Cells obtain energy from ATP molecules, which get their energy by breaking off phosphate groups. Photosynthesis is how plants harness energy from sunlight to produce glucose and oxygen from carbon dioxide and water. The light reactions use sunlight to produce ATP and NADPH, and the Calvin cycle uses these to fix carbon from carbon dioxide into glucose. Respiration is how organisms extract energy from glucose to power their functions and produce ATP.

1. ATP, Photosynthesis, and Respiration
ENERGY IN A CELL

2. Life on Earth depends on the
flow of energy:
• Respiration is one
way living things get
energy
• Photosynthesis is
another way
• First we must look at
cell energy… what is
it???

3. ENERGY is the ability to do work
• There are different states of energy:
– kinetic or potential
• There are different forms of energy:
– heat, mechanical, chemical, nuclear,
electromagnetic

4. Your cells get CHEMICAL energy from foods
eaten.
• Cells will store and release the energy as the body
needs it
• The storage molecule is known as ATP
• ATP: Adenosine TriPhosphate
– molecule that stores and releases energy for a cell’s
functioning

5. • Energy for a cell comes from braking off a
phosphate molecule… NOT directly from food
itself
• Energy is stored by adding a phosphate
molecule to a ADP (Adensosine
DiPhosphate) molecule to create an ATP
molecule

6. Cells use energy to maintain
HOMEOSTASIS
• Homeostasis is balance of molecules inside
and outside the cell
• Energy is also used for:
– enzymes
– building cell or body parts
– eliminating waste
– transporting molecules
– basically, for EVERYTHING!!

7. PHOTOSYNTHESIS
• Photosynthesis is a
process where plants
trap the sun’s energy to
create food
(carbohydrates) for
itself (ENERGY!!)
• Plants are autotrophs;
they have the ability to
make their own food
? ?
?

8. The process of photosynthesis:
• Chemical formula for photosynthesis:
– 6CO2 + 6H2O + E ----> C6H12O6 + 6O2
http://www.physicalgeography.net/fundamentals/9l.html

9. • The E is light energy
from the sun
• This light energy is
changed to chemical
energy inside the
chloroplast of the
plant cell. The
energy is stored to
help make food.
(also known as the
LIGHT
REACTIONS)

10. Steps to the Light Reactions:
• Light from sun strikes chlorophyll, and an electron
(e-) aborbs energy
• The e- leaves chlorphyll and is passed along other
molecules called the e- transport chain
• As they travel the e- transport chain, extra energy
is stored in the plant as ATP

11. Steps to the Light Reactions Continued:
• Once the e- is gone, the chlorophyll picks up and
splits H2O (called photolysis)
• O2 is given off as waste (humans use!)
• H+
and O-
ions are used in the Calvin cycle
• http://www.phschool.com/science/biology_place/b
iocoach/photosynth/calvin1.html

12. The H from H2O and the C from the CO2 are used
in the Calvin Cycle to produce the food
molecules (carbos)
• CO2 enters plant through stems and leaves
• CO2 is changed to glucose (carbos)
• Plant uses the glucose (carbos) to keep surviving

13. • Sometimes the
plant will undergo
CHEMOSYNTHE
SIS instead of
photosynthesis if
no light is present
• Animals use the
plant (source of
glucose or
carbohydrates) for
ENERGY

14. 6CO2 + 6H2O + E ----> C6H12O6 + 6O2
1
2
3
4
5

15. 6CO2 + 6H2O + E ----> C6H12O6 + 6O2
• The 6CO2 comes from aerobic respiration
(the air animals breathe out) and the
atmosphere
• The 6H2O comes from the rain, soil, urine
from animals
• The C6H12O6 are carbohydrates, or food for
the plant (animals eat this by eating the
plant!)
• The 6O2 is a waste product from the light
reactions; plants don’t want but humans do!