUIRE light)
• Produce O2 (Oxygen gas),
ATP, AND NADPH
• NADP+ is an electron
carrier and holds two
HIGH ENERGY electrons,
along with an H+ ion
(another way that some
energy of sunlight can be
trapped in CHEMICAL
FORM)
• Take place in the
THYLAKOID MEMBRANE

Light Absorbtion
• Energy from light and WATER is used
to make ATP and NADPH
• The leftovers after making ATP and
NADPH is O2
– Which is released from the plant as a
“waste” product

LIGHT INDEPENDENT REACTIONS
(does NOT require light)
• Energy from ATP and NADPH is used to
build high energy compounds that can be
USED for a long time
– ATP and NADPH are SHORT-TERM energy
carriers

Light Independent Reactions
• This is also known as the CALVIN cycle
• Produces high energy SUGARS and
STARCHES
• Uses ENERGY from ATP and NADPH
• Also uses CO2 (Carbon Dioxide) to make
sugars
• Takes place in the STROMA of the
chloroplast

Summary of Photosynthesis

Factors that affect the rate of
photosynthesis
• LIGHT intensity an increase in light
increases the rate of photosynthesis
until all electrons are excited and then
the rate of photosynthesis will level out

Factors that affect the rate of
photosynthesis
• TEMPERATURE The rate of
photosynthesis will increase up to 45°C
(115°F) and then decrease above 45°C
(less than optimal rate)

Factors that affect the rate of
photosynthesis
• CARBON DIOXIDE more CO2
present increases the amount of sugar
made

Factors that affect the rate of
photosynthesis
• WATER without enough water the
rate of photosynthesis goes down

Photosynthesis Under Extreme
Conditions
• C4 PLANTS have a special chemical pathway
that allows them to capture very low levels of
CO2
– Photosynthesis can keep working under INTENSE
LIGHT AND HIGH TEMPERATURES
– Requires extra ATP
– Examples: corn, sugar cane, sorghum
• CAM PLANTS admit air into their leaves only at
night and traps carbon in the leaves
– During the daytime the carbon dioxide is released so
sugars can be made
– Photosynthesis can keep working in DRY CLIMATES
– Examples: pineapple trees, desert cacti, icy plants

C4 Plants

CAM Plants