Photosynthesis
and
Cellular
Respiration
Energy Use in Living
Organisms

Step 1


Convert sunlight
energy into
chemical food
energy
 Ends in Glucose
Step 2

Convert chemical
food energy into
chemical energy
that the cell can use
 Ends in ATP
Adenosine Triphosphate
(ATP)
Ribose
Three phosphate
groups Adenine
Energy Cycle
• ATP is a charged battery for
cell
• Made during cellular
respiration
• Used up to complete
activities for cell
• Energy in ATP is stored in high
energy bonds between
phosphate groups
ATP
• ADP is a used battery for cell
• one phosphate has been
removed
• Phosphate must be added
back on to recharge battery
ADP
ATP and ADP
What do Plants do?

Plants do step 1
with chloroplasts

Plants do step 2
with mitochondria

Because plants
make their own
food and then eat
it, they are called
autotrophs
What do Animals do?

Only do step 2
with
mitochondria

Because
animals must
eat food that
others have
made, they
are called
heterotrophs
Step 1: Photosynthesis




Convert sunlight energy into
glucose
Chloroplast performs
photosynthesis
Plants, algae, some
bacteria, and some protists
all perform photosynthesis
Overall reaction


6CO2 + 6H2O → C6H12O6 + 6O2
Occurs in two stages

Light dependent reactions
 Light independent reactions
Chloroplast

Found only in Plant cells

Thylakoid- coin-shape structure containing
chlorophyll and proteins; also called
photosystems

Grana- stacks of thylakoids

Stroma- fluid inside chloroplast (similar to
cytoplasm)
Light Dependent Reactions

Energy from sunlight is absorbed by chlorophyll and other
pigments in the thylakoid membrane

Water is split into oxygen (given off as waste), H+, and
electrons

Electrons go through a series of proteins in the membrane
called the electron transport chain

Electrons provide energy for hydrogen protein pumps to
pump H+ into the thylakoid

More sunlight energy is absorbed

Electrons are added to NADP+ to create NADPH

Hydrogen ion diffuse through another membrane protein

The diffusion fuels the production of ATP by the enzyme ATP
synthase
Light Dependent
Reactions
Light Independent Reactions

Occurs in the stroma

Also called the Calvin cycle

Is a series of reactions controlled by enzymes

The ATP and NADPH made during the light
dependent reactions are used to fuel the
reactions

CO2 provides the carbon used to make the
sugars

Simple sugars (primarily glucose) are made
during the cycle
Light Independent Reactions
Factors that Affect
Photosynthesis


Water

Water shortages can slow or stop photosynthesis

Plants in dry climates

Waxy coating

Thin leaves (needles on cactus)
Temperature

Low temps slow or stop photosynthesis

Enzymes do not work well at low temps
Factors that Affect
Photosynthesis (cont)


Light Intensity/Amount

Increase in light, increase in photosynthesis until at
maximum level

Plants still perform photosynthesis in periods without
light
Density of Other Plants

Crowded plants complete for light and resources

Reduces photosynthesis
Cellular Respiration

Convert glucose into ATP

Mitochondria performs cellular respiration

All organisms

Process is called aerobic because it requires
oxygen

Overall reaction

C6H12O6 + 6O2 → 6CO2 + 6H2O
Mitochondria

Found in animals
and plants

Outer and Inner
membrane

Cristae- folding of
inner membrane

Matrix- area inside
of inner membrane
Glycolysis

Occurs in cytoplasm of
cell

Anaerobic (oxygen not
needed)

2 ATP’s are used to start
the process

Glucose (a 6 carbon
sugar) is broken into two
three carbon sugars

4 ATP’s, 2 NADH’s, and 2
pyruvates are made
What comes next?

With oxygen


Other
processes of
cellular
respiration
occur in the
mitochondria
Without oxygen

Fermentation
occurs in the
cytoplasm
Krebs Cycle






Occurs in the matrix
Pyruvate is broken into a 2 carbon molecule
producing 2 NADH and CO2
Coenzyme A attaches to the 2 carbon
molecule and enters the Krebs cycle
It is converted into citric acid
Citric acid is broken down through a series of
steps producing 3 more NADH’s. one ATP, one
FADH2, and two more CO2’s
Two turns of the cycle are needed to process
the 2 pyruvates from glycolysis
Krebs Cycle
Electron Transport Chain





Occurs along the inner
membrane of the
mitochondria
Electrons from NADH and
FADH2 are used
Electrons fuel hydrogen
protein pumps which
pump H+ out of the matrix
H+ diffuses through a
membrane protein and
fuels ATP production by
ATP synthase
Oxygen picks up the
electrons and H+ to form
water
Summary of Cellular
Respiration
Fermentation

Occurs when oxygen in
unavailable

In humans occurs as
lactic acid fermentaion
(some yeast and plants
do alcohol
fermentation)

Pyruvates are
converted to lactic
acid and NAD+ is
formed

No more ATP are
produced
Comparison
Ps
Rs
Function
Make food for plants
Make energy for ALL
organisms
Location in
cell
Chloroplast
Mitochondria
Uses what?
Water, CO2, Sunlight
Oxygen,
Food/Glucose
Makes what?
Oxygen,
Food/glucose
Water, CO2,
Energy/ATP