Cellular Energy
I.
Molecules used for energy output and storage:
A.
glucose - a 6 carbon sugar converted into ATP as a result of
a process called glycolysis
B.
ATP - adenosine triphosphate; a nucleotide made of an
adenine base, a 5 carbon sugar (ribose) and three
phosphate groups.
*1.
the main energy molecule in the cell*
2.
energy in the bonds between atoms in a molecule of
glucose is transferred to the phosphate bonds in ATP
a.
based on the Laws of Thermodynamics:
- First Law: Law of Conservation of Energy
- Second Law: energy cannot be converted
w/out the loss of usable energy (example =
amount of usable energy at each successive
trophic level of a food chain decreases by 90%);
based on entropy (measure of disorder or
unusable energy)
3.
when bonds between phosphate groups in ATP are
broken, energy is released to fuel a variety of cellular
processes (making new organelles, building proteins,
repairing the cell membrane, active transport, etc.)
4.
when 1 phosphate is removed, ADP is formed; when
another is removed, AMP is formed
5.
when free phosphate groups re-join AMP to make
ADP or re-joins ADP to make ATP, energy is again
stored in the bonds for later use
C.
chemical reactions fueled by ATP make up the cell's
metabolism
D.
a series of chemical reactions in the cell requiring energy
from ATP is called a metabolic pathway - 2 types:
1. catabolic - breaks down large molecules (glucose) into
small molecules to release energy (cellular respiration)
2. anabolic - builds large molecules from smaller ones using
energy (from sunlight) (photosynthesis)
II.
Cellular Respiration
A.
Catabolic - occurs in both autotrophs and heterotrophs but
only in cells containing mitochondria.
B.
process by which mitochondria break down food molecules
to produce ATP: 3 stages.
C.
Aerobic Respiration:
1.
Glycolysis - "sugar dissolving" or "glucose" "break
down"
a.
process in which both plant and animal cells use
2 ATP molecules to break down glucose into 2
pyruvate molecules, resulting in 4 total ATP
molecules or a net production of 2ATPs.
b.
takes place in the cytoplasm but sends the
resulting ATPs to the mitochondria.
c.
uses the electron carrier NAD+ to form NADH
when it accepts 2 electrons
2.
Citric Acid cycle or Kreb's cycle a.
each pyruvate from glycolysis is used to make 1
more ATP, citric acid, and CO2;
b.
takes place in the matrix of the mitochondria
c.
uses the electron carriers NAD+ and FAD to
make NADH and FADH2
d.
3.
produces 2 ATPs
Electron Transport Chain
a.
the final step in the breakdown of glucose.
b.
takes place in the inner membrane of the
mitochondria
c.
electron carriers (NADH and FADH2) deliver
electrons to the top of the chain
d.
electrons are passed from protein (carrier) to
protein, releasing energy at each step (2nd Law
of Thermodynamics)
e.
O2 is the final electron acceptor; no O2 and the
process stops!
f.
Each NADH produces 3 ATPs and each group of
3 FADH2 produces 2 ATPs for a total of 32 ATPs
4.
At the end of the cycle of the transformation of
glucose to ATP, a total of 36 ATPs are produced.
D.
Anaerobic respiration
1.
Fermentation: when no O2 is available, this is the back
up plan!
2.
Allows cellular respiration to continue; follows
glycolysis
3.
2 types:
a.
alcoholic fermentation - occurs only in yeast
and some bacteria
- pyruvate is converted to ethyl alcohol and CO2;
NADH becomes NAD+ so cycle can continue to
electron transport chain
- the reason fruit makes wine, bread rises, etc.
b.
lactic acid fermentation - occurs in muscle cells
and in some bacteria
- pyruvate is converted to lactic acid; NADH
becomes NAD+ so cycle can continue to
electron transport chain
- this keeps the cell alive but is not very
efficient: only 2ATPs result.
- why muscles are sore after a work out
4.
both types of fermentation or anaerobic processes
take place in the cytoplasm then recycle to glycolysis
so glycolysis can continue.
5.
The purpose is to continue cellular respiration w/out
O2.
E.
In summary:

FOOD ---> GLUCOSE ---> ATP ---> ENERGY FOR CELL PROCESSES
 C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy is the formula
for cellular respiration
F.
The mitochondria
III.
Photosynthesis
A.
Anabolic - occurs only in autotrophs in cells containing
chloroplasts/chlorophyll.
1.
chloroplasts - ("green" "form" - greek) - the site of
photosynthesis in plant cells and cells of some other
autotrophic organisms
2.
chlorophyll is a green pigment that occurs in plants makes them green
3.
appears green because green wavelengths of sunlight
are not absorbed; energy for photosynthesis is
obtained from other colors of the spectrum of sunlight
that are absorbed, primarily red, orange, and green,
blue (graph 1)
4.
the more sunlight (light intensity) the chlorophyll is
exposed to, the greater the rate of photosynthesis
(graph 2)
5.
the rate of photosynthesis can be measured by the
amount of CO2 released or the amount of O2
remaining (not used up) (graph 3)
B.
process by which chloroplasts in autotrophs absorb light
energy and convert it to chemical energy (ATP) and then
use ATP to combine and rearrange CO2 and H2O to form
glucose and H2O: 2 stages
1.
Light Dependent reactions - convert light energy to
chemical energy (ATP)
a.
takes place in the chloroplast in the thylakoid
discs that are combined in stacks called grana
(singular = granum); thylakoid contains the
pigment chlorophyll.
b.
chlorophyll absorbs wavelengths of light energy
from the sun
c.
the energy is transferred in the form of high
energy electrons to electron carriers (NADP+)
in the electron transport chain (bucket
brigade); form NADPH
d.
high energy electrons flow down a
concentration gradient, where protons
accumulate in the thylakoid space - called
chemiosmosis; produces ATP which forms in
the stroma
d.
NADPH and ATP are stored in the chloroplast
until used in the next phase
2.
The Calvin Cycle (also called the light independent
reactions) - convert s chemical energy (ATP) to
chemical energy (glucose - a larger, more stable
molecule for storage)
a.
first step is called carbon fixation because CO2
is joined with a 5 carbon compound
b.
After a series of steps in which glucose is
formed, an enzyme called rubisco converts the
remaining molecules to react with CO2 so the
cycle can continue; rubisco converts inorganic
molecules to organic molecules
3.
Plants use the sugars formed in the Calvin cycle as a
source of energy storage and to form complex
carbohydrates such a cellulose, etc.
C.
IV.
The chloroplast
Chemical equations
A.
Cellular respiration
C6H12O6 + 602 --> 6CO2 + 6H2O + energy
Think: What takes in oxygen and gives off CO2? What
process do animals do to accomplish this? What is another
term for breathing? That tells you this is cellular
respiration. What do they breathe out? That tells you that
this is cellular respiration.
B.
Photosynthesis
6CO2 + 6H2O --> C6H12O6 + 602
Think: What do plants take in? What do they give off? What
process do we associate with green plants? That tells you
this is the equation for photosynthesis.
C. The products of one equation are the reactants of the other!