Lesson #3.5Photosynthesis and
Cellular Respiration
Photosynthesis
Two conditions are vital to life
on Earth:
1. Matter must continually be
recycled between the living and
non-living world
– The amount of matter has remained
unchanged since the beginning
of the Earth
Photosynthesis
Two conditions are vital to life
on Earth:
2. Energy must be continually added
to Earth by the sun, since it is
depleted (used up) each time
matter changes form
Photosynthesis
• Only members of 1 entire Kingdom
(Plantae) are able to capture the
sun’s energy and use it to convert
low energy compounds (CO2 and
H2O) to a high energy compound
(glucose) in a process called
photosynthesis
Photosynthesis
• Overall reaction
carbon dioxide
water
6CO2 + 12H2O
glucose
oxygen
water
C6H12O6 + 6O2 + 6H2O
6CO2 + 12H2O  C6H12O6 + 6O2 + 6H2O
Photosynthesis
• Photosynthesis means “to build”
(synthesis) using “light” (photo)
• Takes place in the chloroplasts,
using a green pigment called
chlorophyll to trap the sun’s
energy
Photosynthesis
• It is a 2 step process
a. Light reaction (light dependent)
o
The sun’s energy is used to split H2O
molecules into H2 and O2 molecules and
to make 2 ATP molecules
Photosynthesis
• It is a 2 step process
b. Dark reaction (light INdependent)
o
o
CO2 (from the atmosphere) plus the
products of the light reaction (H2, O2,
ATP) are used to make glucose
This is also called
the “Calvin Cycle”
Cellular Respiration
• Plants are autotrophs (producers)
since they make their own food
– Ex. They make glucose via
photosynthesis
• Animals are heterotrophs
(consumers) that must get their
food from plants (herbivores) or
other animals (carnivores)
Cellular Respiration
• But both autotrophs and
heterotrophs must obtain energy
from the glucose made by plants
– This is done by breaking the bonds of
glucose to forms CO2 and H2O again
– This process is called Cellular
Respiration
Cellular Respiration
• Cellular respiration takes place
mostly in the mitochondria of all
eukaryotic cells (including plants)
• It is a complex, multi-step process
Cellular Respiration
• Overall reaction
glucose
oxygen
C6H12O6 + 6O2
carbon dioxide
water
6CO2 + 6H2O + energy
C6H12O6 + 6O2  6CO2 + 6H2O + energy
Cellular Respiration
• Energy is extracted from glucose
in many small steps instead of 1
big, explosive step, so that the cell
gets many “packets” of energy to
work with from each glucose
molecule
– The energy is used for active
transport, cell division, cell
movement, etc.
Cellular Respiration
– These “packets” of energy that are
produced in cellular respiration are
called ATP (Adenosine TriPhosphate)
adenine
(nitrogenous
base in
DNA/RNA)
ribose
(sugar in RNA)
3 phosphate groups
Cellular Respiration
– Energy from cellular respiration is
used to form this last phosphate bond
– The ATP created can now be used for
active transport, cell division, etc.
adenine
(nitrogenous
base in
DNA/RNA)
ribose
(sugar in RNA)
3 phosphate groups
What happens to ATP
ATP is the energy formed from cellular respiration
ADP + Pi

ADP + Pi

(low energy
molecule)
(inorganic
phosphate)
ATP
(high energy
molecule)
ATP
ATP is used up and ADP and Pi are formed when
energy is used for active transport, cell division…
Adding ATP to the equation
C6H12O6 + 6O2 + 36ADP + 36Pi
6CO2 + 6H2O + 36ATP
**This is aerobic respiration!**
C6H12O6 + 6O2 + 36ADP + 36Pi  6CO2 + 6H2O + 36ATP
Cellular Respiration
• Cellular respiration starts in the
cytoplasm, where 2 ATP molecules
are formed and then finishes in the
mitochondria, where 34 more ATP
Finishes
molecules are formed…
… for a GRAND total of 36
ATP formed per glucose
molecule for aerobic
respiration
Starts
2 Types of Cellular
Respiration
A. Aerobic Cellular Respiration
– Occurs when oxygen is present
– Involves the complete breakdown
of glucose to CO2 and H2O
– Therefore 36 ATP are formed
2 Types of Cellular
Respiration
B. Anaerobic Cellular Respiration
– Occurs when there is NO oxygen or
when oxygen runs out
– The breakdown of glucose is
incomplete
– It is also called fermentation
Alcohol Fermentation
• Occurs in yeast cells and only
yields 2 ATP per glucose molecule
• Products are alcohol (ethanol,
C2H5OH) and CO2
– Ex. The CO2 formed causes bread to
rise and gives bubbles to beer and
sparkling wine
Lactic Acid Fermentation
• Occurs in muscle cells that are
working hard and run out of
oxygen
• Glucose only breaks down partway  to lactic acid, C3H6O3 and
only 2 ATP per glucose molecule
are formed
– Lactic acid causes pain in the side
during intense exercise
Activity and Homework
1. Complete and hand-in
“Photosynthesis” worksheet
2. Read pages 58-66
3. Answer questions
– Page 60 #1,2,5
– Page 64 #1,2
– Page 67 #1,2